Document:

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                                                                   EXHIBIT 10.9

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                                    Lease

                           PACIFIC CORPORATE PLAZA
                            27061 ALISO CREEK ROAD

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                                   Between

                                 PHONEXCHANGE
                                   (Tenant)

                                     and

                        CARRAMERICA REALTY CORPORATION
                                  (Landlord)

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                                      Lease

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1.       LEASE AGREEMENT......................................................3

2.       RENT.................................................................3
         A. Types of Rent.....................................................3
            (1)   Base Rent...................................................3
            (2)   Operating Cost Share Rent...................................3
            (3)   Tax Share Rent..............................................4
            (4)   [Intentionally Omitted.]....................................4
            (5)   Additional Rent.............................................4
            (6)   Rent........................................................4

      B.    Payment of Operating Cost Share Rent and Tax Share Rent ..........4
            (1)   Payment of Estimated Operating Cost Share Rent and
                  Tax Share Rent..............................................4
            (2)   Correction of Operating Cost Share Rent.....................5
            (3)   Correction of Tax Share Rent................................5

      C.    Definitions.......................................................5
            (1)   Included Operating Costs....................................5
            (2)   Excluded Operating Costs....................................6
            Property Management Fee...........................................7
            (4)   Taxes.......................................................7
            (5)   Lease Year..................................................8
            (6)   Fiscal Year.................................................8
      D.    Computation of Base Rent and Rent Adjustments.....................8
            (1)   Prorations..................................................8
            (2)   Default Interest............................................8
            (3)   Rent Adjustments............................................8
            (4)   Books and Records...........................................8
            (5)   Miscellaneous...............................................9

3.    PREPARATION AND CONDITION OF PREMISES; POSSESSION AND
      SURRENDER OF PREMISES ..................................................9
      A.    Condition of Premises.............................................9
      B.    Tenant's Possession...............................................9
      C.    Maintenance.......................................................9
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4.    PROJECT SERVICES ......................................................10
      A.    Heating and Air Conditioning.....................................10
      B.    Elevators........................................................10
      C.    Electricity......................................................10
      D.    Water............................................................11
      E.    Janitorial Service ..............................................11
      F.    Interruption of Services.........................................11
      G.    Parking..........................................................11

5.    ALTERATIONS AND REPAIRS ...............................................11
      A.    Landlord's Consent and Conditions ...............................11
      B.    Damage to Systems ...............................................12
      C.    No Liens ........................................................13
      D.    Ownership of Improvements .......................................13
      E.    Removal at Termination ..........................................13
      F.    Landlord's Work .................................................14

6.    USE OF PREMISES .......................................................14

7.    GOVERNMENTAL REQUIREMENTS AND PROJECT RULES ...........................15

8.    WAIVER OF CLAIMS; INDEMNIFICATION; INSURANCE ..........................15
      A.    Waiver of Claims ................................................15
      B.    Indemnification..................................................15
      C.    Tenant's Insurance...............................................15
      D.    Insurance Certificates...........................................17
      E.    Landlord's Insurance.............................................17

9.    FIRE AND OTHER CASUALTY................................................17
      A.    Termination......................................................17
      B.    Restoration......................................................17

10.   EMINENT DOMAIN.........................................................18

11.   RIGHTS RESERVED TO LANDLORD............................................18
      A.    Name.............................................................18
      B.    Signs............................................................18
      C.    Window Treatments................................................18
      D.    Keys.............................................................18
      E.    Access...........................................................19
      F.    Preparation for Reoccupancy......................................19
      G.    Heavy Articles...................................................19
      H.    Show Premises....................................................19
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      I.    Relocation of Tenant.............................................19
      J.    Use of Lockbox...................................................19
      K.    Repairs and Alterations..........................................20
      L.    Landlord's Agents................................................20
      M.    Building Services................................................20
      N.    Other Actions....................................................20

12.   TENANT'S DEFAULT ......................................................20
      A.    Rent Default ....................................................20
      B.    Assignment/Sublease or Hazardous Substances Default..............20
      C.    Other Performance Default........................................20
      D.    Credit Default...................................................20
      E.    Vacation or Abandonment Default..................................21

13.   LANDLORD REMEDIES .....................................................21
      A.    Termination of Lease or Possession ..............................21
      B.    Lease Termination Damages .......................................21
      C.    Continuation of Lease ...........................................22
      D.    Possession Termination Damages...................................22
      E.    Landlord's Remedies Cumulative...................................22
      F.    WAIVER OF TRIAL BY JURY..........................................22
      G.    Litigation Costs.................................................23

14.   SURRENDER..............................................................23

15.   HOLDOVER...............................................................23

16.   SUBORDINATION TO GROUND LEASES AND MORTGAGES...........................23
      A.    Subordination....................................................23
      B.    Termination of Ground Lease or Foreclosure of Mortgage...........23
      C.    Security Deposit.................................................24
      D.    Notice and Right to Cure.........................................24
      E.    Definitions......................................................24

17.   ASSIGNMENT AND SUBLEASE ...............................................24
      A.    In General ......................................................24
      B.    Landlord's Consent ..............................................24
      C.    Procedure .......................................................25
      D.    Change of Management or Ownership ...............................25
      E.    Excess Payments .................................................25
      F.    Recapture .......................................................26

18.   CONVEYANCE BY LANDLORD ................................................26
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19.   ESTOPPEL CERTIFICATE...................................................26

20.   SECURITY DEPOSIT.......................................................26

21.   FORCE MAJEURE..........................................................28

22.   TENANT'S PERSONAL PROPERTY AND FIXTURES................................28

23.   NOTICES................................................................29
      A.    Landlord.........................................................29
      B.    Tenant...........................................................29

24.   QUIET POSSESSION.......................................................30

25.   REAL ESTATE BROKER.....................................................30

26.   MISCELLANEOUS..........................................................30
      A.    Successors and Assigns...........................................30
      B.    Date Payments Are Due............................................30
      C.    Meaning of "Landlord", "Re-Entry, "including" and "Affiliate" ...30
      D.    Time of the Essence..............................................30
      E.    No Option........................................................30
      F.    Severability.....................................................30
      G.    Governing Law....................................................31
      H.    Lease Modification...............................................31
      I.    No Oral Modification.............................................31
      J.    Landlord's Right to Cure.........................................31
      K.    Captions.........................................................31
      L.    Authority........................................................31
      M.    Landlord's Enforcement of Remedies...............................31
      N.    Entire Agreement.................................................31
      O.    Landlord's Title.................................................31
      P.    Light and Air Rights.............................................31
      Q.    Singular and Plural..............................................31
      R.    No Recording by Tenant...........................................32
      S.    Exclusivity......................................................32
      T.    No Construction Against Drafting Party...........................32
      U.    Survival.........................................................32
      V.    Rent Not Based on Income.........................................32
      W.    Building Manager and Service Providers...........................32
      X.    Late Charge and Interest on Late Payments........................32
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27.    UNRELATED BUSINESS INCOME.............................................32

28.    HAZARDOUS SUBSTANCES..................................................32

29.    EXCULPATION...........................................................35

30.    SIGNAGE...............................................................35

31.    EXTENSION OPTION......................................................36

32.    RIGHT OF FIRST OFFER..................................................37
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APPENDIX A - PLAN OF THE PREMISES
APPENDIX B - RULES AND REGULATIONS
APPENDIX C - TENANT IMPROVEMENT AGREEMENT
APPENDIX D - MORTGAGES CURRENTLY AFFECTING THE PROJECT
APPENDIX E - COMMENCEMENT DATE CONFIRMATION
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                                      LEASE

    THIS LEASE (the "Lease") is made as of April 23, 1999 between CARRAMERICA
REALTY CORPORATION, a Maryland corporation (the "Landlord") and the Tenant as
named in the Schedule below. The term "Project" means the building(s)
(collectively, the "Building") known as "Pacific Corporate Plaza" and the land
(the "Land") located at Aliso Creek Road, Aliso Viejo, California, and any
parking structure Landlord may elect to construct (in its sole discretion and
without obligation) thereon. "Premises" means that part of the Project leased to
Tenant described in the Schedule and outlined on Appendix A.

    The following schedule (the "Schedule") is an integral part of this Lease.
Terms defined in this Schedule shall have the same meaning throughout the Lease.

                                   SCHEDULE

1.    TENANT: PhoneXchange, a Delaware corporation

2.    PREMISES: A portion of the ground floor of Building One of the Project.

3.    RENTABLE SQUARE FEET OF THE PREMISES: 8,642 rentable square feet
      ("Rentable Area").

4.    TENANT'S PROPORTIONATE SHARE: 6.82% (based upon a total of 126,800
      rentable square feet in the Project)

5.    SECURITY DEPOSIT: $50,037 upon the execution and delivery of this Lease,
      with such amount adjusted as provided in Section 20.

6.    TENANT'S REAL ESTATE BROKER FOR THIS LEASE. Lee & Associates

7.    LANDLORD'S REAL ESTATE BROKER FOR THIS LEASE: Lee & Associates

8.    TENANT IMPROVEMENTS, IF ANY: See the Tenant Improvement Agreement attached
      hereto as Appendix C.

9.    COMMENCEMENT DATE. July 1, 1999, but if the Premises are subject to new
      construction pursuant to Appendix C, then the Completion Date, as defined
      therein, if it is later; Landlord and Tenant shall execute a Commencement
      Date Confirmation substantially in the form of Appendix E promptly
      following the Commencement Date.

10.   TERMINATION DATE/TERM: Five (5) years after the Commencement Date, or if
      the Commencement Date is not the first day of a month, then after the
      first day of the following month, subject to Tenant's extension option
      under Section 31.

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11.   BASE RENT: Base Rent for the first Lease Year shall be the sum of the Base
      Component and the TI Rent Component (as defined in Appendix C). The Base
      Component per month for each month of the first Lease Year shall be $1.38
      per rentable square foot multiplied by the number of rentable square feet
      in the Rentable Area. The TI Rent Component for the first Lease Year shall
      be calculated as provided in Appendix C. Upon the commencement of the
      second Lease Year, and upon the commencement of each Lease Year thereafter
      during the initial Term of this Lease, the Base Rent for such Lease Year
      shall be 104% of the Base Rent for the immediately preceding Lease Year.
      The Commencement Date Confirmation executed by Landlord and Tenant as
      provided in this Schedule shall set forth the monthly and annual Base Rent
      for the initial Term of this Lease.

12.   PARKING RENT: None.

13.   SOLE PERMITTED USE: General office purposes, including, without
      limitation, Tenant's telecommunications Network Operations Center (the
      "NOC"); however, in no event in violation of any provision of the Rules
      and Regulations attached as Appendix B hereto or any Governmental
      Requirements (as hereinafter defined) (the "Permitted Use").

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      1. LEASE AGREEMENT. On the terms stated in this Lease, Landlord leases the
Premises to Tenant, and Tenant leases the Premises from Landlord, for the Term
beginning on the Commencement Date and ending on the Termination Date unless
extended or sooner terminated pursuant to this Lease.

      2. RENT.

      A. Types of Rent. Tenant shall pay the following Rent in the form of a
check to Landlord at the following address:

            CarrAmerica Realty Corporation
            t/a Pacific Corporate Plaza
            P.O. Box [To be provided by written notice from Landlord]
            Atlanta, GA 30384-0566

or by wire transfer as follows:

            NationsBank, N.A. (South)
            ABA Number 061-000-052
            Account Number [To be provided by written notice from Landlord]

or in such other manner as Landlord may notify Tenant:

            (1) Base Rent in monthly installments, without deduction or offset,
      in advance. Concurrently with the execution of this Lease, Tenant shall
      pay to Landlord the Base Rent for the first ten (10) months of the Term.
      For the purposes of determining this amount only as of the execution of
      this Lease, and without limiting any of Tenant's obligations under this
      Lease, the initial Base Rent is estimated to be $119,260. Upon the
      completion of the Initial Improvements (as defined in Appendix C) and a
      determination of the actual monthly TI Rent Component, Tenant shall pay to
      Landlord the amount necessary, if any, so that the amount of prepaid Base
      Rent held by Landlord as of the Commencement Date is equal to the Base
      Rent, calculated using the actual TI Rent Component. Thereafter the Base
      Rent shall be paid on or before the first day of each month of the Term in
      the amount provided in the Schedule.

            (2) Operating Cost Share Rent in an amount equal to the Tenant's
      Proportionate Share of the Operating Costs for the applicable fiscal year
      of the Lease. Concurrently with the execution of this Lease Tenant shall
      pay to Landlord the estimated Operating Cost Share Rent for the first ten
      (10) months of the Term (and in the event the estimated Operating Cost
      Share Rent for such period is revised by Landlord, Tenant shall pay to
      Landlord any increased Operating Cost Share Rent for such period within
      ten (10) days after notice from Landlord). For the purposes of determining
      the Operating Cost Share Rent and Tax Share Rent only as of the execution
      of this Lease, and without limiting any of Tenant's obligations under this
      Lease, the payment of Operating Cost

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      Share Rent and Tax Share Rent for such ten (10) month period is initially
      estimated to be $47,531. Thereafter Operating Cost Share Rent shall be
      paid monthly in advance in an estimated amount. Definitions of Operating
      Costs and Tenant's Proportionate Share, and the method for billing and
      payment of Operating Cost Share Rent are set forth in Sections 2B, 2C and
      2D.

            (3) Tax Share Rent in an amount equal to the Tenant's Proportionate
      Share of the excess of Taxes for the applicable fiscal year of this Lease.
      Concurrently with the execution of this Lease Tenant shall pay to Landlord
      the estimated Tax Share Rent for the first ten (10) months of the Term in
      the amount set forth in Subsection (2) above (and in the event the
      estimated Tax Share Rent for such period is revised by Landlord, Tenant
      shall pay to Landlord any increased Tax Share Rent for such period within
      ten (10) days after notice from Landlord). Thereafter Tax Share Rent shall
      be paid monthly in advance in an estimated amount. A definition of Taxes
      and the method for billing and payment of Tax Share Rent are set forth in
      Sections 2B, 2C and 2D.

            (4) [Intentionally Omitted.]

            (5) Additional Rent in the amount of all costs, expenses,
      liabilities, and amounts which Tenant is required to pay under this Lease,
      excluding Base Rent, Operating Cost Share Rent and Tax Share Rent, but
      including any interest for late payment of any item of Rent.

            (6) Rent as used in this Lease means Base Rent, Operating Cost Share
      Rent, Tax Share Rent and Additional Rent. Tenant's agreement to pay Rent
      is an independent covenant, with no right of setoff, deduction or
      counterclaim of any kind. All Rent shall be paid absolutely net to
      Landlord.

      B. Payment of Operating Cost Share Rent and Tax Share Rent.

            (1) Payment of Estimated Operating Cost Share Rent and Tax Share
      Rent. Landlord shall estimate the Operating Costs and Taxes of the Project
      by April 1 of each fiscal year, or as soon as reasonably possible
      thereafter. Landlord may revise these estimates whenever it obtains more
      accurate information, such as the final real estate tax assessment or tax
      rate for the Project.

            Within ten (10) days after receiving the original or revised
      estimate from Landlord setting forth an estimate of Operating Costs for a
      particular fiscal year, Tenant shall pay Landlord one-twelfth (1/12th) of
      Tenant's Proportionate Share of the estimated Operating Costs, multiplied
      by the number of months that have elapsed in the applicable fiscal year to
      the date of such payment including the current month, minus payments
      previously made by Tenant for the months elapsed. On the first day of each
      month thereafter, Tenant shall pay Landlord one-twelfth (1/12th) of
      Tenant's Proportionate Share of this estimate, until a new estimate
      becomes applicable.

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            Within ten (10) days after receiving the original or revised
      estimate from Landlord setting forth an estimate of Taxes for a particular
      fiscal year, Tenant shall pay Landlord one-twelfth (1/12th) of Tenant's
      Proportionate Share of the estimated Taxes, multiplied by the number of
      months that have elapsed in the applicable fiscal year to the date of such
      payment including the current month, minus payments previously made by
      Tenant for the months elapsed. On the first day of each month thereafter,
      Tenant shall pay Landlord one-twelfth (1/12th) of Tenant's Proportionate
      Share of this estimate, until a new estimate becomes applicable.

            (2) Correction of Operating Cost Share Rent. Landlord shall deliver
      to Tenant a report for the previous fiscal year (the "Operating Cost
      Report") by May 15 of each year, or as soon as reasonably possible
      thereafter, setting forth (a) the actual Operating Costs incurred, (b) the
      amount of Operating Cost Share Rent due from Tenant, and (c) the amount of
      Operating Cost Share Rent paid by Tenant. Within twenty (20) days after
      such delivery, Tenant shall, pay to Landlord the amount due minus the
      amount paid. If the amount paid exceeds the amount due, Landlord shall
      apply the excess to Tenant's payments of Rent next coming due.

            (3) Correction of Tax Share Rent. Landlord shall deliver to Tenant a
      report for the previous fiscal year (the "Tax Report") by May 15 of each
      year, or as soon as reasonably possible thereafter, setting forth (a) the
      actual Taxes, (b) the amount of Tax Share Rent due from Tenant, and (c)
      the amount of Tax Share Rent paid by Tenant. Within twenty (20) days after
      such delivery, Tenant shall pay to Landlord the amount due from Tenant
      minus the amount paid by Tenant. If the amount paid exceeds the amount
      due, Landlord shall apply any excess as a credit against Tenant's payments
      of Rent next coming due.

      C. Definitions.

            (1) Included Operating Costs. "Common Areas" means all areas and
      facilities outside the Premises and within the exterior boundary line of
      the Project that are provided and designated by Landlord from time to time
      for the general non-exclusive use of Landlord, Tenant and other tenants of
      the Project and their respective employees, suppliers, shippers, customers
      and invitees, including, without limitation, parking areas, loading and
      unloading areas, trash areas, roadways, sidewalks, walkways, parkways,
      ramps, driveways, landscaped areas and decorative walls. "Operating Costs"
      means any expenses, costs and disbursements of any kind other than Taxes,
      paid or incurred by Landlord in connection with the management,
      maintenance, operation, insurance, repair and other related activities in
      connection with any part of the Project and of the personal property,
      fixtures, machinery, equipment, systems and apparatus used in connection
      therewith, including the cost of providing those services required to be
      furnished by Landlord under this Lease. Operating Costs shall also include
      the costs of any capital improvements which are intended to reduce
      Operating Costs or improve safety, and those made to keep the Project in
      compliance with governmental requirements applicable from

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      time to time (collectively, "Included Capital Items"); provided, that the
      costs of any Included Capital Item shall be amortized by Landlord,
      together with an amount equal to interest at ten percent (10%) per annum,
      over the estimated useful life of such item and such amortized costs are
      only included in Operating Costs for that portion of the useful life of
      the Included Capital Item which falls within the Term.

            If the Project is not fully occupied during any portion of any
      fiscal year, Landlord may adjust (an "Equitable Adjustment") Operating
      Costs to equal what would have been incurred by Landlord had the Project
      been fully occupied; provided that Landlord shall not be entitled to
      collect as a result of any such Equitable Adjustment more than one hundred
      percent (100%) of the Operating Costs which would have been incurred by
      Landlord for the period for which such Equitable Adjustment was made. This
      Equitable Adjustment shall apply only to Operating Costs which are
      variable and therefore increase as occupancy of the Project increases.
      Landlord may incorporate the Equitable Adjustment in its estimates of
      Operating Costs.

            If Landlord does not furnish any particular service whose cost would
      have constituted an Operating Cost to a tenant other than Tenant who has
      undertaken to perform such service itself, Operating Costs shall be
      increased by the amount which Landlord would have incurred if it had
      furnished the service to such tenant.

            (2)   Excluded Operating Costs. Operating Costs shall not include:

            (a)   costs of alterations of tenant premises;

            (b)   costs of capital improvements other than Included Capital
                  Items;

            (c)   interest and principal payments on mortgages or any other debt
                  costs, or rental payments on any ground lease of the Project;

            (d)   real estate brokers' leasing commissions;

            (e)   legal fees, space planner fees and advertising expenses
                  incurred with regard to leasing the Building or portions
                  thereof;

            (f)   any cost or expenditure for which Landlord is reimbursed, by
                  insurance proceeds or otherwise, except by Operating Cost
                  Share Rent;

            (g)   the cost of any service furnished to any office tenant of the
                  Project which Landlord does not make available to Tenant;

            (h)   depreciation (except on any Included Capital Items);

            (i)   franchise or income taxes imposed upon Landlord;

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            (j)   costs of correcting defects in construction of the Building
                  (as opposed to the cost of normal repair, maintenance and
                  replacement expected with the construction materials and
                  equipment installed in the Building in light of their
                  specifications);

            (k)   legal and auditing fees which are for the benefit of Landlord
                  such as collecting delinquent rents, preparing tax returns and
                  other financial statements, and audits other than those
                  incurred in connection with the preparation of reports
                  required pursuant to Section 2B above;

            (l)   the wages of any employee for services not related directly to
                  the management, maintenance, operation and repair of the
                  Building;

            (m)   fines, penalties and interest;

            (n)   any costs related to the removal or remediation of Hazardous
                  Substances at the Project (except as costs required to be paid
                  by Tenant under the terms of this Lease); and

            (o)   without limiting the Property Manager's Fee or any other
                  amount required to paid by Tenant under this Lease, Landlord's
                  general corporate overhead and general and administrative
                  expenses not related to the Project or the management,
                  maintenance, operation, insurance, repair and other related
                  activities in connection with the Project and/or the personal
                  property, fixtures, machinery, equipment, systems and
                  apparatus used in connection therewith.

            (3) Property Management Fee. Landlord also shall serve as the
      Property Manager for an annual fee payable by Tenant equal to three
      percent (3%) of the Base Rent, Operating Cost Share Rent and Tax Share
      Rent, and Landlord may recover from Tenant the actual out-of-pocket costs
      of providing property management services (collectively, the "Property
      Manager's Fee").

            (4) Taxes. "Taxes" means any and all taxes, assessments and charges
      of any kind, general or special, ordinary or extraordinary, levied against
      the Project, which Landlord shall pay or become obligated to pay in
      connection with the ownership, leasing, renting, management, use,
      occupancy, control or operation of the Project or of the personal
      property, fixtures, machinery, equipment, systems and apparatus used in
      connection therewith. Taxes shall include real estate taxes, personal
      property taxes, sewer rents, water rents, special or general assessments,
      transit taxes, ad valorem taxes, and any tax levied on the rents hereunder
      or the interest of Landlord under this Lease (the "Rent Tax"). Taxes shall
      also include all fees and other costs and expenses paid by Landlord in
      reviewing any tax and in seeking a refund or reduction of any Taxes,
      whether or not the Landlord is ultimately successful.

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            For any year, the amount to be included in Taxes (a) from taxes or
      assessments payable in installments, shall be the amount of the
      installments (with any interest) due and payable during such year, and (b)
      from all other Taxes, shall at Landlord's election be the amount accrued,
      assessed, or otherwise imposed for such year or the amount due and payable
      in such year. Any refund or other adjustment to any Taxes by the taxing
      authority, shall apply during the year in which the adjustment is made.

            Taxes shall not include any net income (except Rent Tax), capital,
      stock, succession, transfer, franchise, gift, estate or inheritance tax,
      except to the extent that such tax shall be imposed in lieu of any portion
      of Taxes.

            (5) Lease Year. "Lease Year" means each consecutive twelve-month
      period beginning with the Commencement Date, except that if the
      Commencement Date is not the first day of a calendar month, then the first
      Lease Year shall be the period from the Commencement Date through the
      final day of the twelve months after the first day of the following month,
      and each subsequent Lease Year shall be the twelve months following the
      prior Lease Year.

            (6) Fiscal Year. "Fiscal Year" means the calendar year, except that
      the first fiscal year and the last fiscal year of the Term may be a
      partial calendar year.

      D. Computation of Base Rent and Rent Adjustments.

            (1) Prorations. If this Lease begins on a day other than the first
      day of a month, the Base Rent, Operating Cost Share Rent and Tax Share
      Rent shall be prorated for such partial month based on the actual number
      of days in such month. If this Lease begins on a day other than the first
      day, or ends on a day other than the last day, of the fiscal year,
      Operating Cost Share Rent and Tax Share Rent shall be prorated for the
      applicable fiscal year.

            (2) Default Interest. Any sum due from Tenant to Landlord not paid
      when due shall bear interest from the date due until paid at the lesser of
      twelve percent (12%) per annum. or the maximum rate permitted by law.

            (3) Rent Adjustments. The square footage of the Premises and the
      Building set forth in the Schedule, are conclusively deemed to be the
      actual square footage thereof, without regard to any subsequent
      remeasurement of the Premises or the Building. If any Operating Cost paid
      in one fiscal year relates to more than one fiscal year, Landlord may
      proportionately allocate such Operating Cost among the related fiscal
      years.

            (4) Books and Records. Landlord shall maintain books and records
      reflecting the Operating Costs and Taxes in accordance with sound
      accounting and management practices. Tenant and its certified public
      accountant shall have the right to inspect Landlord's records at
      Landlord's office upon at least seventy-two (72) hours' prior notice

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      during normal business hours during the one hundred eighty (180) days
      following the respective delivery of the Operating Cost Report or the Tax
      Report. The results of any such inspection shall be kept strictly
      confidential by Tenant and its agents, and Tenant and its certified public
      accountant must agree, in their contract for such services, to such
      confidentiality restrictions and shall specifically agree that the results
      shall not be made available to any other tenant of the Building. Unless
      Tenant sends to Landlord any written exception to either such report
      within said one hundred eighty (180) day period, such report shall be
      deemed final and accepted by Tenant. Tenant shall pay the amount shown on
      both reports in the manner prescribed in this Lease, whether or not Tenant
      takes any such written exception, without any prejudice to such exception.
      If Tenant makes a timely exception, Landlord shall cause its independent
      certified public accountant to issue a final and conclusive resolution of
      Tenant's exception. Tenant shall pay the cost of such certification unless
      Landlord's original determination of annual Operating Costs or Taxes
      overstated the amounts thereof by more than five percent (5%).

            (5) Miscellaneous. So long as Tenant is in default of any obligation
      under this Lease, Tenant shall not be entitled to any refund of any amount
      from Landlord. If this Lease is terminated for any reason prior to the
      annual determination of Operating Cost Share Rent or Tax Share Rent,
      either party shall pay the full amount due to the other within fifteen
      (15) days after Landlord's notice to Tenant of the amount when it is
      determined. Landlord may commingle any payments made with respect to
      Operating Cost Share Rent or Tax Share Rent, without payment of interest.

      3. PREPARATION AND CONDITION OF PREMISES; POSSESSION AND SURRENDER OF
PREMISES.

      A. Condition of Premises. Except to the extent of the Tenant Improvements
item on the Schedule, Landlord is leasing the Premises to Tenant absolutely "as
is" (subject to the punch list items to be corrected as provided in Appendix C),
without any obligation to alter, remodel, improve, repair or decorate any part
of the Premises. Landlord shall cause the Premises to be completed in accordance
with the Tenant Improvement Agreement attached as Appendix C. Landlord expressly
disclaims any warranty or representation, express or implied, with respect to
the Project or any portion thereof, including, without limitation, any warranty
or representation as to fitness, condition, the existence of any defect, patent
or latent, merchantability, quality or durability. Landlord shall assign to
Tenant (or otherwise enforce at Landlord's election upon Tenant's written
request) any and all warranties (including statutory) received from or rights
against all contractors and subcontractors regarding the Tenant Improvements (as
defined in Appendix C).

      B. Tenant's Possession. Tenant's taking possession of any portion of the
Premises shall be conclusive evidence that the Premises was in good order,
repair and condition. If Landlord authorizes Tenant to take possession of any
part of the Premises prior to the Commencement Date for purposes of doing
business, all terms of this Lease shall apply to such

                                        9
<PAGE>   17
pre-Term possession, including Base Rent at the rate set forth for the First
Lease Year in the Schedule prorated for any partial month.

      C. Maintenance. Throughout the Term, Tenant shall maintain the Premises in
good order, repair and condition, loss or damage caused by the elements,
ordinary wear, and fire and other casualty excepted, and at the termination of
this Lease, or Tenant's right to possession, Tenant shall return the Premises to
Landlord in broom-clean, safe, neat and sanitary condition. To the extent Tenant
fails to perform either obligation, Landlord may, but need not, restore the
Premises to such condition and Tenant shall pay the cost thereof.

      4. PROJECT SERVICES.

      Landlord shall furnish services as follows:

      A. Heating and Air Conditioning. During the normal business hours of 8:00
a.m to 6:00 p.m., Monday through Friday on generally recognized business days in
the area in which the Project is located, and 8:00 a.m. to 12:00 noon on
Saturday, Landlord shall furnish heating and air conditioning to provide a
comfortable temperature, in Landlord's judgment, for normal business operations
(excluding the operation of the NOC), except to the extent Tenant installs
equipment which adversely affects the temperature maintained by the air
conditioning system. If Tenant installs such equipment including, without
limitation, in connection with the operation of the NOC, Landlord may install,
or may require that Tenant install, supplementary air conditioning units in the
Premises, and Tenant shall pay to Landlord upon demand as Additional Rent the
cost of installation (if not paid by Tenant directly), operation and maintenance
thereof.

      Landlord shall furnish heating and air conditioning after business hours
if Tenant provides Landlord reasonable prior dial-in notice, and pays Landlord
$35 for such additional heating or air conditioning.

      B. Elevators. Landlord shall provide passenger elevator service during
normal business hours to Tenant in common with Landlord and all other tenants.
Landlord shall provide limited passenger service at other times, except in case
of an emergency.

      C. Electricity. Landlord shall provide sufficient electricity to operate
normal office lighting and equipment (excluding the operation of the NOC).
Tenant shall not install or operate in the Premises any electrically operated
equipment or other machinery, other than business machines and equipment
normally employed for general office use which do not require high electricity
consumption for operation, without obtaining the prior written consent of
Landlord; provided that Landlord hereby consents to the equipment necessary to
operate the NOC. If any or all of Tenant's equipment requires electricity
consumption, including, without limitation, in connection with the operation of
the NOC, in excess of that which is necessary to operate normal office
equipment, such consumption (including consumption for the NOC, computer or
telephone rooms and special HVAC equipment) shall be submetered by Landlord at
Tenant's expense, and Tenant shall reimburse Landlord as Additional Rent for the
cost of its submetered

                                       10
<PAGE>   18
consumption based upon Landlord's average cost of electricity. Such additional
rent shall be in addition to Tenant's obligations pursuant to Section 2A(2) to
pay its Proportionate Share of Operating Costs.

      D. Water. Landlord shall furnish hot and cold tap water for drinking and
toilet purposes. Tenant shall pay Landlord for water furnished for any other
purpose, including, without limitation, for Tenant's cooling system, as
Additional Rent at rates fixed by Landlord. Tenant shall not permit water to be
wasted.

      E. Janitorial Service. Landlord shall furnish janitorial service as
generally provided to other tenants in the Building.

      F. Interruption of Services. If any of the Building equipment or machinery
ceases to function properly for any cause Landlord shall use reasonable
diligence to repair the same promptly. Landlord's inability to furnish, to any
extent, the Project services set forth in this Section 4, or any cessation
thereof resulting from any causes, including, without limitation, any entry for
repairs pursuant to this Lease, and any renovation, redecoration or
rehabilitation of any area of the Building shall not render Landlord liable for
damages to either person or property or for interruption or loss to Tenant's
business, nor be construed as an eviction of Tenant, nor work an abatement of
any portion of rent, nor relieve Tenant from fulfillment of any covenant or
agreement hereof. However, in the event that an interruption of the Project
services set forth in this Section 4 is within Landlord's reasonable control
and such interruption causes the Premises to be untenantable for a period of at
least five (5) consecutive business days, monthly Rent shall be abated
proportionately.

      G. Parking. During the Term, Tenant and its employees shall be entitled to
use within the Project's parking area (excluding, however, those areas thereof
designated by Landlord from time to time for the exclusive use of certain
occupants of the Project or for no parking) an aggregate of no more than 36
parking stalls. Landlord reserves the right to designate reserved parking stalls
for other occupants of the Project over any part of the Project's parking area.

      5. ALTERATIONS AND REPAIRS.

      A. Landlord's Consent and Conditions.

      Tenant shall not make any improvements or alterations to the Premises (the
"Work") without in each instance submitting plans and specifications for the
Work to Landlord and obtaining Landlord's prior written consent unless (a) the
cost thereof is less than $10,000, (b) such Work does not impact the base
structural components or systems of the Building, (c) such Work will not impact
any other tenant's premises, and (d) such Work is not visible from outside the
Premises. Tenant shall pay Landlord's standard charge for review of the plans
and all other items submitted by Tenant, which shall not exceed five percent (5
%) of the cost of such Work. Landlord will be deemed to be acting reasonably in
withholding its consent for any Work

                                       11
<PAGE>   19
which (a) impacts the base structural components or systems of the Building, (b)
impacts any other tenant's premises, or (c) is visible from outside the
Premises.

      Tenant shall pay for the cost of all Work. All Work shall become the
property of Landlord upon its installation, except for Tenant's trade fixtures,
the NOC and for items which Landlord requires Tenant to remove at Tenant's cost
at the termination of the Lease pursuant to Section 3E.

      The following requirements shall apply to all Work:

            (1) Prior to commencement, Tenant shall furnish to Landlord building
      permits, certificates of insurance satisfactory to Landlord (including,
      without limitation, certificates evidencing the insurance Tenant, its
      contractors and subcontractors are required to maintain under Section
      8(C)), and, at Landlord's request, security for payment of all costs.

            (2) Tenant shall perform all Work so as to maintain peace and
      harmony among other contractors serving the Project and shall avoid
      interference with other work to be performed or services to be rendered in
      the Project.

            (3) The Work shall be performed in a good and workmanlike manner,
      meeting the standard for construction and quality of materials in the
      Building, and shall comply with all insurance requirements and all
      applicable governmental laws, ordinances and regulations ("Governmental
      Requirements").

            (4) Tenant shall perform all Work so as to minimize or prevent
      disruption to other tenants, and Tenant shall comply with all reasonable
      requests of Landlord in response to complaints from other tenants.

            (5) Tenant shall perform all Work in compliance with Landlord's
      "Policies, Rules and Procedures for Construction Projects" in effect at
      the time the Work is performed (which Policies, Rules and Procedures,
      shall be applied uniformly to the tenants in the Project, taking into
      consideration the use of their space and the nature of the alterations).

            (6) Tenant shall permit Landlord to supervise all Work. Landlord may
      charge a supervisory fee not to exceed five percent (5%) of labor,
      material, and all other costs of the Work, if Landlord's employees or
      contractors perform the Work.

            (7) Upon completion, Tenant shall furnish Landlord with contractor's
      affidavits and full and final statutory waivers of liens, as-built plans
      and specifications, and receipted bills covering all labor and materials,
      and all other close-out documentation required in Landlord's "Policies,
      Rules and Procedures for Construction Projects".

                                       12
<PAGE>   20
      B. Damage to Systems. If any part of the mechanical, electrical or other
systems in the Premises or Common Areas shall be damaged, Tenant shall promptly
notify Landlord, and Landlord shall repair such damage. Landlord may also at any
reasonable time make any repairs or alterations which Landlord deems necessary
for the safety or protection of the Project, or which Landlord is required to
make by any court or pursuant to any Governmental Requirement. Tenant shall at
its expense make all other repairs necessary to keep the Premises, and Tenant's
fixtures and personal property, in good order, condition and repair; to the
extent Tenant fails to do so, Landlord may make such repairs itself. The cost of
any repairs made by Landlord on account of Tenant's default, or on account of
the mis-use or neglect by Tenant or its invitees, contractors or agents anywhere
in the Project, shall become Additional Rent payable by Tenant on demand.

      C. No Liens. Tenant has no authority to cause or permit any lien or
encumbrance of any kind to affect Landlord's interest in the Project; any such
lien or encumbrance shall attach to Tenant's interest only. If any mechanic's
lien shall be filed or claim of lien made for work or materials furnished to
Tenant, then Tenant shall at its expense within ten (10) days thereafter either
discharge or contest the lien or claim. If Tenant contests the lien or claim,
then Tenant shall (i) within such ten (10) day period, provide Landlord adequate
security for the lien or claim, (ii) contest the lien or claim in good faith by
appropriate proceedings, that operate to stay its enforcement, and (iii) pay
promptly any final adverse judgment entered in any such proceeding. If Tenant
does not comply with these requirements, Landlord may discharge the lien or
claim, and the amount paid, as well as attorney's fees and other expenses,
incurred by Landlord, shall become Additional Rent payable by Tenant on demand.
Nothing contained in this Lease shall constitute any consent by Landlord to
subject Landlord's estate to liability under any mechanics' or other lien law.
Tenant shall give Landlord adequate opportunity, and Landlord shall have the
right at all times, to post such notices of nonresponsibility as may be allowed
under California law.

