<PAGE>

             Exhibit C to Sublease, Assumption and Consent Agreement

                                                                    Confidential

                                    SUBLEASE

1.       PARTIES

This Sublease is entered into by and between Carrier Access Corporation, Tenant,
SpectraLink Corporation, Subtenant, as a Sublease under the Master Lease dated
December 13, 1999, as amended, entered into by 2545 Central, LLC, as Landlord,
and the Tenant (the "Master Lease"). A copy of the Master Lease is attached
hereto as Exhibit A.

2.       PROVISIONS CONSTITUTING SUBLEASE

         (a)      This Sublease is subject to all of the terms and conditions of
the Master Lease in Exhibit A and Subtenant shall assume and perform the
obligations of Tenant in said Master Lease, to the extent said terms and
conditions are applicable to the premises subleased pursuant to this Sublease
(the "Subleased Premises"). Subtenant shall not knowingly or willfully commit or
permit to be committed on the Subleased Premises any act or omission that shall
violate any term or condition of the Master Lease. In the event of the
termination of Tenant's interest as Tenant under the Master Lease for any
reason, then this Sublease shall terminate coincidentally therewith without any
liability of Tenant to Subtenant.

         (b)      Except as otherwise stated in the Sublease, all of the terms
and conditions contained in the Exhibit A Master Lease are incorporated herein
as terms and conditions of this Sublease (with each reference therein to
Landlord and Tenant to be deemed to refer to Tenant and Subtenant, respectively)
and, along with all of the following Sections set out in this Sublease, shall be
the complete terms and conditions of this Sublease.

3.       PREMISES

Tenant leases to Subtenant and Subtenant hires from Tenant the following
described Subleased Premises together with the appurtenances, situated in the
City of Boulder, County of Boulder, State of Colorado, approximately 7,483
rentable square feet located at 5766 Central Avenue, Second Floor, Boulder, CO
80301, as shown on Exhibit B attached hereto.

4.       RENTAL

Subtenant shall pay to Tenant as rent ("Base Rent") for the Subleased Premises
in advance on the first day of each calendar month of the term of this Sublease
without deduction, offset, prior notice or demand, in lawful money of the United
States, as follows:

         October 1, 2003 through            $9.00 per rentable square foot per
            September 30,2004               annum, or $5,612.25 per month,
                                            plus triple net adjustment
         October 1, 2004 through            $9.27 per rentable square foot per
            September 30, 2005              annum, or $5,780.62 per month,
                                            plus triple net adjustment
         October 1, 2005 through            $9.55 per rentable square foot per
            September 30, 2006              annum, or $5,955.22 per month,
                                            plus triple net adjustment

<PAGE>

         October 1, 2006 through              $9.84 per rentable square foot per
           June 30, 2007                      annum, or $6,136.06 per month,
                                              plus triple net adjustment

Landlord may at any time give Subtenant written notice to make payments directly
to Landlord, and in such event, Subtenant shall thereafter make all payments due
hereunder directly to Landlord and shall provide Tenant with copies evidencing
each such payment and, in such event, no further payments will be due hereunder
from Subtenant to Tenant. Triple net adjustment shall be calculated and adjusted
from time to time by the Landlord per the terms of the Master Lease. First year
triple net expenses are currently $4.49 per square foot per year
($2797.00/month). Utilities and janitorial shall be contracted for and paid by
Subtenant separately. If the commencement date is not the first day of the
month, or if the Sublease termination date is not the last day of the month, a
prorated monthly installment shall be paid at the then current rate for the
fractional month during which the Sublease commences and/or terminates. Receipt
of $8,409.25 is hereby acknowledged for rental for the first month, and the
additional amount of $5,612.25 as non-interest bearing security for performance
under this Sublease. In the event Subtenant has performed all of the terms and
conditions of this Sublease throughout the term, upon Subtenant vacating the
Subleased Premises, the amount paid as a security deposit shall be returned
within 30 days to Subtenant after first deducting any unpaid amounts which
Subtenant owes to Tenant hereunder.

5.       TERM

         (a)      The term of this Sublease shall be for a period of forty-five
(45) months commencing on October 1, 2003 and ending on June 29, 2007.

         (b)      In the event Tenant is unable to deliver possession of the
Subleased Premises at the commencement of the Sublease term, Tenant shall not be
liable for any damage caused thereby, nor shall this Sublease be void or
voidable, but Subtenant shall not be liable for rent until such time as Tenant
offers to deliver possession of the Subleased Premises to Subtenant, but the
term hereof shall not be extended by such delay. If Subtenant, with Tenant's
consent, takes possession prior to the commencement of the term, Subtenant shall
do so subject to all of the covenants and conditions hereof and shall pay rent
for the period ending with the commencement of the term at the same rental as
that prescribed for the first month of the term, prorated at the rate of l/30
th thereof per day.

6.       USE

Subtenant shall use the Premises for communications hardware and software
research and development, engineering laboratory, and any accessory
administrative office uses and for no other purpose without the prior written
consent of Tenant and Landlord. Subtenant's business shall be established and
conducted throughout the term hereof in a first class manner. Subtenant shall
not use the Subleased Premises for, or carry on, or permit to be carried on, any
offensive, noisy or dangerous trade, business, manufacture or occupation nor
permit any auction sale to be held or conducted on or about the Subleased
Premises. Subtenant shall not do or suffer anything to be done upon the
Subleased Premises that will cause structural injury to the Subleased Premises
or the building of which the Subleased Premises form a part. The Subleased
Premises shall not be overloaded and no machinery, apparatus or other appliance
shall be used or operated in or upon the Subleased Premises that will in any
manner injure, vibrate or shake the Subleased Premises or the building of which
they are a part. No use shall be made of the Subleased Premises that will in any
way impair the efficient operation of the sprinkler system (if any) within the
building containing the Subleased Premises. Subtenant shall not leave the
Subleased Premises unoccupied or vacant during the term. Subtenant shall not
knowingly or willfully use or permit the use of the Subleased Premises or any
part thereof for any purpose that will increase the existing rate of insurance
upon the building in which the Subleased Premises are located, or cause a
cancellation of any insurance policy covering the building or any

                                       2

<PAGE>

part thereof. If any act on the part of Subtenant or use of the Subleased
Premises by Subtenant shall cause directly or indirectly, any increase of
Tenant's insurance expense, said additional expense shall be paid by Subtenant
to Tenant upon demand. No such payment by Subtenant shall limit Tenant in the
exercise of any other rights or remedies, or constitute a waiver of Tenant's
right to require Subtenant to discontinue such act or use.