      D. Ownership of Improvements. All Work as defined in this Section 5,
partitions, hardware, equipment, machinery and all other improvements and all
fixtures except trade fixtures and the NOC, constructed in the Premises by
either Landlord or Tenant, (i) shall become Landlord's property upon
installation without compensation to Tenant, unless Landlord consents otherwise
in writing, and (ii) shall at Landlord's option either (a) be surrendered to
Landlord with the Premises at the termination of the Lease or of Tenant's right
to possession, or (b) be removed in accordance with Subsection 5E below (unless
Landlord at the time it gives its consent to the performance of such
construction expressly waives in writing the right to require such removal).

      E. Removal at Termination. Upon the termination of this Lease or Tenant's
right of possession Tenant shall remove from the Project its trade fixtures,
furniture, moveable equipment and other personal property, the NOC, any
improvements which Landlord elects shall be removed by Tenant pursuant to
Section 5D, and any improvements to any portion of the Project other than the
Premises. If Tenant does not timely remove such property, then Tenant shall be
conclusively presumed to have, at Landlord's election (i) conveyed such property
to

                                       13
<PAGE>   21
Landlord without compensation or (ii) abandoned such property, and Landlord may
dispose of or store any part thereof in any manner at Tenant's sole cost,
without waiving Landlord's right to claim from Tenant all expenses arising out
of Tenant's failure to remove the property, and without liability to Tenant or
any other person. Landlord shall have no duty to be a bailee of any such
personal property. If Landlord elects abandonment, Tenant shall pay to Landlord,
upon demand, any expenses incurred for disposition. Tenant expressly releases
Landlord of and from any and all claims and liability for damage to or
destruction or loss of property left by Tenant upon the Premises at the
expiration or other termination of this Lease and, to the extent permitted by
then applicable law, Tenant shall protect, indemnify, defend and hold Landlord
harmless from and against any and all claims and liability with respect thereto.

      F. Landlord's Work. Landlord shall have the right at any time to change
the arrangement and location of all entrances, passageways, doors, doorways,
corridors, stairs, toilets and other public parts of the Project and, upon
giving Tenant reasonable notice thereof, to change any name, number or
designation by which the Premises or the Project is commonly known.

      6. USE OF PREMISES. Tenant shall use the Premises only for the Permitted
Use. Tenant shall not allow any use of the Premises which will negatively affect
the cost of coverage of Landlord's insurance on the Project. Tenant shall not
allow any inflammable or explosive liquids or materials to be kept on the
Premises. Tenant shall not allow any use of the Premises which would cause the
value or utility of any part of the Premises to diminish or would interfere with
any other Tenant or with the operation of the Project by Landlord. Tenant shall
not cause or permit any nuisance or waste upon the Premises, or allow any
offensive noise or odor in or around the Premises or in any way obstruct or
interfere with the rights of other tenants or occupants of the Project.

      Tenant acknowledges that the Americans With Disabilities Act of 1990 (as
amended and as supplemented by further laws from time to time, the "ADA")
imposes certain requirements upon the owners, lessees and operators of
commercial facilities and places of public accommodation, including, without
limitation, prohibitions on discrimination against any individual on the basis
of disability. Landlord shall be responsible for the compliance of the Premises
and Common Area with the ADA, assuming the use of the Premises for general
office purposes and not as a place of public accommodation. Except for
Landlord's obligations pursuant to this paragraph, and notwithstanding any other
provision of this Lease, Tenant agrees, at Tenant's expense, to take all proper
and necessary action to cause the Premises, any repairs, replacements,
alterations and improvements thereto to be maintained, used and occupied in
compliance with the ADA requirements, to the extent that those requirements are
based upon the Tenant's use of the Premises and, further, to otherwise assume
all responsibility to ensure the Premises' continued compliance with all
provisions of the ADA throughout the Term based upon Tenant's use of the
Premises. Except for Landlord's obligations pursuant to this paragraph, Tenant
shall, at its expense, make any alterations or modifications, with or without
the Premises, to bring Tenant's use and occupancy of the Premises into
compliance with the ADA. The Premises shall not be used as a "place of public
accommodation" under the ADA

                                       14
<PAGE>   22
or similar laws, regulations, statutes and/or ordinances; provided, that if any
governmental authority shall deem the Premises to be a "place of public
accommodation" as a result of Tenant's use, Tenant shall either modify its use
to cause such authority to rescind its designation or be responsible for any
alterations, structural or otherwise, required to be made to the Project or the
Premises under such laws.

      7. Tenant shall Tenant shall comply with all Governmental Requirements
applying to its use of the Premises. Tenant shall also comply with all
reasonable rules established for the Project, including, without limitation, the
parking area, from time to time by Landlord. The present rules and regulations
are contained in Appendix B. Failure by another tenant to comply with the rules
or failure by Landlord to enforce them shall not relieve Tenant of its
obligation to comply with the rules or make Landlord responsible to Tenant in
any way. Landlord shall use reasonable efforts to apply the rules and
regulations reasonably and uniformly with respect to Tenant and tenants in the
Building under leases containing rules and regulations similar to this Lease. In
the event of alterations and repairs performed by Tenant, Tenant shall comply
with the provisions of Section 5 of this Lease and also Landlord's "Policies,
Rules and Regulations for Construction Projects".

      8. WAIVER OF CLAIMS; INDEMNIFICATION; INSURANCE.

      A. Waiver of Claims. To the extent permitted by law, Tenant waives any
claims it may have against Landlord or its officers, directors, employees or
agents for business interruption or damage to property sustained by Tenant as
the result of any act or omission of Landlord.

      To the extent permitted by law, Landlord waives any claims it may have
against Tenant or its officers, directors, employees or agents for loss of rents
or damage to property sustained by Landlord as the result of any act or omission
of Tenant.

      B. Indemnification. Tenant shall indemnify, defend and hold harmless
Landlord and its officers, directors, employees and agents against any claim by
any third party for injury to any person or damage to or loss of any property
occurring in the Project and arising from any act or omission or negligence of
Tenant or any of Tenant's employees or agents. Tenant's obligations under this
section shall survive the termination of this Lease.

      Landlord shall indemnify, defend and hold harmless Tenant and its
officers, directors, employees and agents against any claim by any third party
for injury to any person or damage to or loss of any property occurring in the
Project and arising from any act or omission or negligence of Landlord or any of
Landlord's employees or agents. Landlord's obligations under this section shall
survive the termination of this Lease.

      C. Tenant's Insurance. Tenant shall maintain insurance as follows, with
such other terms, coverages and insurers, as Landlord shall reasonably require
from time to time:

                                       15
<PAGE>   23
            (1) Commercial General Liability Insurance, with (a) Contractual
      Liability including the indemnification provisions contained in this
      Lease, (b) a severability of interest endorsement, (c) limits of not less
      than One Million Dollars ($1,000,000) combined single limit per occurrence
      and not less than Two Million Dollars ($2,000,000) in the aggregate for
      bodily injury, sickness or death, and property damage, and umbrella
      coverage of not less than Two Million Dollars ($2,000,000).

            (2) Property Insurance against "All Risks" of physical loss covering
      the replacement cost of all improvements, fixtures and personal property.
      Tenant waives all rights of subrogation, and Tenant's property insurance
      shall include a waiver of subrogation in favor of Landlord.

            (3) Workers' compensation or similar insurance in form and amounts
      required by law, and Employer's Liability with not less than the following
      limits:

<TABLE>
<S>                                                     <C>
                    Each Accident                       $500,000
                    Disease--Policy Limit               $500,000
                    Disease--Each Employee              $500,000
</TABLE>

            Such insurance shall contain a waiver of subrogation provision in
      favor of Landlord and its agents.

      Tenant's insurance shall be primary and not contributory to that carried
by Landlord, its agents, or mortgagee. Landlord, and if any, Landlord's building
manager or agent and ground lessor shall be named as additional insureds as
respects to insurance required of the Tenant in Section 8C(l). The company or
companies writing any insurance which Tenant is required to maintain under this
Lease, as well as the form of such insurance, shall at all times be subject to
Landlord's approval, and any such company shall be licensed to do business in
the state in which the Project is located. Such insurance companies shall have a
A.M. Best rating of A VI or better.

      Tenant shall cause any contractor of Tenant performing work on the
Premises to maintain insurance as follows, with such other terms, coverages and
insurers, as Landlord shall reasonably require from time to time:

            (1) Commercial General Liability Insurance, including contractor's
      liability coverage, contractual liability coverage, completed operations
      coverage, broad form property damage endorsement, and contractor's
      protective liability coverage, to afford protection with limits, for each
      occurrence, of not less than One Million Dollars ($1,000,000) with respect
      to personal injury, death or property damage.

            (2) Workers' compensation or similar insurance in form and amounts
      required by law, and Employer's Liability with not less than the following
      limits:

                                       16
<PAGE>   24
<TABLE>
<S>                                             <C>
                       Each Accident            $500,000
                       Disease--Policy Limit    $500,000
                       Disease--Each Employee   $500,000
</TABLE>

            Such insurance shall contain a waiver of subrogation provision in
      favor of Landlord and its agents.

      Tenant's contractor's insurance shall be primary and not contributory to
that carried by Tenant, Landlord, their agents or mortgagees. Tenant and
Landlord, and if any, Landlord's building manager or agent, mortgagee or ground
lessor shall be named as additional insured on Tenant's contractor's insurance
policies.

      D. Insurance Certificates. Tenant shall deliver to Landlord certificates
evidencing all required insurance no later than five (5) days prior to the
Commencement Date and each renewal date. Each certificate will provide for
thirty (30) days prior written notice of cancellation to Landlord and Tenant.

      E. Landlord's Insurance. Landlord shall maintain "All-Risk" property
insurance at replacement cost, including loss of rents, on the Building, and
Commercial General Liability insurance policies covering the common areas of the
Project, each with such terms, coverages and conditions as are normally carried
by reasonably prudent owners of properties similar to the Project. With respect
to property insurance, Landlord and Tenant mutually waive all rights of
subrogation, and the respective "All-Risk" coverage property insurance policies
carried by Landlord and Tenant shall contain enforceable waiver of subrogation
endorsements.

      9. FIRE AND OTHER CASUALTY.

      A. Termination. If a fire or other casualty causes substantial damage to
the Building or the Premises, Landlord shall engage a registered architect to
certify within one (1) month of the casualty to both Landlord and Tenant the
amount of time needed to restore the Building and the Premises to tenantability,
using standard working methods. If the time needed exceeds twelve (12) months
from the beginning of the restoration, or two (2) months therefrom if the
restoration would begin during the last twelve (12) months of the Lease, then in
the case of the Premises either Landlord or Tenant may terminate this lease,
and in the case of the Building, Landlord may terminate this Lease, by notice to
the other party within ten (10) days after the notifying party's receipt of the
architect's certificate. The termination shall be effective thirty (30) days
from the date of the notice and Rent shall be paid by Tenant to that date with
an abatement for any portion of the space which has been untenantable after the
casualty.

      B. Restoration. If a casualty causes damage to the Building or the
Premises but this Lease is not terminated for any reason, then subject to the
rights of any mortgagees or ground lessors, Landlord shall obtain the applicable
insurance proceeds and diligently restore the Building and the Premises subject
to current Governmental Requirements. Tenant shall replace its damaged
improvements, personal property and fixtures. Rent shall be abated on a per diem

                                       17
<PAGE>   25
basis during the restoration for any portion of the Premises which is
untenantable, except to the extent that Tenant's negligence caused the casualty.

      10. EMINENT DOMAIN. If a part of the Project is taken by eminent domain or
deed in lieu thereof which is so substantial that the Premises cannot reasonably
be used by Tenant for the operation of its business, then either party may
terminate this Lease effective as of the date of the taking. If any substantial
portion of the Project is taken without affecting the Premises, then Landlord
may terminate this Lease as of the date of such taking. Rent shall abate from
the date of the taking in proportion to any part of the Premises taken. The
entire award for a taking of any kind shall be paid to Landlord. Tenant may
pursue a separate award for its trade fixtures and moving expenses in connection
with the taking, but only if such recovery does not reduce the award payable to
Landlord. All obligations accrued to the date of the taking shall be performed
by each party.

      11. RIGHTS RESERVED TO LANDLORD.

     Landlord may exercise at any time any of the following rights respecting
the operation of the Project without liability to the Tenant of any kind:

      A. Name. To change the name or street address of the Building or the suite
number(s) of the Premises.

      B. Signs. To install, remove and maintain any signs on the exterior and in
the interior of the Building, and to approve at its sole discretion, prior to
installation, any of Tenant's signs in the Premises visible from the Common
Areas or the exterior of the Building.

      C. Window Treatments. To approve, at its discretion, prior to
installation, any shades, blinds, ventilators or window treatments of any kind,
as well as any lighting within the Premises that may be visible from the
exterior of the Building or any interior Common Area.

      D. Keys. Subject to the terms of this Lease, to retain and use at any time
passkeys to enter the Premises or any door within the Premises. Subject to the
terms of this Lease, Tenant shall not alter or add any lock or bolt. If Tenant
complies with all of the requirements set forth in this Section, Tenant may
provide its own locks to the NOC. At least ten (10) days prior to the
Commencement Date, Tenant shall notify Landlord of the name of the
representative of Tenant to be contacted and the manner of contact to avoid a
forcible entry to the NOC. Tenant need not furnish Landlord with keys to the
NOC. Upon the termination of this Lease, Tenant shall surrender all keys to
Landlord. Landlord shall have no obligation to provide janitorial or any other
service to the NOC.

      If Landlord determines in its sole discretion that a suspected fire or
flood or other emergency in the Building requires Landlord to gain access to the
NOC, Landlord may forcibly enter. Landlord shall make a reasonable effort to
contact Tenant to secure access, but Landlord shall not be obligated to contact
Tenant. Landlord shall have no liability whatsoever to Tenant,

                                       18
<PAGE>   26
and Tenant shall pay all expenses in repairing any damage to the NOC or any
other portion of the Premises or Building resulting therefrom. In no event shall
Landlord have any liability to Tenant for any failure to enter the NOC,
including, without limitation, in the event of any fire, flood or other
emergency.

      E. Access. To have access to inspect the Premises, and to perform its
obligations, or make repairs, alterations, additions or improvements, as
permitted by this Lease.

     F. Preparation for Reoccupancy. To decorate, remodel, repair, alter or
otherwise prepare the Premises for reoccupancy at any time after Tenant abandons
the Premises, without relieving Tenant of any obligation to pay Rent.

     G. Heavy Articles. To approve the weight, size, placement and time and
manner of movement within the Building of any safe, central filing system or
other heavy article of Tenant's property. Tenant shall move its property
entirely at its own risk.

     H. Show Premises. To show the Premises to prospective purchasers, brokers,
lenders, investors, rating agencies or others at any reasonable time, and to
show the Premises to prospective tenants at any time during the last six (6)
months of the Term or at any time that Tenant is, or has been within the
previous three (3) months, in default of its obligations under this Lease,
provided that Landlord gives prior notice to Tenant and does not materially
interfere with Tenant's use of the Premises.

     I. Relocation of Tenant. To relocate the Tenant, upon thirty days' prior
written notice, from all or part of the Premises (the "Old Premises") to another
area in the Project (the "new premises"), provided that:

            (1) the size of the new premises is at least equal to the size of
      the Old Premises;

            (2) Landlord pays all reasonable, direct out-of-pocket costs
      incurred by Tenant in connection with such move and the improvement of the
      new premises to the standard of the Old Premises. Tenant shall cooperate
      with Landlord in all reasonable ways to facilitate the move, including
      supervising the movement of files or fragile equipment, designating new
      locations for furniture, equipment and new telephone and electrical
      outlets, and determining the color of paint in the new premises.

     J. Use of Lockbox. To designate a lockbox collection agent for collections
of amounts due Landlord. In that case, the date of payment of Rent or other sums
shall be the date of the agent's receipt of such payment or the date of actual
collection if payment is made in the form of a negotiable instrument thereafter
dishonored upon presentment. However, Landlord may reject any payment for all
purposes as of the date of receipt or actual collection by mailing to Tenant
within 21 days after such receipt or collection a check equal to the amount sent
by Tenant.

                                       19
<PAGE>   27
      K. Repairs and Alterations. To make repairs or alterations to the Project
and in doing so transport any required material through the Premises, to close
entrances, doors, corridors, elevators and other facilities in the Project, to
open any ceiling in the Premises, or to temporarily suspend services or use of
common areas in the Project. Landlord may perform any such repairs or
alterations during ordinary business hours, except that Tenant may require any
Work in the Premises to be done after business hours if Tenant pays Landlord for
overtime and any other expenses incurred. Landlord shall use reasonable efforts
to cause such repairs and alterations to be performed without unreasonably
affecting Tenant's use of the Premises. Landlord may do or permit any work on
any nearby building, land, street, alley or way.

      L. Landlord's Agents. If Tenant is in default under this Lease, possession
of Tenant's funds or negotiation of Tenant's negotiable instrument by any of
Landlord's agents shall not waive any breach by Tenant or any remedies of
Landlord under this Lease.

      M. Building Services. To install, use and maintain through the Premises,
pipes, conduits, wires and ducts serving the Building, provided that such
installation, use and maintenance does not unreasonably interfere with Tenant's
use of the Premises.

      N.    Other Actions.  To take any other action which Landlord deems
reasonable in connection with the operation, maintenance or preservation of
the Project.

      12. TENANT'S DEFAULT.

      Any of the following shall constitute a default by Tenant:

      A. Rent Default. Tenant fails to pay any Rent when due;

      B. Assignment/Sublease or Hazardous Substances Default. Tenant defaults in
its obligations under Section 17 Assignment and Sublease or Section 28 Hazardous
Substances;

      C. Other Performance Default. Tenant fails to perform any other obligation
to Landlord under this Lease, and, in the case of only the first two (2) such
failures during any calendar year, this failure continues for ten (10) days
after written notice from Landlord (provided, however, that any such notice
shall be in lieu of, and not in addition to, any notice required under Section
1161 et seq. of the California Code of Civil Procedure), except that if Tenant
begins to cure its failure within the ten (10) day period but cannot reasonably
complete its cure within such period, then, so long as Tenant continues to
diligently attempt to cure its failure, the ten (10) day period shall be
extended to sixty (60) days, or such lesser period as is reasonably necessary to
complete the cure;

      D. Credit Default. One of the following credit defaults occurs:

            (1) Tenant commences any proceeding under any law relating to
      bankruptcy, insolvency, reorganization or relief of debts, or seeks
      appointment of a receiver, trustee,

                                       20
<PAGE>   28
      custodian or other similar official for the Tenant or for any substantial
      part of its property, or any such proceeding is commenced against Tenant
      and either remains undismissed for a period of sixty (60) days or results
      in the entry of an order for relief against Tenant which is not fully
      stayed within seven days after entry;

            (2) Tenant becomes insolvent or bankrupt, does not generally pay its
      debts as they become due, or admits in writing its inability to pay its
      debts, or makes a general assignment for the benefit of creditors;

            (3) Any third party obtains a levy or attachment under process of
      law against Tenant's leasehold interest.

     E. Vacation or Abandonment Default. Tenant vacates or abandons the Premises
and fails to pay any amount payable under this Lease when due.

      13. LANDLORD REMEDIES.

      A. Termination of Lease or Possession. If Tenant defaults, Landlord may
elect by notice to Tenant either to terminate this Lease or to terminate
Tenant's possession of the Premises without terminating this Lease. In either
case, Tenant shall immediately vacate the Premises and deliver possession to
Landlord, and Landlord may repossess the Premises and may, at Tenant's sole
cost, remove any of Tenant's signs and any of its other property, without
relinquishing its right to receive Rent or any other right against Tenant.
Without limiting the generality of the foregoing, upon the termination of this
Lease or the termination of Tenant's right of possession, it shall be lawful for
the Landlord, without formal demand or notice of any kind, to re-enter the
Premises by summary dispossession proceedings or any other action or proceeding
authorized by law and to remove Tenant and all persons and property therefrom,

      B. Lease Termination Damages. Except as otherwise provided in Section 13C,
if Tenant abandons the Premises prior to the end of the term hereof, or if
Tenant's right to possession is terminated by Landlord because of a default by
Tenant under this Lease, this Lease shall terminate. Upon such termination,
Landlord may recover from Tenant the following, as provided in Section 1951.2 of
the California Civil Code: (i) the worth at the time of award of the unpaid Rent
and other charges under this Lease that had been earned at the time of
termination; (ii) the worth at the time of award of the amount by which the
unpaid Rent and other charges under this Lease which would have been earned
after termination until the time of award exceeds the amount of such rental loss
that Tenant proves could have been reasonably avoided; (iii) the worth at the
time of award of the amount by which the unpaid Rent and other charges under
this Lease for the balance of the term of this Lease after the time of award
exceeds the amount of such rental loss that Tenant proves could have been
reasonably avoided; and (iv) any other amount necessary to compensate Landlord
for all the detriment proximately caused by Tenant's failure to perform its
obligations under this Lease or that in the ordinary course of things would be
likely to result therefrom. As used herein, the following terms are defined: (a)
The "worth at the time of award" of the amounts referred to in Sections (i) and
(ii)

                                       21
<PAGE>   29
is computed by allowing interest at the lesser of 12% per annum or the maximum
lawful rate. The "worth at the time of award" of the amount referred to in
Section (iii) is computed by discounting such amount at the discount rate of the
Federal Reserve Bank of San Francisco at the time of award plus 1%.

      C. Continuation of Lease. Even if Tenant has abandoned the Premises, this
Lease shall continue in effect for so long as Landlord does not terminate
Tenant's right to possession, and Landlord may enforce all its rights and
remedies under this Lease, including the right to recover rent as it becomes
due. This remedy is intended to be the remedy described in California Civil Code
Section 1951.4, and the following provision from such Civil Code Section is
hereby repeated: "The Lessor has the remedy described in California Civil Code
Section 1951.4 (lessor may continue lease in effect after lessee's breach and
abandonment and recover rent as it becomes due, if lessee has right to sublet or
assign, subject only to reasonable limitations)." Any such payments due
Landlord shall be made upon demand therefor from time to time and Tenant agrees
that Landlord may file suit to recover any sums falling due from time to time.
Notwithstanding any such reletting without termination, Landlord may at any time
thereafter elect in writing to terminate this Lease for such previous breach.

      D . Possession Termination Damages. If Landlord terminates Tenant's right
to possession without terminating the Lease and Landlord takes possession of the
Premises itself, Landlord may relet any part of the Premises for such Rent, for
such time, and upon such terms as Landlord in its sole discretion shall
determine, without any obligation to do so prior to renting other vacant areas
in the Building. Any proceeds from reletting the Premises shall first be applied
to the expenses of reletting, including redecoration, repair, alteration,
advertising, brokerage, legal, and other reasonably necessary expenses. If the
reletting proceeds after payment of expenses are insufficient to pay the full
amount of Rent under this Lease, Tenant shall pay such deficiency to Landlord
monthly upon demand as it becomes due. Any excess proceeds shall be retained by
Landlord.

      E. Landlord's Remedies Cumulative. All of Landlord's remedies under this
Lease shall be in addition to all other remedies Landlord may have at law or in
equity. Waiver by Landlord of any breach of any obligation by Tenant shall be
effective only if it is in writing, and shall not be deemed a waiver of any
other breach, or any subsequent breach of the same obligation. Landlord's
acceptance of payment by Tenant shall not constitute a waiver of any breach by
Tenant, and if the acceptance occurs after Landlord's notice to Tenant, or
termination of the Lease or of Tenant's right to possession, the acceptance
shall not affect such notice or termination. Acceptance of payment by Landlord
after commencement of a legal proceeding or final judgment shall not affect such
proceeding or judgment. Landlord may advance such monies and take such other
actions for Tenant's account as reasonably may be required to cure or mitigate
any default by Tenant. Tenant shall immediately reimburse Landlord for any such
advance, and such sums shall bear interest at the default interest rate until
paid.

      F. WAIVER OF TRIAL BY JURY. EACH PARTY WAIVES TRIAL BY JURY IN THE EVENT
OF ANY LEGAL PROCEEDING BROUGHT BY THE OTHER IN

                                       22
<PAGE>   30
CONNECTION WITH THIS LEASE. EACH PARTY SHALL BRING ANY ACTION AGAINST THE OTHER
IN CONNECTION WITH THIS LEASE IN A FEDERAL OR STATE COURT LOCATED IN CALIFORNIA,
CONSENTS TO THE JURISDICTION OF SUCH COURTS, AND WAIVES ANY RIGHT TO HAVE ANY
PROCEEDING TRANSFERRED FROM SUCH COURTS ON THE GROUND OF IMPROPER VENUE OR
INCONVENIENT FORUM.

      G. Litigation Costs. Tenant shall pay Landlord's reasonable attorneys'
fees and other costs in enforcing this Lease, whether or not suit is filed.

      14. SURRENDER. Upon termination of this Lease or Tenant's right to
possession, Tenant shall return the Premises to Landlord in good order and
condition, ordinary wear and casualty damage excepted. If Landlord requires
Tenant to remove any alterations, then Tenant shall remove the alterations in a
good and workmanlike manner and restore the Premises to its condition prior to
their installation.

      15. HOLDOVER. If Tenant retains possession of any part of the Premises
after the Term, Tenant shall become a month-to-month tenant for the entire
Premises upon all of the terms of this Lease as might be applicable to such
month-to-month tenancy, except that Tenant shall pay all of Base Rent, Operating
Cost Share Rent and Tax Share Rent at 150% of the rate in effect immediately
prior to such holdover, computed on a monthly basis for each full or partial
month Tenant remains in possession. Tenant shall also pay Landlord all of
Landlord's direct damages and, if Tenant retains possession of any part of the
Premises for more than thirty (30) days, Tenant shall also pay Landlord all of
Landlord's consequential damages. No acceptance of Rent or other payments by
Landlord under these holdover provisions shall operate as a waiver of Landlord's
right to regain possession or any other of Landlord's remedies.

      16. SUBORDINATION TO GROUND LEASES AND MORTGAGES.

      A. Subordination. This Lease shall be subordinate to any present or future
ground lease or mortgage respecting the Project, and any amendments to such
ground lease or mortgage, at the election of the ground lessor or mortgagee as
the case may be, effected by notice to Tenant in the manner provided in this
Lease. The subordination shall be effective upon such notice, but at the request
of Landlord or ground lessor or mortgagee, Tenant shall within ten (10) days of
the request, execute and deliver to the requesting party any reasonable
documents provided to evidence the subordination.

      B. Termination of Ground Lease or Foreclosure of Mortgage. If any ground
lease is terminated or mortgage foreclosed or deed in lieu of foreclosure given
and the ground lessor, mortgagee, or purchaser at a foreclosure sale shall
thereby become the owner of the Project, Tenant shall attorn to such ground
lessor or mortgagee or purchaser without any deduction or setoff by Tenant, and
this Lease shall continue in effect as a direct lease between Tenant and such
ground lessor, mortgagee or purchaser. The ground lessor or mortgagee or
purchaser shall be liable as Landlord only during the time such ground lessor or
mortgagee or purchaser is the

                                       23
<PAGE>   31
owner of the Project. At the request of Landlord, ground lessor or mortgagee,
Tenant shall execute and deliver within ten (10) days of the request any
document furnished by the requesting party to evidence Tenant's agreement to
attorn,

      C. Security Deposit. Any ground lessor or mortgagee shall be responsible
for the return of any security deposit by Tenant only to the extent the security
deposit is received by such ground lessor or mortgagee.

      D. Notice and Right to Cure. The Project is subject to any ground lease
and mortgage identified with name and address of ground lessor or mortgagee in
Appendix D to this Lease (as the same may be amended from time to time by
written notice to Tenant). Tenant agrees to send by registered or certified mail
to any ground lessor or mortgagee identified either in such Appendix or in any
later notice from Landlord to Tenant a copy of any notice of default sent by
Tenant to Landlord. If Landlord fails to cure such default within the required
time period under this Lease, but ground lessor or mortgagee begins to cure
within ten (10) days after such period and proceeds diligently to complete such
cure, then ground lessor or mortgagee shall have such additional time as is
necessary to complete such cure, including any time necessary to obtain
possession if possession is necessary to cure, and Tenant shall not begin to
enforce its remedies so long as the cure is being diligently pursued.

      E. Definitions. As used in this Section 16, "mortgage" shall include
"trust deed" and "mortgagee" shall include "trustee", "mortgagee" shall include
the mortgagee of any ground lessee, and "ground lessor", "mortgagee", and
"purchaser at a foreclosure sale" shall include, in each case, all of its
successors and assigns, however remote.

      17. ASSIGNMENT AND SUBLEASE.

   A. In General. Tenant shall not, without the prior consent of Landlord in
each case, make or allow any assignment or transfer, by operation of law or
otherwise, of any part of Tenant's interest in this Lease, (ii) grant or allow
any lien or encumbrance, by operation of law or otherwise, upon any part of
Tenant's interest in this Lease, (iii) sublet any part of the Premises, or (iv)
permit anyone other than Tenant and its employees to occupy any part of the
Premises. Tenant shall remain primarily liable for all of its obligations under
this Lease, notwithstanding any assignment or transfer. No consent granted by
Landlord shall be deemed to be a consent to any subsequent assignment or
transfer, lien or encumbrance, sublease or occupancy. Tenant shall pay all of
Landlord's attorneys' fees and other expenses incurred in connection with any
consent requested by Tenant or in reviewing any proposed assignment or
subletting. Any assignment or transfer, grant of lien or encumbrance, or
sublease or occupancy without Landlord's prior written consent shall be void. If
Tenant shall assign this Lease or sublet the Premises in its entirety any rights
of Tenant to renew this Lease, extend the Term or to lease additional space in
the Project shall be extinguished thereby and will not be transferred to the
assignee or subtenant, all such rights being personal to the Tenant named
herein. If no default on the part of Tenant has occurred and is continuing,
Tenant may assign this Lease to an entity into which Tenant is merged or
consolidated or to an entity to which substantially all

                                       24

<PAGE>   32
of Tenant's assets are transferred, without first obtaining Landlord's written
consent, if Tenant notifies Landlord at least ten (10) business days prior to
the proposed transaction, providing information satisfactory to Landlord in
order to determine the net worth both of the successor entity and of Tenant
immediately prior to such assignment, and showing the net worth of the successor
to be at least equal to the net worth of Tenant (a "Permitted Affiliate
Transfer" and the transferee, a "Permitted Affiliate Transferee").

      B. Landlord's Consent. Landlord will not unreasonably withhold its consent
to any proposed assignment or subletting. It shall be reasonable for Landlord to
withhold its consent to any assigmment or sublease if (i) Tenant is in default
under this Lease, (ii) the proposed assignee or sublessee is a tenant in the
Project or an affiliate of such a tenant or a party that Landlord has identified
as a prospective tenant in the Project, (iii) the financial responsibility,
nature of business, and character of the proposed assignee or subtenant are not
all reasonably satisfactory to Landlord, (iv) in the reasonable judgment of
Landlord the purpose for which the assignee or subtenant intends to use the
Premises (or a portion thereof) is not in keeping with Landlord's standards for
the Building or are in violation of the terms of this Lease or any other leases
in the Project, (v) the proposed assignee or subtenant is a government entity,
or (vi) the proposed assignment is for less than the entire Premises or for less
than the remaining Term of the Lease. The foregoing shall not exclude any other
reasonable basis for Landlord to withhold its consent.

      C. Procedure. Tenant shall notify Landlord of any proposed assignment or
sublease at least thirty (30) days prior to its proposed effective date. The
notice shall include the name and address of the proposed assignee or subtenant,
its corporate affiliates in the case of a corporation and its partners in a case
of a partnership, an execution copy of the proposed assignment or sublease, and
sufficient information to permit Landlord to determine the financial
responsibility and character of the proposed assignee or subtenant. As a
condition to any effective assignment of this Lease, the assignee shall execute
and deliver in form satisfactory to Landlord at least fifteen (15) days prior to
the effective date of the assignment, an assumption of all of the obligations of
Tenant under this Lease. As a condition to any effective sublease, subtenant
shall execute and deliver in form satisfactory to Landlord at least fifteen (15)
days prior to the effective date of the sublease, an agreement to comply with
all of Tenant's obligations under this Lease, and at Landlord's option, an
agreement (except for the economic obligations which subtenant will undertake
directly to Tenant) to attorn to Landlord under the terms of the sublease in the
event this Lease terminates before the sublease expires.

      D. Change of Management or Ownership. Any transfer of the direct or
indirect power to affect the management or policies of Tenant or direct or
indirect change in thirty-five percent (35%) or more in the aggregate of the
ownership interest in Tenant shall constitute an assignment of this Lease.

      E. Excess Payments. If Tenant shall assign this Lease or sublet any part
of the Premises for consideration in excess of the pro-rata portion of Rent
applicable to the space subject to the assignment or sublet, after deducting the
out-of-pocket leasing commissions, tenant

                                       25
<PAGE>   33
improvements and marketing costs incurred by Tenant in connection with such
assignment or subletting, then Tenant shall pay to Landlord as Additional Rent
50% of any such excess immediately upon receipt.

      F. Recapture. Landlord may, by giving written notice to Tenant within
thirty (30) days after receipt of Tenant's notice of assignment or subletting,
other than a Permitted Affiliate Transfer, terminate this Lease with respect to
the space described in Tenant's notice, as of the effective date of the proposed
assignment or sublease and all obligations under this Lease as to such space
shall expire except as to any obligations that expressly survive any termination
of this Lease; provided that Landlord shall not be entitled to the rights under
this Section 17(F) (i) in the event subleases of less than thirty-three percent
(33%) of the Rentable Area in the aggregate during the first Lease Year, or
(ii) with respect to any sublease if within ten (10) days after Landlord's
notice to Tenant under this Section 17(F) Tenant delivers written notice to
Landlord rescinding and terminating the proposed sublease.

      18. CONVEYANCE BY LANDLORD. If Landlord shall at any time transfer its
interest in the Project or this Lease, Landlord shall be released of any
obligations occurring after such transfer, except the obligation to return to
Tenant any security deposit not delivered to its transferee, and Tenant shall
look solely to Landlord's successors for performance of such obligations.
Subject to the provisions of Section 16, this Lease shall not be affected by any
such transfer.

      19. ESTOPPEL CERTIFICATE. Each party shall, within ten (10) days of
receiving a request from the other party, execute, acknowledge in recordable
form, and deliver to the other party or its designee a certificate stating,
subject to a specific statement of any applicable exceptions, that the Lease as
amended to date is in full force and effect, that the Tenant is paying Rent and
other charges on a current basis (except as provided in this Lease with respect
to the prepaid Rent), and that to the best of the knowledge of the certifying
party, the other party has committed no uncured defaults and has no offsets or
claims. The certifying party may also be required to state the date of
commencement of payment of Rent, the Commencement Date, the Termination Date,
the Base Rent, the current Operating Cost Share Rent and Tax Share Rent
estimates, the status of any improvements required to be completed by Landlord,
the amount of any security deposit, and such other matters as may be reasonably
requested. Failure to deliver such statement within the time required shall be
conclusive evidence against the non-certifying party that this Lease, with any
amendments identified by the requesting party, is in full force and effect, that
there are no uncured defaults by the requesting party, that not more than one
month's Rent has been paid in advance, except for the remaining portion of the
prepaid rent expressly provided in this Lease, that the non-certifying party has
not paid any security deposit, other than the security deposit provided in
Section 20 below, and that the non-certifying party has no claims or offsets
against the requesting party.

      20. SECURITY DEPOSIT. Tenant shall deposit with Landlord on the date of
this Lease, security for the performance of all of its obligations in the amount
set forth on the Schedule (the "Initial Security Deposit"). The Initial Security
Deposit has been calculated as

                                       26
<PAGE>   34
three (3) times the sum of the monthly Base Rent, monthly Operating Cost Share
Rent and monthly Tax Share Rent due under this Lease. For the purposes of
determining the Initial Security Deposit, the monthly Base Rent, Operating Cost
Share Rent and Tax Share Rent have been estimated. Tenant acknowledges and
agrees that the estimates of Base Rent, Operating Cost Share Rent and Tax Share
Rent for the Initial Security Deposit have been made solely for the parties'
ease in calculating the Initial Security Deposit and such estimate shall not
limit or affect any of the provisions of this Lease, including, without
limitation, the provisions of this Lease regarding the payment of Base Rent,
Operating Cost Share Rent and Tax Share Rent and the provisions of this Section
20.

      The Security Deposit shall be increased upon the Commencement Date and the
determination of the TI Rent Component and any increase from time to time in the
monthly Base Rent, monthly Operating Cost Share Rent and monthly Tax Share Rent
due under this Lease, and concurrently therewith Tenant shall deliver to
Landlord, in immediately available funds, the amount necessary to increase the
Security Deposit then held by Landlord to an amount equal to three (3) times the
sum of the monthly Base Rent, monthly Operating Cost Share Rent and monthly Tax
Share Rent, as the same may be reduced as provided in the next paragraph.

      If as of the commencement of the thirty-first (31st) month of the Term,
(a) no default by Tenant and no event which with the giving of notice or the
passage of time would constitute a default by Tenant, exists under this Lease,
and (b) Tenant's annual audited, and quarterly, financial statements for the
fiscal year and fiscal quarter immediately preceding the thirty-first (31st)
month of the Term show Tenant's net worth to be not less than $3,000,000, then
the amount of the Security Deposit then held by Landlord shall be reduced to the
sum from time to time of the monthly Base Rent, monthly Operating Cost Share
Rent and monthly Tax Share Rent. Prior to any reduction of the Security Deposit
Tenant shall deliver to Landlord Tenant's financial statements for the
applicable fiscal year and fiscal quarter, prepared in accordance with generally
accepted accounting principles consistently applied, with annual statements
audited by an independent certified public accountant. Any reduction in the
Security Deposit shall be held by Landlord and applied to the next payment(s) of
Rent due under this Lease. The provisions of this paragraph allowing for the
reduction of the Security Deposit are applicable only if and when PhoneXchange
or a Permitted Affiliate Transferee is the Tenant hereunder (and if at any time
PhoneXchange or a Permitted Affiliate Transferee is not the Tenant hereunder
there shall be no such reduction of the Security Deposit).

      If Tenant defaults under this Lease, Landlord may use any part of the
Security Deposit to make any defaulted payment, to pay for Landlord's cure of
any defaulted obligation, or to compensate Landlord for any loss or damage
resulting from any default. To the extent any portion of the deposit is used,
Tenant shall within five (5) days after demand from Landlord restore the deposit
to its full amount. Landlord may keep the Security Deposit in its general funds
and shall not be required to pay interest to Tenant on the deposit amount. If
Tenant shall perform all of its obligations under this Lease and return the
Premises to Landlord at the end of the Term, Landlord shall return all of the
remaining Security Deposit to Tenant not later than thirty (30) days after the
delivery of possession of the Premises to Landlord. The Security

                                       27
<PAGE>   35
Deposit shall not serve as an advance payment of Rent or a measure of Landlord's
damages for any default under this Lease. If the Base Rent, Operating Cost Share
Rent or Tax Share Rent shall, from time to time, increase during the term of
this Lease (as extended from time to time), Tenant shall, upon Landlord's
election, deposit with Landlord additional money as a Security Deposit so that
the total amount of Security Deposit held by Landlord shall at all times bear
the same proportion to the then current Base Rent, Operating Cost Share Rent and
Tax Share Rent as the initial Security Deposit bears to the initial Base Rent,
Operating Cost Share Rent and Tax Share Rent.

      If Landlord transfers its interest in the Project or this Lease, Landlord
shall either (a) transfer the portion of the Security Deposit then held by
Landlord to its transferee or (b) return to Tenant the portion of the Security
Deposit then held by Landlord and remaining after the deductions permitted
herein. Upon such transfer to such transferee or the return of the Security
Deposit to Tenant, Landlord shall have no further obligation with respect to the
Security Deposit, and Tenant's right to the return of the Security Deposit shall
apply solely against Landlord's transferee.

      Tenant waives the provisions of California Civil Code Section 1950.7, and
all other provisions of law now in force or that become in force after the date
of execution of this Lease, that provide that Landlord may claim from a security
deposit only those sums reasonably necessary to remedy any defaults in the
payment of Rent, to repair damage caused by Tenant, or to clean the Premises.
Landlord and Tenant agree that Landlord may, in addition, claim those sums
reasonably necessary to compensate Landlord for any other foreseeable or
unforeseeable loss or damage caused by the act or omission of Tenant or Tenant's
officers, agents, employees, independent contractors, or invitees.

     21. FORCE MAJEURE. Neither Landlord nor Tenant shall be in default under
this Lease to the extent such party is unable to perform any of its obligations
on account of any strike or labor problem, energy shortage, governmental
pre-emption or prescription, flood, earthquake, national emergency, or any other
cause of any kind beyond the reasonable control of such party (with financial
inability of a party not being a cause beyond the reasonable control of such
party) ("Force Majeure").

      22. TENANT'S PERSONAL PROPERTY AND FIXTURES. Tenant hereby grants to
Landlord all of its personal property and fixtures now or hereafter located
within the Premises as security for performance of all of Tenant's obligations
under this Lease. Tenant may replace such personal property and fixtures with
items of equal or better quality, but shall not otherwise remove them from the
Premises without the consent of Landlord until all of the obligations of Tenant
under this Lease have been performed. This Lease constitutes a security
agreement creating a security interest in such property in favor of Landlord,
subject only to the liens of existing creditors, and Landlord may at any time
file this Lease as a financing statement under the Uniform Commercial Code of
the state in which the Project is located. Upon Tenant's reasonable request,
Landlord will subordinate such security interest (pursuant to an agreement

                                       28
<PAGE>   36
in form and substance acceptable to Landlord in its reasonable discretion) to
personal property financing obtained by Tenant in the ordinary course of its
business.

      23. NOTICES. All notices, consents, approvals and similar communications
to be given by one party to the other under this Lease (including, without
limitation, any notice required by law to be given by Landlord to Tenant as a
condition to the filing of an action alleging an unlawful detainer of the
Premises and any three (3) day notice under Section 1161(2) or (3) of the
California Code of Civil Procedure), shall be given in writing, mailed or
personally delivered as follows:

      A. Landlord. To Landlord as follows:

         CarrAmerica Realty Corporation
         3611 South Harbor Boulevard, Suite 230
         Santa Ana, California 92704
         Attn: Market Officer

         with a copy to:

         CarrAmerica Realty Corporation
         1850 K Street, N.W., Suite 500
         Washington, D.C. 20006
         Attn: Lease Administration

or to such other person at such other address as Landlord may designate by
notice to Tenant.

      B. Tenant. To Tenant as follows:

         Prior to the Commencement Date:

         PhoneXchange
         4685 MacArthur Court, Suite 300
         Newport Beach, California 92660
         Attention: Chief Financial Officer

         After the Commencement Date:

         PhoneXchange
         27061 Aliso Creek Road
         Aliso Viejo, California
         Attention: Chief Financial Officer

or to such other person at such other address as Tenant may designate by notice
to Landlord.

                                       29
<PAGE>   37
     Mailed notices shall be sent by United States certified or registered mail,
or by a reputable national overnight courier service, postage prepaid. Mailed
notices shall be deemed to have been given on the earlier of actual delivery or
three (3) business days after posting in the United States mail in the case of
registered or certified mail, and one business day in the case of overnight
courier.

      24. QUIET POSSESSION. Subject to the provisions of Section 16, so long as
Tenant shall perform all of its obligations under this Lease, Tenant shall enjoy
peaceful and quiet possession of the Premises against any party claiming through
the Landlord.

      25. REAL ESTATE BROKER. Tenant represents to Landlord that Tenant has not
dealt with any real estate broker with respect to this Lease except for any
broker(s) listed in the Schedule, and no other broker is in any way entitled to
any broker's fee or other payment in connection with this Lease. Tenant shall
indemnify and defend Landlord against any claims by any other broker or third
party for any payment of any kind in connection with this Lease.

      26. MISCELLANEOUS.

      A. Successors and Assigns. Subject to the limits on Tenant's assignment
contained in Section 17, the provisions of this Lease shall be binding upon and
inure to the benefit of all successors and assigns of Landlord and Tenant.

      B. Date Payments Are Due. Except for payments to be made by Tenant under
this Lease which are due upon demand, Tenant shall pay to Landlord any amount
for which Landlord renders a statement of account within fifteen (15) days of
Tenant's receipt of Landlord's statement.

      C. Meaning of "Landlord", "Re-Entry, "including" and "Affiliate". The term
"Landlord" means only the owner of the Project and the lessor's interest in this
Lease from time to time. The words "re-entry" and "re-enter" are not restricted
to their technical legal meaning The words "including" and similar words shall
mean "without limitation." The word "affiliate" shall mean a person or entity
controlling, controlled by or under common control with the applicable entity.
"Control" shall mean the power directly or indirectly, by contract or otherwise,
to direct the management and policies of the applicable entity.

      D. Time of the Essence. Time is of the essence of each provision of this
Lease.

      E. No Option. This document shall not be effective for any purpose until
it has been executed and delivered by both parties; execution and delivery by
one parry shall not create any option or other right in the other party.

      F. Severability. The unenforceability of any provision of this Lease shall
not affect any other provision.

                                       30
<PAGE>   38
      G. Governing Law. This Lease shall be governed in all respects by the laws
of the state in which the Project is located, without regard to the principles
of conflicts of laws.

      H. Lease Modification. Tenant agrees to modify this Lease in any way
requested by a mortgagee which does not cause increased expense to Tenant or
otherwise materially adversely affect Tenant's interests under this Lease.

      I. No Oral Modification. No modification of this Lease shall be effective
unless it is a written modification signed by both parties.

      J. Landlord's Right to Cure. If Landlord breaches any of its obligations
under this Lease, Tenant shall notify Landlord in writing and shall take no
action respecting such breach so long as Landlord immediately begins to cure the
breach and diligently pursues such cure to its completion. Landlord may cure any
default by Tenant; any expenses incurred shall become Additional Rent due from
Tenant on demand by Landlord.

      K. Captions. The captions used in this Lease shall have no effect on the
construction of this Lease.

      L. Authority. Landlord and Tenant each represents to the other that it has
full power and authority to execute and perform this Lease.

      M. Landlord's Enforcement of Remedies. Landlord may enforce any of its
remedies under this Lease either in its own name or through an agent.

      N. Entire Agreement. This Lease, together with all Appendices, constitutes
the entire agreement between the parties. No representations or agreements of
any kind have been made by either party which are not contained in this Lease.

      O. Landlord's Title. Landlord's title shall always be paramount to the
interest of the Tenant, and nothing in this Lease shall empower Tenant to do
anything which might in any way impair Landlord's title.

      P. Light and Air Rights. Landlord does not grant in this Lease any rights
to light and air in connection with Project. Landlord reserves to itself, the
Land, the Building below the improved floor of each floor of the Premises, the
Building above the ceiling of each floor of the Premises, the exterior of the
Premises and the areas on the same floor outside the Premises, along with the
areas within the Premises required for the installation and repair of utility
lines and other items required to serve other tenants of the Building.

      Q. Singular and Plural. Wherever appropriate in this Lease, a singular
term shall be construed to mean the plural where necessary, and a plural term
the singular. For example, if at any time two parties shall constitute Landlord
or Tenant, then the relevant term shall refer to both parties together.

                                       31
<PAGE>   39
      R. No Recording by Tenant. Tenant shall not record in any public records
any memorandum or any portion of this Lease.

      S. Exclusivity. Landlord does not grant to Tenant in this Lease any
exclusive right except the right to occupy its Premises.

      T. No Construction Against Drafting Party. The rule of construction that
ambiguities are resolved against the drafting party shall not apply to this
Lease.

      U. Survival. All obligations of Landlord and Tenant under this Lease shall
survive the termination of this Lease.

      V. Rent Not Based on Income. No rent or other payment in respect of the
Premises shall be based in any way upon net income or profits from the Premises.
Tenant may not enter into or permit any sublease or license or other agreement
in connection with the Premises which provides for a rental or other payment
based on net income or profit.

      W. Building Manager and Service Providers. Landlord may perform any of its
obligations under this Lease through its employees or third parties hired by
the Landlord.

      X. Late Charge and Interest on Late Payments. Without limiting the
provisions of Section 12A, if Tenant fails to pay any installment of Rent or
other charge to be paid by Tenant pursuant to this Lease within five (5)
business days after the same becomes due and payable, then Tenant shall pay a
late charge equal to the greater of five percent (5%) of the amount of such
payment or $250. In addition, interest shall be paid by Tenant to Landlord on
any late payments of Rent from the date due until paid at the rate provided in
Section 2D(2). Such late charge and interest shall constitute additional Rent
due and payable by Tenant to Landlord upon the date of payment of the delinquent
payment referenced above.

      27. UNRELATED BUSINESS INCOME. If Landlord is advised by its counsel at
any time that any part of the payments by Tenant to Landlord under this Lease
may be characterized as unrelated business income under the United States
Internal Revenue Code and its regulations, then Tenant shall enter into any
amendment proposed by Landlord to avoid such income, so long as the amendment
does not require Tenant to make more payments or accept fewer services from
Landlord, than this Lease provides.

      28. HAZARDOUS SUBSTANCES.

      A. Tenant shall not cause or permit any Hazardous Substances to be brought
upon, produced, stored, used, discharged or disposed of in or near the Project
unless Landlord has consented to such storage or use in its sole discretion. If
any lender or governmental agency shall require testing for Hazardous Substances
in the Premises, Tenant shall pay for such testing.

                                       32
<PAGE>   40
     B. "Hazardous Substances" means (a) any chemical, compound, material,
mixture or substance that is now or hereafter defined or listed in, or otherwise
classified pursuant to, any Environmental Laws as a "hazardous substance",
"hazardous material", "hazardous waste", "extremely hazardous waste", "acutely
hazardous waste", "radioactive waste", "infectious waste", "biohazardous waste",
"toxic substance", "pollutant", "toxic pollutant", "contaminant" as well as any
formulation not mentioned herein intended to define, list, or classify
substances by reason of deleterious properties such as ignitability,
corrosivity, reactivity, carcinogenicity, toxicity, reproductive toxicity, "EP
toxicity", or "TCLP toxicity"; (b) petroleum, natural gas, natural gas liquids,
liquefied natural gas, synthetic gas usable for fuel (or mixtures of natural gas
and such synthetic gas) and ash produced by a resource recovery facility
utilizing a municipal solid waste stream, and drilling fluids, produced waters
and other wastes associated with the exploration, development or production of
crude oil, natural gas, or geothermal resources; (c) "hazardous substance" as
defined in Section 25281(f) of the California Health and Safety Code; (d)
"waste" as defined in Section 13050(d) of the California Water Code; (e)
asbestos in any form; (f) urea formaldehyde foam insulation; (g) polychlorinated
biphenyls (PCBs); (h) radon; and (i) any other chemical, material, or substance
exposure to which is limited or regulated by any Governmental Agency because of
its quantity, concentration, or physical or chemical characteristics, or which
poses a significant present or potential hazard to human health or safety or to
the environment if released into the workplace or the environment. "Hazardous
Substances" shall not include ordinary office supplies, repair, maintenance and
cleaning supplies, and backup batteries for computer equipment, all maintained
in reasonable and necessary quantities and used in accordance with all
Environmental Laws. "Environmental Laws" means any and all present and future
federal, state and local laws, ordinances, regulations, policies and any other
requirements of any Governmental Agency relating to health, safety, the
environment or to any Hazardous Substances, including without limitation, the
Comprehensive Environmental Response, Compensation, and Liability Act of 1980
(CERCLA), the Resource Conservation Recovery Act (RCRA), the Hazardous
Substances Transportation Act, the Toxic Substance Control Act, the Endangered
Species Act, the Clean Water Act, the Occupational Safety and Health Act, the
California Environmental Quality Act and the applicable provisions of the
California Health and Safety Code, California Labor Code and the California
Water Code, each as hereafter amended from time to time, and the present and
future rules, regulations and guidance documents promulgated under any of the
foregoing.

     C. Without limiting Tenant's liability and obligations under Sections
28(D), (E), (F) and (G), the foregoing covenant set forth in Section 28(A) shall
not extend to insignificant amounts of substances typically found or used in
general office applications so long as (i) such substances are maintained only
in such quantities as are reasonably necessary for Tenant's operations in the
Premises, (ii) such substances are used strictly in accordance with the
manufacturers' instructions therefor and all applicable Environmental Laws,
(iii) such substances are not disposed of in or about the Project in a manner
which would constitute a release or discharge thereof, and (iv) all such
substances are removed from the Project by Tenant upon the expiration or earlier
termination of this Lease. Tenant shall, within thirty (30) days after demand
therefor, provide to Landlord a written list identifying any Hazardous
Substances then maintained by Tenant in the Building, the use of each such
Hazardous Substance so maintained

                                       33
<PAGE>   41
by Tenant together with written certification by Tenant stating, in substance,
that neither Tenant nor any person for whom Tenant is responsible has released
or discharged any Hazardous Substances in or about the Project.

      D. In order to obtain Landlord's consent under this Section 28 with
respect to any Hazardous Substance other than as specified in Section 28(C)
above, Tenant shall first submit a detailed hazardous material management plan
describing all relevant aspects of the same to Landlord for approval, which
approval may be withheld by Landlord in its sole and absolute discretion. No
approval by Landlord shall relieve Tenant of any obligation of Tenant pursuant
to this Section 28, including all removal, clean-up and indemnification
obligations. Tenant shall, within five (5) days after receipt thereof, furnish
to Landlord copies of all notices or other communications received by Tenant
with respect to any actual or alleged release or discharge of any Hazardous
Substance in or about the Premises or the Project and shall, whether or not
Tenant receives any such notice or communication, notify Landlord in writing of
any discharge or release of Hazardous Substance by Tenant or anyone for whom
Tenant is responsible in or about the Premises or the Project. In the event
Tenant is required to maintain any hazardous materials license or permit in
connection with any use conducted by Tenant or any equipment operated by Tenant
in the Premises, copies of each such license or permit, each renewal thereof,
and any communication relating to suspension, renewal or revocation thereof
shall be furnished to Landlord within five (5) days after receipt thereof by
Tenant. Compliance by Tenant with this Section 28(C) shall not relieve Tenant of
any other obligation of Tenant pursuant to this Section 28.

      E. Upon any violation of the foregoing covenants and in all events upon
any expiration of the Term, Tenant shall be obligated, at Tenant's sole cost, to
clean up and remove from the Project all Hazardous Substances introduced into
the Project by Tenant or any third party for whom Tenant is responsible. Such
clean-up and removal shall include all testing and investigation required by any
governmental authorities having jurisdiction and preparation and implementation
of any remedial action plan required by any governmental authorities having
jurisdiction. All such clean-up and removal activities of Tenant shall, in each
instance, be conducted to the satisfaction of Landlord and all governmental
authorities having jurisdiction. Landlord's right of entry pursuant to Section
11 of this Lease shall include the right (but not the obligation) to enter and
inspect the Premises for violations of Tenant's covenant herein and to supervise
any of Tenant's clean-up and removal activities.

      F. To the extent permitted by then applicable law, Tenant shall protect,
indemnify, defend and hold harmless Landlord, the partners of any entity
constituting Landlord and Landlord's partners, officers, employees, agents,
lenders and attorneys from and against any and all claims, liabilities, losses,
actions, costs and expenses (including attorneys' fees and costs of defense)
incurred by such indemnified persons, or any of them, as the result of (i) the
introduction into the Project by Tenant, its employees, agents, licensees,
invitees, contractors or any other person or entity for whom Tenant is
responsible of any Hazardous Substance, (ii) the usage by Tenant or anyone for
whom Tenant is responsible of Hazardous Substances in or about the Project,
(iii) the discharge or release in or about the Project by Tenant or anyone

                                       34
<PAGE>   42
for whom Tenant is responsible of any Hazardous Substance, (iv) any injury to or
death of persons or damage to or destruction of property resulting from the use
by Tenant or anyone for whom Tenant is responsible of Hazardous Substances in or
about the Project, and (v) any failure of Tenant or anyone for whom Tenant is
responsible to observe the foregoing covenants. Payment shall not be a condition
precedent to enforcement of the foregoing indemnification provision.

     G. Upon any violation of any of the foregoing covenants, Landlord shall be
entitled to exercise all remedies available to a landlord against the defaulting
tenant, including but not limited to those set forth in Section 13 of this
Lease. Without limiting the generality of the foregoing, Tenant expressly agrees
that upon any such violation Landlord may, at its option (i) immediately
terminate this Lease, or (ii) continue this Lease in effect until compliance by
Tenant with its clean-up and removal covenant (notwithstanding the expiration of
the term of this Lease). No action by Landlord hereunder shall impair the
obligations of Tenant pursuant to this Section 28.

     29. EXCULPATION. Landlord shall have no personal liability under this
Lease; its liability shall be limited to its interest in the Project, and shall
not extend to any other property or assets of the Landlord. In no event shall
any officer, director, employee, agent, shareholder, partner, member or
beneficiary of Landlord be personally liable for any of Landlord's obligations
hereunder.

     30. SIGNAGE. Subject to the terms and approvals provided herein, Tenant
shall be entitled to space on a monument sign (the "Monument Sign") (which may
include signage for any other tenant(s) as elected by Landlord) installed by
Landlord at the Project, to the extent permitted by, and subject to the
satisfaction of all Governmental Requirements and, without limiting the
foregoing, subject to the approval of Landlord and the County of Orange. The
Monument Sign design, size, color, material, composition shall be selected by
Landlord, and the Monument Sign shall be in the location elected by Landlord.
Tenant acknowledges that the Monument Sign may not be permitted by the
Governmental Requirements, that Landlord has made no representation or warranty
regarding the availability of the Monument Sign and any unavailability of the
Monument Sign under any Governmental Requirements shall not affect or limit
Landlord's or Tenant's rights or obligations under this Lease. If the Monument
Sign is permitted and approved as provided herein, (a) Tenant's share of the
cost of the installation of the Monument Sign and the maintenance thereof shall
be paid by Tenant, and (b) if Tenant fails to approve and acknowledge in writing
in a manner acceptable to Landlord the Monument Sign and all costs to be paid by
Tenant in connection with the installation of the Monument Sign within thirty
(30) days after written notice from Landlord, all of Tenant's rights with
respect to the Monument Sign and under this Section 30 shall terminate and be of
no further force or effect. Upon the expiration or earlier termination of the
Lease Tenant shall, at its sole cost and expense, remove Tenant's signage from
the Monument Sign and repair all damage caused thereby and restore the
applicable portion of the Monument to its condition prior to the installation
and removal of Tenant's signage. The rights granted under this Section 30 are

                                       35
<PAGE>   43
personal to PhoneXchange and any Permitted Affiliate Transferee and may not
be transferred or assigned.

     31. EXTENSION OPTION. Subject to Subsections B and C below, Tenant may at
its option extend the Term of this Lease for the entire Premises for one period
of five (5) years (the "Renewal Term") upon the same terms contained in this
Lease, excluding the provisions of Appendix C of the Lease and except for the
amount of Base Rent payable during the Renewal Term; and any reference to the
"Term" of the Lease shall be deemed to include the Renewal Term and apply
thereto, unless it is expressly provided otherwise. Tenant shall have no
additional extension option.

      A. The Base Rent during the Renewal Term shall be the greater of (i) the
Base Rent applicable to the last day of the final Lease Year prior to the
applicable Renewal Term, or (ii) the then prevailing market rate for a
comparable term commencing on the first day of the Renewal Term for tenants of
comparable size and creditworthiness for comparable built-out space in the
Building and other first class office buildings in the vicinity of the Building
as reasonably determined by Landlord.

     B. To exercise any option, Tenant must deliver a binding notice to Landlord
not less than ten (10) months prior to the expiration of the initial Term of
this Lease. Thereafter, the Market Rate for the Renewal Term shall be calculated
pursuant to Subsection C below and Landlord shall inform Tenant of the Market
Rate. Such calculations shall be final and shall not be recalculated at the
actual commencement of the Renewal Term. If Tenant fails to timely give its
notice of exercise, Tenant will be deemed to have waived its option to extend.

      C. Market Rate shall be determined as follows:

            (i) If Tenant provides Landlord with its binding notice of exercise
      pursuant to Subsection B above, then at some point between eleven (11) and
      nine (9) months prior to the commencement of the Renewal Term (or, at
      Landlord's election, at an earlier point), Landlord shall calculate and
      inform Tenant of the Market Rate. If Tenant rejects the Market Rate as
      calculated by Landlord, Tenant shall inform Landlord of its rejection
      within ten (10) days after Tenant's receipt of Landlord's calculation, and
      Landlord and Tenant shall commence negotiations to agree upon the Market
      Rate. If Tenant fails to timely reject Landlord's calculation of the
      Market Rate it will be deemed to have accepted such calculation. If
      Landlord and Tenant are unable to reach agreement within twenty-one (21)
      days after Landlord's receipt of Tenant's notice of rejection, then the
      Market Rate shall be determined in accordance with (ii) below.

            (ii) If Landlord and Tenant are unable to reach agreement on the
      Market Rate within said twenty-one (21) day period, then within seven (7)
      days, Landlord and Tenant shall each simultaneously submit to the other in
      a sealed envelope its good faith estimate of the Market Rate. If the
      higher of such estimates is not more than one hundred five percent (105%)
      of the lower, then the Market Rate shall be the average of the two.

                                       36
<PAGE>   44
      Otherwise, the dispute shall be resolved by arbitration in accordance with
      (iii) and (iv) below.

            (iii) Within seven (7) days after the exchange of estimates, the
      parties shall select as an arbitrator an independent MAI appraiser with at
      least five (5) years of experience in appraising office space in the
      metropolitan area in which the Project is located (a "Qualified
      Appraiser"). If the parties cannot agree on a Qualified Appraiser, then
      within a second period of seven (7) days, each shall select a Qualified
      Appraiser and within ten (10) days thereafter the two appointed Qualified
      Appraisers shall select a third Qualified Appraiser and the third
      Qualified Appraiser shall be the sole arbitrator. If one party shall fail
      to select a Qualified Appraiser within the second seven (7) day period,
      then the Qualified Appraiser chosen by the other party shall be the sole
      arbitrator.

            (iv) Within twenty-one (21) days after submission of the matter to
      the arbitrator, the arbitrator shall determine the Market Rate by choosing
      whichever of the estimates submitted by Landlord and Tenant the arbitrator
      judges to be more accurate. The arbitrator shall notify Landlord and
      Tenant of its decision, which shall be final and binding. If the
      arbitrator believes that expert advice would materially assist him, the
      arbitrator may retain one or more qualified persons to provide expert
      advice. The fees of the arbitrator and the expenses of the arbitration
      proceeding, including the fees of any expert witnesses retained by the
      arbitrator, shall be paid by the party whose estimate is not selected.
      Each party shall pay the fees of its respective counsel and the fees of
      any witness called by that party.

      D. Tenant's option to extend this Lease is subject to the conditions that:
(i) on the date that Tenant delivers its final binding notice exercising its
option to extend, Tenant is not in default under this Lease after the expiration
of any applicable notice and cure periods, and (ii) Tenant shall not have
assigned this Lease, except an assignment to a Permitted Affiliate Transferee in
accordance with the terms of this Lease, or sublet any portion of the Premises
under a sublease which is in effect at any time during the final 12 months prior
to the applicable Renewal Term.

      32. RIGHT OF FIRST OFFER. Subject to Subsection B below, and subject to
any expansion or renewal options of any current tenant in the Building (a "Prior
Tenant"), or the right of Landlord to extend the Lease of any current tenant in
the Building, Landlord hereby grants to Tenant for the term of the Lease a right
of first offer for 4,000 net rentable square feet of space in the portion of the
ground floor of Building One not originally demised to Tenant under this Lease
(collectively, the "ROFO Space"), to be exercised in accordance with Subsection
A below.

      A. If any ROFO Space becomes available for lease to anyone other than a
Prior Tenant, Landlord shall so notify Tenant ("Landlord's ROFO Notice")
identifying the available ROFO Space (the "Subject ROFO Space"). Landlord's ROFO
Notice may be given up to sixteen (16) months in advance of such availability
and shall contain the terms upon which

                                       37
<PAGE>   45
Landlord intends to offer the Subject ROFO Space for lease to the market. Tenant
shall notify Landlord within five (5) business days of receipt of Landlord's
ROFO Notice whether it desires to lease the Subject ROFO Space on the terms set
forth in Landlord's ROFO Notice. If Tenant does not notify Landlord within said
five (5) business day period that it will lease the Subject ROFO Space, Tenant
shall be deemed to have refused the Subject ROFO Space. After any refusal,
Tenant shall have no further right of first offer for such Subject ROFO Space
and Landlord shall be free to lease such space to any party for any term and
upon any terms it desires. If Tenant exercises its right of first offer with
respect to the Subject ROFO Space, such space shall be added to the Premises for
all purposes of this lease for the remaining Term of the Lease (but in no event
less than three (3) years) on (a) the terms specified in Landlord's ROFO Notice,
and (b) the terms of this Lease to the extent that they do not conflict with the
terms specified in Landlord's ROFO Notice, except that the terms of Landlord's
ROFO Notice shall not apply during any Renewal Term, and instead, the terms of
the Lease applying to the remainder of the Premises during the Renewal Term
shall also apply to the Subject ROFO Space.

      B. Tenant's right of first offer is subject to the conditions that: (i) on
the date that Tenant delivers its notice exercising its right of first offer,
Tenant is not in default under this Lease after the expiration of any applicable
notice and cure periods, and (ii) Tenant shall not have assigned the Lease,
except an assignment to a Permitted Affiliate Transferee in accordance with the
terms of this Lease, or sublet any portion of the Premises under a sublease
which is in effect at any time during the period commencing with Tenant's
delivery of its notice and ending on the date the ROFO Space is added to the
Premises.

      C, Promptly after Tenant's exercise of its right of first offer, Landlord
shall execute and deliver to Tenant an amendment to the Lease to reflect changes
in the Premises, Base Rent, Tenant's Proportionate Share and any other
appropriate terms changed by the addition of the ROFO Space. Within 15 days
thereafter, Tenant shall execute and return the amendment.

                                       38
<PAGE>   46
      IN WITNESS WHEREOF, the parties hereto have executed this Lease.

                                       LANDLORD:

                                       CARRAMERICA REALTY CORPORATION,
                                       a Maryland corporation

                                       By /s/ PHILIP L. HAWKINS
                                          --------------------------------------
                                       Print Name: Philip L. Hawkins
                                                   -----------------------------
                                       Print Title: Chief  Operating Officer
                                                    ----------------------------

                                       TENANT:

                                       PHONEXCHANGE,
                                       a Delaware corporation

                                       By: /s/ DAVID J. CHADWICK
                                           -------------------------------------
                                       Print Name: David J. Chadwick
                                                   -----------------------------
                                       Print Title: PRESIDENT
                                                    ----------------------------

                                       By:
                                          --------------------------------------
                                       Print Name:
                                                   -----------------------------
                                       Print Title:
                                                    ----------------------------

                                       39
<PAGE>   47
                                   APPENDIX A
                              PLAN OF THE PREMISES

                                    Attached.

                                   APPENDIX A
                                   Page 1 of 1

<PAGE>   48
                                   Diagram of floor plan

<PAGE>   49
                                   APPENDIX B

                              RULES AND REGULATIONS

      1. Tenant shall not place anything, or allow anything to be placed near
the glass of any window, door, partition or wall which may, in Landlord's
judgment, appear unsightly from outside of the Project.

      2. The Project directory shall be available to Tenant solely to display
names and their location in the Project, which display shall be as directed by
Landlord.

      3. The sidewalks, halls, passages, exits, entrances, elevators and
stairways shall not be obstructed by Tenant or used by Tenant for any purposes
other than for ingress to and egress from the Premises. Tenant shall lend its
full cooperation to keep such areas free from all obstruction and in a clean and
sightly condition and shall move all supplies, furniture and equipment as soon
as received directly to the Premises and move all such items and waste being
taken from the Premises (other than waste customarily removed by employees of
the Building) directly to the shipping platform at or about the time arranged
for removal therefrom. The halls, passages, exits, entrances, elevators,
stairways, balconies and roof are not for the use of the general public and
Landlord shall, in all cases, retain the right to control and prevent access
thereto by all persons whose presence in the judgment of Landlord, reasonably
exercised, shall be prejudicial to the safety, character, reputation and
interests of the Project. Neither Tenant nor any employee or invitee of Tenant
shall go upon the roof of the Project.

      4. The toilet rooms, urinals, wash bowls and other apparatuses shall not
be used for any purposes other than that for which they were constructed, and no
foreign substance of any kind whatsoever shall be thrown therein, and to the
extent caused by Tenant or its employees or invitees, the expense of any
breakage, stoppage or damage resulting from the violation of this rule shall be
borne by Tenant.

      5. Tenant shall not cause any unnecessary janitorial labor or services by
reason of Tenant's carelessness or indifference in the preservation of good
order and cleanliness.

      6. Tenant shall not install or operate any refrigerating, heating or air
conditioning apparatus, or carry on any mechanical business without the prior
written consent of Landlord or as provided in the Lease; use the Premises for
housing, lodging or sleeping purposes; or permit preparation or warming of food
in the Premises (warming of coffee and individual meals with employees and
guests excepted). Tenant shall not occupy or use the Premises or permit the
Premises to be occupied or used for any purpose, act or thing which is in
violation of any Governmental Requirement or which may be dangerous to persons
or property.

      7. Tenant shall not bring upon, use or keep in the Premises or the Project
any kerosene, gasoline or inflammable or combustible fluid or material, or any
other articles deemed

                                   APPENDIX B
                                   Page 2 of 5
<PAGE>   50
hazardous to persons or property, or use any method of heating or air
conditioning other than that supplied by Landlord.

      8. Landlord shall have sole power to direct electricians as to where and
how telephone and other wires are to be introduced. No boring or cutting for
wires is to be allowed without the consent of Landlord. The location of
telephones, call boxes and other office equipment affixed to the Premises shall
be subject to the approval of Landlord.

      9. No additional locks shall be placed upon any doors, windows or transoms
in or to the Premises. Tenant shall not change existing locks or the mechanism
thereof. Upon termination of the lease, Tenant shall deliver to Landlord all
keys and passes for offices, rooms, parking lot and toilet rooms which shall
have been furnished Tenant.

         In the event of the loss of keys so furnished, Tenant shall pay
Landlord therefor. Tenant shall not make, or cause to be made, any such keys and
shall order all such keys solely from Landlord and shall pay Landlord for any
keys in addition to the two sets of keys originally furnished by Landlord for
each lock.

      10. Tenant shall not install linoleum, tile, carpet or other floor
covering so that the same shall be affixed to the floor of the Premises in any
manner except as approved by Landlord.

      11. No furniture, packages, supplies, equipment or merchandise will be
received in the Project or carried up or down in the freight elevator, except
between such hours and in such freight elevator as shall be designated by
Landlord. Tenant shall not take or permit to be taken in or out of other
entrances of the Building, or take or permit on other elevators, any item
normally taken in or out through the trucking concourse or service doors or in
or on freight elevators.

      12. Tenant shall cause all doors to the Premises to be closed and securely
locked and shall turn off all utilities, lights and machines before leaving the
Project at the end of the day.

      13. Without the prior written consent of Landlord, Tenant shall not use
the name of the Project or any picture of the Project in connection with, or in
promoting or advertising the business of, Tenant, except Tenant may use the
address of the Project as the address of its business.

      14. Tenant shall cooperate fully with Landlord to assure the most
effective operation of the Premises' or the Project's heating and air
conditioning, and shall refrain from attempting to adjust any controls, other
than room thermostats installed for Tenant's use. Tenant shall keep corridor
doors closed.

                                   APPENDIX B
                                   Page 2 of 5
<PAGE>   51
      15. Tenant assumes full responsibility for protecting the Premises from
theft, robbery and pilferage, which may arise from a cause other than Landlord's
negligence, which includes keeping doors locked and other means of entry to the
Premises closed and secured.

      16. Peddlers, solicitors and beggars shall be reported to the office of
the Project or as Landlord otherwise requests.

      17. Tenant shall not advertise the business, profession or activities of
Tenant conducted in the Project in any manner which violates the letter or
spirit of any code of ethics adopted by any recognized association or
organization pertaining to such business, profession or activities.