7.       DEFAULT

"Default" shall be defined as any one of the following events:

         i.       If Subtenant shall fail to make due and punctual payment of
                  rent or any other amounts payable under this Sublease and such
                  failure shall continue for ten (10) days;

         ii.      If Subtenant shall abandon the Subleased Premises or remove
                  leasehold improvements or fixtures constituting property of
                  Tenant or Landlord;

         iii.     If this Sublease shall be transferred to or shall pass to or
                  devolve upon any person or party other than Subtenant, except
                  pursuant to the written consent of Tenant and Landlord;

         iv.      If Subtenant shall fail to perform any of the other
                  agreements, terms, covenants or conditions of this Sublease or
                  the Master Lease (except as modified by this Sublease) and
                  such non-performance shall continue for a period of fifteen
                  (15) days after written notice by Tenant or Landlord to
                  Subtenant, or if such performance cannot be reasonably had
                  within the fifteen (15) day period, Subtenant shall not in
                  good faith have commenced such performance within the
                  fifteen-day period and does not thereafter diligently proceed
                  to cure the breach.

(a)      In addition to and separate from any rights and remedies described in
the Master Lease, the following remedies shall apply to Default by Subtenant: If
any one or more events of Default shall happen, then Tenant and Landlord shall
have the right, then or any time thereafter, without demand or notice to
re-enter and take possession of the Subleased Premises and expel Subtenant and
remove its possessions without being deemed guilty of any manner of trespass and
without prejudice to any remedies for arrearages of rent or other breaches of
this Sublease. The exercise or beginning of the exercise by Tenant or Landlord
of any one or more of the rights or remedies provided for in this Sublease, or
in the Master Lease, or now or hereafter existing at law or in equity shall not
preclude the simultaneous or later exercise by Tenant or Landlord of any other
available right or remedy. In the event of any litigation between Subtenant and
Tenant or Landlord, arising out of or related to this Sublease or the Master
Lease, the prevailing party shall be entitled to recover its reasonable
attorney's fees, arbitration fees, court costs and any other expenses.

8.       NOTICES

All notices or demands of any kind required or desired to be given by Tenant or
Subtenant hereunder shall be in writing and shall be deemed delivered
forty-eight (48) hours after depositing the notice or demand in the United
States mail, certified or registered, postage prepaid, addressed to the Tenant
or Subtenant respectively at the addresses set forth after their signatures at
the end of this Sublease. All rent and other payments due under this Sublease or
the Master Lease shall be made by Subtenant to Tenant at the same address or as
otherwise instructed by Tenant or Landlord pursuant to Section 4 above. A copy
of any notice given by Tenant or Subtenant hereunder shall be sent at the same
time and in the same manner to the Landlord at c/o Flatiron Park Company, 5540
Central Avenue, Boulder, CO 80301.

                                       3

<PAGE>

9.       CONDITIONS OF PREMISES

Subtenant has inspected the Subleased Premises and accepts the Subleased
Premises in their present state and condition.

10.      ADDITIONAL PROVISIONS

         (a)      This Sublease is contingent upon Tenant receiving written
approval from the Landlord in the form of the Sublease, Assumption and Consent
Agreement to which this Sublease Agreement is an attachment.

         (b)      Any improvements required by Subtenant shall be paid for by
Subtenant.

         (c)      All Real Estate commissions involved in this transaction shall
be paid by Tenant.

         (d)      Tenant is not and has not been in violation of Article 9 of
the Master Lease and has no knowledge of any activities conducted on the
Premises during its tenancy that could be considered a violation of Article 9.

         (e)      Base rent shall be increased annually by the amount and at the
time specified in Section 4, above.

         (f)      Buyout of Master Lease. Subtenant understands that Tenant is
interested in the possibility of negotiating a buyout of the Master Lease with
Landlord. Tenant agrees to participate and cooperate in an assignment of the
Sublease to the Landlord in the event that any such buyout is negotiated during
the term of the Sublease, provided that the terms of the Sublease remain
unchanged and that there is no detriment to Subtenant. Except as provided
herein, the terms of any such buyout of the Master Lease are within the sole
discretion of Tenant and Landlord.

                                       4

<PAGE>

DATED: September 30, 2003

TENANT: Carrier Access Corporation            SUBTENANT: SpectraLink Corporation

By: TIMOTHY R AMBER                           By: NANCY K HAMILTON
    -------------------------                     ------------------------------
Title: CFO                                    Title: CFO

Address: 5395 Pearl Parkway, Boulder,         Address: 5755 Central Avenue,
         CO 80301                                      Boulder, CO 80301

FAX (303) 218-5567                            FAX (303) 440-5330

                                       5
<PAGE>

            Exhibit B to Sublease, Assumption and Consent Agreement

                                  [FLOOR PLAN]

                         5766 CENTRAL AVENUE 2ND FLOOR

<PAGE>

             Exhibit A to Sublease, Assumption and Consent Agreement
                                 And to Sublease

                                      LEASE

                                     Between

                                2545 Central LLC

                                       and

                           Carrier Access Corporation

Copyright (c) 1999 Flatiron Park Company

<PAGE>

                          SUMMARY OF BASIC LEASE TERMS

1.       Tenant: Carrier Access Corporation

         (a)      Tenant's entity and jurisdiction: Delaware corporation

         (b)      Tenant's federal taxpayer identification number: 84-1208770

2.       Building Address: 5766 Central Avenue
                           Boulder, CO 80301

         Type: Single User

3.       Demised Premises:

         (a)      Approx. Total Rentable Square Footage: 14,966

         (b)      Suite Number: 100

4.       Initial Lease Term:

         (a)      Period: 7 years

         (b)      Commencement Date: July 1, 2000

         (c)      Expiration Date: June 30, 2007

5.       Basic Rent:

         Rent Schedule:

<TABLE>
<S>               <C>    <C>                   <C>
July 1, 2000      to     June 30, 2001         $18,708.00 per month
July 1, 2001      to     June 30, 2002         $19,643.00 per month
July 1, 2002      to     June 30, 2003         $20,625.00 per month
July 1, 2003      to     June 30, 2004         $21,656.00 per month
July 1, 2004      to     June 30, 2005         $22,739.00 per month
July 1, 2005      to     June 30, 2006         $23,876.00 per month
July 1, 2006      to     June 30, 2007         $25,070.00 per month
</TABLE>

6.       Additional Rent

         Tenant's Pro Rata Share (for Additional Rent): 100%

7.       Security Deposit Amount: $18,708.00

Copyright (c) 1999 Flatiron Park Company

                                                        Landlord Initials RLH
                                                          Tenant Initials WW



<PAGE>

8.    Place for Payments:

      2545 Central LLC
      c/o Flatiron Park Company
      5540 Central Avenue
      Boulder, CO 80301

9.    Place for Notices:

      2545 Central, LLC.         with a copy to:  Hutchinson Black and Cook, LLC
      c/o Flatiron Park Company                   1215 Spruce Street
      5540 Central Avenue                         P.O. Box 1170
      Boulder, CO 80301                           Boulder, CO 80306
                                                  Attn: David M. Packard and
                                                        Bruce D. Dierking

      Carrier Access Corporation
      5395 Pearl Parkway
      Boulder, CO 80301


10.   Permitted Use(s) by Tenant: Communication hardware and software
      research and development, engineering laboratory, and accessory
      administrative office uses to include customer support, training, sales
      and general administration.