      18. No bicycle or other vehicle and no animals or pets shall be allowed in
the Premises, halls, freight docks, or any other parts of the Building except
that blind persons may be accompanied by "seeing eye" dogs. Tenant shall not
make or permit any noise, vibration or odor to emanate from the Premises, or do
anything therein tending to create, or maintain, a nuisance, or do any act
tending to injure the reputation of the Building.

      19. Tenant acknowledges that Building security problems may occur which
may require the employment of extreme security measures in the day-to-day
operation of the Project.

      Accordingly:

            (a) Landlord may, at any time, or from time to time, or for
regularly scheduled time periods, as deemed advisable by Landlord and/or its
agents, in their sole discretion, require that persons entering or leaving the
Project or the Property identify themselves to watchmen or other employees
designated by Landlord, by registration, identification or otherwise.

            (b) Tenant agrees that it and its employees will cooperate fully
with Project employees in the implementation of any and all security procedures.

            (c) Such security measures shall be the sole responsibility of
Landlord, and Tenant shall have no liability for any action taken by Landlord in
connection therewith, it being understood that Landlord is not required to
provide any security procedures and shall have no liability for such security
procedures or the lack thereof.

      20. Tenant shall not do or permit the manufacture, sale or purchase of any
fermented, intoxicating or alcoholic beverages, or the use thereof except at
reasonable corporate functions, without obtaining written consent of Landlord,

      21. Tenant shall not disturb the quiet enjoyment of any other tenant.

                                   APPENDIX B
                                   Page 3 of 5
<PAGE>   52
      22. Tenant shall not provide any janitorial services or cleaning without
Landlord's written consent and then only subject to supervision of Landlord and
at Tenant's sole responsibility and by janitor or cleaning contractor or
employees at all times satisfactory to Landlord.

      23. Landlord may retain a pass key to the Premises and be allowed
admittance thereto at all times to enable its representatives to examine the
Premises from time to time and to exhibit the same and Landlord may place and
keep on the windows and doors of the Premises at any time signs advertising the
Premises for Rent.

      24. No equipment. mechanical ventilators, awnings, special shades or other
forms of window covering shall be permitted either inside or outside the windows
of the Premises without the prior written consent of Landlord, and then only at
the expense and risk of Tenant, and they shall be of such shape, color,
material, quality, design and make as may be approved by Landlord.

      25. Tenant shall not during the term of this Lease canvas or solicit other
tenants of the Building for any purpose.

      26. Except as necessary in connection with the NOC in accordance with the
Lease, Tenant shall not install or operate any phonograph, musical or sound-
producing instrument or device, radio receiver or transmitter, TV receiver or
transmitter, or similar device in the Building, nor install or operate any
antenna, aerial, wires or other equipment inside or outside the Building, nor
operate any electrical device from which may emanate electrical waves which may
interfere with or impair radio or television broadcasting or reception from or
in the Building or elsewhere, without in each instance the prior written
approval of Landlord. The use thereof, if permitted, shall be subject to control
by Landlord to the end that others shall not be disturbed.

      27. Tenant shall promptly remove all rubbish and waste from the Premises.

      28. Tenant shall not exhibit, sell or offer for sale, Rent or exchange in
the Premises or at the Project any article, thing or service, except those
ordinarily embraced within the use of the Premises specified in Section 6 of
this Lease, without the prior written consent of Landlord.

      29. Tenant shall list all furniture, equipment and similar articles Tenant
desires to remove from the Premises or the Building and deliver a copy of such
list to Landlord and procure a removal permit from the Office of the Building
authorizing Building employees to permit such articles to be removed.

      30. Tenant shall not overload any floors in the Premises or any public
corridors or elevators in the Building.

                                   APPENDIX B
                                   Page 4 of 5
<PAGE>   53
     31. Tenant shall not do any painting in the Premises, or mark, paint, cut
or drill into, drive nails or screws into, or in any way deface any part of the
Premises or the Building, outside or inside, without the prior written consent
of Landlord.

      32. Whenever Landlord's consent, approval or satisfaction is required
under these Rules, then unless otherwise stated, any such consent, approval or
satisfaction must be obtained in advance, such consent or approval may be
granted or withheld in Landlord's sole discretion, and Landlord's satisfaction
shall be determined in its sole judgment.

     33. Tenant and its employees shall cooperate in all fire drills conducted
by Landlord in the Building.

                                   APPENDIX B
                                   Page 5 of 5

<PAGE>   54
                                   APPENDIX C

                          TENANT IMPROVEMENT AGREEMENT

      1. INITIAL IMPROVEMENTS. Landlord shall cause to be performed the
improvements (the "Initial Improvements") in the Premises in accordance with
plans and specifications approved by Tenant and Landlord (the "Plans"), which
approvals shall not be unreasonably withheld. The Initial Improvements shall be
performed at the Tenant's cost, subject to the Landlord's Contribution
(hereinafter defined). The Initial Improvements shall include any necessary HVAC
ducting.

      Landlord shall cause the Plans to be prepared, at Tenant's cost, by a
registered professional architect and mechanical and electrical engineer(s).
Such engineer(s) shall be approved, in advance, by the Landlord. On or before
March 20, 1999 Tenant shall provide reasonable comments to such Plans or approve
the same. Tenant shall be deemed to have approved such Plans if it does not
timely provide reasonable comments on such Plans. If Tenant provides Landlord
with reasonable comments to the initial draft of the Plans, Landlord shall
provide revised Plans to Tenant incorporating Landlord's comments. Tenant shall
within one week after receipt then either provide reasonable comments to such
revised Plans or approve such Plans. Tenant shall be deemed to have approved
such revised Plans if Tenant does not timely provide reasonable comments on such
Plans. Tenant hereby agrees that the Plans for the Initial Improvements shall
comply with all applicable Governmental Requirements. The fact that Landlord has
caused to be prepared any of the Plans (or any modifications or changes thereto)
shall not impose upon Landlord or its agents or representatives any obligation
with respect to the design of the Initial Improvements or the compliance of such
Initial Improvements or the Plans with applicable Governmental Requirements.

      Landlord, with consultation of Tenant, shall select a contractor to
perform the construction of the Initial Improvements. Landlord shall use
commercially reasonable efforts to cause the Initial Improvements to be
substantially completed, except for minor "Punch List" items, on or before the
Commencement Date specified in the Schedule to the Lease, subject to Tenant
Delay (as defined in Section 4 hereof) and Force Majeure.

      Landlord, or an agent of Landlord, shall provide project management
services in connection with the construction of the Initial Improvements and the
Change Orders (hereinafter defined). Such project management services shall be
performed, at Tenant's cost, for a fee of five percent (5%) of all costs
related to the preparation of the Plans and the construction of the Initial
Improvements and the Change Orders.

      2. CHANGE ORDERS. If, prior to the Commencement Date, Tenant shall require
improvements or changes (individually or collectively, "Change Orders") to the
Premises in addition to, revision of or substitution for the Initial
Improvements, Tenant shall deliver to Landlord for its approval plans and
specifications for such Change Orders. If Landlord does not

                                   APPENDIX C
                                   Page 1 of 3
<PAGE>   55
approve of the plans for Change Orders, Landlord shall advise Tenant of the
revisions required. Tenant shall revise and redeliver the plans and
specifications to Landlord within five (5) business days of Landlord's advice or
Tenant shall be deemed to have abandoned its request for such Change Orders.
Tenant shall pay for all preparations and revisions of plans and specifications,
and the construction of all Change Orders, subject to Landlord's Contribution.

      3. LANDLORD'S CONTRIBUTION. Landlord shall contribute an amount up to
$172,840 ("Landlord's Contribution") toward the costs incurred for the Initial
Improvements and Change Orders; provided that up to a maximum of $1,296 of
Landlord's Contribution may be used for the payment of the costs of the space
planner used for the preparation of a space plan for the Premises. Except as
provided below with respect to the Improvement Allowance (as defined below),
Landlord has no obligation to pay for costs of the Initial Improvements or
Change Orders in excess of Landlord's Contribution. If the cost of the Initial
Improvements and/or Change Orders exceeds the Landlord's Contribution and the
Improvement Allowance funded by Landlord Tenant shall pay such overage to
Landlord prior to commencement of construction of the Initial Improvements
and/or Change Orders.

      If the costs of the Initial Improvements and Change Orders are in excess
of the Landlord's Contribution, and so long as Tenant is not in default under
this Lease, Landlord will lend Tenant an amount not to exceed $43,210 (the
"Improvement Allowance") solely for the payment of the costs of the Initial
Improvements and Change Orders. The Improvement Allowance funded by Landlord,
together with interest thereon at the rate set forth herein, shall be paid by
Tenant to Landlord as part of the Base Rent. For the purposes of determining the
Base Rent for the first Lease Year, the "TI Rent Component" per month for the
first Lease Year shall mean an amount equal to the total Improvement Allowance
funded by Landlord, together with interest on such amount at a rate of ten
percent (10%) per annum from the date of disbursement by Landlord until repaid
by Tenant, amortized in equal monthly installments over the initial term of this
Lease. Landlord and Tenant agree that all unpaid amounts of the Improvement
Allowance constitute Base Rent under this Lease. Without limiting any of the
foregoing provisions, at Landlord's request, Tenant shall within five (5) days
after such request, duly execute and deliver to Landlord a promissory note, in
form and substance satisfactory to Landlord, evidencing Tenant's obligation to
repay the Improvement Allowance with interest thereon as provided herein (the
"Improvement Note"). Tenant acknowledges and agrees that (a) Tenant's failure to
deliver the Improvement Note to Landlord as provided herein, or (b) any breach
of any of the terms of the Improvement Note, shall constitute a material breach
and default under this Lease. Tenant's failure to execute and deliver the
Improvement Note to Landlord as provided herein shall not affect Tenant's
obligation to repay the Improvement Allowance together with interest thereon as
provided herein. The Improvement Note may be prepaid by Tenant at any time. Any
unpaid Improvement Allowance, together with interest thereon as provided herein,
shall be immediately due and payable upon any default by Tenant under this
Lease. Tenant agrees to pay any and all of Landlord's attorneys' fees and costs
relating to the enforcement of Landlord's rights under the Improvement Note or
with respect to the repayment of the Improvement Allowance.

                                   APPENDIX C
                                   Page 2 of 3
<PAGE>   56
      4. COMMENCEMENT DATE DELAY. Commencement Date shall be delayed until the
Initial Improvements have been substantially completed (the "Completion Date"),
except to the extent that the delay shall be caused by any one or more of the
following (a "Tenant Delay"):

              (a) Tenant's request for Change Orders whether or not any such
Change Orders are actually performed; or

              (b) Contractor's performance of any Change Orders; or

              (c) Tenant's request for materials, finishes or installations
requiring unusually long lead times; or

              (d) Tenant's delay in reviewing, revising or approving plans and
specifications beyond the periods set forth herein; or

              (e) Tenant's delay in providing information critical to the normal
progression of the project. Tenant shall provide such information as soon as
reasonably possible, but in no event longer than one week after receipt of such
request for information from the Landlord; or

              (f) Tenant's delay in making payments to Landlord for costs of the
Initial Improvements and/or Change Orders in excess of the Landlord's
Contribution; or

              (g) Any other act or omission by Tenant, its agents, contractors
or persons employed by any of such persons.

If the Commencement Date is delayed for any reason, then Landlord shall cause
Landlord's Architect to certify the date on which the Initial Improvements would
have been completed but for such Tenant Delay, or were in fact completed without
any Tenant Delay.

      Prior to Tenant's occupancy of the Premises, Landlord and Tenant shall
agree up a punch list of items to be corrected.

      5. ACCESS BY TENANT PRIOR TO COMMENCEMENT OF TERM. Landlord at its
discretion may permit Tenant and its agents to enter the Premises prior to the
Commencement Date to prepare the Premises for Tenant's use and occupancy. Any
such permission shall constitute a license only, conditioned upon Tenant's:

              (a) working in harmony with Landlord and Landlord's agents,
contractors, workmen, mechanics and suppliers and with other tenants and
occupants of the Building;

              (b) obtaining in advance Landlord's approval of the contractors
proposed to be used by Tenant and depositing with Landlord in advance of any
work (i) security satisfactory to

                                   APPENDIX C
                                   Page 3 of 3
<PAGE>   57
Landlord for the completion thereof, and (ii) the contractor's affidavit for the
proposed work and the waivers of lien from the contractor and all subcontractors
and suppliers of material; and

      (c) furnishing Landlord with such insurance as Landlord may require
against liabilities which may arise out of such entry.

     Landlord shall have the right to withdraw such license for any reason upon
twenty-four (24) hours' written notice to Tenant. Landlord shall not be liable
in any way for any injury, loss or damage which may occur to any of Tenant's
property or installations in the Premises prior to the Commencement Date. Tenant
shall protect, defend, indemnify and save harmless Landlord from all
liabilities, costs, damages, fees and expenses arising out of the activities of
Tenant or its agents, contractors, suppliers or workmen in the Premises or the
Building. Any entry and occupation permitted under this Section shall be
governed by Section 5 and all other terms of the Lease.

      6. MISCELLANEOUS.

     Terms used in this Appendix C shall have the meanings assigned to them in
the Lease. The terms of this Appendix C are subject to the terms of the Lease.

                                   APPENDIX C
                                   Page 4 of 4
<PAGE>   58
                                   APPENDIX D
                    MORTGAGES CURRENTLY AFFECTING THE PROJECT

                                      None.

                                   APPENDIX D
                                  Page 1 of 1
<PAGE>   59
                                   APPENDIX E

                         COMMENCEMENT DATE CONFIRMATION

Landlord:   CarrAmerica Realty Corporation, a Maryland corporation

Tenant:     PhoneXchange, a Delaware corporation

      This Commencement Date Confirmation is made by Landlord and Tenant
pursuant to that certain Lease dated as of April 23, 1999 (the "Lease") for
certain premises known as Suite ___ in the building commonly known as Building
One of Pacific Corporate Plaza (the "Premises"). This Confirmation is made
pursuant to Item 9 of the Schedule to the Lease.

      1. Lease Commencement Date. Termination Date. Landlord and Tenant hereby
agree that the Commencement Date of the Lease is ______ 199_, and the
Termination Date of the Lease is ____________, _____.

      2. The monthly Base Rent for the initial Term is as follows:

<TABLE>
<CAPTION>
                                       Monthly            Monthly TI          Monthly
                                    Base Component      Rent Component       Base Rent
<S>                                 <C>                 <C>                <C>
              Lease Year 1          $_____________      $_____________     $____________
              Lease Year 2          $_____________      $_____________     $____________
              Lease Year 3          $_____________      $_____________     $____________
              Lease Year 4          $_____________      $_____________     $____________
              Lease Year 5          $_____________      $_____________     $____________
</TABLE>

      3. Acceptance of Premises. Tenant has inspected the Premises and affirms
that the Premises is acceptable in all respects in its current "as is"
condition.

      4. Incorporation. This Confirmation is incorporated into the Lease, and
forms an integral part thereof. This Confirmation shall be construed and
interpreted in accordance with the terms of the Lease for all purposes.

                                   APPENDIX E
                                   Page 1 of 1
<PAGE>   60
                                       TENANT:

                                       PhoneXchange, a Delaware corporation

                                       By:______________________________________
                                       Name:____________________________________
                                       Title:___________________________________

                                       LANDLORD:

                                       CarrAmerica Realty Corporation,
                                       a Maryland corporation

                                       By:______________________________________
                                       Name:____________________________________
                                       Title:___________________________________

                                   APPENDIX E
                                   Page 1 of 1<PAGE>   1

                                                                  EXHIBIT 10.10

                    ---------------------------------------
                                QUINBY BUILDING

                    ---------------------------------------
                                     LEASE

                    ---------------------------------------
                     (CALIFORNIA -- TELECOMMUNICATIONS USE)

                        TENANT: GLOBAL NETWORK PROVIDERS

                               DATE; JUNE 1, 1997

<PAGE>   2
E.   Schedule of Monthly Base Rents:

     The following schedule of monthly Base Rents (subject to the Rent
     Escalation Rider) shall apply during the term of the Lease:

<TABLE>
<CAPTION>

                                                Monthly
                         Period                Base Rent
                         ------                ---------
<S>                      <C>                   <C>
From June 1, 1997        to May 31, 2002       $2,475.00

     </TABLE>
     The Base Rent for the period from June 1, 1997 to July 1, ???? shall be
prepaid by Tenant upon execution of this Lease. If the actual Commencement Date
is before or after the Estimated Commencement Date, then all dates set forth
above shall be correspondingly accelerated or delayed, as the case may be. In
the event of any default by Tenant under this Lease which is not cured within
the applicable cure period set forth in Section 13.2, Tenant shall be obligated
to pay to Landlord, without any further notice from Landlord, a sum equal to all
rent credits previously credited to Tenant pursuant to the above schedule, and
no further rent credits shall be applicable for the balance of the Lease term.
The Base Rent shall be increased annually in accordance with the Rent Escalation
Rider attached hereto.

F.   Base Years for Expenses: Real Estate Taxes--1997-1998: Operating and
     Utility Costs--1997.

G.   Tenant's "Percentage Share" of Real Estate Taxes, Operating and Utility
     Costs: 2%.

H.   Security Deposit:  $4,950.00 (2 months rent).

I.   Permitted Use: Installation and operation of telecommunications switching
     equipment and related office use.

J.   Maximum Tenant Improvement Allowance: None. Tenant to take Premises "as is"
     as described in Section 35.

K.   Tenant's Parking Allotment: None.

L.   Landlord's Brokers: None.

M.   Riders:

     The following exhibits, riders and addenda are attached to and are part of
     this Lease:

     Exhibit A -- Floor Plan of Premises
     Exhibit B -- Rules and Regulations
     Emergency Generator Rider
     Rent Escalation Rider
     Telecommunications Conduit and Conduit Interconnection Room Rider

     __________________________________________________________________________

N.   Guaranty: A personal guaranty of this Lease is being executed by

     /s/ [signature illegible]
     -------------------------

                                   AGREEMENT

                                       2
<PAGE>   3
                    ---------------------------------------
                                QUINBY BUILDING

                    ---------------------------------------
                                     LEASE

                    ---------------------------------------
                     (CALIFORNIA -- TELECOMMUNICATIONS USE)

                               TABLE OF CONTENTS

<TABLE>
<CAPTION>
<S>                                                                         <C>
SUMMARY OF LEASE TERMS.....................................................  1

AGREEMENT..................................................................  3

     1. PREMISES...........................................................  3
     2. TERM...............................................................  3
     3. RENT...............................................................  3
     4. RENT ESCALATION....................................................  3
     5. TAX ON TENANT'S PROPERTY; OTHER TAXES..............................  6
     6. SECURITY DEPOSIT...................................................  7
     7. LATE PAYMENTS......................................................  7
     8. USE OF PREMISES....................................................  7
     9. BUILDING SERVICES..................................................  8
    10. CONDITION OF PREMISES.............................................. 10
    11. DAMAGE TO PREMISES OR BUILDING..................................... 10
    12. EMINENT DOMAIN..................................................... 11
    13. DEFAULT............................................................ 12
    14. REMEDIES UPON DEFAULT.............................................. 12
    15. SURRENDER OF PREMISES; REMOVAL OF PROPERTY......................... 14
    16. COSTS OF SUIT; ATTORNEYS' FEES; WAIVER OF JURY TRIAL............... 15
    17. ASSIGNMENT AND SUBLETTING.......................................... 15
    18. TRANSFER OF LANDLORD'S INTEREST.................................... 19
    19. HOLDING OVER....................................................... 19
    20. NOTICES............................................................ 19
    21. QUIET ENJOYMENT.................................................... 19
    22. TENANT'S FURTHER OBLIGATIONS....................................... 19
    23. ESTOPPEL CERTIFICATE BY LESSEE..................................... 20
    24. SUBORDINATION AND ATTORNMENT....................................... 20
    25. RIGHTS RESERVED TO LANDLORD........................................ 20
    26. FORCE MAJEURE...................................................... 21
    27. WAIVER OF CLAIMS; INDEMNITY........................................ 21
    28. INSURANCE.......................................................... 22
    29. FIXTURES, TENANT IMPROVEMENTS AND ALTERATIONS...................... 23
    30. MECHANIC'S LIENS................................................... 24
    31. ALTERNATE SPACE.................................................... 24
    32. HAZARDOUS MATERIALS................................................ 24
    33. MISCELLANEOUS...................................................... 25
    34. RULES AND REGULATIONS AFFECTING TELECOMMUNICATIONS USE............. 28
    35. "AS IS" CONDITION.................................................. 28

EXHIBITS AND RIDERS
</TABLE>
<PAGE>   4
                                QUINBY BUILDING

                                     LEASE

     THIS LEASE is made as of the 1 day of JUNE, 1997, between Quinby
Building, LLC, a California Limited Liability Company (hereinafter called
"Landlord"), and Global Network Providers, 5330L Derry Ave., Agoura Hills
CA 91301 hereinafter called "Tenant").

                             SUMMARY OF LEASE TERMS

A.   Address: 650 So. Grand Ave., Suite 901, Los Angeles, Ca 90017

     1.   Tenant's Premises and Notice Address:
                                               --------------------------------

     2.   Landlord's Notice Address:         Quinby Building, LLC, 650 S. Grand
                                             Avenue, Suite 502
                                             Los Angeles, CA 90017

          With copy to:                      Peter Schwartz, Attorney at Law,
                                             2049 Century Park East, Suite 2790,
                                             Los Angeles, CA 90067

     3.   Landlord's Address for Rent
          Payments:                          Quinby Building, LLC, 650 S. Grand
                                             Avenue, Suite 502
                                             Los Angeles, CA 90017
                                             Attn: Gene Elmore

B.   Approximate Rentable Area of the Premises:

     1350 rentable square feet. The parties agree that such figure is only a
reasonable estimate of the area of the Premises. The figures in Items E, G, H
and J below and the other provisions of this Lease shall not be adjusted due to
any difference between the actual area of the Premises and the estimated area
shown above.

C.   Lease Term: 5 years and 0 months.

D.   1.   Estimated Commencement Date:  June 1, 1997.

     2.   Commencement Date: The earlier of the following 2 dates:

          (a) The date upon which Tenant takes possession of or commences the
operation of its business in the Premises; or June 1, 1997.

          (b) The date upon which both (1) Landlord tenders possession of the
Premises to Tenant, and (2) the improvements described in the Landlord's
Improvement Construction Rider, if any, have been substantially completed as
determined by Landlord's architect or space planner, or would have been
substantially completed but for delays caused by Tenant.

                                       1
<PAGE>   5
E.   Schedule of Monthly Base Rents:

     The following schedule of monthly Base Rents shall apply during the term
of the Lease:

<TABLE>
<CAPTION>

                                              Monthly
                    Period                   Base Rent
                    ------                   ---------
     <S>                                     <C>
     From June 1, 1997 to May 31, 1998       $2,475.00

     From June 1, 1998 to May 31, 1999       $2,475.00

     From June 1, 1999 to May 31, 2000       $2,475.00

     From June 1, 2000 to May 31, 2001       $2,475.00
</TABLE>

     The Base Rent for the period from June 1, 1997 to July 1, 1997, shall be
prepaid by Tenant upon execution of this Lease. If the actual Commencement Date
is before or after the Estimated Commencement Date, then all dates set forth
above be correspondingly accelerated or delayed, as the case may be. In the
event of any default by Tenant under this Lease which is not within the
applicable cure period set forth in Section 13.2, Tenant shall be obligated to
pay to Landlord, without any further notice from Landlord, a sum equal to all
rent credits previously credited to Tenant pursuant to the above schedule, and
no further rent credits be applicable for the balance of the Lease term.

F.   Base Years for Expenses: Real Estate Taxes -- 1997-1998; Operating and
     Utility Costs -- 1997.

G.   Tenant's "Percentage Share" of Real Estate Taxes, Operating and Utility
     Costs: 2%.

H.   Security Deposit: $4,950.00 (2 months rent).

I.   Permitted Use: Installation and operation of telecommunications switching
     equipment and related office use. (No retail sales.)

J.   Maximum Tenant Improvement Allowance: None. Tenant to take Premises "as
     is" as described in Section 35.

K.   Tenant's Parking Allotment: None.

L.   Landlord's Brokers: None.

M.   Riders:

     The following exhibits, riders and addenda are attached to and are part of
this Lease:

          Exhibit A -- Floor Plan of Premises
          Exhibit B -- Rules and Regulations
          Emergency Generator Rider
          Parking Space Rider
          Telecommunications Conduit and Conduit Interconnection Room Rider

          -----------------------------------------------------------------

                                       2
<PAGE>   6
N. Guaranty: A personal guaranty of this Lease is being executed by ___________.

                                   AGREEMENT

      1.    PREMISES. Landlord hereby leases the Premises to Tenant and Tenant
herby hires and takes the Premises from Landlord. The Premises are located at
the address set forth in Section A(1) on page 1 and are more particularly shown
on Exhibit "A" attached hereto and incorporated herein by this reference. The
office building in which the premises are located is referred to herein as the
"Building."

      2.    TERM.

      2.1   The term of this Lease shall commence on the "Commencement Date"
indicated in Section D on page 1 and shall extend for the period set forth in
Section (1 on Page 1. In the event that Landlord, for any reason, cannot tender
possession of the Premises to Tenant on or before the "Estimated Commencement
Date" indicated in Section D on Page 1, this Lease shall not be void or
voidable, nor shall Landlord be liable to Tenant in any way as a result of such
failure to tender possession. In the event that Landlord cannot tender
possession of the Premises to the Tenant for any reason other than the acts or
omissions of Tenant, Tenant's obligation to pay rent hereunder shall be deferred
by a period of time equal to the delay in Landlord's delivery of possession not
caused by Tenant. If such inability to tender possession of the Premises for
reasons other than the acts or omissions of Tenant continues for a period in
excess of 90 days after the Estimated Commencement Date, Tenant shall have the
right, exercisable by notice to Landlord, to terminate this Lease, but the
suspension of rent obligations and the right of termination pursuant to this
Section 2.1 shall be Tenant's sole remedies in the circumstances herein
described.

      2.2   In the event that Tenant is allowed to enter into possession of the
Premises prior to the Commencement Date, such possession shall be deemed to be
pursuant to, and shall be governed by, the terms, covenants and conditions of
this Lease, including without limitation the covenant to pay rent, as though the
Commencement Date occurred upon the date of taking of possession by Tenant.

      2.3   In the event that the Commencement Date falls on other than the
first day of a month, rent for any initial partial month of the term hereof
shall be appropriately prorated; and if the date of commencement of tenant's
rent obligations is delayed, pursuant to Section 2.1, the end of the term hereof
shall be correspondingly delayed. At the request of either party hereto, both
parties shall execute a memorandum confirming the date of commencement of
Tenant's rent obligations.

      3.    RENT. Beginning on the Commencement Date (subject to adjustment
pursuant to Section 2.1 above), the base rent ("Base Rent") for the Premises
shall be in accordance with the Schedule of Monthly Base Rents set forth in
Section E on Page 2. Each installment of Base Rent shall be payable in advance
on the first day of each and every month throughout the term of this Lease.
Tenant agrees to pay all rent, without offset, demand or deduction of any kind,
to Landlord by mail to the address set forth in Section A(3) on page 1 or in
such manner, to such other person or at such other place as Landlord may from
time to time designate. Tenant agrees that no payment made to Landlord by check
or other instrument shall contain a restrictive endorsement of any kind, and if
any such instrument should contain a restrictive endorsement in violation of the
foregoing, that endorsement shall have no legal effect whatever, notwithstanding
that such item is processed for payment.

      4.    RENT ESCALATION.

      4.1   Tenant shall pay, as monthly rent hereunder, in addition to the Base
Rent, the sums provided in this Section 4. Tenant shall be advised of any
change, from time to time, in rent escalation payments required hereunder by
written notice from Landlord, which shall include information in such detail as
Landlord may reasonably determine to be necessary in support of such change.
Tenant shall have 30 days after the receipt of any such notice to protest the
change indicated therein, and Tenant's failure to make such protest in a written
notice to Landlord within such 30-day period shall be conclusively deemed to be
tenant's agreement to such changes. Notwithstanding any such protest all rent
escalation payments falling due after service of such notice shall be made in
accordance with such notice until the protest has been resolved, whereupon any
necessary adjustment shall be made between Landlord and Tenant. Any audit
arising out of such a protest by Tenant shall be done, at Tenant's expense in
accordance with generally accepted auditing and management standards by a major
public accounting firm selected by Tenant and approved by Landlord in its
reasonable discretion. Such audit shall be performed at the Quinby Building in
Los Angeles or at such other location in the United States as Landlord may
select from time to time for the maintenance of its accounting records for the
Building.

                                       3

<PAGE>   7

      4.2     Following the first December 31 during the term of the Lease,
Tenant shall pay Landlord in a single lump sum upon billing therefor. Tenant's
Percentage Share (as defined in Section G on Page 2 of the Lease) of each of the
following amounts (collectively, "Excess Expenses"): (1) the amount (if any) by
which Real Estate Taxes for the then current tax fiscal year exceed the Real
Estate Taxes for the Base Year for Real Estate Taxes set forth in Section F on
Page 2; (2) the amount (if any) by which Operating Costs for the just completed
calendar year exceed the Operating Costs for the Base Year for Operating Costs
set forth in Section F on Page 2; and (3) the amount (if any) by which Utility
Costs for the just completed calendar year exceed the Utility Costs for the Base
Year for Utility Costs set forth in Section F on Page 2. At the same time Tenant
shall also pay to Landlord one-twelfth of Tenant's Percentage Share of such
amounts for each month that has commenced since December 31, as estimated
payments towards Tenant's share of the Excess Expenses for the following year.
(If Landlord estimates in good faith that the Excess Expenses for the following
year will exceed the Excess Expenses for the just completed calendar year,
Landlord shall notify Tenant in writing of such estimate, and Tenant's new
monthly payment shall be one-twelfth of Tenant's monthly payment not more than
twice during any calendar year.) Following each succeeding December 31, Landlord
again shall determine in the same fashion the increase or decrease (if any) in
annual Real Estate Taxes, Operating Costs, and Utility Costs over or under those
for the previous year. If there is an increase in one or more of the three
categories, Tenant shall pay to Landlord in a single lump sum upon billing
Tenant's Percentage Share of the increase. Tenant shall pay Landlord at the same
time one-twelfth of Tenant's Percentage Share of such increase (or if Landlord
gives a written estimate as described above that Excess expenses will increase
in the new year, then one-twelfth of Landlord's new estimate of annual Excess
Expenses) for each month that has then commenced in the new calendar year. If
there is a decrease in one or more of the three categories, Landlord shall
refund to Tenant or, at Landlord's option, credit against the next rent falling
due under the Lease the amount of the overpayment made by Tenant during the
preceding calendar year, provided that the amount of such refund or credit shall
in no event exceed the total payments previously made by Tenant for such
calendar year toward Tenant's Percentage Share of excess charges for the
category in question. Thereafter, with each month's Base Rent until the next
adjustments hereunder, Tenant shall pay one-twelfth of Tenant's Percentage Share
of each of the following amounts: (I) the excess (if any) of annual Real Estate
Taxes (based on the then-current fiscal year) over the Base Year Real Estate
Taxes; (II) the excess (if any) of annual Operating Costs (based on the
preceding calendar year) over the Base Year Operating Costs; and (III) the
excess (if any) of annual Utility Costs (based on the preceding calendar year)
over Base Year Utility Costs. The Real Estate Taxes for any partial fiscal year
at the end of the Lease term and the Operating Costs and Utility Costs for any
partial calendar year at the end of the Lease term shall be appropriately
prorated.

      For purposes hereof, "Real Estate Taxes" shall include any form of
assessment, license fee, license tax, business license fee, commercial rental
tax, levy, penalty, charge, tax or similar imposition (other than net income,
inheritance or estate taxes), imposed by any authority having the direct or
indirect power to tax, including any city, county, state or federal government,
or any school, agricultural, lighting, drainage, flood control, public transit
or other special district thereof, as against any legal or equitable interest of
Landlord in the Premises or in the real property of which the Premises and the
Building are a part, including, but not limited to, the following:

      (i)   Any tax on Landlord's "right" to rent or "right" to other income
from the Premises or as against Landlord's business of leasing the Premises;

      (ii)  Any assessment, tax, fee levy or charge in substitution, partially
or totally, if any assessment, tax, fee, levy or charge previously included
within the definition of Real Estate Taxes, it being acknowledged by Tenant and
Landlord that Proposition 13 was adopted by the voters of the State of
California in the June, 1978 Election and that assessments, taxes, fee, levies
and charges may be imposed by governmental agencies for such services as fire
protection, street, sidewalk and road maintenance, refuse removal and for other
governmental services formerly provided without charge to property owners or
occupants. It is the intention of Tenant and Landlord that all such new and
increased assessments, taxes, fee, levies and changes be included within the
definition of "Real Property Taxes" for the purpose of this Lease;

      (iii) Any assessment, tax, fee levy or charge allocable to or measured by
the area of the Premises or the rent payable hereunder, including, without
limitation, any gross income tax or excise tax levied by the State, City or
Federal government, or any political subdivision thereof, with respect to the
receipt of such rent, or upon or with respect to the possession, leasing,
operating, management, alteration, repair, use or occupancy by Tenant of the
Premises, or any portion thereof;

      (iv)  Any assessment, tax, fee, levy or charge upon this transaction or
any document to which Tenant is a party, creating or transferring an interest or
an estate in the Premises;

      (v)   Any assessment, tax, fee, levy or charge by any governmental agency
related to any transportation

                                       4
<PAGE>   8
plan, fund or system instituted within the geographic area of which the
Building is a part; or

          (vi)      Reasonable legal and other professional fees, costs and
disbursements incurred in connection with proceedings to contest, determine or
reduce real property taxes.

     The definition of "Real Estate Taxes," including any additional tax the
nature of which was previously included within the definition of "Real Estate
Taxes," shall include any increases in such taxes, levies, charges or
assessments occasioned by increases in tax rates or increases in assessed
valuations, whether occurring by sale or otherwise.

     As used in this Lease, the term "Operating Costs" shall mean 107% of all
costs and expenses of management, operation, maintenance, overhaul, improvement
or repair of the Building, the common areas and the site, as determined by
standard accounting practices, including the following costs by way of
illustration but not limitation:

          (a)       Any and all assessments imposed with respect to the
Building, common areas, and/or the site on which the Building is located,
pursuant to any covenants, conditions and restrictions affecting the site,
common areas or Building;

          (b)       Any costs, levies or assessments resulting from statutes or
regulations promulgated by any governmental authority in connection with the use
or occupancy of the Building or the Premises;

          (c)       Costs of all insurance obtained by Landlord;

          (d)       Wages, salaries and other labor costs (including but not
limited to social security taxes, unemployment taxes, other payroll taxes and
governmental charges and the costs, if any, of providing disability,
hospitalization, medical welfare, pension, retirement or other employee
benefits, whether or not imposed by law) of employees, independent contractors
and other persons engaged in the management, operation, maintenance, overhaul,
improvement or repair of the Building;

          (e)       Building management office and storage rental;

          (f)       Management and administrative fees (which Tenant
acknowledges are presently 6% of accrued gross revenues of the Building and
which may be adjusted from time to time);

          (g)       Supplies, materials, equipment and tools;

          (h)       CostS of, and appropriate reserves for, repair, painting,
resurfacing, and maintenance of the Building, the common areas, the site and
the parking facilities, and their respective fixtures and equipment systems,
including but not limited to the elevators, the structural portions of the
Building, and the plumbing, heating, ventilation, air-conditioning, telephone
cable riser, and electrical systems installed or furnished by Landlord;

          (i)       Depreciation on a straight-line basis and rental of
personal property used in maintenance;

          (j)       Amortization on a straight-line basis over the useful life
(together with interest at the interest rate defined in Subsection 33.9 of this
Lease on the unamortized balance) of all costs of a capital nature (including,
without limitation, capital improvements, capital replacements, capital
repairs, capital equipment and capital tools):

                    (1)  reasonably intended to produce a reduction in
Operating Costs, Utility Costs or energy consumption; or

                    (2)  required under any governmental or quasi-governmental
law, rule, order, ordinance or regulation that was not applicable to the
Building at the time it was originally constructed; or

                    (3)  for repair or replacement of any Building equipment
needed to operate the Building at the same quality levels as prior to the
replacement;

          (k)  Costs and expenses of gardening and landscaping;

          (l)  Maintenance of signs (other than signs of tenants of the
Building);

          (m)  Personal property taxes levied on or attributable to personal
property used in connection with the

                                       5
<PAGE>   9
Building, the common areas, or the site;

          (n)       Costs of all service contracts pertaining to the Premises,
the Building or the site;

          (o)       Reasonable accounting, audit, verification, legal and other
consulting fees;

          (p)       Costs and expenses of lighting, janitorial service,
cleaning, refuse removal, security and similar items, including appropriate
reserves;

          (q)       Any costs incurred with respect to a transportation systems
manager, rider share coordinator or any private transportation system
established for the benefit of tenants in the Building, whether or not imposed
by any governmental authority; and

          (r)       Fees imposed by any federal, state or local government for
fire and police protection, trash removal or other similar services which do
not constitute Real Estate Taxes.