11.   Broker(s): None

12.   Utilities: Direct to Tenant

Copyright (c) 1999 Flatiron Park Company

                                                        Landlord Initials RLH
                                                          Tenant Initials WW



<PAGE>

                               TABLE OF CONTENTS


<TABLE>
<CAPTION>
                                                                           PAGE
                                                                           ----
<S>                                                                        <C>
ARTICLE 1 GENERAL........................................................    1
     1.1  Consideration..................................................    1
     1.2  Exhibits and Addenda to Lease..................................    1

ARTICLE 2 DEFINITIONS; DEMISE OF PREMISES................................    1
     2.1  Demise.........................................................    1
     2.2  Demised Premises...............................................    1
     2.3  Square Footage and Address.....................................    1
     2.4  Land...........................................................    1
     2.5  Building.......................................................    1
     2.6  Improvements...................................................    2
     2.7  Property.......................................................    2
     2.8  Common Facilities..............................................    2
     2.9  Parking Area...................................................    2
     2.10 Use of Common Facilities and Parking Area......................    2
     2.11 Covenant of Quiet Enjoyment....................................    2
     2.12 Condition of Demised Premises..................................    2

ARTICLE 3 TERM OF LEASE..................................................    3
     3.1  Lease Term.....................................................    3
     3.2  Commencement Date..............................................    3
     3.3  Early Occupancy or Entry.......................................    3

ARTICLE 4 RENT AND OTHER AMOUNTS PAYABLE.................................    3
     4.1  Basic Rent.....................................................    3
     4.2  Monthly Rent...................................................    3
     4.3  Place of Payments..............................................    3
     4.4  Lease a Net Lease and Rent Absolute............................    3
     4.5  Additional Rent................................................    3
     4.6  Tenant's Pro Rate Share........................................    4
     4.7  Monthly Deposits for Taxes, Insurance, and
          Common Facilities Charges......................................    4
     4.8  Security Deposit...............................................    4
     4.9  General Provisions as to Monthly Deposits and Security Deposit.    4
     4.10 Rent Regulations...............................................    5

ARTICLE 5 TAXES AND ASSESSMENTS..........................................    5
     5.1  Covenant to Pay Taxes and Assessments..........................    5
     5.2  Proration at Commencement and Expiration of Term...............    5
     5.3  Special Assessments............................................    5
     5.4  New or Additional Taxes........................................    5
     5.5  Landlord's Sole Right to Contest Taxes.........................    6

ARTICLE 6 INSURANCE......................................................    6

     6.1  Casually Insurance.............................................    6
</TABLE>


Copyright (c) 1999 Flatiron Park Company

                                       i

<PAGE>

<TABLE>
<S>                                                                        <C>
     6.2  Liability Insurance............................................    6
     6.3  Other Insurance................................................    6
     6.4  General Provisions Respecting Insurance........................    6
     6.5  Cooperation in the Event of Loss...............................    7

ARTICLE 7 UTILITY, OPERATING, MAINTENANCE AND REPAIR EXPENSES............    7
     7.1  Utility Charges................................................    7
     7.2  Common Facilities Charges......................................    7
     7.3  Tenant's Maintenance Obligation................................    7
     7.4  Landlord's Maintenance Obligation..............................    7

ARTICLE 8 OTHER COVENANTS OF TENANT......................................    8
     8.1  Limitation on Use by Tenant....................................    8
     8.2  Compliance with Laws...........................................    8
     8.3  Compliance with Insurance Requirements.........................    8
     8.4  No Waste or Impairment of Value................................    8
     8.5  No Overloading.................................................    8
     8.6  No Nuisance, Noxious or Offensive Activity.....................    8
     8.7  No Annoying Lights, Sounds or Odors............................    8
     8.8  No Unsightliness...............................................    8
     8.9  No Animals.....................................................    9
     8.10 Restriction on Signs and Exterior Lighting.....................    9
     8.11 No Violation of Covenants......................................    9
     8.12 Restriction on Changes and Alterations.........................    9
     8.13 No Mechanic's Liens............................................    9
     8.14 No Other Encumbrances..........................................   10
     8.15 Subordination to Landlord Mortgages............................   10
     8.16 Assignment or Subletting.......................................   10
     8.17 Annual Financial Statements... ................................   11
     8.18 Payment of Income and Other Taxes..............................   11
     8.19 Estoppel Certificates..........................................   11
     8.20 Landlord Right to Inspect and Show Premises and to Install
          "For Sale" Signs...............................................   12
     8.21 Landlord Right to Renovate, Expand or Modify Building..........   12
     8.23 Landlord Title to Fixtures, Improvements and Equipment.........   12
     8.24 Removal of Tenants Equipment...................................   12
     8.25 Tenant Indemnification of Landlord.............................   13
     8.26 Liability of Landlord..........................................   13
     8.27 Release upon Transfer by Landlord..............................   13
     8.28 Rules and Regulations..........................................   13
     8.29 Monitoring Equipment...........................................   13

ARTICLE 9 ENVIRONMENTAL MATTERS..........................................   14
     9.1  Definitions....................................................   14
          9.1.1 Hazardous Material.......................................   14
          9.1.2 Environmental Requirements...............................   14
          9.1.3 Environmental Damages....................................   14
     9.2  Tenant's Obligation to Indemnify, Defend and Hold Harmless.....   14
     9.3  Tenant's Obligation to Remediate...............................   15
     9.4  Notification...................................................   15
     9.5  Negative Covenants.............................................   15
</TABLE>