     The following shall be excluded from Operating Costs: federal and state
income taxes imposed on Landlord's net income; any and all costs or expenses to
procure tenants for the Building, including but not limited to brokerage
commissions, legal fees, and costs of remodeling suites; costs of asbestos
removal work excluded from Operating Costs by Section 32.4 below; mortgage or
debt service; and depreciation, except that amortization of improvements of the
type specified in Subsection (j) above shall in no event be considered
"depreciation."

     For purposes hereof, "Utility Costs" shall include 107% of all charges,
surcharges and other costs of all utilities paid for by Landlord in connection
with the Premises and/or Building, including without limitation costs of
heating, ventilation and air conditioning for the Premises and/or Building,
costs of furnishing gas, electricity and other fuels or power sources to the
Premises and/or Building, and costs of furnishing water and sewer services to
the Premises and/or Building.

     The term "Building" as used in this Section 4.2 shall be deemed to include
not only the Building but also any parking facility owned, leased or operated
by Landlord in order to meet the parking requirements of the Building.

     If the average occupancy of the rentable area of the Building during the
Tenant's Base Year for Operating and Utility Costs as set forth in Section F on
page 2 or during any other calendar year of the Lease term is less than 90% of
the total rentable area of the Building, the Operating Costs and Utility Costs
shall be adjusted by Landlord for such Base Year or other calendar year, prior
to the pass-through of Operating Costs and Utility Costs to Tenant pursuant to
this Section 4.2, to reflect what they would have been had 90% of the rentable
area been occupied during that year. In making such calculation, the Landlord's
reasonable opinion of what portion, if any, of each cost was affected by
changes in occupancy shall be binding upon the parties.

     5.   TAX ON TENANT'S PROPERTY: OTHER TAXES.

     5.1  Tenant shall be liable for, and shall pay at least 10 days before
delinquency, and Tenant hereby indemnifies and holds Landlord harmless from and
against any liability in connection with, all taxes levied directly or
indirectly against any personal property, fixtures, machinery, equipment,
apparatus, systems and appurtenances placed by Tenant in or about, or utilized
by Tenant at, upon or in connection with, the Premises ("Equipment Taxes"). If
any Equipment Taxes are levied against Landlord or Landlord's property or if the
assessed value of Landlord's property is increased by the inclusion therein of a
value placed upon such personal property, fixtures, machinery, equipment,
apparatus, systems or appurtenances of Tenant, and if Landlord, after written
notice to Tenant, pays the Equipment Taxes or taxes based upon such an increased
assessment (which Landlord shall have the right to do regardless of the validity
of such levy, but only under proper protest if requested by Tenant prior to such
payment and if payment under protest is permissible), Tenant shall pay to
Landlord upon demand, as additional rent hereunder, the taxes so levied against
Landlord or the proportion of such taxes resulting from such increase in the
assessment; provided, however, that in any such event Tenant shall have the
right, in the name of Landlord and with Landlord's full cooperation, but at no
cost to Landlord, to bring suit in any court of competent jurisdiction to
recover the amount of any such tax so paid under protest, and any amount so
recovered shall belong to Tenant.

     5.2  If the tenant improvements in the Premises, whether installed and/or
paid for by Landlord or Tenant and whether or not affixed to the real property
so as to become a part thereof, are assessed for real property tax purposes at
a valuation higher than the valuation at which tenant improvements conforming
to Landlord's building standards in other space in the Building are assessed,
then the real property taxes and assessments levied against Landlord or
Landlord's property by

                                       6
<PAGE>   10
reason of such excess assessed valuation shall be deemed to be Equipment Taxes
and shall be governed by the provisions of Section 5.1. Any such amounts, and
any similar amounts attributable to excess improvements by other tenants of the
Building and recovered by Landlord from such other tenants under comparable
lease provisions, shall not be included in Real Estate Taxes for purposes of
rent escalation under Section 4 of this Lease.

     5.3  Tenant shall pay, as additional rent hereunder, upon demand and in
such manner and at such times as Landlord shall direct from time to time by
written notice to Tenant, any excise, sales, privilege or other tax, assessment
or other charge (other than income or franchise taxes) imposed, assessed or
levied by any governmental or quasi-governmental authority or agency upon
Landlord on account of this Lease, the rent or other payments made by Tenant
hereunder, any other benefit received by Landlord hereunder, Landlord's
business as a lessor hereunder, or otherwise in respect of or as a result of
the agreement or relationship of Landlord and Tenant hereunder.

     6.   SECURITY DEPOSIT. A deposit (the "Security Deposit") in the amount
set forth in Section H on page 2 shall be paid by Tenant upon execution of this
Lease and shall be held by Landlord without liability for interest and as
security for the performance by Tenant of Tenant's covenants and obligations
under this Lease, it being expressly understood that the Security Deposit shall
not be considered an advance payment of rent or a measure of Landlord's damages
in case of default by Tenant. Upon the occurrence of any breach or default under
this Lease by Tenant, Landlord may, from time to time, without prejudice to any
other remedy, use the Security Deposit or any portion thereof to the extent
necessary to make good any arrearages of rent or any other damage, injury,
expense, or liability caused to Landlord by such breach or default. Following
any application of the Security Deposit, Tenant shall pay to Landlord on demand
an amount to restore the Security Deposit to its original amount. In the event
of bankruptcy or other debtor relief proceedings by or against Tenant, the
Security Deposit shall be deemed to be applied first to the payment of rent and
other charges due Landlord, in the order that such rent or charges became due
and owing, for all periods prior to filing of such proceedings. Landlord shall
not be required to keep the Security Deposit separate from its general funds.
Upon termination of this Lease any remaining balance of the Security Deposit
shall be returned by Landlord to Tenant within 14 days after termination of
Tenant's tenancy.

     7.   LATE PAYMENTS. All covenants and agreements to be performed by Tenant
under any of the terms of this Lease shall be performed by Tenant at Tenant's
sole cost and expense and without any abatement of rent. Tenant acknowledges
that the late payment by Tenant to Landlord of any sums due under this Lease
will cause Landlord to incur costs not contemplated by this Lease, the exact
amount of such cost being extremely difficult and impractical to fix. Such
costs include, without limitation, processing and accounting charges, and late
charges that may be imposed on Landlord by the terms of any note or other
obligation secured by any encumbrance covering the Premises or the Building of
which the Premises are a part. Therefore, if any monthly installment of rent is
not received by Landlord by the date when due, or if Tenant fails to pay any
other sum of money due hereunder, Tenant shall pay to Landlord, as additional
rent, the sum of ten percent (10%) of the overdue amount as a late charge.
Landlord's acceptance of any late charge, or interest pursuant to Section 33.9,
shall not be deemed to be liquidated damages, nor constitute a waiver of
Tenant's default with respect to the overdue amount, nor prevent Landlord from
exercising any of the other rights and remedies available to Landlord under
this Lease or any law now or hereafter in effect. Further, in the event such
late charge is imposed by Landlord for 2 consecutive months for whatever
reason, Landlord shall have the option to require that, beginning with the
first payment of rent due following the imposition of the second consecutive
late charge, rent shall no longer be paid in monthly installments but shall be
payable 3 months in advance.

     8.   USE OF PREMISES. Tenant, and any permitted subtenant or assignee,
shall use the Premises only for the use described in Section 1 on page 2. Any
other use of the Premises is absolutely prohibited. Tenant shall not use or
occupy the Premises in violation of any recorded covenants, conditions and
restrictions affecting the land on which the Building is located nor of any
law, ordinance, rule and regulation. Tenant shall not do or permit to be done
anything which will invalidate or increase the cost of any fire, extended
coverage or any other insurance policy covering the Building or property
located therein and shall comply with all rules, orders, regulations and
requirements of any applicable fire rating bureau or other organization
performing a similar function. Tenant shall promptly upon demand reimburse
Landlord an additional rent for 107% of any additional premium charged for any
insurance policy by reason of Tenant's failure to comply with the provisions of
this Section 8. Tenant shall not do or permit anything to be done in or about
the Premises which will in any way obstruct or interfere with the rights of
other tenants or occupants of the Building, or injure or annoy them, or use or
allow the Premises to be used for any improper, immoral, unlawful or
objectionable purpose, nor shall Tenant cause, maintain or permit any nuisance
in, on or about the Premises. Tenant shall not commit or suffer to be committed
any waste in or upon the Premises and shall keep the Premises in first class
repair and appearance. Tenant shall not place a load upon the Premises
exceeding the average pounds of live load per square foot of floor area
specified for the Building by Landlord's architect, with any partitions to be
considered a part of the live load. Landlord reserves the right to prescribe
the weight and position of all safes, files and heavy equipment which Tenant
desires to place in the Premises so as to distribute properly the weight
thereof. Tenant's business machines and mechanical equipment which cause
vibration or noise that may be transmitted to the Building structure or to any
other space

                                       7
<PAGE>   11

in the Building shall be so installed, maintained and used by Tenant as to
eliminate such vibration or noise. Tenant shall be responsible for the cost of
all structural engineering required to determine structural load. In any event,
unless specifically authorized herein, Tenant shall not prepare or serve, or
authorize the preparation or service of, food or beverages in the Premises,
except only the occasional preparation of coffee, tea, hot chocolate and other
such common refreshments for Tenant and its employees. Tenant shall not conduct
any auction in or about the Premises or the Building without Landlord's prior
written consent.

        9.    BUILDING SERVICES.

        9.1    Throughout the term of this Lease, subject to shortage and
accidents beyond Landlord's reasonable control, and subject to reimbursement
pursuant to Section 4.2, Landlord shall repair and maintain all structural
elements of the Building and common areas (including, without limitation, the
structural walls, doors, floors, ceilings, roof, elevators, stairwells, lobby,
heating system, air conditioning system, telephone cable riser for
Building-standard service from the Building's main terminal to the terminal box
on the same floor as the Premises [but excluding Tenant's telephone equipment
and the cable and wiring from such equipment to the terminal box, and any of
Tenant's Telecommunication equipment used to provide Telecommunication services
to any customer of Tenant], plumbing and electrical wiring) and maintain the
exterior of the Premises, including grounds, walks, drives and loading area, if
any. Tenant shall reimburse Landlord upon demand, as additional rent hereunder,
107% of the cost of any repairs or extraordinary maintenance necessitated by
acts of Tenant or Tenant's employees, contractors, agents, licensees or
invitees.

        9.2    Provided that Tenant is not in default hereunder, subject to
shortages and accidents beyond Landlord's reasonable control, Landlord shall
furnish building standard heating and air conditioning service Monday through
Friday from 8:00 A.M. to 6:00 P.M., and Saturday from 8:00 A.M. to 1:00 P.M.,
except for holidays. No heating or air conditioning will be furnished by
Landlord on Sundays, holidays or during hours other than as set forth above,
except upon prior arrangement with Tenant and at an extra charge as may be
agreed to between Landlord and Tenant. For purposes of this Section 9.2,
"holidays" shall mean and refer to the holidays of Christmas, New Year's Day,
Martin Luther King Day, President's Day, Memorial Day, the Fourth of July, Labor
Day, Thanksgiving and the day after Thanksgiving, as those holidays are defined,
recognized or established by governmental authorities or agencies from time to
time and such other days the New York Stock Exchange is closed. Tenant shall
install, at its expense, such additional air conditioning equipment as may be
reasonably determined by Landlord to be necessary in order to maintain building
air conditioning standards resulting from Tenant's installation and operation of
computer equipment or other special equipment or facilities placing a greater
burden on the air conditioning system than would general office use. Without
limiting the foregoing, Tenant shall have the right to install in the Premises
its own self-contained 24-hour heating, ventilating and air-conditioning unit,
subject to compliance with the other provisions of this Lease, including but not
limited to obtaining Landlord's prior written consent to the plans and
specifications for the work and electrical requirements of the unit. Tenant's
right to install such unit is also subject to Landlord's prior approval of the
location for exhaust to be vented from the Building. Tenant shall pay all costs
of electricity for such unit and, at Landlord's election, the electrical
requirements for such unit shall be separately metered to Tenant at Tenant's
expense.

        Landlord shall furnish electric current to the Premises in amounts
reasonably sufficient for normal business use, including operation of building
standard lighting and operation of typewriters and standard fractional
horsepower office machinery, as well as electric current reasonably sufficient
as determined by Landlord in its reasonable discretion, for normal
telecommunications operations and machinery, all subject to the obligations of
Tenant for payment of the costs of such electricity as provided herein. Tenant
agrees that, at all times during the term of this Lease, Tenant's use of
electric current shall never exceed the capacity of the feeders to the Building
or the risers or wiring installation in the Building.

        Landlord may, at its election, separately meter at Tenant's expense the
electrical usage of some or all of Tenant's equipment, facilities or Premises.
Tenant shall pay the charges for all such separately metered electrical usage
within 15 days after receipt of a billing therefor.

        Except as provided above, Tenant shall not install or use or permit the
installation or use upon or about the Premises of any computer or electronic
data processing or other equipment requiring in excess of 120 volts or requiring
power in excess of 1800 watts, without the express prior written consent of
Landlord. Such consent shall not be unreasonably withheld, conditioned or
delayed. Landlord shall not use its approval rights to arbitrarily or
discriminatorily prevent Tenant's installation of and use of equipment
customarily used in a telecommunications business, but Landlord may impose
reasonable conditions on such installation and use, regarding such matters as
the placement, venting, power sources, and structural requirements for such
equipment.

        Tenant shall pay monthly upon billing as additional rent under this
Lease such sums as Landlord's building engineer

                                       8

<PAGE>   12
may reasonably determine to be necessary in order to reimburse Landlord for the
additional cost of any utilities which have not been separately metered to
Tenant (including, without limitation, electricity, gas and other fuels or
power sources, and water, and Landlord's reasonable costs of administration,
which costs of administration shall not exceed 10% of the other costs)
attributable to any requirements in excess of those for normal office use by
reason of the operation of computer or telecommunications equipment or other
special equipment or facilities, or attributable to Tenant's conducting
business beyond the business hours described in the first sentence of this
Section 9.2.

     Any utility charges billed directly to Tenant shall not be included in the
Building's "Utility Costs" for purposes of Section 4 above. Any extra
maintenance charges or service calls attributable to the actions of Tenant
(e.g., continual adjustments of the thermostats or the failure to keep window
coverings closed as necessary) shall be payable by Tenant to Landlord upon
demand, as additional rent hereunder.

     9.3  Landlord shall furnish unheated water from mains for drinking,
lavatory and toilet purposes drawn through fixtures installed by Landlord, or
by Tenant with Landlord's express prior written consent, and heated water for
lavatory purposes from regular building supply in such quantities as required
in Landlord's judgment for the comfortable and normal use of the Premises.
Tenant shall pay Landlord for additional water which is furnished for any other
purpose. The amount that Tenant shall pay Landlord for such additional water
shall be the average price per gallon charged to the Landlord for the Building
by the entity providing water, increased 10% to cover Landlord's administrative
expense.

     9.4  Landlord shall furnish janitor service (including washing of windows
with reasonable frequency as determined by Landlord) in and about the Premises,
to the extent necessitated by normal office use of the Premises, Monday through
Friday, holidays excepted. Landlord shall have no obligation to furnish janitor
service for any portion of the Premises which is occupied after 7:00 p.m., is
locked or may be used (to the extent permitted under this Lease) for the
preparation, dispensing or consumption of food or beverages or for any purpose
other than general office use, and Tenant shall keep all such portions of the
Premises in a clean and orderly condition at Tenant's sole cost and expense. In
the event that Tenant shall fail to keep such portions of the Premises in a
clean and orderly condition, Landlord may do so and any costs incurred by
Landlord in connection therewith shall be payable by Tenant to Landlord upon
demand, as additional rent hereunder. Tenant shall also pay to Landlord, as
additional rent hereunder, amounts equal to 107% of any increase in cost of
janitor service in and about the Premises if such increase in costs is due to
(a) use of the Premises by Tenant during hours other than normal business hours,
or (b) location in or about the Premises of any fixtures, improvements,
materials or finish items (including without limitation wall coverings and
floor coverings) other than those which are of the standard type adopted by
Landlord for the Building. Only those persons who have been approved by
Landlord may perform janitorial services.

     9.5  Landlord shall furnish passenger and freight elevator service in
common with Landlord and other tenants Monday through Friday from 8:00 A.M. to
6:00 P.M. and Saturday from 8:00 A.M. to 1:00 P.M. Landlord shall provide
limited passenger elevator service daily at all times such normal passenger
service is not furnished.

     9.6  Landlord does not warrant that any service will be free from
interruptions caused by repairs, renewals, improvements, changes of service,
alterations, strikes, lockouts, labor controversies, accidents, inability to
obtain fuel, steam, water or supplies or other cause. Landlord agrees to give
Tenant notice of any extended interruptions of which Landlord has prior
knowledge. No interruption of service shall be deemed an eviction or disturbance
of Tenant's use and possession of the Premises or any part thereof, nor relieve
Tenant from payment of rent or performance of Tenant's other obligations under
this Lease except as provided below in this Section 9.6. Landlord shall not be
responsible for correcting any such interruption in service which is not curable
by Landlord on a commercially reasonable basis, as determined by Landlord in its
sole discretion. Subject to Section 11 below, and subject to Landlord's rights
to recover certain costs under other provisions of this Lease. If Landlord
determines that such interruption in service is curable on such a commercially
reasonable basis, Landlord shall make good faith efforts to so correct the
interruption within a reasonable time after Landlord receives written notice
from Tenant of the interruption in service. In doing such work Landlord shall
use commercially reasonable, good faith efforts to interfere as little as
reasonably practicable with the conduct of Tenant's business in the Premises,
without, however, being obligated to incur liability for overtime or other
premium payment to its agents, employees or contractors in connection therewith.
Landlord shall in no event be liable for any injury to or interference with
Tenant's business or any punitive, incidental or consequential damages, whether
foreseeable or not, arising from the making of or failure to make any repairs,
alterations or improvements, or provision of or failure to provide or restore
any service in or to any portion of the Building, including the Premises, or the
fixtures, appurtenances and equipment therein. However, if Tenant's beneficial
use of all or a substantial portion of the Premises is prevented for a period in
excess of 5 consecutive business days (excluding Saturdays, Sundays, and
holidays) due to interruptions in service, the Base Rent shall be equitably
abated commencing with the sixth business day and continuing until such use is
no longer prevented. Moreover, if Tenant's beneficial use of all or substantial
portion of the Premises is prevented by such an interruption in services, Tenant
shall have the right to terminate the Lease in the manner and subject to the
time

                                       9

<PAGE>   13
limitations set forth in more detail in Section 11.1 below. Such abatement and
such right of termination, to the extent provided above, shall be Tenant's sole
remedies. Except as provided above, Tenant shall not be entitled to any
abatement or reduction of rent or other remedy by reason of Landlord's failure
to furnish any of the services or Building systems called for by this Lease
whether such failure is caused by accident, breakage, repairs, strikes,
lockouts or other labor disturbances or labor disputes of any character, or any
other cause. As a material inducement to Landlord's entry into this Lease,
Tenant waives and releases any rights it may have to make repairs at Landlord's
expense under Sections 1941 and 1942 of the California Civil Code.

     10.  CONDITION OF PREMISES. By occupying the Premises, Tenant shall be
deemed to accept the same and acknowledge that they comply fully with
Landlord's covenants and obligations hereunder, subject to completion of any
items which it is Landlord's responsibility hereunder to furnish and which are
listed by Landlord and Tenant upon inspection of the Premises prior to the
Commencement Date. Tenant acknowledges that neither Landlord nor any agent,
employee or representative of Landlord has made any representation or warranty
with respect to any matter, including but not limited to any matter regarding
the Building or Premises, the applicable zoning or the effect of other
applicable laws, or the suitability or fitness of the Building or Premises for
the conduct of Tenant's business or any other purpose. Tenant is relying solely
on its own investigations with respect to all such matters. During the term of
this Lease, Tenant shall maintain the Premises in as good condition as when
Tenant took possession, ordinary wear and tear and repairs which are
specifically made the responsibility of Landlord hereunder excepted, and shall
repair all damage or injury to the Building or to fixtures, appurtenances and
equipment of the Building caused by Tenant's installation or removal of its
property or resulting from the negligence or tortious conduct of Tenant, its
employees, contractors, agents, licensees and invitees. In the event of failure
by Tenant to perform its covenants of maintenance and repair hereunder,
Landlord may perform such maintenance and repair, and 107% of any amounts
expended by Landlord in connection therewith shall be payable by Tenant to
Landlord upon demand, as additional rent hereunder.

     11.  DAMAGE TO PREMISES OR BUILDING.

     11.1 In the event that the Building should be totally destroyed by fire or
other casualty, this Lease shall terminate as of the date of such casualty. If
the Building is damaged but not totally destroyed by the casualty or if there
is an interruption in services or utilities provided by Landlord pursuant to
Section 9.6 of this Lease, and if such damage or interruption in services or
utilities prevents Tenant's beneficial use of all or a substantial portion of
the Premises, then Landlord shall notify Tenant in writing, within 45 days
after the date Tenant's beneficial use is so prevented, of whether Landlord
intends to restore the Building or the services or utilities in question and of
how long, in Landlord's opinion, the restoration will take to complete. In the
event that the repairs and restoration can, in Landlord's reasonable opinion,
be completed within 270 days after the date Tenant's beneficial use is so
prevented, and Landlord will receive insurance proceeds sufficient to cover the
costs of such repairs and restoration, Landlord shall restore the Building or
the services or utilities in question. In the event the Premises or a
substantial portion of the Building or the delivery system for Building
services or utilities should be so damaged or destroyed that restoration or
repairs cannot, in Landlord's opinion, be completed within 270 days after the
date Tenant's beneficial use is so prevented, or Landlord will not receive
insurance proceeds sufficient to cover the costs of such repairs and
restoration, Landlord may at its option terminate this Lease upon notice to
Tenant, or Landlord may elect to proceed to restore the Building. Similarly, in
the event Landlord's notice notifies Tenant that the restoration in Landlord's
opinion will not be completed within 270 days after the date Tenant's
beneficial use is so prevented, Tenant shall have twenty (20) days from the
date of Tenant's receipt of Landlord's notice to elect to terminate this Lease
by delivering written notice of such termination to Landlord. If either
Landlord or Tenant terminates this Lease as provided above, such termination
shall be effective immediately upon the other party's receipt of the notice of
termination, and Tenant shall be entitled to an abatement of the Base Rent as
provided below as of the date 5 business days after Tenant's beneficial use of
the Premises was first prevented. In the event that Landlord is obligated or
elects to restore the Building or the services or utilities in question,
Landlord shall commence such work reasonably promptly and shall proceed with
reasonable diligence to restore the Building or the services or utilities to
substantially the condition in which they were immediately prior to the
casualty, except that Landlord shall not be required to rebuild, repair or
replace any part of the partitions, fixtures, alterations, decorations or other
improvements which may have been constructed by or specifically for Tenant, or
by or for other tenants within the Building.

     If neither Landlord nor Tenant terminates this Lease due to the casualty,
the Lease shall remain in full force and effect. However, if Tenant is
dispossessed by reason of such casualty from all or a substantial portion of
the Premises for more than 5 consecutive business days, Tenant shall be
entitled to a ratable abatement of the Base Rent during the time and to the
extent the Premises are unfit for occupancy, commencing with the sixth business
day. After Landlord completes Landlord's restoration work on the Premises
(i.e., any necessary repair work on the Building shell and the Building systems
originally provided by Landlord in the core of the Building), Tenant shall
diligently complete Tenant's repairs to its tenant improvements. If Tenant is
unable to conduct its business in all or a substantial portion of the Premises
during Tenant's repairs, then Tenant's ratable rental abatement shall continue
during such repairs, but in no event for more than 90 days after Landlord
completes Landlord's

                                       10
<PAGE>   14
restoration work. The parties shall cooperate in performing their respective
repairs simultaneously if, in Landlord's reasonable opinion, that is feasible
and appropriate. Tenant shall have the right to terminate this Lease upon notice
served upon Landlord prior to actual completion of Landlord's restoration work
on the Premises if such restoration work is not substantially completed within
365 days after the date Tenant's beneficial use is first prevented (provided,
however, that if Landlord's original notice to Tenant estimated that the
restoration work would take more than 270 days after the date Tenant's
beneficial use is so prevented, and Tenant did not elect to terminate the Lease
on that basis, then Tenant shall not be entitled to terminate the Lease pursuant
to this sentence unless Landlord fails to substantially complete such
restoration work at least within 95 days after the estimated restoration period
given in Landlord's original notice). For purposes of this Section, "substantial
completion" of Landlord's work shall mean completion to such a degree that
Tenant can commence in the Premises or the damaged portion thereof its own
reconstruction of tenant improvements as contemplated by this Lease.
"Substantial completion" shall not require full completion of all "punch list"
type items which do not materially affect Tenant's use of the Premises. Rental
abatement or lease termination, to the extent provided above, shall be Tenant's
sole remedies. Notwithstanding the foregoing to the contrary, if the damage is
due to the negligence or willful misconduct of Tenant or any of Tenant's agents,
employees or invitees, there shall be no abatement of rent. Except for abatement
of rent as provided above, Tenant shall not be entitled to any compensation or
damages for loss of, or interference with, Tenant's business or use or access of
all or any part of the Premises resulting from any such damage, repair,
reconstruction or restoration.

     11.2  In the event of any damage or destruction of all or any part of the
Premises or any interruption in utilities or services, Tenant shall immediately
notify Landlord thereof.

     11.3  In the event any holder of a mortgage or deed of trust on the
Building should require that the insurance proceeds payable upon damage or
destruction to the Building by fire or other casualty be used to retire the debt
secured by such mortgage or deed of trust, or in the event any lessor under any
underlying or ground lease should require that such proceeds be paid to such
lessor, Landlord shall in no event have any obligation to rebuild, and at
Landlord's election this Lease shall terminate.

     11.4  With the exception of insurance required to be carried by Tenant
under Section 28 of this Lease, any insurance which may be carried by Landlord
or Tenant against loss or damage to the Building or to the Premises shall be for
the sole benefit of the party carrying such insurance and under its sole
control. Landlord shall not be required to carry insurance of any kind on
Tenant's property and, except by reason of the breach by Landlord of any of its
obligations hereunder, shall no be obligated to repair any damage thereto or to
replace the same.

     11.5  In addition to its termination rights in Subsection 11.1 above,
Landlord shall have the right to terminate this Lease if any damage to the
Building or Premises occurs during the last 12 months of the Term of this Lease
and Landlord estimates that the repair, reconstruction or restoration of such
damage cannot be completed within the earlier of (a) the scheduled expiration
date of the Lease Term, or (b) 60 days after the date of such casualty.

     11.6  Tenant, as a material inducement to Landlord's entering into this
Lease, irrevocably waives and releases its rights under the provisions of
Sections 1932(2) an 1933(4) of the California Civil Code (and any successor
statutes permitting Tenant to terminate this Lease as a result of any damage or
destruction), it being the intention of the parties hereto that the express
terms of this Lease shall control under any circumstances in which those
provisions might otherwise apply.

     12.   EMINENT DOMAIN.

     12.1  In the event that the whole of the Premises, or so much thereof as to
render the balance unusable to Tenant for the purposes leased hereunder, as
reasonably determined by Landlord, shall be lawfully condemned or taken in any
manner for any public or quasi-public use, or conveyed by Landlord in lieu
thereof (a "Taking"), this Lease and the term hereby granted shall forthwith
cease and terminate on the date of the taking of possession by the condemning
authority (the "Date of Taking").

     12.2  In the event of a Taking of a portion of the Premises which does not
result in the termination of this Lease pursuant to Section 12.1, above, the
Base Rent shall be abated in proportion to the part of the Premises so taken and
thereby rendered unusable to Tenant for the purposes leased hereunder, as
reasonable determined by Landlord.

     12.3  In the event that there is a Taking of a portion of the Building
other than the Premises, and if, in the opinion of Landlord, the Taking is so
substantial as to render the remainder of the Building uneconomic to maintain
despite reasonable reconstruction or remodeling, or if it would be necessary to
alter the Building or Premises materially, Landlord may terminate this Lease by
notifying Tenant of such termination within 60 days following the Date of
Taking, and this Lease shall end up on the date specified in the notice of
termination, which shall not be less than 60 days after the giving of such
notice.

                                       11
<PAGE>   15
     12.4 No temporary Taking of the Building or Premises and/or of Tenant's
rights therein or under this Lease shall terminate this Lease or give Tenant
any right to abatement of rent hereunder. Tenant shall be entitled to receive
such portion of any award as is specifically made for such a temporary use with
respect to the period of the Taking which is within the term of this Lease,
provided that the Taking renders the Premises unusable to Tenant for the
purposes leased hereunder, as reasonably determined by Landlord. If such Taking
shall remain in force at the expiration or earlier termination of this Lease,
then Tenant shall pay to Landlord a sum equal to the reasonable costs of
performing Tenant's obligations under Section 15 with respect to Tenant's
surrender of the Premises and, upon such payment, shall be excused from such
obligations. For purposes of this Section 12.4, a temporary Taking shall be
defined as a Taking for a period of 270 days or less.

     12.5 Except for the award in the event of a temporary Taking as
contemplated in Section 12.4, above, Tenant hereby releases and shall have no
interest in, or right to participate with respect to the determination of, any
compensation for any Taking, except only that Tenant shall be entitled to the
portion of any award specifically designated by the condemning authority to be
for any personal property of Tenant included in any such Taking or for any
relocation expenses or business interruption loss incurred by Tenant.

     13.  DEFAULT.

     13.1 The following events shall be deemed to be events of default by
Tenant under this Lease:

          (a)  If Tenant shall fail to pay any installment of rent or any other
sum required to be paid by Tenant under this Lease as due.

          (b)  If Tenant shall fail to comply with any term, provision or
covenant of this Lease, other than provisions pertaining to the payment of
money.

          (c)  If Tenant shall make an assignment for the benefit of creditors.

          (d)  If Tenant shall file a petition under any section or chapter of
the federal Bankruptcy Code, as amended from time to time, or under any similar
law or statute of the United States or any State thereof pertaining to
bankruptcy, insolvency or debtor relief, or Tenant shall have a petition or
other proceedings filed against Tenant under any such law or chapter thereof
and such petition or proceeding shall not be vacated or set aside within 60
days after such filing.

          (e)  If a receiver or trustee shall be appointed for all or
substantially all of the assets of Tenant and such receivership shall not be
terminated and possession of such assets restored to Tenant within 30 days
after such appointment.

          (f)  If Tenant shall desert or vacate any substantial portion of the
Premises and the same shall remain unoccupied for more than 14 days thereafter.

          (g)  If Tenant shall assign this Lease or sublet the Premises in
violation of the terms hereof.

     13.2 Any shorter period for cure provided by law notwithstanding, and in
lieu thereof, including without limitation California Code of Civil Procedure
Section 1161, Tenant may cure any monetary default under Subsection 13.1(a),
above, at any time within 5 days after written notice of default is received by
Tenant from Landlord; and (except as specifically provided otherwise in Section
24) Tenant may cure any non-monetary default within 15 days after written
notice of default is received by Tenant from Landlord, provided that if such
non-monetary default is curable but is of such a nature that the cure cannot be
completed within 15 days, Tenant shall be allowed to cure the default if Tenant
promptly commences the cure upon receipt of the notice and diligently
prosecutes the same to completion, which completion shall occur not later than
60 days from the date of such notice from Landlord.

     14.  REMEDIES UPON DEFAULT.

     14.1 Upon the occurrence of any event of default by Tenant, Landlord shall
have, in addition to any other remedies available to Landlord at law or in
equity, the option to pursue any one or more of the following remedies (each
and all of which shall be cumulative and non-exclusive) without any notice or
demand whatsoever:

          (a)  Terminate this Lease, in which event Tenant shall immediately
surrender the Premises to Landlord, and if Tenant fails to do so, Landlord may,
without prejudice to any other remedy which it may have for possession or
arrearages in rent, enter upon and take possession of the Premises and expel or
remove Tenant and any other person who may

                                       12
<PAGE>   16
be occupying the Premises or any part thereof, without being liable for
prosecution or any claim or damages therefor; and Landlord may recover from
Tenant the following:

               (1)  The worth at the time of award of any unpaid rent which has
been earned at the time of such termination; plus

               (2)  The worth at the time of award of the amount by which the
unpaid rent which would have been earned after termination until the time of
award exceeds the amount of such rental loss that Tenant proves could have been
reasonably avoided; plus

               (3)  The worth at the time of award of the amount by which the
unpaid rent for the balance of the term after the time of award exceeds the
amount of such rental loss that Tenant proves could have been reasonably
avoided; plus

               (4)  Any other amount necessary to compensate Landlord for all
the detriment proximately caused by Tenant's failure to perform its obligations
under this Lease or which in the ordinary course of things would be likely to
result therefrom, specifically including but not limited to attorneys' fees,
removal and storage (or disposal) of Tenant's personal property, unreimbursed
leasehold improvement costs (e.g., the amounts Landlord has expended for
leasehold improvements which have not been recovered as of the termination of
the Lease when amortized on a straight-line basis over the originally scheduled
lease term), brokerage commissions and advertising expenses incurred, expenses
of remodeling the Premises or any portion thereof for a new tenant, whether for
the same or a different use, and any special concessions made to obtain a new
tenant; and

               (5)  At Landlord's election, such other amounts in addition to or
in lieu of the foregoing as may be permitted from time to time by applicable
law.

The term "rent" as used in this Subsection 14.1(a) shall be deemed to be and to
mean all sums of every nature required to be paid by Tenant pursuant to the
terms of this Lease, whether to Landlord or to others. Any such sums which are
based on percentages of income, increased costs or other historical data shall
be reasonable estimates or projections computed by Landlord on the basis of the
amounts thereof accruing during the 24-month period immediately prior to
default, except that if it becomes necessary to compute such sums before a
24-month period has expired, then the computation shall be made on the basis of
the amounts accruing during such shorter period. As used in Subsections
14.1(a)(1) and (2), above, the "worth at the time of award" shall be computed by
allowing interest from the date the sums became due at the lesser of (i) the
Bank of America prime rate on the due date plus 6%, or (ii) the maximum rate
permitted by law. As used in Subsection 14.1(a)(3), above, the "worth at the
time of award" shall be computed by discounting such amount at the discount rate
of the Federal Reserve Bank of San Francisco at the time of award plus 1%.

          (b)  In the event of any such default by Tenant, in addition to any
other remedies available to Landlord under this Lease, at law or in equity,
Landlord shall also have the right, with or without terminating this Lease, to
re-enter the Premises and remove all persons and property from the Premises;
such property may be removed, stored and/or disposed of pursuant to any
procedures permitted by applicable law, including but not limited to those
described in Section 15.3. No re-entry or taking possession of the Premises by
Landlord pursuant to this Subsection 14.1(b), and no acceptance of surrender of
the Premises or other action on Landlord's part, shall be construed as an
election to terminate this Lease unless a written notice of such intention be
given to Tenant or unless the termination thereof be decreed by a court of
competent jurisdiction.

          (c)  In the event of any such default by Tenant, in addition to any
other remedies available to Landlord under this Lease, at law or in equity,
Landlord shall have the right to continue this Lease in full force and effect,
whether or not Tenant shall have abandoned the Premises. The foregoing remedy
shall also be available to Landlord pursuant to California Civil Code Section
1951.4 and any successor statute in the event Tenant has abandoned the Premises.
In the event Landlord elects to continue this Lease in full force and effect
pursuant to this Subsection 14.1(c), then Landlord shall be entitled to enforce
all of its rights and remedies under this Lease, including the right to recover
rent as it becomes due. Landlord's election not to terminate this Lease pursuant
to this Subsection 14.1(c) or pursuant to any other provision of this Lease, at
law or in equity, shall not preclude Landlord from subsequently electing to
terminate this Lease or pursuing any of its other remedies.