Copyright (c) 1999 Flatiron Park Company

                                       ii

<PAGE>

<TABLE>
<S>                                                                        <C>
            9.5.1  No Hazardous Material on Demised Premises.............   15
            9.5.2  No Violations of Environmental Requirements...........   16
     9.6    Landlord's Right to Inspect and to Audit Tenant's Records....   16
     9.7    Landlord's Right to Remediate................................   16
     9.8    Survival of Environmental Obligations........................   16

ARTICLE 10  DAMAGE OR DESTRUCTION........................................   16
     10.1   Damage to Demised Premises...................................   16
     10.2   Options to Terminate if Damage to Demised Premises is
            Substantial..................................................   16
     10.3   Damage to Building...........................................   17
     10.4   Obligations to Repair and Restore............................   17
     10.5   Application of Insurance Proceeds...........................    17

ARTICLE 11  CONDEMNATION.................................................   17
     11.1   Taking - Substantial Taking - Insubstantial Taking...........   17
     11.2   Termination on Substantial Taking............................   17
     11.3   Restoration on Insubstantial Taking..........................   17
     11.4   Right to Award...............................................   18

ARTICLE 12  DEFAULTS BY TENANT...........................................   18
     12.1   Defaults Generally...........................................   18
     12.2   Failure to Pay Rent or Other Amounts.........................   18
     12.3   Violation of Lease Terms.....................................   18
     12.4   Nonoccupancy of Demised Premises.............................   18
     12.5   Transfer of Interest Without Consent.........................   18
     12.6   Execution and Attachment Against.............................   18
     12.7   Bankruptcy or Related Proceedings............................   18

ARTICLE 13  LANDLORD'S REMEDIES..........................................   19
     13.1   Remedies Generally...........................................   19
     13.2   Cure by Landlord.............................................   19
     13.3   Termination of Lease and Damages.............................   19
     13.4   Repossession and Reletting...................................   19
     13.5   Security Interest............................................   20
     13.6   Suits by Landlord............................................   20
     13.7   Recovery of Landlord Enforcement Costs.......................   20
     13.8   Administrative Late Charge...................................   20
     13.9   Interest on Past-Due Payments and Advances...................   20
     13.10  Landlord's Bankruptcy........................................   20
     13.11  Remedies Cumulative..........................................   21

ARTICLE 14  SURRENDER AND HOLDING OVER...................................   21
     14.1   Surrender upon Lease.........................................   21
     14.2   Holding Over.................................................   21

ARTICLE 15  MISCELLANEOUS................................................   21
     15.1   No Implied Waiver............................................   21
     15.2   Survival of Provisions.......................................   21
</TABLE>


Copyright (c) 1999 Flatiron Park Company

                                       iii

<PAGE>

<TABLE>
<S>                                                                        <C>
     15.3   Covenants Independent........................................   21
     15.4   Covenants as Conditions......................................   21
     15.5   Tenant's Remedies............................................   21
     15.6   Binding Effect...............................................   22
     15.7   Short Form Lease.............................................   22
     15.8   Notices and Demands..........................................   22
     15.9   Force Majeure................................................   22
     15.10  Time of the Essence..........................................   22
     15.11  Captions for Convenience.....................................   22
     15.12  Severability.................................................   22
     15.13  Governing Law and Venue......................................   22
     15.14  Entire Agreement/Further Assurances..........................   22
     15.15  No Oral Amendment or Modifications...........................   23
     15.16  Real Estate Brokers..........................................   23
     15.17  Relationship of Landlord and Tenant..........................   23
     15.18  Authority of Tenant..........................................   23
</TABLE>


Copyright (c) 1999 Flatiron Park Company

                                       iv

<PAGE>

                                     LEASE

         This Lease is made this 13 day of December, 1999, between 2545 Central
LLC, a Colorado limited liability company, ("Landlord), whose address is c/o
Flatiron Park Company, 5540 Central Avenue, Boulder, Colorado 80301, and Carrier
Access Corporation, a Delaware corporation, ("Tenant"), whose address is 5766
Central Avenue, Boulder, CO 80301.

                                   ARTICLE 1
                                    GENERAL

         1.1      Consideration. Landlord enters into this Lease in
consideration of the payment by Tenant of the Rents herein reserved and the
keeping, observance and performance by Tenant of the covenants and agreements of
Tenant herein contained.

         1.2      Exhibits and Addenda to Lease. The Exhibits and Addenda listed
below shall be attached to this Lease and be deemed incorporated in this Lease
by this reference. In the event of any inconsistency or conflict between such
Exhibits and Addenda and the terms and provisions of this Lease, the terms and
provisions of the Exhibits and Addenda shall control. The Attachments, Exhibits
and Addenda to this Lease are:

         Summary of Basic Lease Terms
         Exhibit A       Legal Description of Land
         Exhibit B       Location of Demised Premises within Building
         Exhibit C       Notice of Non-Liability for Mechanics' Liens
         Exhibit D       Form of Subordination, Non-Disturbance and
                         Attornment Agreement
         Exhibit E       Form of Sublease, Assumption and Consent Agreement
         Exhibit F       Form of Assignment, Assumption and Consent Agreement
         Exhibit G       Form of Estoppel Certificate
         Exhibit H       Declaration of Protective Covenants

                                    ARTICLE 2
                         DEFINITIONS: DEMISE OF PREMISES

         2.1      Demise. Subject to the provisions, covenants and agreements
herein contained, Landlord hereby leases and demises to Tenant, and Tenant
hereby leases from Landlord, the Demised Premises as hereinafter defined, for
the Lease Term as hereinafter defined, subject to existing covenants,
conditions, restrictions, easements and encumbrances affecting the same.

         2.2      Demised Premises. The "Demised Premises" shall mean the space
to be occupied by Tenant as depicted on Exhibit B attached hereto. The Demised
Premises are within the Building which is located on the Land, as the terms
"Building" and "Land" are hereinafter defined.

         2.3      Square Footage and Address. The Demised Premises contains
approximately the rentable floor area set forth in the Summary of Basic Lease
Terms. The address of the Demised Premises is the address set forth in the
Summary of Basic Lease Terms.

         2.4      Land. "Land" shall mean the parcel of real property more
particularly described in Exhibit A attached hereto, as the same may be
replatted, resubdivided or adjusted from time to time by Landlord in its sole
discretion; PROVIDED, HOWEVER, THAT NO SUCH REPLAT OR RESUBDIVISION SHALL HAVE
ANY MATERIAL ADVERSE IMPACT ON TENANT'S USE AND ENJOYMENT OF THE DEMISED
PREMISES, INCLUDING THE PARKING AREA.