          (d)  Whether or not Landlord elects to terminate this Lease on account
of any default by Tenant, Landlord shall have the right to terminate any and all
subleases, licenses, concessions or other consensual arrangements for possession
entered into by Tenant and affecting the Premises or may, in Landlord's sole
discretion, succeed to Tenant's interest in such subleases, licenses,
concessions or arrangements. If Landlord so elects to succeed to Tenant's
interest, Tenant shall, as

                                       13
<PAGE>   17
of the date of notice by Landlord of such election, have no further right to or
interest in the rent or other consideration receivable thereunder.

     14.2 Following the occurrence of an event of default by Tenant, Landlord
shall have the right to require that any or all subsequent amounts paid by
Tenant to Landlord hereunder, whether in cure of the default in question or
otherwise, be paid in the form of cash, money order, cashier's or certified
check drawn on an institution acceptable to Landlord, or by other means approved
by Landlord, notwithstanding any prior practice of accepting payments in any
different form.

     14.3 All rights, options and remedies of Landlord contained in this
Section 14 and elsewhere in this Lease shall be construed and held to be
cumulative, and no one of them shall be exclusive of the other, and Landlord
shall have the right to pursue any one or more of such remedies or any other
remedy or relief which may be provided by law or in equity, whether or not
stated in this Lease. Nothing in this Section 14 shall be deemed to limit or
otherwise affect Tenant's indemnification of Landlord pursuant to any provision
of this Lease.

     14.4 Landlord shall not be deemed in default in the performance of any
obligation required to be performed by Landlord under this Lease unless Landlord
has failed to perform such obligation within 30 days after the receipt of
written notice from Tenant specifying in detail Landlord's failure to perform;
provided however, that if the nature of Landlord's obligation is such that more
than 30 days are required for its performance, then Landlord shall not be deemed
in default if it commences such performance within such 30-day period and
thereafter diligently pursues the same to completion. Upon any such uncured
default by Landlord, Tenant shall be entitled, as Tenant's sole and exclusive
remedy, to recover from Landlord Tenant's actual damages (but not lost profits
or any punitive, incidental or consequential damages) shown by Tenant to have
been directly caused thereby; provided, however: (a) Tenant shall have no right
to offset or abate rent in the event of any default by Landlord under this
Lease, except to the extent offset rights are specifically provided to Tenant in
this Lease; (b) Tenant shall in no event be entitled to terminate this Lease by
reason of Landlord's default; and (c) Tenant's rights and remedies hereunder
shall be subject to any specific limitations set forth in other provisions of
this Lease.

     14.5 No waiver by Landlord or Tenant of any violation or breach of any of
the terms, provisions and covenants herein contained shall be deemed or
construed to constitute a waiver of any other or later violation or breach of
the same or any other of the terms, provisions, and covenants herein contained.
Forbearance by Landlord in enforcement of one or more of the remedies herein
provided upon an event of default shall not be deemed or construed to
constitute a waiver of such default. The acceptance of any rent hereunder by
Landlord following the occurrence of any default, whether or not known to
Landlord, shall not be deemed a waiver of any such default, except only a
default in the payment of the rent so accepted, subject to the provisions
of Section 33.1.

     15.  SURRENDER OF PREMISES; REMOVAL OF PROPERTY.

     15.1 No act or thing done by Landlord or any agent or employee of Landlord
during the term hereof shall be deemed to constitute an acceptance by Landlord
of a surrender of the Premises unless such intent is specifically acknowledged
in a writing signed by Landlord. The delivery of keys to the Premises to
Landlord or any agent or employee of Landlord shall not constitute a surrender
of the Premises or effect a termination of this Lease, whether or not the keys
are thereafter retained by Landlord, and notwithstanding such delivery Tenant
shall be entitled to the return of such keys at any reasonable time upon
request until this Lease shall have been properly terminated. The voluntary or
other surrender of this Lease by Tenant, whether accepted by Landlord or not,
or a mutual termination hereof, shall not work a merger, and at the option of
Landlord shall operate as an assignment to Landlord of all subleases or
subtenancies affecting the Premises.

     15.2 Upon the expiration of the term of this Lease, or upon any earlier
termination of this Lease, Tenant shall, subject to the provisions of this
Section 15, quit and surrender possession of the Premises to Landlord in as
good order and condition as when Tenant took possession and as thereafter
improved by Landlord and/or Tenant, reasonable wear and tear and repairs which
are specifically made the responsibility of Landlord hereunder excepted. Upon
such expiration or termination, Tenant shall, without expense to Landlord,
remove or cause to be removed from the Premises all debris and rubbish, and such
items of furniture, equipment, free-standing cabinet work, movable partitions
and other articles of personal property owned by Tenant or installed or placed
by Tenant at its expense in the Premises, and such similar articles of any other
persons claiming under Tenant, as Landlord may, in its sole discretion, require
to be removed, and Tenant shall repair at its own expense all damage to the
Premises and Building resulting from such removal.

     15.3 Whenever Landlord shall re-enter the Premises as provided in this
Lease, any personal property of Tenant not removed by Tenant upon the
expiration of the term of this Lease, or within 48 hours after a termination by
reason of Tenant's default as provided in this Lease, shall be deemed abandoned
by Tenant and may be disposed of by Landlord (without

                                       14

<PAGE>   18
liability to Tenant) in accordance with Sections 1980 through 1991 of the
California Civil Code and Section 1174 of the California Code of Civil
Procedure, or in accordance with any laws or judicial decisions which may
supplement or supplant those provisions from time to time, or in accordance
with any other legally permissible procedure, whether by public or private sale
or otherwise. Landlord shall be entitled to apply any proceeds of the sale of
such items to any sums due to Landlord by Tenant and to Landlord's costs of
removal, storage and sale of such items. Alternatively, Landlord shall be
entitled to treat Tenant's failure to remove such items from the Premises as
either a permitted or unpermitted holdover pursuant to Section 19 of this Lease.

     15.4      All fixtures, alterations, additions, repairs, improvements
and/or appurtenances attached to or built into or on or about the Premises
prior to or during the term hereof, whether by Landlord at its expense or at
the expense of Tenant, or by Tenant at its expense, or by previous occupants of
the Premises, shall be and remain part of the Premises and shall not be removed
by Tenant at the end of the term of this Lease. Such fixtures, alterations,
additions, repairs, improvements and/or appurtenances shall include, without
limitation, floor coverings, drapes, paneling, molding, doors, kitchen and
dishwashing fixtures and equipment, plumbing systems, electrical systems,
lighting systems, silencing equipment, all fixtures and outlets for the systems
mentioned above and for all telephone, radio, telegraph and television
purposes, and any special flooring or ceiling installations (but excluding
Tenant's telecommunications switch and other telecommunications trade fixtures
and equipment, which Tenant agrees to remove upon the expiration or termination
of this Lease). Notwithstanding the foregoing, Landlord may, in its sole
discretion, require Tenant, at Tenant's sole cost and expense, to remove any
fixtures, alterations, additions, repairs, improvements and/or appurtenances
attached or built into or on or about the Premises. Tenant shall repair any
damage to the Building and Premises occasioned by the installation,
construction, operation and/or removal of any fixtures, trade fixtures,
equipment, alterations, additions, repairs, improvements and/or appurtenances
pursuant to this section. If Tenant shall fail to complete such removal and
repair such damage, Landlord may do so and may charge the reasonable cost
thereof to Tenant.

     15.5      Tenant hereby waives all claims for damages or other liability
in connection with Landlord's re-entering and taking possession of the Premises
or removing, retaining, storing or selling the property of Tenant as herein
provided, and Tenant hereby indemnifies and holds Landlord harmless from any
such damages or other liability, and no such re-entry shall be considered or
construed to be a forcible entry.

     16.       COST OF SUIT; ATTORNEYS' FEES; WAIVER OF JURY TRAIL.

     16.1      If Tenant or Landlord shall bring any action for any relief,
declaratory or otherwise, against the other arising out of or under this Lease,
including any suit by Landlord for the recovery of rent or possession of the
Premises, the losing party shall pay the successful party its costs of suit,
including, without limitation, a reasonable sum for attorneys' and other
professional fees relating to such suit, and such fees shall be deemed to have
accrued on the commencement of such action and shall be paid whether or not such
action is contested or prosecuted to judgment.

     16.2      In the event that Landlord shall, without fault on Landlord's
part, be made party to any litigation instituted by Tenant or by any third
party against Tenant, or by or against any person holding under or using the
Premises by license of Tenant, or for the foreclosure of any lien for labor or
material furnished to or for Tenant or of any such other person, Tenant hereby
indemnifies and holds Landlord harmless from and against all costs and
expenses, including reasonable attorneys' fees, incurred by Landlord in or in
connection with such litigation.

     16.3      In order to limit the cost of resolving any disputes between the
parties, and as a material inducement to each party to enter into this Lease,
each party hereby waives the right to a jury trial with respect to any
litigation between the parties arising out of this Lease, Tenant's occupancy of
the Premises, or Landlord's ownership, operation or management of the Building,
irrespective of any rights to a jury trial which either party otherwise then
would have under applicable statutes, constitutions, judicial decisions or
other laws.

     17.       ASSIGNMENT AND SUBLETTING

     17.1      Except as hereinafter provided, Tenant shall not sublet all or
any part of the Premises, nor assign this Lease nor enter any license,
"co-location agreement" or other agreement permitting a third party (other than
Tenant's employees and occasional guests) to use or occupy any portion of the
Premises, without Landlord's express prior written consent, which consent shall
not unreasonably be withheld. (For purposes of the balance of this Section 17.1
and Sections 17.2 through 17.5, the term "sublease" shall be deemed to include
licenses, co-location agreements, and other agreements for use or occupancy of
the Premises as described in the preceeding sentence. The terms "subtenant" and
"sublet" shall be construed accordingly.)

     In order to assist Landlord in evaluating any proposed assignment
"co-location agreement", or sublease, Tenant agrees

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<PAGE>   19
to provide Landlord with the proposed subtenant or assignee's current financial
statement and financial statements for the preceding 2 years and such other
information concerning the business background and financial condition of the
proposed subtenant or assignee and of Tenant as Landlord may reasonably request.

     Landlord and Tenant hereby agree that Landlord's disapproval of any
proposed sublease or assignment hereunder shall be deemed reasonable if based
upon any reasonable factor, including, without limitation, any or all of the
following factors:

               (a)  The proposed transfer would result in more than two
subleases of portions of the Premises being in effect at any time during the
term;

               (b)  The rent payable by the proposed transferee would be less
than the fair market rental value for the space as determined pursuant to the
last paragraph of this Section 17.1 (except as otherwise provided in Section
17.2);

               (c)  The proposed transferee is an existing tenant or occupant
of the Building or has negotiated with Landlord within the last twelve months
for space in the Building or is another transferee prohibited by the next to
last paragraph of this Section 17.1;

               (d)  The proposed transferee is a governmental entity;

               (e)  The transaction calls for new demising walls to be built,
and the portion of the Premises proposed to be sublet or assigned is irregular
in shape and/or has inadequate means of ingress and egress;

               (f)  The use of the Premises by the proposed transferee (1) is
not permitted by the use provisions of this Lease, or ??? Landlord's reasonable
opinion, violate any right for an exclusive use granted by Landlord to another
Tenant in the Building;

               (g)  The transfer would likely result, in Landlord's reasonable
opinion, in a significant increase in the use of the parking areas or common
areas of the Building due to the transferee's employees or visitors, and/or
significant increase in the demand for utilities and services to be provided by
Landlord to the Premises;

               (h)  The assignee or subtenant does not, in Landlord's
reasonable opinion, have the financial capability to fulfill the obligations
imposed by the transfer, or in the case of an assignment, the assignee does
not, in Landlord's reasonable opinion, have income and net worth at least equal
to that of Tenant;

               (i)  The transferee is not, in the Landlord's reasonable
opinion, of reputable or good character or consistent with Landlord's desired
tenant mix;

               (j)  The transferee is a real estate developer or landlord or is
acting directly or indirectly on behalf of a real estate developer or landlord;

               (k)  The proposed transferee may, in Landlord's reasonable
opinion, increase the chances of significant hazardous waste contamination
within the Premises or the Building; or

               (l)  In the reasonable judgment of the Landlord, the purpose for
which the transferee intends to use the Premises is not an ??? with the
standards of the Landlord for the Building or is in violation of the terms of
any other lease in the Building.

     Notwithstanding the foregoing, Tenant may, subject to the rest of the
terms hereof, sublet all of the Premises or assign this Lease to any entity
controlling, controlled by or under common control with Tenant, (including
assignment or subletting to any corporation resulting from a merger or
consolidation with Tenant, or to any person or entity which acquires all the
assets of Tenant's business as a going concern) provided that, with regard to
each such assignment or subletting: (A) Landlord receives the financial
statements prescribed above and such other financial and background information
as Landlord may request regarding the assignee or subtenant at least 20 days
prior to such proposed assignment or sublease; (B) the Landlord determines, in
its reasonable discretion, that the income and net worth of the assignee or
subtenant comply with the standards prescribed in item (h) above; (C) the use
of the Premises is not altered; (D) the Landlord determines, in its sole and
absolute discretion, that the transaction is not being entered into as a
subterfuge to avoid the restrictions on assignment and subletting in the Lease;
and (E) the sum ??? assignee expressly assumes the obligations of Tenant
hereunder as prescribed below in this Section 17.1.

                                       16
<PAGE>   20
     Neither this Lease nor the term hereby demised shall be mortgaged by
Tenant, nor shall Tenant mortgage, assign, pledge or otherwise transfer the
interest of Tenant in and to any sublease or the rentals payable thereunder or
in the Security Deposit.

     Any sublease, assignment, mortgage, pledge, encumbrance, or transfer made
in violation of this Section 17.1 shall be void and at Landlord's election
shall terminate this Lease.

     Each subtenant, assignee or transferee of Tenant, other than Landlord,
shall assume all obligations of Tenant under this Lease and shall be and remain
liable jointly and severally with Tenant for the payment of the rent, and for
the due performance of all the terms, covenants, conditions and agreements
herein contained on Tenant's part to be performed for the term of this Lease
(provided that in the case of a sublease, the subtenant's obligations shall be
limited to those obligations relating to the subleased space and the common
areas during the sublease term). No sublease or assignment shall be deemed
approved by Landlord unless such subtenant or assignee and Tenant shall deliver
to Landlord a counterpart of such sublease or assignment and an instrument in a
form acceptable to Landlord, which contains a covenant of assumption by the
subtenant or assignee satisfactory in substance and form to Landlord, consistent
with the requirements of this Section 17.1, but the failure or refusal of the
subtenant or assignee to execute such instrument of assumption shall not release
or discharge the subtenant or assignee from its liability as set forth above.

     No subtenant or assignee not complying with the foregoing requirements
shall have any interest in the Security Deposit. Any assignee that does comply
with the foregoing requirements shall automatically succeed to Tenant's position
with respect to the Security Deposit, and Landlord shall have the right to
refund all or any portion of the Security Deposit to the assignee at any time
or under any circumstances with no liability to the assignor.

     Landlord may require that the assignee or subtenant remit directly to
Landlord on a monthly basis, all monies due to Tenant by said assignee or
subtenant. In such event Landlord shall apply the sums received to the
obligations of Tenant and its successors under this Lease.

     In the event of default by any assignee or subtenant or any successor of
Tenant in the performance of any of the terms hereof, Landlord may proceed
directly against Tenant without the necessity of exhausting remedies against
such assignee, subtenant or successor.

     Landlord may consent to subsequent assignments of the Lease or sublettings
or amendments or modifications to the Lease with the assignee or other
successor of Tenant, and without obtaining Tenant's consent thereto, and any
such actions shall not relieve Tenant of liability under this Lease.

     Consent by Landlord to one assignment or subletting shall not be deemed
consent to any subsequent assignment or subletting.

     If Tenant is a corporation which, under California law, is not deemed a
publicly-held corporation, or is an unincorporated association or partnership,
the transfer, assignment or hypothecation of any stock or interest controlling
such corporation, association or partnership shall be deemed an assignment
within the meaning and provisions of this Section 17. For purposes hereof,
"control" shall be deemed to refer to any amount, in the aggregate, exceeding
25% of the voting power of such corporation, association or partnership.
Notwithstanding the foregoing, the immediately preceding sentence shall not
apply to any transfer of stock of Tenant if Tenant is a publicly-held
corporation and such stock is transferred publicly over a recognized security
exchange or over-the-counter market.

     Subject to Section 17.2, Tenant agrees that all advertising by Tenant to
market the space in the Premises to be sublet or assigned shall require
Landlord's prior written approval, which shall not be unreasonably withheld.
Subject to Section 17.2, Tenant further agrees that it shall not, without
Landlord's prior written consent, which may be granted or withheld in
Landlord's sole discretion, market any space in the Premises, assign the lease
or sublet any space in the Premises to existing tenants or occupants of the
Building, or to any entity controlling, controlled by, or under common control
with any existing tenant or occupant of the Building, except for any entity
controlling, controlled by or under common control with Tenant.

     Subject to Section 17.2, Tenant agrees that it shall not sublet, nor
assign, nor advertise as available for subletting or assignment, nor list with
brokers for subletting or assignment, all or any portion of the Premises for a
consideration which is equal to less than the fair market rental value, as
determined by Landlord in its reasonable discretion, for comparable space in
the Building on a comparable term commencing concurrently with the assignment
or sublease term, with comparable rent credits and tenant improvement
allowances. Within 10 days after Landlord receives any written request from
Tenant for

                                       17

<PAGE>   21
Landlord's estimate of the fair market rental value for specified space (which
request shall identify the space in question, the proposed term and the
proposed rent credits and improvement allowances), Landlord shall notify Tenant
in writing of the fair market rental value for such space for a comparable term
with comparable rent credits and tenant improvement allowances.

     17.2 Landlord acknowledges that Tenant's business to be conducted on the
Premises requires the installation on the Premises of certain communications
equipment by telecommunications customers of Tenant ("Customers") in order for
such Customers to interconnect with Tenant's terminal facilities.
Notwithstanding anything contained elsewhere in this Section 17, Landlord
agrees not to withhold its consent to any license agreement, sublease or
"co-location agreement" between Tenant and such a Customer for the purposes of
permitting such a telecommunications connection, so long as (a) such Customer
agrees in writing (in a form approved by Landlord in advance in writing) to
comply with all obligations imposed on Tenant under this Lease to the extent
relating to the portion of the Premises in question (including but not limited
to insurance, waiver and indemnity requirements); (b) such licenses, subleases
or co-location agreements do not collectively cover more than 50% of the
Premises at any one time; and (c) each such license, sublease or co-location
agreement is on a form for this purpose approved by Landlord in writing in
advance. Provided that Tenant's transactions with Customers comply with items
(a), (b) and (c) above, they need not comply with those requirements of Section
17.1 above regarding financial statements, advertising, and minimum rental
rates. Tenant represents that Tenant's Customers will require only infrequent
access to their equipment placed in the Premises pursuant to such a
transaction, and Tenant agrees not to permit any Customers to have such access
unless they are accompanied by a representative of Tenant. Tenant shall be
liable to Landlord for any violation by its Customers of any provisions of this
Lease.

     17.3 In the event that Tenant desires to assign this Lease, or to enter
into a sublease, as to all or any portion of the Premises, except (a) where the
subtenant or assignee is an entity controlling, controlled by or under common
control with Tenant, or (b) as permitted under Section 17.2 herein, Tenant
shall, prior to solicitation of offers therefor, give Landlord notice of
Tenant's desire to assign or sublet and of the portion of the Premises to be
affected by the proposed assignment or sublease. Landlord shall have the right,
exercisable by notice to Tenant within 60 days after Landlord's receipt of
Tenant's notice of desire to assign or sublet, to terminate this Lease as to
the portion of the Premises affected by the proposed assignment or sublease,
such termination to be effective as of the date 60 days after notice by
Landlord to Tenant of such termination.

     In the event of a termination of this Lease as to a portion of the
Premises pursuant to this Section 17.3, effective as of such termination, the
Premises shall be deemed to no longer include the portion of the Premises
subject to such termination, Tenant shall surrender possession of that portion
of the Premises in accordance with the provisions of this Lease, and the rent
payable hereunder and Tenant's Percentage Share shall be appropriately adjusted
based upon the rentable area remaining within the Premises.

     If Landlord does not elect to terminate pursuant to this Section 17.3, and
if Tenant does not enter into an assignment or sublease as specified in
Tenant's notice of desire to assign or sublet within 6 months after the
expiration of Landlord's 60-day period for election to terminate, then Tenant
shall again comply with the provisions of this Section 17.3 before assigning
this Lease, or entering into a sublease, as to all or any portion of the
Premises.

     17.4 In the event that Tenant has sought and received Landlord's consent
to assign this Lease, or to enter into a sublease as to all or any portion of
the Premises, the monthly rent payable by Tenant to Landlord, pursuant to
Section 3, shall be increased by the amount to be received by Tenant during
each month pursuant to the terms of the assignment or sublease, in excess of
Tenant's monthly rental payable to Landlord for the space subject to the
assignment or sublease. The amounts referred to in the previous sentence
include rent, additional rent, or any other payment in respect of use or
occupancy, or in reimbursement of costs of leasehold improvements installed by
Tenant, and whether paid in a lump sum or periodic payments; provided however,
such amounts shall not include any fees charged by Tenant to its Customers to
the extent such fees are based on Tenant's services (not square footage of
space used by the Customers) as provided under Section 17.2 herein. In no event
shall the total sums payable to the Landlord be less than the monthly rental
Landlord would have received but for such assignment or sublease.

     The additional rent shall be due and payable to Landlord in accordance
with the schedule specified in the sublease or assignment instrument, and the
failure of any subtenant or assignee to make any payments in accordance with
that schedule shall not affect the obligation of Tenant to pay the additional
rent to Landlord.

     The calculation of the amount of rentable space being sublet shall be made
by Landlord in accordance with its usual standards. Landlord may require
acknowledgment by Tenant of Tenant's concurrence on the Landlord's calculation
of the amount of rentable space being sublet as a condition to Landlord's
consent to any sublease.

                                       18
<PAGE>   22

      The provisions of a sublease or assignment instrument consented to by
Landlord cannot be modified, nor the sublease or assignment terminated, other
than in accordance with its terms, without the prior written consent of the
Landlord, which consent shall not be unreasonably withheld. The terms of this
Section 17.4 shall apply to any subleasing or assignment by any subtenant or
assignee.

      17.5  Tenant shall pay to Landlord, promptly upon receipt of a billing
from Landlord, the amount of Landlord's reasonable attorney fees incurred in
connection with Landlord's review or approval of any sublease or assignment
transaction requiring landlord's consent hereunder.

      18.   TRANSFER OF LANDLORD'S INTEREST. In the event of any transfer of
Landlord's interest in the Building or Premises, other than a transfer for
security purposes only, the transferor shall be automatically relieved of any
and all obligations and liabilities on the part of Landlord accruing from and
after the date of such transfer, including, without limitation, the obligation
of Landlord to return the Security Deposit as provided in this Lease; provided
that the transferor shall, within a reasonable time, transfer any Security
Deposit then held by Landlord, or any portion thereof remaining after proper
deductions therefrom, to the transferee and shall thereafter notify Tenant of
such transfer, of any claims made against the Security Deposit, and of the
transferee's name and address, by written notice delivered personally (in which
case Tenant shall acknowledge receipt of such notice by signing Landlord's copy
of such notice) or by registered or certified mail.

      19.   HOLDING OVER. If Tenant holds over after the term hereof, with or
without the express or implied consent of Landlord, such tenancy shall be from
month-to-month only, and shall not constitute a renewal hereof or an extension
for any further term, and in such case, Base Rent shall be payable at a monthly
rate equal to the greater of: (a) two hundred percent (200%) of the Base Rent
applicable to the Premises immediately prior to the date of such expiration or
earlier termination; or (b) one hundred fifty percent (150%) of the prevailing
market rate excluding any rental or other concessions (as reasonably determined
by Landlord) for the Premises in effect on the date of such expiration or
earlier termination. Such month-to-month tenancy shall be subject to every other
term, covenant and agreement contained herein. Nothing contained in this Section
19 shall be construed as consent by Landlord to any holding over by Tenant, and
Landlord expressly reserves the right to require Tenant to surrender possession
of the Premises to Landlord as provided in this Lease upon the expiration or
other termination of this Lease.

      20.   NOTICES. In every case when, under the provisions of this Lease, it
shall be necessary or desirable for one party hereto to serve any notice,
request or demand on the other, such notice or demand shall be in writing and
shall be served personally or by deposit in the United States mail, postage and
fees fully prepaid, registered or certified mail, with return receipt requested,
addressed to the applicable address for notice set forth in Section A on page 1.
Landlord or Tenant may, from time to time, by notice in writing served upon the
other as aforesaid, designate a different mailing address or a different person
to whom all such notices or demands are thereafter to be addressed. Service of
any such notice or demand if given personally shall be deemed complete upon
delivery, and if made by mail shall be deemed complete on the day of actual
delivery as shown by the addressee's registry or certification receipt or at the
expiration of 2 business days after the date of mailing, whichever is earlier.

      Notwithstanding the provisions of this Section 20, any notice of default
as described in Section 13.2 and any pleadings or notices given by either party
to the other with respect to any, judicial proceeding between the parties shall
be served in the manner prescribed by applicable California law without
reference to this paragraph, and shall be deemed served at such time as is
provided by such applicable law without reference to this paragraph.

      21.   QUIET ENJOYMENT.  Landlord covenants that Tenant, upon paying the
rent performing the covenants of this Lease on Tenant's part to be performed,
shall and may peaceably and quietly have, hold and enjoy the Premises for the
term of this Lease.

      22.   TENANT'S FURTHER OBLIGATIONS.

      22.1  Except for ordinary wear and as otherwise provided in this Lease,
Tenant shall, at Tenant's expense, keep in good order, condition and repair the
interior of the Premises and shall promptly and adequately repair all damage to
the interior of the Premises and replace or repair all glass, fixtures,
equipment and appurtenances therein damaged or broken, under the supervision and
with the approval of Landlord and, if Tenant does not do so, Landlord may, but
need not, make such repairs and replacements. If Landlord does so, Tenant shall
pay Landlord the cost thereof promptly upon demand, as additional rent
hereunder.

      22.2  Tenant shall comply with all laws, ordinances, rules, regulations,
orders and directives of governmental and quasi-governmental bodies and
authorities having jurisdiction over Tenant or the Premises from time to time
and shall obtain

                                       19
<PAGE>   23
and keep in effect all licenses, permits (including but not limited to
conditional use permits) and other authorizations required with respect to the
business or businesses conducted by Tenant within or from the Premises or with
respect to any special equipment or facilities of Tenant permitted under the
other provisions of this Lease. Tenant and its employees, agents, licensees and
invitees shall also comply with all reasonable rules and regulations which
Landlord may adopt from time to time for the protection and welfare of the
Building and its tenants and occupants; provided that Tenant shall not be
responsible for compliance with any rule or regulation adopted by Landlord
unless or until Tenant is furnished with a copy thereof. The present rules and
regulations for the Building are attached hereto as Exhibit "B". Landlord shall
have no liability to Tenant for the failure of any other tenant in the Building
to observe the rules and regulations.

     23. ESTOPPEL CERTIFICATE BY TENANT. At any time and from time to time,
within 15 days after written request by Landlord, Tenant shall execute,
acknowledge and deliver to Landlord a statement in writing certifying that this
Lease is unmodified and in full force and effect (or if there have been
modifications, that this Lease is in full force and effect as modified and
stating the modifications), that Tenant knows of no default hereunder by
Landlord and has no right of offset or deduction against the rent or any other
charge payable to Landlord (or specifying any claimed), the amount of any
security posted by Tenant, the dates to which the rent and other charges have
been paid in advance, any increases or decreases of rent that are anticipated,
the commencement date of the Lease and such other matters as may be reasonably
requested by Landlord. It is intended that any statement delivered pursuant to
this Section 23 may be relied upon by any purchaser of the fee or mortgage or
beneficiary or assignee of any mortgage or trust deed upon the fee of the
Building or Premises. Tenant's failure to deliver the statement within the
period specified above shall be conclusive and binding upon Tenant that the
Lease is in full force and effect without modification except as may be
represented by Landlord, that there are no uncured defaults in Landlord's
performance and that Tenant has no right of offset, counterclaim or deduction
against rental, and that no more than one month's rental has been paid in
advance.

     24.  SUBORDINATION AND ATTORNMENT. This Lease is and at all times shall be
subject and subordinate to any ground or underlying leases, mortgages, trust
deeds or like encumbrances, which may now or hereafter affect the Building or
Premises, and to all renewals, modifications, consolidations, replacements and
extensions of any such lease, mortgage, trust deed or like encumbrance. As a
condition precedent to the effectiveness of any such subordination of this
Lease to any future ground or underlying leases or the lien of any future
mortgages, deeds of trust, or like encumbrances, Landlord shall provide to
Tenant a commercially reasonable non-disturbance and attornment agreement in
favor of Tenant executed by such future ground lessor, master lessor, mortgagee
or deed of trust beneficiary, as the case may be, which shall provide that
Tenant's quiet possession of the Premises shall not be disturbed on account of
such subordination to such future lease or lien so long as Tenant is not in
default under any provisions of this Lease. Notwithstanding the foregoing,
Landlord shall have the right to subordinate or cause to be subordinated any or
all ground or underlying leases or the lien of any or all mortgages, deeds of
trust or like encumbrances to the Lease. In the event that any ground or
underlying lease terminates for any reason or any mortgage, deed of trust or
like encumbrance is foreclosed or a conveyance in lieu of foreclosure is made
for any reason, then at the election of Landlord's successor-in-interest,
Tenant shall attorn to and become the tenant of such successor. Tenant hereby
waives its rights under any current or future law which gives or purports to
give Tenant any right to terminate or otherwise adversely affect this Lease and
the obligations of Tenant hereunder in the event of any such foreclosure
proceeding or sale. Tenant covenants and agrees to execute and deliver to
Landlord in the form reasonably required by Landlord, within 10 days after
receipt of written demand by Landlord, any additional documents evidencing the
priority or subordination of this Lease with respect to any ground or
underlying lease or the lien of any mortgage, deed of trust, or like
encumbrance. Should Tenant fail to sign and return any such documents within
said 10-day period, Tenant shall be in default hereunder without the benefit of
any additional notice or cure periods, except as may be required by statute.

     25.  RIGHTS RESERVED TO LANDLORD.

     25.1 All portions of the Building are reserved to Landlord, including
exterior building walls, core corridor walls and doors and any core corridor
entrance, but excluding the Premises and the inside surfaces of all walls,
windows and doors bounding the Premises. Landlord also reserves any space in or
adjacent to the Premises used for shafts, stacks, pipes, conduits, fan rooms,
ducts, electric or other utilities, sinks or other building facilities, and the
use thereof, as well as the right to access thereto through the Premises for
the purposes of operation, maintenance, decoration and repair.

     25.2 Landlord shall have the following rights exercisable without notice
and without liability to Tenant for damage or injury in property, person or
business (all claims for damage being hereby released), and without effecting
an eviction or disturbance of Tenant's use or possession or giving rise to any
claim for setoffs or abatement of rent:

          (a)  To enter the Premises at all reasonable times during the term of
this Lease for the purpose of inspecting the same, supplying janitorial
service, posting notices of non-responsibility, exhibiting the Premises to
prospective

                                       20
<PAGE>   24
tenants, purchasers or others, or making such repairs or replacements therein
as may be required by this Lease or as Landlord may deem appropriate; provided
that Landlord shall use all reasonable efforts not to disturb Tenant's use and
occupancy and shall, when practical, give Tenant prior notice of such repairs.
For each of the foregoing purposes, Tenant shall provide to Landlord a key with
which to unlock at any time all of the doors in, upon and about the Premises,
excluding Tenant's vaults and safes. Landlord may use any other means which
Landlord may deem proper to open such doors in an emergency in order to obtain
entry to the Premises. Any entry to the Premises obtained by Landlord by any
means shall not under any circumstances be construed or deemed to be a forcible
or unlawful entry into, or a detainer of, the Premises, or an eviction of
Tenant from the Premises or any portion thereof, or grounds for any abatement or
reduction of rent. Any damages or losses on account of any such entry by
Landlord shall be Tenant's sole responsibility except as otherwise expressly
provided herein. Nothing in this Section 25 shall be construed as obligating
Landlord to perform any repairs, alterations or decorations, except as
otherwise expressly required in this Lease.

          (b)  To change the name or street address of the Premises or Building.

          (c)  To install and maintain signs on the exterior and interior of
the Building, except within the Premises.

          (d)  To have pass keys to the Premises.

          (e)  To decorate, remodel, repair, alter or otherwise prepare the
Premises for reoccupancy during the last 6 months of the term hereof if, during
or prior to such time, Tenant has vacated the Premises, or at any time after
Tenant abandons the Premises.

          (f)  To have access to all mail chutes according to the rules of the
United States Postal Service.

          (g)  To do or permit to be done any work in or about the exterior of
the Building or any adjacent or nearby building, land, street or alley.

          (h)  To grant to anyone the exclusive right to conduct any business
or render any service in the Building, provided such exclusive right shall not
operate to exclude Tenant from the use expressly permitted by this Lease.

     26.  FORCE MAJEURE. Whenever there is provided in this Lease a time
limitation for performance by Landlord or Tenant of any construction, repair,
maintenance or service, the time provided for shall be extended for as long as
and to the extent that delay in compliance with such limitation is due to an
act of God, governmental control or other factors beyond the reasonable control
of Landlord or Tenant, respectively.

     27.  WAIVER OF CLAIMS INDEMNITY.

     27.1 Tenant, as a material part of the consideration to Landlord, hereby
assumes all risk of, and waives all claims it may have against Landlord, its
agents, employees, partners, officers, directors, affiliates and successors in
interest (collectively, the "Landlord Group") for damage to or loss of property
or personal injury or loss of life resulting from the Building or Premises or
any part thereof becoming out of repair, by reason of any repair or alteration
thereof, or resulting from any accident within the Building or Premises or on or
about any space adjoining the Building or Premises, or resulting directly or
indirectly from any act or omission of any person, or due to any condition,
design or defect of the Building or Premises, or any space adjoining the
Building or Premises, or the mechanical systems of the Building or Premises,
which may exist or occur, whether such damage, loss or injury results from
conditions arising upon the Premises or upon other portions of the Building, or
from other sources or places, and regardless of whether the cause of such
damage, loss or injury or the means of repairing the same is accessible to
Tenant; provided such assumption and waiver shall not apply to claims caused by
the gross negligence or willful misconduct of Landlord or its agents.

     27.2 Tenant hereby agrees to indemnify, defend, and hold Landlord and the
Landlord Group harmless from and against (a) any and all claims, demands, suits,
fines, losses, expenses and liabilities (collectively, "Claims") for or
relating to injury or loss of life to persons or damage to or loss of property
arising from Tenant's use of the Building or the Premises, or from the conduct
of Tenant's business, or from any work done, permitted or suffered by Tenant in
or about the Premises or elsewhere, or from any negligence or intentional
conduct of Tenant or Tenant's agents, employees, contractors, licensees,
invitees, customers, representatives or successors in interest; (b) any and all
Claims arising from any breach or default in the performance of any obligation
on Tenant's part to be performed under the terms of this Lease; and for all
costs, attorneys' and other professional fees, expenses and liabilities
incurred by Landlord or any

                                       21
<PAGE>   25
member of the Landlord Group in or in connection with any such Claim. In the
event that any action or proceeding is brought against Landlord or any member
of the Landlord Group by reason of any such Claim, Tenant upon notice from
Landlord shall defend such action or proceeding at Tenant's cost and expense by
counsel approved by Landlord, such approval not to be unreasonably withheld.
Tenant's obligations under this Section 27.2 shall survive the expiration or
termination of this Lease as to any matters arising prior to such expiration or
termination or prior to Tenant's vacation of the Building.

     Notwithstanding anything to the contrary contained herein, in no event
shall Landlord or its agents be liable to Tenant, Tenant's agents, employees,
customer, licensees, representatives or successors for lost profits or
consequential incidental or punitive damages of any kind.