         2.5      Building "Building" shall mean the building or buildings
constructed on the Land, as the same may be expanded, remodeled, reconstructed
or otherwise modified from time to time by Landlord in its sole

Copyright (c) 1999 Flatiron Park Company

<PAGE>

discretion, currently containing approximately the number of square feet of
interior floor area set forth on the Summary of Basic Lease Terms. If there is
more than one building constructed on the Land, the term "Building" shall mean
collectively all buildings constructed upon the Land; PROVIDED, HOWEVER, THAT NO
SUCH CONSTRUCTION SHALL HAVE ANY MATERIAL ADVERSE IMPACT ON TENANT'S USE AND
ENJOYMENT OF THE DEMISED PREMISES, INCLUDING THE PARKING AREA.

         2.6      Improvements. "Improvements" shall mean the Building, the
Parking Area as hereinafter defined, and all other fixtures and improvements on
the land, including landscaping thereon.

         2.7      Property. "Property" shall mean the Land, the Building and the
Improvements and any fixtures and personal property used in operation and
maintenance of the Land, Building and Improvements other than fixtures and
personal property of Tenant and other users of space in the Building.

         2.8      Common Facilities. "Common Facilities" shall mean all of the
Property except (a) the Demised Premises and (b) the other premises in the
Building leased or held for lease to other tenants that is intended to be used
in common by Tenant and other tenants. Common Facilities shall include, without
limitation, the Parking Area and any walks, driveways, and, if applicable, lobby
areas, halls, stairs, elevators, restrooms, utility rooms, and janitorial
closets designed for common use of Tenant and other users of space in the
Building.

         2.9      Parking Area. "Parking Area" shall mean that portion of the
Land which is or is to be paved and otherwise improved or designated unimproved
land for the parking of motor vehicles.

         2.10     Use of Common Facilities and Parking Area. Tenant is hereby
granted the non-exclusive right and license to use, in common with others
entitled to such use, the Common Facilities, as they from time to time exist,
subject to the rights of Landlord reserved herein. Tenant shall not interfere,
at any time, with the rights of Landlord and others entitled to use any part of
the Common Facilities, and shall not store, either permanently or temporarily,
any materials, supplies or equipment on the Common Facilities. Landlord shall
have the right, at any time, to change, reduce or otherwise alter the Common
Facilities, in its sole discretion and without compensation to Tenant; provided,
however, Landlord shall provide reasonable parking in the Parking Areas, loading
areas and access to the Demised Premises to Tenant. LANDLORD SHALL NOT
MATERIALLY REDUCE THE PARKING AREA WITHOUT TENANT'S PRIOR WRITTEN CONSENT.
Tenant covenants and agrees not to make excessive use of the Parking Area.
Landlord shall have the right at any time to assign spaces in the Parking Area
to individual tenants, in its sole discretion, provided that Landlord shall
provide a reasonable number of spaces for Tenant. Landlord shall not be
responsible for any injuries to any person nor any damage to any automobile,
vehicle or other property which occurs in or about the Parking Area. Tenant
shall not park nor permit the parking of any vehicles in the Parking Area
overnight without Landlord's prior, written permission; PROVIDED, HOWEVER, THAT
TENANT SHALL NOT BE REQUIRED TO OBTAIN LANDLORD'S PERMISSION FOR OVERNIGHT
PARKING OF OPERATIONAL VEHICLES BELONGING TO EMPLOYEES WHO ARE TRAVELING OR FOR
OTHER OCCASIONS WHEN VEHICLES ARE PARKED OVERNIGHT FOR SHORT PERIODS FOR A BONA
FIDE BUSINESS PURPOSE.

         2.11     Covenant of Quiet Enjoyment. Landlord covenants and agrees
that, provided Tenant is not in default and keeps, observes and performs the
covenants and agreements of Tenant contained in this Lease, Tenant shall have
quiet and peaceable possession of the Demised Premises and such possession shall
not be disturbed or interfered with by Landlord or by any person claiming by,
through or under Landlord.

         2.12     Condition of Demised Premises. Except as may be provided on an
Addendum hereto, Tenant covenants and agrees that, upon taking possession of the
Demised Premises, Tenant shall be deemed to have accepted the Demised Premises
"as is" and Tenant shall be deemed to have waived any warranty of condition or
habitability, suitability for occupancy, use or habitation, fitness for a
particular purpose or merchantability, express or implied, relating to the
Demised Premises.

                                    ARTICLE 3

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                                  TERM OF LEASE

         3.1      Lease Term. "Lease Term" shall mean the period of time
specified in the Summary of Basic Lease Terms commencing at midnight on the
Commencement Date as defined below and expiring at midnight on the Expiration
Date, as specified in the Summary of Basic Lease Terms.

         3.2      Commencement Date. The term "Commencement Date" shall mean the
later of the Commencement Date set forth in the Summary of Basic Lease Terms or
the date that possession of the Demised Premises is tendered by Landlord to
Tenant as ready for occupancy when circumstances beyond the reasonable control
of Landlord have caused a delay in the Demised Premises being ready for
occupancy by Tenant. In the event of such a delay, this Lease shall not be void
or voidable by Tenant, and Landlord shall not be liable to Tenant for any loss
or damage resulting from such delay.

Notwithstanding anything to the contrary herein, if Landlord has not tendered
possession of the Demised Premises to Tenant within thirty (30) days after the
Commencement Date set forth in the summary of basic lease terms, Tenant shall
have the right to terminate this lease by written notice to Landlord. Landlord
shall give written notice to Tenant as soon as practicable should Landlord have
reason to believe it will not be able to tender possession to Tenant on the
Commencement Date.

         Should Landlord not tender possession of the Demised Premises to Tenant
         within 30 days after the commencement Date, Landlord will return the
         Security Deposit with Interest based on the Prime Rate.

RLH
WW

         3.3      Early Occupancy or Entry. In the event Landlord permits Tenant
or its agents or contractors to occupy or enter the Demised Premises for any
reason prior to the Commencement Date, Tenant shall be subject to all terms and
provisions hereof.

                                    ARTICLE 4
                         RENT AND OTHER AMOUNTS PAYABLE

         4.1      Basic Rent. Tenant covenants and agrees to pay to Landlord,
without offset, deduction or abatement, basic rent for the full Lease Term in
the amount specified as Basic Rent in the Summary of Basic Lease Terms ("Basic
Rent").