     28.       INSURANCE.

     28.1      Tenant shall procure and shall maintain in effect, at Tenant's
sole cost and expense throughout the term of this Lease, including any
extensions and renewals thereof, public liability and property damage insurance
against claims for bodily injury, death or property damage occurring upon or
about the Premises or Building, in each case naming Landlord and its managing
agents as additional insureds and, upon request by Landlord, naming the holder
of any mortgage, deed of trust or like encumbrance or the lessor under any
underlying lease covering the Building as additional insured, with a limit of
liability of not less than $3,000,000.00 single limit. If from time to time, the
limits of liability set forth above are, in the reasonable opinion of Landlord,
inadequate, Tenant shall increase such insurance coverage to an amount as shall
be designated by Landlord's notice to Tenant.

     Tenant shall also procure and maintain, at Tenant's sole cost and expense
throughout the term of this Lease, casualty insurance on Tenant's personal
property in the Premises and any leasehold improvements which the Tenant
installed at its own cost in an amount at least equal to the full replacement
cost of such property, providing coverage against all perils insured against by
a "fire and extended coverage" policy, as well as sprinkler damage, vandalism
and malicious mischief.

     Tenant shall also obtain the following insurance:

          (a)  Worker's compensation and employer's liability insurance in form
and amount satisfactory to Landlord.

          (b)  Loss of income and extra expense insurance in such amounts as
will reimburse Tenant for direct or indirect loss of earnings attributable to
all perils commonly insured against by prudent tenants or attributable to
prevention of access to or use of the Premises or the Building as a result of
such perils.

          (c)  Liquor liability insurance coverage in limits of not less than
Five Hundred Thousand Dollars ($500,000) if at any time during the term hereof
any alcoholic beverages of any nature are served on the Premises.

          (d)  Any other form or forms of insurance as Landlord or Landlord's
lender or ground or primary lessors may reasonably require from time to time in
form, in amounts, and for insurance risks against which a prudent tenant of a
comparable size and in a comparable business would protect itself.

     Such policies of insurance shall be with insurance companies acceptable to
Landlord, shall not have a deductible amount exceeding $5,000.00 in the
aggregate, and shall specifically provide that the insurance afforded by such
policies for the benefit of Landlord and its managing agents and Landlord's
mortgagees and ground lessors shall be primary, and that any insurance carried
by Landlord or Landlord's mortgagees and ground lessors shall be excess and
non-contributing. Such policies shall be evidenced by certificates of insurance
delivered to Landlord from time to time showing such insurance to be at all
times prepaid in full force and effect and providing that such insurance cannot
be cancelled or modified upon less than 30 days' prior written notice to
Landlord. If at any time Tenant has not provided Landlord with a then currently
effective certificate of insurance acceptable to Landlord as to any insurance
required to be maintained by Tenant, Landlord may, without further inquiry as to
whether such insurance is actually in force, obtain such a policy and Tenant
shall reimburse Landlord, upon demand as additional rent hereunder, for the cost
thereof, together with Landlord's administrative fee equal to 25% of the
premium.

     28.2 Tenant hereby waives its rights against Landlord and its managing
agent and their respective partners, officers, directors, shareholders,
employees, agents, representatives, contractors, affiliates, successors,
licensees, and invitees with respect to any claims or damages or losses
(including any claims for bodily injury to persons and/or damage to property)
which are caused by or result from (a) risks insured against under any insurance
policy carried by Tenant at the time of such claim, damage, loss or injury, or
(b) risks which would have been covered under any insurance required to be
obtained and maintained by Tenant under this Lease had such insurance been
obtained and maintained as required. The foregoing waivers shall be in addition
to, and not a limitation of, any other waivers or releases contained in this
Lease.

     28.3 Tenant shall cause each insurance policy required to be obtained by
it pursuant to this Section 28 to provide that the insurer waives all rights of
recovery by way of subrogation against Landlord and its managing agent and
their respective partners.

                                       22
<PAGE>   26

officers, directors, shareholders, employees, agents, representatives,
contractors, affiliates, successors, licensees, and invitees in connection with
any claims, losses and damages covered by such policy. If Tenant fails to
maintain insurance required hereunder, Tenant shall be deemed to be self-insured
with a deemed full waiver of subrogation as set forth in the immediately
preceding sentence.

        29.    FIXTURES, TENANT IMPROVEMENTS AND ALTERNATIONS.

        29.1    Except as otherwise provided in any rider to this Lease, all
improvements, fixtures and/or equipment which Tenant may install or place in or
about the Premises, and all alterations, repairs or changes to the Premises, and
all signs installed in, on or about the Premises, from time to time, shall be at
the sole cost of Tenant. Landlord shall be without any obligation in connection
therewith. Tenant hereby agrees to indemnify, defend, and hold Landlord harmless
from any liability, cost, obligation, expense or claim of lien in any manner
relating to the installation, placement, removal or financing of any such
alterations, repairs, changes, improvements, fixtures, and/or equipment in, on
or about the Premises. Tenant's obligations under the preceding sentence shall
survive the expiration or termination of this Lease as to any matters arising
prior to such expiration or termination or prior to Tenant's vacating of the
Building.

        29.2    Notwithstanding any provision in this Section 29 to the
contrary, and except as expressly permitted in the Addendum, Tenant is
absolutely prohibited from making any alterations, additions, improvements or
decorations which: (i) affect any area outside the Premises; (ii) affect the
Building's structure, equipment, services or systems, or the proper functioning
thereof, or Landlord's access thereto; (iii) affect the outside appearance,
character or use of the Building or the common areas; (iv) weaken or impair the
structural strength of the Building; (v) in the opinion of Landlord, lessen the
value of the Building; (vi) will violate or require a change in any occupancy
certificate applicable to the Premises; or (vii) in the opinion of Landlord,
will increase the Building's Operating Costs or Utility Costs.

        29.3    Before proceeding with any alteration, repair or change which is
not otherwise prohibited in Subsection 29.2 above, Tenant must first obtain
Landlord's written approval of (i) the plans and specification for all such
work; (ii) with respect to any connecting lines that will be outside the
Premises (if such lines are permitted by Landlord in its sole discretion), a
description of the areas of the Building to which Tenant will require access
both for the initial work and for ongoing maintenance of the improvements or
installations; (iii) the names of all contractors and subcontractors who will
perform such work, all of whom shall be selected from Landlord's then-current
list of approved contractors, which Landlord may compile in Landlord's sole
discretion and will provide to Tenant within ten days following Landlord's
receipt of Tenant's written request; (iv) copies of all construction contracts
entered by Tenant with any contractor for the work; (v) copies of all liability,
casualty, worker's compensation and builder's risk insurance applicable to the
construction, maintenance and ongoing operation of the improvements and
installations; and (vi) copies of all governmental permits required for the
work. Landlord's consent to such matters shall not unreasonably be withheld;
provided, however, that with regard to any such matters which may affect the
structural members, the heating, ventilation, air conditioning or other building
systems, exterior walls, windows and doors of the Building, and with regard to
the installation of any signs outside the Premises. Landlord may grant or
withhold its consent in its unlimited discretion. Landlord may impose, as a
condition of its consent to any alterations, repairs or changes of the Premises,
such requirements as Landlord in tis sole discretion may deem desirable,
including, but not limited to, the requirement that Tenant utilize for such
purposes only contractors, materials, mechanics and materialmen previously used
and currently approved by Landlord for work in the Building.

        29.4    After Landlord has approved the change, repair or alteration and
the other items listed in Section 19.3, Tenant shall enter into an agreement for
the performance of such change, repair or alternation with the contractors and
subcontractors approved by Landlord, as provided in Section 29.3. Before
proceeding with any change, repair or alteration Tenant shall (i) provide
Landlord with 10 days' prior written notice thereof; and (ii) pay to Landlord,
within 10 days after written demand, the costs of any increased insurance
premiums incurred by Landlord as a result of such changes, repairs or
alterations. In addition, before proceeding with any change, repair or
alteration, Tenant's contractors shall obtain, on behalf of Tenant and at
Tenant's sold cost sand expense: (A) all necessary governmental permits and
approvals fort the commencement and completion of such change, repair or
alteration; and (B) a completion and lieu indemnity bond, or other surety,
satisfactory to Landlord for such change, repair or alteration. Landlord's
approval of permits pursuant to Section 29.3 shall not relieve Tenant of the
obligation to obtain any other or supplemental permits required by the preceding
sentence.

        29.5    Tenant shall pay to Landlord, as additional rent, the reasonable
costs of Landlord's engineers and other consultants (but not Landlord's on-site
management personnel) for review of all plans, specifications and working
drawings for the change, repair or alteration within 10 business days after
Tenant's receipt of invoices either from Landlord or such consultants. In
addition to such costs, Tenant shall pay to Landlord, within 10 business days
after completion of any change, repair or alteration, the actual, reasonable
costs incurred by Landlord for services rendered by Landlord's management
personnel and engineers to coordinate and/or supervise any of the change, repair
or alteration to the extent such services are provided in excess of or after the
normal on-site hours of such engineers and management personnel.

        29.6    All changes, repairs and alterations shall be performed: (i) in
accordance with the approved plans, specifications and working drawings; (ii)
lien-free and in a first-class and workmanlike manner; (iii) in compliance with
all laws, rules, and regulations of all governmental agencies and authorities;
(iv) in such a manner so as to not to interfere with the occupancy of any other
tenant in

                                       23
<PAGE>   27
the Building, nor impose any additional expense or delay upon Landlord in the
maintenance and operation of the Building; and (v) at such times in such manner
and subject to rules and regulations as Landlord may from time to time
reasonably designate. Following completion of the work. Tenant shall promptly
provide to Landlord a set of "as built" plans and specifications for the work
and copies of all warranties and guarantees provided by Tenant's contractors and
subcontractors.

     29.7  Throughout the performance of any such change, repair or alteration
Tenant shall obtain, or cause its contractors to obtain, workers' compensation
insurance and general liability insurance covering the work in compliance with
provisions of Section 28 of this Lease, and builder's risk insurance for the
work reasonably acceptable to Landlord.

     29.8  With respect to any construction, alteration, decorating or repair
work undertaken by Tenant's contractors under a direct contract with Tenant,
Tenant shall pay Landlord as additional rent a fee equal to 8% of the contract
price in order to compensate Landlord for monitoring the compliance of Tenant's
construction with the Building's rules and regulations and the provisions of
this Lease. Such fee shall be paid by Tenant to Landlord in monthly progress
payments as calculated and billed by Landlord in its reasonable discretion.
Tenant shall pay such amounts to Landlord within 15 days after Tenant's receipt
of a billing therefor. Tenant acknowledges that such monitoring of Tenant's
construction is for Landlord's benefit only and shall not release Tenant from
any obligations hereunder, nor impose on Landlord any obligations to Tenant or
any third party relating to Tenant's construction.

     In the event Tenant orders any construction, alteration, decorating or
repair work directly from Landlord, or from the contractor selected by Landlord,
the charges for such work together with Landlord's administration fee equal to
15% of the contract price, shall be deemed additional rent under this Lease,
payable upon billing therefor, either in advance of the start of work, or
periodically during construction, or upon the substantial completion of such
work, at Landlord's option.

     30.0  MECHANIC'S LIENS. Tenant agrees to give Landlord written notice of
the commencement date of any alterations, improvements or repairs to be made in,
to or upon the Premises not later than 10 days prior to the commencement of any
such work, in order to give Landlord time to post notices of nonresponsibility.
Tenant will not permit any mechanic's, materialman's or other lien to be placed
upon the Premises or Building or improvements therein during the term hereof;
and in the event that any mechanic's, materialman's or other lien is filed
against the Premises or Building or improvements therein in connection with any
alteration, repair, improvement or change of, or installation of fixtures or
equipment in, the Premises, Tenant shall cause such lien to be released within
10 days after such filing, either by satisfaction of such claim or by posting of
a bond. Notwithstanding the foregoing, Landlord shall have the right and
privilege at Landlord's option of paying the amount of any such lien or claim,
or any portion thereof, without inquiry as to the validity thereof, and any
amounts so paid, including expenses and interest, shall be deemed additional
rent hereunder due from Tenant to Landlord upon demand.

     31.   ALTERNATE SPACE. If the Premises comprise less than a full floor in
the Building, Landlord shall have the privilege of moving Tenant to other space
in the Building comparable to the Premises, and all terms hereof shall apply to
the new space with equal force. In such event Landlord shall give Tenant at
least 60 days' prior notice in writing and shall move Tenant's effects to the
new space at Landlord's sole cost and expense at such time and in such manner as
to inconvenience Tenant as little as practicable and without causing an
interruption of Tenant's Telecommunication business in excess of six hours.

     32.   HAZARDOUS MATERIALS.

     32.1  In addition to its other obligations under this Lease, Tenant
covenants to comply with all laws relating to Hazardous Materials, as defined
below, with respect to the Premises and the Building. Tenant shall have the
right to use general office supplies typically used in an office area in the
ordinary course of business (such as copier toner, liquid paper, glue, ink and
cleaning solvents) and items typically used in a comparable telecommunications
business, provided that Tenant uses them in the manner for which they were
designed and only in accordance with all Hazardous Materials laws and the
highest standards prevailing in the industry for such use and then only in such
amounts as may be normal for the office business operations or
telecommunications operations conducted by Tenant on the Premises. Except as
provided in the preceding sentence, neither Tenant nor any of Tenant's agents,
employees, contractors, subtenants, assignees, licensees, invitees, successors,
or representatives ("Tenant's Parties") shall use, handle, store or dispose of
any Hazardous Materials in, on, under or about the Premises, the Building or the
site on which the Building is located. Tenant shall promptly take all actions at
its sole cost and expense, as are necessary to return the Premises, Building and
site to the condition existing prior to the introduction of any such Hazardous
Materials by Tenant or any Tenant Parties, provided Landlord's approval of such
actions shall first be obtained. Furthermore, Tenant shall immediately notify
Landlord of any inquiry, test, investigation or enforcement proceeding for or
against Tenant or the Premises concerning the presence of any Hazardous
Material.

     32.2  Tenant's obligations under Section 27.2 to indemnify, defend and hold
Landlord harmless from and against certain Claims shall be deemed to include,
without limitation, any and all Claims (as defined in Section 27.2) relating in
any way to investigation and clean-up cost, attorneys' fees, consultant fees and
court costs that arise during or after the term of this Lease as a result of the
breach of any of the obligations and covenants set forth in this Section 32, or
relating in any way to any contamination of the Premises, Building or site
directly or indirectly arising from the activities of Tenant or any Tenant
Parties. Tenant's obligations under the preceding sentence shall survive the
expiration or earlier termination of this Lease as to any matters arising prior
to such expiration or termination or prior to Tenant's vacating of the Building.

                                       24
<PAGE>   28
     32.3 For purposes of this Lease, the term "Hazardous Materials" shall mean,
collectively, asbestos, any petroleum fuel, and any hazardous or toxic
substance, material or waste which is or becomes regulated or defined as
hazardous or toxic by any local governmental authority, the State of California
or the United States Government, including, but not limited to, any material or
substance defined as hazardous or toxic under the Comprehensive Environmental
Response, Compensation and Liability Act, 42 U.S.C. Section 9601, et seq.; the
Resource Conservation and Recovery Act, 42 U.S.C. Sections 6901, et seq.; the
Toxic Substances Control Act, 15 U.S.C. Sections 2601, et seq.; the Federal
Water Pollution Control Act, 33 U.S.C. Sections 1251, et seq.; the California
Hazardous Substance Account Act, California Health and Safety Code Sections
25330, et seq.; the California Hazardous Waste Control Act, California Health
and Safety Code Sections 25100, et seq.; the California Safe Drinking Water and
Toxic Health Enforcement Act, California Health and Safety Code Sections
25249.5, et seq.; California Health and Safety Code Sections 25280, et seq.
(Underground Storage of Hazardous Substances); the California Hazardous Waste
Treatment Reform Act, California Health and Safety Code Sections 25179.1, et
seq.; California Health and Safety Code Sections 25501, et seq. (Hazardous
Materials Release Response Plans and Inventory); Petroleum Underground Storage
Tank Cleanup, Health and Safety Code Sections 25299.10, et seq.; and the
Porter-Cologne Water Quality Control Act, California Water Code Sections 13000,
et seq., as such laws may be amended from time to time.

     32.1 Tenant acknowledges that Tenant has received and read the notice from
Landlord regarding Landlord's asbestos in the Building. Landlord agrees that
the costs of asbestos removal work in the Building shall not be charged to
Tenant or included in the Building's Operating Costs for purposes of
calculating Tenant's obligations for rent escalations under Section 4 above.
The preceding sentence shall not apply to costs for such work necessitated by
the acts or omissions of Tenant or Tenant's Parties (as defined in Section
32.1), including but not limited to alteration work undertaken by Tenant.

     33.  MISCELLANEOUS.

     33.1 No receipt of money by Landlord from Tenant after the termination of
this Lease, the service of any notice, the commencement of any suit or final
judgment for possession shall reinstate, continue or extend the term of this
Lease or affect any such notice, demand, suit or judgment. No payment by Tenant
or receipt by Landlord of a lesser amount than the rent payment herein
stipulated shall be deemed to be other than on account of the rent, nor shall
any endorsement or statement on any check or any letter accompanying any check
or payment as rent be deemed an accord and satisfaction, and Landlord may
accept such check or payment without prejudice in Landlord's right to recover
the balance of such rent or pursue any other remedy provided in this Lease. Any
amount billed by Landlord to Tenant under this Lease or in connection with
Tenant's occupancy of space in the Building, which Tenant does not dispute in a
written notice delivered to Landlord within thirty days after Tenant's receipt
of such billing, shall be conclusively deemed to be correct, and Tenant shall
be obligated for such amount. Such thirty-day period to give notice of a
dispute shall not be deemed to extend the due date for any payments, but Tenant
shall be entitled to make the payment in question under protest by timely
giving such notice. Tenant agrees that each of the foregoing covenants and
agreements shall be applicable to all obligations of Tenant to Landlord,
whether expressly contained in this Lease or imposed by any statute or at
common law.

     33.2 If any provision of this Lease or its applicants to any party or
circumstances shall be determined by any court of competent jurisdiction to be
invalid or unenforceable to any extent, the remainder of this Lease or the
application of such provision to such person or circumstances, other than those
as to which it is so determined invalid or unenforceable to any extent, shall
not be affected thereby, and each provision hereof shall be valid and shall be
enforced to the fullest extent permitted by law; and it is the intention of the
parties in this Lease that in lieu of each clause or provision of this Lease
that is illegal, invalid or unenforceable, there be added as a part of this
Lease a clause or provision as similar in terms to such illegal, invalid or
unenforceable clause or provision as may be possible and be legal, valid and
enforceable.

     33.3 The covenants and obligations of Tenant pursuant to this Lease shall
be independent of performance by Landlord of the covenants and obligations of
Landlord pursuant to this Lease, and performance by Tenant of each covenant and
obligation of Tenant pursuant to this Lease shall be a condition precedent to
the duty of Landlord to perform the covenants and obligations of Landlord
pursuant to this Lease.

     33.4 The headings of Sections of this Lease are for convenience only and
do not define, limit or construe the contents thereof. References made in this
Lease to numbered Sections, Paragraphs and Subparagraphs shall refer to
numbered Sections, Paragraphs or Subparagraphs of this Lease unless otherwise
indicated.

     33.5 Where appropriate, words in the singular, including without
limitation the words "Landlord" and "Tenant", include the plural, and vice
versa. Words in the neuter gender include the masculine and feminine genders,
and vice versa, and words in the masculine gender include the feminine gender,
and vice versa.

     33.6 If more than one person or entity executes this Lease as Tenant: (a)
each of them is and shall be jointly and severally liable for the covenants,
conditions, provisions and agreements of this Lease to be kept, observed and
performed by Tenant; and (b) the act or signature of, or notice from or to, any
one or more of them with respect to this Lease shall be binding upon each and
all of the persons and entities executing this Lease as Tenant with the same
force and effect as if each and all of them had so acted or signed, or given or
received such notice.

                                       25
<PAGE>   29
     33.7      Time is of the essence of this Lease. Failure of either party to
perform any act strictly within the applicable period specified herein shall
entitle the other to exercise all remedies herein contemplated. All references
in this Lease to "days" shall mean calendar days unless specifically stated
herein to be "business" days.

     33.8      This lease shall be governed by and interpreted in accordance
with the laws of the State of California.

     33.9      All monetary obligations of Tenant remaining past due 10 days or
more after the date specified herein for payment shall bear interest until paid
at the lesser of (i) the Bank of America prime rate as of the due date plus 6%,
or (ii) the maximum rate permitted by law.

     33.10     This instrument, along with any riders, exhibits and attachments
or other documents referred to in Section M on page 2 (all of which riders,
exhibits, attachments and other documents are hereby incorporated into this
instrument by this reference), constitutes the entire and exclusive agreement
between Landlord and Tenant relating to the Premises, and this agreement and
said riders, exhibits and attachments and other documents may be altered,
amended or revoked only by an instrument in writing signed by the party to be
charged thereby. All prior or contemporaneous oral agreements, understandings
and/or practices relative to the leasing of the Premises are merged herein or
revoked hereby. References in this instrument to this "Lease" shall mean, refer
to and include this instrument as well as any riders, exhibits, attachments or
other documents referred to in Section M, and references to any covenant,
condition, obligation and/or undertaking "herein", "hereunder", or "pursuant
hereto" (or language of like import) shall mean, refer to and include the
covenants, conditions, obligations and undertakings existing pursuant to this
instrument and such riders, exhibits, attachments or other documents. All terms
defined in this instrument shall be deemed to have the same meanings in all
riders, exhibits, attachments or other documents referred to in Section M
unless the context thereof clearly requires the contrary.

     33.11     Tenant hereby consents to amendment of this Lease as and to the
extent required by any lender which makes a loan to Landlord secured in whole
or in part by the Building, provided that no such change shall increase the
rent payable hereunder or impair Tenant's use of the Premises.

     33.12     Unless otherwise agreed in writing, if Tenant has dealt with any
real estate broker or other person or firm with respect to leasing or renting
space in the Building, Tenant shall be solely responsible for the payment of
any fee due said broker, person or firm and Tenant hereby indemnifies and holds
Landlord harmless from and against any liability with respect thereto.
Notwithstanding the foregoing, Landlord agrees to pay, and to hold Tenant
harmless from, the commission owing to the brokers identified in Section L on
page 2, as provided in a separate agreement between Landlord and such brokers.

     33.13     Tenant agrees to pay to Landlord as additional rent hereunder
any taxes required by law to be paid by Tenant and collected from Tenant by
Landlord.

     33.14     Submission of this Lease for examination, even though executed
by Tenant, shall not bind Landlord in any manner, and no lease or other
obligation on the part of Landlord shall arise until this Lease is executed and
delivered by Landlord to Tenant. This Lease shall not be binding and in effect
until a counterpart hereof has been executed and delivered by the parties, each
to the other.

     33.15     Tenant shall not cause the recordation of this Lease, a short
form memorandum of this Lease or any reference to this Lease.

     33.16     Upon 10 days' prior written request from Landlord (which
Landlord may make at any time during the term but no more often than two times
in any calendar year), Tenant shall deliver to Landlord (a) a current financial
statement of Tenant and any guarantor of this Lease, and (b) financial
statements of Tenant and such guarantor for the two years prior to the current
financial statement year. Such statements shall be prepared in accordance with
generally acceptable accounting principles, and certified as true in all
material respects by Tenant (if Tenant is an individual) or by an authorized
officer or general partner of Tenant (if Tenant is a corporation or
partnership, respectively).

     33.17     Notwithstanding anything contained in this Lease to the
contrary, the obligations of Landlord under this Lease (including any actual or
alleged breach or default of Landlord) do not constitute personal obligations
of the individual partners, directors, officers, shareholders, agents or
employees of Landlord or of Landlord's partners or agents, and Tenant shall not
seek recourse against any such persons or entities or any of their personal
assets for satisfaction of any liability with respect to this Lease. In
addition, in consideration of the benefits accruing hereunder to Tenant and
notwithstanding anything contained in this Lease to the contrary, Tenant hereby
covenants and agrees for itself and all of its successors and assigns that the
liability of Landlord for its obligations under this Lease (including any
liability as a result of any actual or alleged failure, breach or default
hereunder by Landlord) shall be limited solely to, and Tenant's and its
successors' and assigns' sole and exclusive remedy shall be against, Landlord's
interest in the Building and proceeds therefrom, and no other assets of
Landlord.

     33.18     If Tenant is identified herein as a corporation, then the
persons executing this Lease on behalf of Tenant hereby represent that they are
duly authorized to execute and deliver this Lease on behalf of Tenant pursuant
to Tenant's by-laws or a resolution of its board of directors.

                                       26
<PAGE>   30
If Tenant is identified herein as a partnership, the undersigned represent that
they are all of the general partners of Tenant, that Tenant has been formed
under the laws of the State of California and is duly qualified to do business
in the State of California and that this Lease is being executed on behalf of
Tenant. Each of the partners of Tenant executing this Lease agrees that he or
she and Tenant are irrevocably bound by execution of any amendment to or
modification of this Lease by one or more of the partners of Tenant. Tenant
agrees that each new partner in Tenant shall be obligated under this Lease, in
the same fashion as the existing partners, and that each new partner shall
execute a copy of this Lease and deliver it to Landlord within 60 days after
that partner's admissions to the partnership. In the event that such newly
admitted partner is a corporation, the principal or principals for whose benefit
the corporation has been organized shall execute and deliver to Landlord a
lease guaranty in form acceptable to Landlord. Each newly admitted partner in
Tenant shall be jointly and severally liable with the remaining partners for
the performance and satisfactions of all obligations of the Tenant under this
Lease accruing from and after the effective date of the admission of the new
partner to the Partnership. If the provisions of this paragraph are satisfied,
the admission of a new partner shall not be considered an assignment of the
Lease for the purposes of Section 17 hereof.

     33.19     Subject to the provisions of Section 17 above, and except as
otherwise provided in this Lease, all of the covenants, conditions and
provisions of this Lease shall be binding upon, and shall inure to the benefit
of the parties hereto and their respective heirs, personal representatives and
permitted successors and assigns; provided, however, that no rights shall inure
to the benefit of any transferee of Tenant unless the transfer to such
transferee is made in compliance with the provisions of Section 17, and no
options or other rights which are expressly made personal to the original
Tenant hereunder or in any rider attached hereto shall be assignable to or
exercisable by anyone other than the original Tenant under this Lease.

     33.20     The voluntary or other surrender of this Lease by Tenant or a
mutual termination thereof shall not work as a merger and shall, at the option
of Landlord, either (a) terminate all and any existing subleases, or (b)
operate as an assignment to Landlord of Tenant's interest under any or all such
subleases.

     33.21     Except for Tenant's identity sign on the entry doors of the
Premises and Tenant's elevator lobby identity sign on any full floor of the
Building leased by Tenant (which signs shall be consistent with the Building's
signage program and otherwise subject to Landlord's prior written approval),
Tenant shall have no right to place any sign upon the Premises, the Building
or the site on which the Building is located or which can be seen from outside
the Premises.

     33.22     The effectiveness of this Lease and Landlord's obligations
hereunder are subject to and conditional upon Tenant's delivery to Landlord of a
lease guaranty in the form prescribed by Landlord in its sole discretion, fully
executed by the guarantor or guarantors specified in Section N on page 2 of this
Lease.

     34        RULES AND REGULATIONS AFFECTING TELECOMMUNICATIONS USE. Nothing
in the Rules and Regulations attached hereto as Exhibit B (or any further rules
and regulations promulgated by Landlord as described in Section 22.2) shall be
deemed to prohibit Tenant from installing in the Premises telecommunications
switching equipment or any other equipment specifically permitted in the other
provisions of this Lease, which does not pose a safety hazard or create a
nuisance or illegal condition; provided, however, that Tenant shall comply with
the provisions of this Lease (including the Rules and Regulations) regarding
the moving, installation, operation, use, maintenance, removal, power
requirements, and structural support of all such equipment, and shall obtain
any approvals from Landlord required under this Lease as to such matters.

     35.       "AS IS" CONDITION. Tenant is taking the Premises in its "as is"
condition existing as of the execution date of this Lease. Landlord shall have
no obligation for the construction or modification of tenant improvements for
Tenant. In constructing its own tenant improvements to the Premises, Tenant
shall comply with the other applicable provisions of this Lease (including but
not limited to Section 29) and shall utilize only contractors, materials,
mechanics, materialmen, architects and engineers used and currently approved in
writing by Landlord for work in the Building.

     IN WITNESS WHEREOF, this instrument has been duly executed by the parties
hereto, as of the date first above written.

                              TENANT:
                              GLOBAL NETWORK PROVIDERS
                              By: /s/ [Signature Illegible]
                                  ---------------------------------

                              Its: President
                                  ---------------------------------

                              By:
                                  ---------------------------------

                              Its:
                                  ---------------------------------

                                       27
<PAGE>   31
                                        LANDLORD;
                                        QUINBY BUILDING, LLC
                                        a California limited liability company
                                        By: GTD LLC, its Managing Member

                                            By: /s/ [Signature Illegible]
                                                --------------------------------

                                            Its: President
                                                 -------------------------------

                                            By:
                                                --------------------------------

                                            Its:
                                                 -------------------------------

                                       28

<PAGE>   32
                             FLOOR PLAN OF PREMISES

                                [TO BE ATTACHED]

<PAGE>   33
                                   EXHIBIT A

<PAGE>   34
                        _______________________________
                                QUINBY BUILDING
                        _______________________________
                                     LEASE
                        _______________________________

                                   EXHIBIT B
                             RULES AND REGULATIONS

     1.   Tenant shall not obstruct or interfere with the rights of other
tenants of the Building, or of persons having business in the Building, or in
any way injure or annoy such tenants or persons. Tenant shall not obstruct any
sidewalks, halls, passages, corridors, exits, entrances, courts, lobby areas,
vestibules, garages, parking areas, elevators, escalators, or stairways in and
about the Building (collectively, the "Common Areas").  Such Common Areas are
not for the general public, and Landlord shall in all cases retain the right to
control and prevent access thereto of all persons whose presence in the judgment
of Landlord would be prejudicial to the safety, character, reputation and
interests of the Building and its tenants; provided that nothing herein
contained shall be construed to prevent such access to persons with whom any
tenant normally deals in the ordinary course of its business, unless such
persons are engaged in illegal activities.

     2.   Tenant shall not commit any act or permit any thing in or about the
Building which shall or might subject Landlord to any liability or
responsibility for injury to any person or property by reason of any business
or operation being carried on in or about the Building or for any other reason.

     3.   Tenant shall not use the Building for lodging, sleeping, cooking, or
for any immoral or illegal purpose or for any purpose that will damage the
Building, or the reputation thereof, or for any purposes other than those
specified in the Lease.

     4.   Canvassing, soliciting and peddling in the Building are prohibited,
and Tenant shall cooperate to prevent such activities.

     5.   Tenant shall not bring or keep within the Building any bicycle or
motorcycle.

     6.   Tenant shall not conduct mechanical or manufacturing operations, cook
or prepare food, or place or use any inflammable, combustible, explosive or
hazardous fluid, chemical, device, substance or material in or about the
Building without the prior written consent of Landlord. Tenant shall comply
with all statutes, ordinances, rules, orders, regulations and requirements
imposed by governmental or quasi-governmental authorities or by Landlord from
time to time in connection with security, fire and panic safety and fire
prevention and shall not commit any act, or permit any object to be brought or
kept in the Building, which shall result in a change of the rating of the
Building by the Insurance Services Office or any similar person or entity.
Tenant shall not commit any act or permit any object to be brought or kept in
the Building which shall increase the rate of fire insurance on the Building or
on property located therein. Tenant shall provide Landlord with a name of a
designated responsible employee to represent Tenant on all matters pertaining
to fire or security regulations. Tenant shall cooperate fully in all matters
concerning fire and other emergency procedures.

     7.   Tenant shall not use the Building for manufacturing or for the
storage of goods, wares or merchandise, except as such storage may be
incidental to the use of the Premises for general office purposes and except in
such portions of the Premises as may be specifically designated by Landlord for
such storage. Tenant shall not occupy the Building or permit any portion of the
Building to be occupied for the manufacture or direct sale of liquor,
narcotics, or tobacco in any form, or as a medical office, barber shop, manicure
shop, music or dance studio or employment agency. Tenant shall not conduct in
or about the Building any auction, public or private, without the prior written
approval of Landlord.

     8.   Tenant shall not install or use in the Building any air conditioning
unit, engine, boiler, generator, machinery heating unit, stove, water cooler,
ventilator, radiator or any other similar apparatus without the express prior
written consent of Landlord, and then only as Landlord may direct.

     9.   Tenant shall not use in the Building any machines, other than
standard office machines such as typewriters, calculators, copying machines and
similar machines, without the express prior written consent of Landlord. If
Tenant requires telegraphic, telephonic, burglar alarm or similar services, it
shall first obtain, and comply with, Landlord's

                                      B-1

<PAGE>   35
instructions in their installation. Tenant shall not install, maintain or
operate upon the Premises any vending machine without the consent of Landlord.

     10.  Tenant shall move all freight, supplies, furniture, fixtures and other
personal property into, within and out of the Building only at such times and
through such entrances as may be designated by Landlord, and such movement of
such items shall be under the supervision of Landlord. Landlord reserves the
right to inspect all such freight, supplies, furniture, fixtures, and other
personal property to be brought into the Building and to exclude from the
Building all such objects which violate any of these rules and regulations or
the provisions of the Lease. Tenant shall not move or install such objects in or
about the Building in such a fashion as to unreasonably obstruct the activities
of other tenants, and all such moving shall be at the sole expense, risk and
responsibility of Tenant. Prior to permitting access into the Building of the
moving company or other persons performing such moving activities, Landlord may
require from such moving company or other persons evidence of insurance
reasonably acceptable to Landlord, from an insurer and with coverage and amounts
reasonably acceptable to Landlord, covering the moving activities and naming
Landlord and its managing agent as additional insureds. Tenant shall not use in
the delivery, receipt or other movement of freight, supplies, furniture,
fixtures and other personal property to, from or within the Building, any hand
trucks other than those equipped with rubber tires and side guards. Any freight
elevator shall be available for use by Tenant in common with other tenants in
the Building, subject to such reasonable scheduling as Landlord in its
discretion shall deem appropriate. No equipment, materials, furniture, packages,
supplies, merchandise or other property will be received in the Building or
carried in the elevators except between such hours and in such elevators as may
be designated by Landlord.

     11.  Tenant shall not place a load upon any floor of the Premises which
exceeds the load per square foot which such floor was designed to carry and
which is allowed by law. Landlord shall have the right to prescribe the weight,
size and position of all equipment, materials, furniture or other property
brought into the Building. Heavy objects, if such objects are considered
necessary by Tenant, and are permitted by Landlord, shall stand on such
platforms, as determined by Landlord to be necessary to properly distribute the
weight. Business machines and mechanical equipment belonging to Tenant, which
cause noise or vibration that may be transmitted to the structure of the
Building or to any space therein to such a degree as to be objectionable to
Landlord or to any tenants in the Building, shall be placed and maintained by
Tenant, at Tenant's expense, on vibration eliminators or other devices
sufficient to eliminate noise or vibration. The persons employed to move such
equipment in or out of the Building must be acceptable to Landlord. Landlord
will not be responsible for loss of, or damage to, any such equipment or other
property from any cause, and all damage done to the Building by maintaining or
moving such equipment or other property shall be repaired at the expense of
Tenant.

     12.  Tenant shall not deposit any trash, refuse, cigarettes, or other
substances of any kind within or out of the Building, except in the refuse
containers provided therefor. Tenant shall not introduce into the Building any
substance which might add an undue burden to the cleaning or maintenance of the
Premises or the Building, and Tenant shall not place in any trash box or
receptacle any material which cannot be disposed of in the ordinary and
customary manner of trash and garbage disposal. All garbage and refuse disposal
shall be made in accordance with directions reasonably issued from time to time
by Landlord. Tenant shall exercise its best efforts to keep the Common Areas
clean and free from rubbish.

     13.  Tenant shall use the Common Areas only as a means of ingress and
egress, and Tenant shall permit no loitering by any persons upon Common Areas or
elsewhere within the Building. The Common Areas and roof of the Building are not
for the use of the general public, and Landlord shall in all cases retain the
right to control or prevent access thereto by all persons whose presence, in the
judgment of Landlord, shall be prejudicial to the safety, character, reputation
or interests of the Building and its tenants. Neither Tenant nor any employee or
invitee of Tenant shall enter the mechanical rooms, air conditioning rooms,
electrical closets, janitorial closets, or similar areas or go upon the roof of
the Building without the express prior written consent of Landlord.