         4.2      Monthly Rent. Basic Rent shall be payable monthly in advance,
without notice, in equal installments, together with installments of Additional
Rent, in the amount of monthly rent specified in the Summary of Basic Lease
Terms ("Monthly Rent"). One such monthly installment shall be due and payable on
the date hereof and a like monthly installment shall be due and payable on or
before the first day of each calendar month succeeding the commencement date
recited in the Summary of Basic Lease Terms during the hereby demised term,
except that the rental payment for any fractional calendar month at the
commencement or end of the Lease Term shall be prorated based on a thirty (30)
day month.

         4.3      Place of Payments. Basic Rent and all other sums payable by
Tenant to Landlord under this Lease shall be paid to Landlord at the place for
payments specified in the Summary of Basic Lease Terms, or such other place as
Landlord may, from time to time, designate in writing.

         4.4      Lease a Net Lease and Rent Absolute. It is the intent of the
parties that the Basic Rent provided in this Lease shall be a net payment to
Landlord; that, except as otherwise expressly provided herein, the Lease shall
continue for the full Lease Term notwithstanding any occurrence preventing or
restricting use and occupancy of the Demised Premises, including any damage or
destruction affecting the Demised Premises, and any action by governmental
authority relating to or affecting the Demised Premises; that the Basic Rent
shall be absolutely payable without offset, reduction or abatement for any cause
except as otherwise specifically provided in this Lease; that Landlord shall not
bear any costs or expenses relating to the Demised Premises or provide any
services or do any act in connection with the Demised Premises except as
otherwise specifically provided in this Lease; and that Tenant shall pay, in
addition to Basic Rent, Additional Rent to cover costs and expenses relating to
the Demised Premises, the Common Facilities, and the Property, all as
hereinafter provided.

         4.5      Additional Rent. Tenant covenants and agrees to pay, as
Additional Rent, all costs and expenses relating to the Demised Premises
including utilities, maintenance and repair thereof AS PROVIDED IN ARTICLE 7
BELOW; Tenant's Pro Rata Share of all costs and expenses relating to the Common
facilities, including but not limited to the repair and maintenance thereto
described in Section 7.2 hereof; Tenant's Pro Rata Share of all Taxes and
Assessments and costs and expenses of Casualty Insurance; all costs and expenses
of Liability Insurance and Other Insurance; and all other costs and expenses
which Tenant is obligated to pay under this Lease.

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         4.6      Tenant's Pro Rata Share. "Tenant's Pro Rata Share" shall mean
the percentage set forth in the Summary of Basic Lease Terms as Tenant's Pro
Rata Share which is the percentage derived by dividing the approximate rentable
floor area of the Demised Premises, as set forth in the Summary of Basic Lease
Terms, by the approximate rentable floor area within the Building, as set forth
in the Summary of Basic Lease Terms. The percentage set forth in the Summary of
Basic Lease Terms shall be conclusive and not subject to adjustment for
remeasurement of the area of the Demised Premises or the Building. Landlord may
modify Tenant's Pro Rata Share from time to time based upon any increase or
reduction in the rentable floor area of the Building or of the Demised Premises.

         4.7      Monthly Deposits for Taxes, Insurance, and Common Facilities
Charges. Tenant will pay to Landlord, monthly in advance, without notice, on
each day that payment of Monthly Rental is due, amounts, as hereinafter
specified, for payment of Tenant's Pro Rata Share of Taxes and Assessments
(defined in Section 5.1), "Casualty Insurance" (defined in Section 6.1),
Landlord liability insurance, if applicable, (defined in Section 6.2), "Common
Facilities Charges" (defined in Section 7.2), and any other charges payable with
respect to the Property hereunder as Additional Rent (collectively "Monthly
Deposits") and, if the Monthly Deposits are insufficient to pay Tenant's Pro
Rata Share of the actual cost of such items, to pay to Landlord, within ten (10)
days after demand by Landlord, such amounts as are necessary to provide Landlord
with sufficient funds to pay Tenant's Pro Rata Share of the same. The Monthly
Deposits shall each be equal to Tenant's Pro Rata Share of 1/12 of the amounts,
as reasonably estimated and re-estimated from time to time by Landlord, of the
annual Taxes and Assessments, annual Casualty Insurance premiums, annual
Landlord liability insurance premiums, and annual Common Facilities Charges
payable with respect to the Property. The initial Monthly Deposit shall be
subject to adjustment as herein provided. To the extent the Monthly Deposits
exceed Tenant's Pro Rata Share of the actual cost of such items, the excess
amount shall, at Landlord's option, except as may be otherwise provided by law,
either be paid to Tenant or credited against future Monthly Deposits or against
Basic Rent, Additional Rent or other amounts payable by Tenant under this Lease.
If Tenant so requests in writing within thirty (30) days after the date of
Landlord's annual reconciliation of Monthly Deposits, Landlord shall furnish
Tenant with a copy of invoices or receipts for Taxes, Insurance, and Common
Facilities Charges. The amounts of such taxes, insurance premiums and expenses
payable by Tenant for the years in which the Lease Term commences and expires
shall be subject to the provisions hereinafter contained in this Lease for
proration of such amounts in such years. Prior to the dates on which payment is
due for such items, Landlord shall make payment of the same, to the extent funds
from Monthly Deposits available therefor. Except for Landlord's obligation to
make payments out of funds available from Monthly Deposits, the making of
Monthly Deposits by Tenant shall not limit or alter Tenant's obligation to pay
taxes and assessments and to maintain insurance as elsewhere provided in this
Lease.

         4.8      Security Deposit. Upon execution of this Lease by Tenant,
Tenant shall deposit with Landlord, the amount specified as a security deposit
in the Summary of Basic Lease Terms ("Security Deposit"). The Security Deposit
shall be retained by Landlord and may be applied by Landlord, to the extent
necessary, to pay and cover any loss, cost, damage or expense, including
attorneys' fees, sustained by Landlord by reason of the failure of Tenant to
comply with any provisions, covenant or agreement of Tenant contained in this
Lease. To the extent not necessary to cover such loss, cost, damage or expense,
the Security Deposit, without any interest thereon, shall be returned to Tenant
within sixty (60) days after expiration of the Lease Term or as may be otherwise
provided by law; provided, however, that Landlord may also deduct any amount
from the Security Deposit Landlord estimates may be required to cover any
shortfall in Additional Rent deposits made by Tenant in the final year of the
Lease until such time as Landlord has completed its annual Additional Rent
reconciliation for such year. The Security Deposit shall not be considered as an
advance payment of rent or as a measure of the loss, cost, damage or expense
which is or may be sustained by Landlord. In the event all or any portion of the
Security Deposit is applied by Landlord to pay any such loss, cost, damage or
expense, Tenant shall, from time to time, promptly upon demand, deposit with
Landlord such amounts as may be necessary to replenish the Security Deposit to
its original amount.