     14.  Landlord reserves the right to exclude or expel from the Building any
person who, in the judgment of Landlord, is intoxicated or under the influence
of liquor or drugs or who shall in any manner act in violation of the rules and
regulations of the Building.

     15.  Landlord shall have the right to designate the area or areas, if any,
in which Tenant and Tenant's servants, employees, contractors, jobbers, agents,
licensees, invitees, guests and visitors may park vehicles, and Tenant an its
servants, employees, contractors, jobbers, agents, licensees, invitees, guests,
and visitors shall observe and comply with all driving and marking signs and
markers within and about the Building. All parking ramps and areas and any
pedestrian walkways, plazas or other public areas forming a part of the Building
or the land upon which the Building is situated shall be under the sole and
absolute control of Landlord, who shall have the exclusive right to regulate and
control those areas.

                                      B-2
<PAGE>   36
     16.  Tenant shall not use the washrooms, restrooms and plumbing fixtures
of the Building, and appurtenances thereto, for any other purpose than the
purpose for which they were constructed, and Tenant shall not deposit any
sweepings, rubbish, rags or other improper substances therein. Tenant shall not
waste water by interfering or tampering with the faucets or otherwise. If
Tenant or Tenant's servants, employees, contractors, jobbers, agents,
licensees, invitees, guests or visitors cause any damage to such washrooms,
restrooms, plumbing fixtures or appurtenances, such damage shall be repaired at
Tenant's expense, and Landlord shall not be responsible therefor.

     17.  Tenant shall not mark, paint, drill into, cut, string wires within, or
in any way deface any part of the Building, without the express prior written
consent of Landlord, and as Landlord may direct. Upon removal of any wall
decorations or installations or floor coverings by Tenant, any damage to the
walls or floors shall be repaired by Tenant at Tenant's sole cost and expense.
All cleaning and janitorial services for the Building and the Premises shall be
provided exclusively through Landlord, and except with the written consent of
Landlord, no person or persons other than those approved by Landlord shall be
employed by Tenant or permitted to enter the Building for the purpose of
cleaning the same. Tenant shall not cause any unnecessary labor by carelessness
or indifference to the good order and cleanliness of the Premises. Landlord
shall not in any way be responsible to Tenant for any loss of property on the
Premises, however occurring, or for any damage to any Tenant's property by the
janitor or any other employee or any other person. Without limitation upon any
of the provisions of the Lease, Tenant shall refer all contractors'
representatives, installation technicians, janitorial workers and other
mechanics, artisans and laborers rendering any service in connection with the
repair, maintenance or improvement of the Premises to Landlord for Landlord's
supervision, approval and control before performance of any such service. This
Paragraph 17 shall apply to all work performed in the Building, including
without limitation installation of telephones, telegraph equipment, electrical
devices and attachments and installations of any nature affecting floors, walls,
woodwork, trim, windows, ceilings, equipment or any other portion of the
Building. Plans and specifications for such work prepared at Tenant's sole
expense, shall be submitted to Landlord and shall be subject to Landlord's
express prior written approval in each instance before the commencement of work.
All installations, alterations and additions shall be constructed by Tenant in a
good and workmanlike manner and only good grades of material shall be used in
connection therewith. The means by which telephone, telegraph and similar wires
are to be introduced to the Premises and the location of telephones, call boxes
and other office equipment affixed to the Premises shall be subject to the
express prior written approval of Landlord. Tenant shall not lay linoleum or
similar floor coverings so that the same shall come into direct contact with the
floor of the Premises and, if linoleum or other similar floor covering is to be
used, such use shall be subject to the prior written approval of Landlord, and
Landlord may require, among other things, that an interlining of builder's
deadening felt shall be first affixed to the floor, by a past or other material
soluble in water. The use of cement or other similar adhesive material is
expressly prohibited.

     18.  No signs, awnings, showcases, advertising devices or other projections
or obstructions shall be attached to the outside walls of the Building or
attached or placed upon any Common Areas. No window shades, blinds, drapes or
other window coverings shall be installed in the Building without the express
prior written consent of Landlord. No sign, picture, advertisement, window
display or other public display or notice shall be inscribed, exhibited, painted
or affixed by Tenant upon or within any part of the Premises in such a fashion
as to be seen from the outside of the Premises or the Building without the
express prior written consent of Landlord. In the event of the violation of any
of the foregoing by Tenant, Landlord may remove the articles constituting the
violation without any liability and Tenant shall reimburse Landlord for the
expense incurred in such removal upon demand as additional rent under the Lease.
Interior signs on doors and upon the Building directory shall be subject to the
express prior written approval of Landlord and shall be inscribed, painted, or
affixed by Landlord at the expense of Tenant. Tenant shall not install any radio
or television antenna, loudspeaker, or other device on the roof or exterior
walls of the Building, unless explicitly permitted elsewhere in this Lease, and
Tenant shall not interfere with radio or television broadcasting or reception
from or in the Building or elsewhere.

     19.  Tenant shall not use the name of the Building or of the Landlord in
its business name, trademarks, signs, advertisements, descriptive material,
letterhead, insignia or any other similar item without Landlord's express prior
written consent, except for the purpose of identifying Tenant's address.

     20.  Tenant shall be entitled to have its name entered upon the directory
of the Building. In the event that Tenant wishes to have additional entries made
upon the Building directory for the names of employees of Tenant who occupy
office space within the Premises, such entries may be allowed by Landlord in its
reasonable discretion, and Landlord may require that Tenant pay a reasonable fee
for each such additional entry. However, the directory of the Building is
provided primarily for the display of the name and location of tenants only, and
Landlord reserves the right to exclude any other names therefrom at any time.
All entries upon the Building directory shall be in uniform print of a size,
style and format selected by Landlord.

                                      B-3
<PAGE>   37
      21.   The sashes, sash doors, skylights, windows and doors that reflect or
admit light or air into the Common Areas shall not be covered or obstructed by
Tenant, through placement of objects upon window sills or otherwise. Tenant
shall cooperate with Landlord in obtaining maximum effectiveness of the cooling
and heating systems of the Building by keeping corridor doors closed and by
closing drapes and other window coverings when the sun's rays fall upon windows
of the Premises and at the end of the business day. Tenant shall not obstruct,
alter or in any way impair the efficient operation of Landlord's heating,
ventilation, air conditioning, electrical, fire, safety or lighting systems, nor
shall Tenant tamper with or change the setting of any thermostat or temperature
control valves in the Building. Tenant shall not waste electricity, water or air
conditioning and agrees to cooperate fully with Landlord to assure the most
effective operation of the Building's heating and air conditioning and to comply
with any governmental energy-savings rules, laws or regulations of which Tenant
has actual notice.

      22.   Subject to applicable fire or other safety regulations, all doors
opening onto Common areas and all doors upon the perimeter of the Premises shall
be kept closed and, during non-business hours, locked, except when in use for
ingress or egress. If Tenant uses the Premises after regular business hours or
on non-business days Tenant shall lock any entrance doors to the Building or to
the Premises used by Tenant immediately after using such doors.

      23.   The requirements of Tenant will be attended to only upon
appropriate application to the office of the Building by an authorized
individual. Tenant shall not request employees of Landlord to perform any work
to do anything outside of their regular duties unless under special
instructions from Landlord or the project manager for the Building. Tenant
shall not request any employee of Landlord to admit any person (Tenant or
otherwise) to any office without specific instructions from Landlord or the
project manager for the Building. Employees of Landlord shall not receive or
carry messages for or to Tenant or any other person, nor contract with nor
render free or paid services to Tenant or Tenant's servants, employees,
contractors, jobbers, agents, invitees, licensees, guests or visitors. In the
event that any of Landlord's employees perform any such services, such
employees shall be deemed to be the agents of Tenant regardless of whether or
how payment is arranged for such services, and Tenant hereby indemnifies and
holds Landlord harmless from any and all liability in connection with any such
services and any associated injury or damage to property or injury or death to
persons resulting therefrom.

      24.   All keys to the exterior doors of the Premises shall be obtained by
Tenant from Landlord, and Tenant shall pay to Landlord a reasonable deposit
determined by Landlord from time to time for such keys. Landlord will furnish
Tenant, free of charge except for the deposit, with two keys to each door lock
in the Premises. Landlord may make a reasonable charge for any additional keys.
Tenant shall not make or have made duplicate copies of such keys. Tenant shall
not install additional locks or bolts of any kind upon any of the doors or
windows of, or within, the Building, nor shall Tenant make any changes in
existing locks or the mechanisms thereof. Tenant shall, upon the termination of
its tenancy, provide Landlord with the combination locks on safes, safe cabinets
and vaults and deliver to Landlord all keys to the Building, the Premises and
all interior doors, cabinets, and other key-controlled mechanisms therein,
whether or not such keys were furnished to Tenant by Landlord. In the event of
the loss of any key furnished to Tenant by Landlord. Tenant shall pay to
Landlord the cost of replacing the same or of changing the lock or locks opened
by such lost key if Landlord shall deem it necessary to make such a change.

      25.   Access may be had by Tenant to the Common Areas and to the Premises
at any time between the hours of 8:00 A.M. and 6:00 P.M., Monday through Friday,
legal holidays excepted. At other times access to the Building may be refused
unless the person seeking admission is known to the watchman in charge, if any,
and/or has a pass or is properly identified. Tenant shall be responsible for all
persons for whom Tenant requests passes, and shall be liable to Landlord for all
acts of such persons. In the event Building has, or there is subsequently, a
card access system for using the elevators at other than normal operating hours
for the Building, Landlord may deny access to any area served by the elevators
by anyone not having the necessary elevator access card. Landlord shall in no
case be liable for damages for the admission or exclusion of any person from the
Building. In case of invasion, mob, riot, public excitement, or other commotion,
Landlord reserves the right to prevent access to the Building for the safety of
tenants and protection of property in the Building.

      26.   Landlord shall not be responsible for, and Tenant hereby
indemnifies and holds Landlord harmless from any liability in connection with,
the loss, theft, misappropriation or other disappearance of furniture,
furnishings, fixtures, machinery, equipment, money, jewelry or other items of
personal property from the Premises or other parts of the Building, regardless
of whether the Premises or Building are locked at the time of such loss.

      27.   Tenant shall not use or permit to be used in the Premises any foul
or noxious gas or substance, or permit or allow the Premises to be occupied or
used in a manner offensive or objectionable to Landlord or other occupants of
the

                                      B-4
<PAGE>   38
Building by reason of noise, odors or vibrations, nor shall Tenant bring into
or keep in or about the Premises any birds or animals, except for seeing-eye
dogs when accompanied by their masters.

     28.  Tenant shall provide to Landlord upon the execution of the Lease such
identifying information as the Landlord shall request, including but not
limited to residence addresses, residence telephone numbers, social security
numbers and driver's license or comparable identification numbers, regarding
Tenant (if Tenant is an individual or individuals), all general partners of
Tenant (if Tenant is a partnership), and all officers of Tenant (if Tenant is a
corporation). Tenant shall promptly advise Landlord of any change or addition
to the information provided and shall confirm the accuracy of the information
previously provided as may be requested by Landlord from time to time. Tenant
shall designate in writing to Landlord one or more of such persons as Tenant's
representatives for Landlord to contact if Landlord wishes to reach Tenant
outside normal business hours due to an emergency at the Premises or any other
reason. However, the decisions as to whether and when to contact such persons
shall remain in Landlord's sole discretion, and Landlord shall have no liability
for any failure or delay in contacting such persons or Tenant in case of an
emergency.

     29.  Tenant shall close and lock the doors of its Premises and entirely
shut off all water faucets or other water apparatus, and, except with regard to
Tenant's computers and other equipment which require utilities on a twenty-four
hours basis, all electricity, gas or air outlets before Tenant and its employees
leave the Premises. Tenant shall be responsible for any damage or injuries
sustained by other tenants or occupants of the Building or by Landlord for
noncompliance with this rule.

     30.  Tenant shall not obtain for use on the Premises, ice, food, beverage,
towel or other similar services, or barbering or bootblacking services, except
at such hours and under such regulations as may be reasonably fixed by Landlord.

     31.  Tenant agrees that Landlord shall have the right to provide to TRW
and to any other credit-checking or credit-evaluation service, and to any other
landlord, any information regarding Tenant's history of payments on Tenant's
monetary obligations under this Lease and such other information as such
services or landlords shall collect or request from time to time. Landlord, its
agents and the employees of Landlord and its agents shall have no liability for
the completeness or accuracy of such information, nor for the uses to which
such information is put by any persons or entities receiving such information.

     32.  All telephone and other telecommunications service which Tenant
wishes to obtain for the Premises shall be at Tenant's sole cost and expense
and shall be obtained from telecommunications suppliers and contractors
approved by Landlord in writing in advance for work in the Building. Landlord
may grant or withhold such approval as to specific suppliers and contractors in
Landlord's sole and absolute discretion. Access to the telephone closet on each
floor of the Building shall, at Landlord's election, be restricted so that no
entry to the closet will be permitted unless Landlord's designated contractor
or other representative is present.

     33.  Landlord may waive any one or more of these Rules and Regulations for
the benefit of Tenant or any other tenant, but no such waiver by Landlord shall
be construed as a waiver of such Rules and Regulations in favor of anyone other
than the tenant for whose benefit such waiver was expressly intended, nor
prevent Landlord from thereafter enforcing any such Rules and Regulations
against any or all of the tenants of the building, including Tenant.

     34.  These Rules and Regulations (including the Parking Rules and
Regulations in any Parking Space Rider to this Lease) are in addition to the
terms, covenants, agreements and conditions of any lease of premises in the
Building. In the event these Rules and Regulations conflict with any provision
of the Lease, the Lease shall control.

     35.  Landlord reserves the right to make such other and reasonable Rules
and Regulations (including Parking Rules and Regulations) as, in its judgment,
may from time to time be needed for safety and security, for care and
cleanliness of the building and for the preservation of good order therein.
Tenant agrees to abide by all such Rules and Regulations hereinabove stated and
any additional rules and regulations which are adopted.

     36.  For purposes hereof, the terms "Landlord," "Tenant," "Building" and
"Premises" are defined as those terms are defined in the Lease to which these
Rules and Regulations are attached. Whenever Tenant is obligated under these
Rules and Regulations to do or refrain from doing an act or thing, such
obligation shall include the exercise by Tenant of its best efforts to secure
compliance with such obligation by the servants, employees, contractors,
jobbers, agents, invitees, licensees, guests and visitors of Tenant. The term
"Building" shall include the Premises, and any obligations of Tenant hereunder
with regard to the Building shall apply with equal force to the Premises and to
other parts of the Building.

                                      B-5

<PAGE>   39

                             ---------------------
                                QUINBY BUILDING
                             ---------------------

                           EMERGENCY GENERATOR RIDER

        1. The parties acknowledge that Landlord has installed or intends to
install an Emergency Generator in the Building. Tenant is granted the right to
use up to 50 kilowatts of emergency power from such Emergency Generator in the
event of an interruption of normal electrical service to the Premises during the
Lease term. Such right of Tenant is conditioned upon Tenant's paying Landlord,
upon execution of this Lease, a one-time nonrefundable fee in an amount equal
to $300.00 per kilowatt of additional emergency power so reserved. In addition,
Tenant shall pay the costs to connect Tenant's Premises to the Emergency
Generator as described in Section 4 below.

       2. Tenant shall pay Landlord as additional rent under the Lease a
monthly sum as prescribed below to cover Landlord's costs of operation, use,
maintenance, fuel, oil, governmental permits, licenses and fees, insurance,
Landlord's profit and administration and other expenses relating to the
Emergency Generator. The monthly amount of such additional rent initially shall
be $100.00 per month. Each additional monthly rent payment described in this
section shall be due on the first day of each month with Tenant's other rent
payments, with the first such payment due at the commencement of the Lease
term. Such monthly amount may be increased annually, in Landlord's discretion,
during the term of the Lease and any extension thereto, provided that following
any such increase, the required monthly payment shall not be more than 10%
greater than it was immediately prior to such increase.

       3. Tenant's use of such emergency power shall be in accordance with such
rules and regulations as may be established by Landlord from time to time.

       4. Landlord shall repair and maintain the Emergency Generator, provided
that Tenant shall reimburse Landlord upon demand, as additional rent hereunder,
for the cost of any repairs or extraordinary maintenance for the Emergency
Generator necessitated by acts of Tenant or Tenant's employees, contractors,
assignees, sublessees, agents, licenses or invitees. In addition, any
installation of equipment, wiring or cabling in the Premises or the Building
for the purpose of enabling Tenant to access the Emergency Generator shall be
performed by Landlord in accordance with plans and specifications approved by
the parties in writing in advance, and Tenant shall reimburse Landlord for the
costs of such installation, including, but not limited to, design fees, costs
of demolition and construction, and Landlord's administrative fee equal to 10%
of the other costs.

       5. The provision for Emergency Generator service by Landlord to Tenant
shall be subject to the limitations on Landlord's liability set forth in
Section 9.6 of the Lease.

       6. This Emergency Generator Rider supersedes all prior or
contemporaneous understandings, negotiations, or agreements between the
parties, whether written or oral, with respect to its subject matter. This
Emergency Generator Rider is part of and shall be attached to the Lease.

       7. All terms of the Lease which have not been expressly altered by this
Emergency Generator Rider shall remain in full force and effect.

                                     EGR-1
<PAGE>   40
                        -------------------------------
                                QUINBY BUILDING
                        -------------------------------

                           TELECOMMUNICATIONS CONDUIT
                     AND CONDUIT INTERCONNECTION ROOM RIDER

      1.   License for Use of Conduit. The parties acknowledge that Landlord has
set aside a portion the basement level of the Building for use as a special
conduit interconnection room (the "Conduit Room"). The parties further
acknowledge Tenant's desire to use the Conduit Room as well as certain conduit
space contained within one 2-inch conduit containing fiber optic cable running
from the Premises to the Conduit Room (the "Connecting Conduit"). Landlord
hereby grants to Tenant a non-exclusive license, revocable by Landlord at will
under the circumstances described in Section 6 below, for use of the Conduit
Room, in common with others, and the Connecting Conduit. Such use shall be on
the terms and conditions set forth in this Rider. Tenant shall have the right to
commence such use on or after the date Landlord first makes the Conduit Room
available for use by Landlord's licensees following Landlord's construction of
the Conduit Room and installation of the Connecting Conduit (the "Effective
Date"). If for any reason the Conduit Room has not been constructed or the
Connecting Conduit has not been installed by the estimated Effective Date of
____________________, Landlord shall have no liability to Tenant for such delay.
However, in such event, Tenant, as Tenant's sole and exclusive remedy, shall
have no obligation for the monthly license fee described in Section 2 until the
Conduit Room has been constructed, the Connecting Conduit has been installed,
and the Effective Date has occurred.

      In connection with Tenant's use of the Conduit Room, Tenant shall be
provided with use of the following items ("Landlord Installations") in the
Conduit Room in the quantities indicated:

      1/2  22-inch relay racks          _____ 110 volt outlets

      ____ 2' by 2' lockable cabinets         _____ backup generator
                                                    connections for 110 volts AC
      ____ 4' by 6' lockable cages

      The Connecting Conduit shall run from the Premises to one of Tenant's
racks, cages or cabinets in the Conduit Room, as designated by Tenant. Landlord,
in its reasonable discretion, shall designate the precise rout of the Connecting
Conduit.

      Tenant acknowledges that other tenants and licensees in the Building will
also be using similar Landlord Installation in the Conduit Room, Tenant agrees
to use the Conduit Room only for the purpose of (a) facilitating
interconnections between Tenant's telecommunications systems of other tenants
and licensees who reserve Landlord installations in the Conduit Room and who
consent in writing to such an interconnection, or (b) making connections to
Landlord's telecommunications system which provides access to certain other
offsite telecomunications companies, provided that Landlord permits such
connections pursuant to a separate written agreement between Landlord and
Tenant, or (c) making connections to the systems of other telecommunications
carriers who are given access to the Building by Landlord and who agree in
writing to permit such connections by Tenant. Tenant agrees not to store,
install or use any equipment, conduit, cable, wiring, connecting line or other
property of Tenant in the Conduit Room for any other purpose. Tenant shall
cooperate in keeping the Conduit Room locked and in restricting access to the
Conduit Room to employees, contractors and other persons who need access in
order to facilitate such interconnections. In no event shall Tenant cause (or
permit its employees, representatives, contractors or invitees to cause) any
interference with or damage to the Landlord Installations, equipment, conduits,
cable, wiring or connecting lines owned or used by other tenants or licensees in
the Conduit Room. At Landlord's election, Landlord may equip the Conduit Room
with security cameras and a 24-hour security access system. Landlord shall also
provide all tenants and licensees of Landlord who use the Conduit Room with
standard specifications for all wiring, cabling and connecting lines to be
installed in the Conduit Room by such measures and installation guidelines as
Landlord deems appropriate. However, Landlord shall have no liability to Tenant
for any damage or interference caused by any person to the Landlord
Installations assigned to Tenant or to the cable, wiring, connecting lines,
equipment or other property of Tenant in the Conduit Room or the Connecting
Conduit.

      Landlord's only obligation to Tenant regarding the installation of
facilities to this Rider shall be to install the Landlord Installations assigned
to Tenant in the Conduit Room, the Connecting Conduit, and telecommunications
fiber optic cable in the Connecting Conduit, all of which shall remain the
property of Landlord. The cost of such work, together

                                     TCR-1
<PAGE>   41
with Landlord's related administrative fee, is included in Tenant's installation
payment to Landlord described in item (b) in Section 2 below. Tenant's share of
Landlord's cost of constructing the Conduit Room is included in Tenant's
one-time participation payment described in item (a) in Section 2.

     All installation of wiring, cabling and connections for Tenant's use
within the Conduit Room, including but not limited to any wiring, cabling or
connections in or about the Landlord Installations, shall be performed at
Tenant's sole expense by a qualified, duly licensed contractor selected by
Tenant. Landlord shall have no obligation or liability with respect to such
work by Tenant's contractors. Tenant shall cause all such work by Tenant's
contractors to be completed and paid for promptly to prevent any mechanic's
liens being filed. Tenant shall also cause all such work by Tenant's
contractors to comply with Landlord's rules and regulations in effect from time
to time for work in the Building, as well as the requirements in Landlord's
Conduit Room Rules in effect from time to time. (The Conduit Room Rules
initially shall be as set forth in Exhibit A.) Such requirements include, but
shall not be limited to, the requirements that, prior to starting the work, the
contractor or Tenant must provide to Landlord (i) evidence of insurance
coverage for the work in conformity with the standards in Landlord's rules,
(ii) copies of all legally required permits for the work, and (iii) a copy of
the written consent of any other licensee or other entity in the Conduit Room
with whose facilities a connection will be made as part of the work. Tenant
shall notify Landlord in writing before Tenant's contractor commences any such
work, so that Landlord may, if Landlord so elects, post notices of
nonresponsibility. Landlord shall be responsible for installation of fiber
optic cable within the Connecting Conduit, as described in the preceding
paragraph. Tenant shall have no right to install any wiring, cabling or
connections within the Connecting Conduit.

     Tenant's ongoing used of the Conduit Room, the Connecting Conduit and
Tenant's cable, wiring and connecting lines shall comply with all applicable
laws, the other provisions of the Lease, and the Building's rules (including
but not limited to the Special Conduit Room Rules) adopted by Landlord from time
to time. Tenant's use shall not interfere in any way with the operation of the
Building or with the occupancy or activities of any other tenant.

     2.   License Fees. Tenant agrees to pay Landlord a license fee for use of
the Conduit Room and the Connecting Conduit, which initially shall be (a) a
one-time participation fee of $500.00 for use of the Conduit Room, plus (b)
installation costs of $1,000.00 for the Connecting Conduit (including
installation of fiber optic cable) and for the Landlord Installations assigned
to Tenant in the Conduit Room (not including Tenant's cable, wiring, or
connecting lines in the Conduit Room). Such amounts shall be due and payable
upon execution of this Lease. (No portion of such amounts shall be refundable
if the Lease or this license is terminated for any reason.)

     After Tenant's initial payment, the license fee for the Conduit Room and
the Connecting Conduit shall be $100.00 per month, subject to adjustment as
provided below. Such license fee shall be due and payable to Landlord on the
first day of each month or portion of a calendar month throughout the balance of
the Lease term, unless and until this license is revoked by Landlord in
accordance with Section 6 below. (Any such revocation shall not affect the
balance of the Lease, except that Landlord may treat any default by Tenant
hereunder as a default under the Lease.) Such license fee shall be paid
together with Tenant's Base Rent and other monthly charges, with the first such
installment of the license fee due on the Effective Date. The monthly license
fee for any partial calendar month shall be equitably prorated, as calculated
by Landlord in its reasonable discretion.

     The amount of the monthly license fee shall be adjusted as of each January
1 during the Lease term. For purposes of calculating such adjustment, the
Consumer Price Index for All Urban Consumers, U.S. City Average, All Items
(1967=100), unadjusted (herein the "Index") published by the Bureau of Labor
Statistics of the United States Department of Labor for the month during which
the Effective Date occurs shall be the base Index figure (the "Base Index").
The Base Index shall be compared to the Index figure for December of each year
during the term of the Lease, including the initial partial calendar year
during which the Effective Date occurs. In the event that the Index figure for
December of any year during the term of the Lease shall be greater than the
Base Index, then in addition to the monthly license fee, Tenant shall pay to
Landlord a monthly amount equal to the same percentage increase in the monthly
license fee as the percentage increase in the Index for such December over the
Base Index. Such amount shall be payable monthly commencing with the payment of
the license fee for the January immediately following such December.

     In the event that the Index for any December during the term of the Lease
is not yet available upon the date that any installment of the monthly license
fee is due. Tenant shall continue paying the monthly license fee, as previously
adjusted, in the amount applicable for such December until the Index for that
month is published, whereupon Tenant shall immediately pay Landlord the
adjustments which would have been due in the months following such December had
the Index for such December been available. In the event that publication of
the Index is discontinued, Landlord and Tenant agree that the index of consumer
prices which is most closely analogous to the Index shall be used in place of
the Index for calculation of the adjustments payable hereunder. In the event
that the references or techniques employed in the calculation of the Index
shall be modified and such modification would have resulted in a different
figure for the Base Index,

                                     TCR-2
<PAGE>   42
Landlord and Tenant agree that the Base Index shall be appropriately adjusted
and that the Index, as modified, shall be used as provided hereunder.

     3. Electrical Usage. If the Landlord Installations include electrical
outlets, Landlord may elect to separately meter at Tenant's expense the
electrical usage of some or all of such outlets. Tenant shall pay the charges
for all such separately metered electrical usage within 15 days after receipt of
a billing therefor. Tenant shall also pay monthly within 15 days after Tenant's
receipt of a billing such sums as Landlord's building engineer may reasonably
determine to be necessary in order to reimburse Landlord for the additional cost
of any electrical usage by Tenant within the Conduit Room which has not been
separately metered to Tenant.

     4. Indemnity and Waiver. Tenant hereby agrees to indemnify and hold
harmless Landlord and its managers and members, and their respective managers,
members, officers, directors, shareholders, agents and employees (collectively,
the "Landlord Group") from and against any and all claims (including but not
limited to claims for bodily injury or property damage), actions, mechanic's
liens, losses, liabilities, and expenses (including reasonable attorney fees and
costs of defense by Landlord's legal counsel) (collectively, "Claims"), which
may arise from the installation, operation, use, maintenance or removal of
conduit, cable, wiring, connecting lines, equipment or other property pursuant
to this Rider or from Tenant's use of the Conduit Room, the Connecting Conduit,
or the Landlord Installations. Similarly, Tenant shall pay upon demand by
Landlord the costs to repair any physical damage to the Building caused by such
installation, operation, use, maintenance or removal. Tenant hereby waives and
releases the Landlord Group from any Claims Tenant may have at any time
(including but not limited to Claims relating to interruptions in services)
arising out of or relating in any way to the installation, operation, use,
maintenance, or removal of conduit, cable, wiring, connecting lines, equipment
or other property described in this Rider or Tenant's use of the Conduit Room,
the Connecting Conduit, or the Landlord Installations, whether or not caused by
the negligence of any member of the Landlord Group or Landlord's contractors.
Such waiver and release shall not apply to Claims to the extent caused by
Landlord's wilful misconduct. However, in no event shall Landlord or any member
of the Landlord Group be liable to Tenant for lost profits or consequential,
incidental or punitive damages of any kind.

     5. Removal of Cable, Wiring and Connecting Lines. Tenants agrees that, upon
the termination of this license as described in Section 6 below, Tenant (or, at
Landlord's election, the contractor designated by Landlord) shall promptly
remove, at Tenant's sole cost and expense, all cable, wiring, connecting lines,
and other installations, equipment or property installed or placed by or for
Tenant in the Conduit Room (excepting the Landlord Installations, which shall
remain the property of Landlord), and restore those portions of the Building
damaged by such removal to their condition immediately prior to the installation
or placement of such items. If Tenant fails to promptly remove all such items
pursuant to this Section 5, or if Landlord elects to have such work performed by
Landlord's contractor, Landlord may remove such items and restore those portions
of the Building damaged by such removal to their condition immediately prior to
the installation or placement of such items, in which case Tenant agrees
promptly to pay Landlord's reasonable costs of removal and restoration,
including Landlord's administrative fee.

     6. No Lease or Easement of Conduit Room or Connecting Conduit; Termination
of License. Tenant acknowledges that the rights granted to Tenant hereunder do
not constitute a lease of any portion of the Conduit Room, the Connecting
Conduit or the Landlord Installations nor an easement, but rather constitute a
non-exclusive license for use in common with others. Such license is revocable
by Landlord in Landlord's sole discretion upon any default by Tenant under the
Lease which is not cured within the applicable cure period. Landlord shall
retain such rights of revocation notwithstanding any expenditure of money on the
installations described herein or other actual or alleged reliance by Tenant.
Such revocation shall be made by written notice from Landlord to Tenant. The
license shall terminate in any event, without notice from Landlord, upon the
expiration or termination of the Lease. Such license is personal to Tenant, and
Tenant's rights hereunder may not be assigned (except in connection with a
permitted assignment of Tenant's entire interest in the Lease), sub-licensed, or
otherwise transferred in any fashion, regardless of whether such an arrangement
is called an assignment, a sub-license, a co-location agreement or any other
name. Tenant agrees not to permit any third party to place, use or operate their
own equipment, wiring, cabling or connecting lines in or about Tenant's Landlord
Installations or Connecting Conduit. Any default by Tenant under this Rider
shall be deemed to be a default under the Lease. The license fee described in
Section 2 above shall be deemed to be additional rent for the Premises described
in the Lease, and Tenant acknowledges that the availability of the license
enhances the value of those Premises. Tenant shall remain obligated for such
additional rent for the balance of the Lease term, and shall remain obligated
for Tenant's other obligations under this Rider, regardless of whether Tenant
actually makes use of the license, or whether Tenant surrenders the license, or
whether the license is terminated due to Tenant's default under the Lease.

                                     TCR-3
<PAGE>   43
     7.  Applicability of Other Provisions. Except as explicitly provided
otherwise herein, Tenant's obligations under the Lease for the protection of
the Building, Landlord, the Landlord Group, and third parties, including but
not limited to Tenant's obligations regarding maintenance, repairs, mechanic's
liens, insurance, attorneys' fees and costs of suit, shall apply in the same
fashion with respect to Tenant's use of the Conduit Room, the Connecting
Conduit and the Landlord Installations as they do with respect to Tenant's use
of the Premises.

     8.  Miscellaneous. This Rider supersedes all prior or contemporaneous
understandings, negotiations, or agreements between the parties, whether
written or oral, with respect to its subject matter. The Lease, as amended
herein, may be further amended only in a writing signed by both Landlord and
Tenant.

                                     TCR-4
<PAGE>   44
                                   EXHIBIT A

                                QUINBY BUILDING
                               CONDUIT ROOM RULES

     The Conduit Room is a room located on the basement level of the Quinby
Building located at 650 S. Grand Avenue, Los Angeles, California 90017 (the
"Building"), a purpose of which is to facilitate interconnections between
various telecommunications providers and users who currently hold licenses with
the Building for the use of such facilities ("Participants") and for the purpose
of facilitating connections with Landlord's telecommunications system which
provides access to certain other offsite telecommunications companies, and
facilitating connections with other telecommunications companies who have access
to the Building. As a condition to maintaining their license and to the ongoing
use of the Conduit Room, all Participants must comply with the Conduit Room
Rules set forth herein and as may be adopted or revised by the Building in its
reasonable discretion from time to time.

     These Conduit Room Rules are in addition to the terms, covenants, and
conditions of any agreement (including but not limited to a lease) between
Participant and the Building for use of the Conduit Room. In the event these
Rules conflict with any provision of such agreement, such agreement shall
control.

     The Building may waive any one or more of these Conduit Room Rules for the
benefit of a Participant, but no such waiver by the Building shall be construed
as a waiver of such Rules in favor of anyone other than such Participants for
whose benefit such waiver was expressly intended, nor prevent the Building from
thereafter enforcing such Rules against such Participant or any or all of the
other Participants.

     The Building reserves the right to make such other and reasonable Conduit
Room Rules as, in its judgment, may from time to time be necessary or desirable.
Participant agrees to abide by all such Conduit Room Rules as stated herein and
any additional rules and regulations which are adopted.

1.   Participants must furnish the Building with the names (and other necessary
     identification as Building may require) of its personnel who are authorized
     by Participant to enter the Conduit Room. Participants are responsible for
     keeping such authorized user list current.

2.   Participants wishing to enter into the Conduit Room must sign in at the
     Conduit Room log book located at the Building Security Desk.

3.   Each person wishing to enter the Conduit Room must be on the authorized
     user list. Positive proof of identity is required before entrance to the
     Conduit Room is permitted. A driver's license or other authenticated
     photograph identification is the only acceptable form of positive proof.
     Such form of identification will be held as security until Participant
     completes Participant's activities in the Conduit Room.

4.   Each person wishing to enter the Conduit Room must obtain a security access
     card from Building Security each time he or she wishes to enter. On
     entering or leaving the Conduit Room, Participant must make sure the door
     is shut and not left ajar.

5.   If Participant intends to perform cross-connect work in the Conduit room,
     upon entry Participant must submit a fully executed (by Participant and the
     Building's authorized representative) Cross-Connect Authority Form in the
     form provided by the Building.

6.   Upon leaving the Conduit Room, Participant must sign out in the Conduit
     Room log book at which time Participant's photo identification will be
     returned.

7.   All activities in the Conduit Room must be in compliance with the law
     including all applicable local, state, and federal laws, rules, codes and
     regulations.

8.   Participants desiring to interconnect to another Participant's or other
     entity's cross-connect array must negotiate such interconnection directly
     with such other Participant or entity, and the Building shall have no
     obligation in that regard.

                                     TCR-5

<PAGE>   45
 9.  All cross-connects must be accomplished utilizing Building-standard cable
     and wire and following approved procedures.

10.  All wiring shall be routed through the furnished channels, raceways, etc.
     All cable shall be dressed-in and secured so as to ensure a professional
     appearance, run straight and level, with 90 degree corners where possible.
     Where tie wraps are used, the end shall be cut to preserve the
     professional appearance.

11.  Groups of cable routed to the Conduit Room shall remain bundled together
     to the degree possible for easy identification.

12.  All cables must be clearly labeled utilizing Building-provided tags.

13.  The Conduit Room must be kept clean and free of debris at all times.

14.  Tampering in any way with Landlord's or other Participant's circuits and
     cross-connects is not permissible and is grounds for immediate revocation
     of Participant's Conduit Room rights. All other infractions of Conduit
     Room Rules must be corrected within 24 hours of notification.

15.  If circuit tampering is detected at any time by any Participant, it must
     be reported immediately to the Building Security Desk.

16.  Notification of infraction is accomplished by Building Management's
     delivery of a written warning to the Participant.

17.  Receipt of three (3) warnings within a six-month period is cause for
     immediate revocation of Conduit Room participation rights.

18.  Conduit Room participation rights are subject to revocation for any
     default under the agreement between the Building and Participant regarding
     Participant's use of the Conduit Room.

19.  Upon expiration or revocation of Conduit Room participation rights,
     Participant must make arrangements to vacate the Conduit Room and remove
     all cross-connects associated with Participant's assigned array(s) within
     30 calendar days of notification.

                                     TCR-6

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