         4.9      General Provisions as to Monthly Deposits and Security
Deposit. Landlord shall not be required to hold the Security Deposit in an
escrow or trust deposit account, and Landlord may commingle the Monthly Deposits
with Landlord's own funds. Landlord shall not be obligated to pay interest to
Tenant on account of the

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Monthly Deposits and Security Deposit. In the event of a transfer by Landlord of
Landlord's interest in the Demised Premises, Landlord or the property manager of
Landlord may deliver the Monthly Deposits and Security Deposit to the transferee
of Landlord's interest and Landlord and such property manager shall thereupon be
discharged from any further liability to Tenant with respect to such Monthly
Deposits and Security Deposit. In the event of a transfer by Tenant of Tenant's
interest in the Demised Premises, Landlord shall be entitled to return the
Monthly Deposits and Security Deposit to Tenant's successor in interest and
Landlord shall thereupon be discharged from any further liability with respect
to the Monthly Deposits and Security Deposit.

         4.10     Rent Regulations. If the Basic Rent, Additional Rent, or any
other amounts to be paid by the Tenant to the Landlord hereunder is or becomes
at any time subject to regulation by law, then the rent or other amounts to be
so paid shall be the maximum rental or other amounts permitted by said laws, but
in no event in excess of the rent or other amounts provided for or determined in
accordance with the applicable provisions of this Lease.

                                   ARTICLE 5
                              TAXES AND ASSESSMENTS

         5.1      Covenant to Pay Taxes and Assessments. Tenant covenants and
agrees to pay, as Additional Rent, Tenant's Pro Rata Share of Taxes and
Assessments, as hereinafter defined, which accrue during or are attributable to
the Lease Term. "Taxes and Assessments" shall mean all taxes, assessments or
other impositions, general or special, ordinary or extraordinary, or every kind
or nature, which may be levied, assessed or imposed upon or with respect to the
Property or any part thereof, or upon any building, improvements or personal
property at any time situated thereon. "TAXES AND ASSESSMENTS" SHALL NOT INCLUDE
ANY PENALTIES, INTEREST, OR OTHER CHARGES INCURRED BY LANDLORD AS A RESULT OF
FAILING TO PAY ANY TAX OR ASSESSMENT WHEN DUE, PROVIDED THAT TENANT HAS NOT
FAILED TO PAY MATERIAL AMOUNTS OF ADDITIONAL RENT WHEN DUE HEREUNDER.

         5.2      Proration at Commencement and Expiration of Term. Taxes and
Assessments shall be prorated between Landlord and Tenant for the year in which
the Lease Term commences and for the year in which the Lease Term expires as of,
respectively, the date of commencement of the Lease Term and the date of
expiration of the Lease Term, except as herein provided. Additionally, for the
year in which the Lease Term expires, Tenant shall be liable without proration
for the full amount of Taxes and Assessments relating to any improvements,
fixtures, equipment or personal property which Tenant is required to remove or
in fact removes as of the expiration of the Lease Term. Proration of Taxes and
Assessments shall be made on the basis of actual Taxes and Assessments. Tenant's
Pro Rata Share of Taxes and Assessments for the years in which the Lease Term
commences and expires shall be paid and deposited with the Landlord through
Monthly Deposits as hereinabove provided, but, in the event actual Taxes and
Assessments for either year are greater or less than as estimated for purposes
of Monthly Deposits, appropriate adjustment and payment shall be made between
the parties, at the time the actual Taxes and are known, as may be necessary to
accomplish proration, as hereinafter provided, and such obligation shall survive
the termination or expiration of this Lease.

         5.3      Special Assessments. If any Taxes or Assessments are payable
in installments over a period of years, Tenant shall be responsible only for
installments for periods during the Lease Term with proration, as above
provided, of any installment payable prior to or after expiration of the Lease
Term.

         5.4      New or Additional Taxes. Tenant's obligation to pay Tenant's
Pro Rata Share of Taxes and Assessments shall include any Taxes and Assessments
of a nature not presently in effect but which may hereafter be levied, assessed
or imposed upon Landlord or upon the Property if such tax shall be based upon or
arise out of the ownership, use or operation of or the rents received from the
Property, other than income taxes or estate taxes of Landlord. For the purposes
of computing Tenant's liability for such new type of tax or assessment, the
Property shall be deemed the only Property of Landlord.

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<PAGE>

         5.5      Landlord's Sole Right to Contest Taxes. Landlord shall have
the sole right to contest any Taxes or Assessments. Landlord shall pay to or
credit Tenant with Tenant's Pro Rata Share of any abatement, reduction or
recovery of any Taxes and Assessments attributable to the Lease Term less
Tenant's Pro Rata Share of all costs and expenses incurred by Landlord,
including attorneys' fees, in connection with such abatement, reduction or
recovery.

                                    ARTICLE 6
                                    INSURANCE

         6.1      Casualty Insurance. Landlord covenants and agrees to obtain
and keep in full force and effect during the Lease Term, Casualty Insurance as
hereinafter defined. "Casualty Insurance' shall mean property insurance
including "all risk" coverage with respect to the Property, in an amount equal
to the full replacement cost thereof, with coinsurance clauses of no less than
ninety percent (90%), and with coverage, at Landlord's option, by endorsement or
otherwise, for all risks, vandalism and malicious mischief, sprinkler leakage,
boilers, and rental loss and with a deductible in the amount for each occurrence
as Landlord, in its sole discretion, may determine from time to time. Casualty
Insurance obtained by Landlord need not name Tenant as an insured party and may,
at Landlord's option, may name any mortgagee or holder of a deed of trust as an
insured party as its interest may appear. Tenant covenants and agrees to pay, as
Additional Rent, its Pro Rata Share of the cost of Casualty Insurance obtained
by Landlord, and to pay, as Additional Rent, its Pro Rata Share of the cost of
any deductible under such Casualty Insurance. Tenant shall be responsible for
obtaining, at Tenant's option, cost and expense, insurance coverage for personal
property and leasehold improvements of Tenant and for business interruption of
Tenant.

         6.2      Liability Insurance. Tenant covenants and agrees to obtain and
keep in full force and effect during the Lease Term, and to pay the premiums and
costs of, Liability Insurance as herein defined. "Liability Insurance" shall
mean comprehensive general liability insurance covering public liability for
claims for bodily injury, personal injury, and property damage with respect to
the ownership, use and operation of the Demised Premises and the Common
Facilities, with limits of not less than two million dollars ($2,000,000.00)
combined single limit of liability, with endorsements for assumed contractual
liability with respect to the liabilities assumed by Tenant under Sections 8.25
and 9.2 of this Lease, and with no deductible, retention or self-insurance
provision contained therein, unless otherwise approved in writing by Landlord.
Landlord may also obtain and keep in full force and effect during the Lease Term
liability insurance covering public liability with respect to the ownership, use
and operation of the Property. Tenant covenants and agrees to pay Tenant's Pro
Rata Share of the premiums and costs of such liability insurance as Additional
Rent hereunder.

         6.3      Other Insurance. Tenant covenants and agrees to obtain and
keep in full force and effect during the Lease Term, and to pay the premiums and
costs of, any other types of insurance relating to the Property or Tenant's
occupancy, use, and operation of the Demised Premises that Landlord or any
mortgagee or holder of a deed of trust on the Property may hereafter, reasonably
require. Tenant shall cause such other insurance to be in effect within thirty
(30) days after receipt of written notice from Landlord.

         6.4      General Provisions Respecting Insurance. Except as otherwise
approved in writing by Landlord, all insurance obtained by Tenant shall be on
forms and with insurers selected or approved by Landlord, which approval shall
not be unreasonably withheld; shall name Landlord, Landlord's manager(s) and
agent(s), and the holder of any mortgage or deed of trust encumbering the
Property as insured parties, as their interests may appear; shall contain a
waiver of rights of subrogation as among Tenant, Landlord and the holder of any
such mortgage or deed of trust; shall provide coverage on an occurrence basis;
and shall provide, by certificate of insurance or otherwise, that the insurance
coverage shall not be canceled or altered except upon thirty (30) days' prior
written notice to Landlord and the holder of any such mortgage or deed of trust.
Certificates of insurance obtained by Tenant shall be delivered to Landlord who
may deposit the same with the holder of any such first mortgage or deed of
trust. Upon written request, Tenant agrees to provide Landlord with copies of
all policies of insurance obtained by Tenant hereunder.

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         6.5      Cooperation in the Event of Loss. Landlord and Tenant shall
cooperate with each other in the collection of any insurance proceeds which may
be payable in the event of any loss, including the execution and delivery of any
proof of loss or other actions required to effect recovery.

                                    ARTICLE 7
               UTILITY, OPERATING, MAINTENANCE AND REPAIR EXPENSES

         7.1      Utility Charges. Tenant covenants and agrees to contract in
Tenant's own name and to pay, as Additional Rent, all charges for water, sewage,
disposal, storm drainage fees, gas, electricity, light, heat, power, telephone
or other utility services used, rendered or supplied to or for the Demised
Premises. If any such utility charges are not separately metered or billable to
the Demised Premises, then Landlord shall have the right to apportion utility
charges based upon Landlord's estimation of relative use of such utilities, and
such apportionment shall be final and binding upon Tenant. Tenant shall pay to
Landlord the apportioned amount of such utilities as Additional Rent.

         7.2      Common Facilities Charges. Tenant covenants and agrees to pay,
as Additional Rent, Tenant's Pro Rata Share of all costs and expenses of
operating, repairing, maintaining and upkeep of the Common Facilities including,
without limitation, upkeep and replanting of grass, trees, shrubs and
landscaping; removal of dirt, debris, obstructions and litter from Parking
Areas, landscaped areas, sidewalks and driveways; repairs, resurfacing,
resealing, restriping, sweeping and snow removal from the Parking Areas,
sidewalks and driveways; sprinkler systems; building signs; stairways; heating,
ventilation and air conditioning systems; utilities for the Common Facilities;
fire protection systems and sprinkler systems; exterior painting; water and
sewage disposal systems; storm drainage systems; supplies, personnel, and the
cost of any rental of equipment in implementing such services; charges for
professional management of the Property and Common Facilities, including wages,
salaries, benefits and payroll taxes paid by Landlord with respect to its
employees for providing such services; all alterations, additions, improvements
and other changes made to the Improvements in order to conform to changes
subsequent to the date of this Lease in any laws, ordinances, rules, regulations
or orders of any applicable governmental authority, subject to amortization of
such costs at a market rate of interest over the useful life thereof, as
determined by Landlord's accountants; and personal property taxes, licenses and
permits. Landlord may cause any or all of such services to be provided by
employees of Landlord or by independent contractor(s) and subcontractor(s).
Tenant shall pay to Landlord, monthly in advance, without notice, on each day
that payment of Monthly Rental is due, the estimated monthly charge for the
Common Facilities, as determined and redetermined from time to time by Landlord.
The initial monthly charge for Common Facilities is set forth in the Summary of
Basic Lease Terms attached hereto. If the total monthly charges paid by Tenant
are less than the Tenant's Pro Rata Share of the actual charges for Common
Facilities, Tenant shall pay the difference to Landlord within ten (10) days
after demand by Landlord. If Tenant's Pro Rata Share of such actual charges is
less than the total monthly charges paid by Tenant, the difference shall, at
Landlord's option, except as may be otherwise required by law, either be paid to
Tenant or credited against future monthly charges on the next applicable
invoice for Basic Rent, Additional Rent or other amounts payable by Tenant under
this Lease.

         7.3      Tenant's Maintenance Obligation. Tenant, at its sole cost and
expense to maintain, will repair, replace and keep the Demised Premises and all
improvements, fixtures and personal property thereon in good, safe and sanitary
condition, order and repair and in accordance with all applicable laws,
ordinances, orders, rules and regulations of governmental authorities having
jurisdiction. Tenant will perform or contract for and promptly pay for trash and
garbage disposal, janitorial and cleaning services, security services, interior
painting, interior window washing, replacement of damaged or broken glass and
other breakable materials, replacement of interior light bulbs and light
fixtures in or serving the Demised Premises. All costs of maintenance and
repairs to be performed by Tenant shall be considered Additional Rent hereunder.
All maintenance and repairs to be performed by Tenant shall be done promptly, in
a good and workmanlike fashion, and without diminishing the original quality of
the Demised Premises or the Property.

         7.4      Landlord's Maintenance Obligation. Landlord shall be
responsible for and shall bear the costs and expenses of replacement of, or
extraordinary maintenance and repairs to, roofs, foundations, exterior walls,
structural elements of the Building, and pipes for water and sewer. Landlord
shall maintain and repair the

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Common Facilities, and Tenant shall pay its Pro Rata Share of all costs and
expenses with respect thereto, pursuant to Section 7.2 above.

                                    ARTICLE 8
                           OTHER COVENANTS OF TENANT

         8.1      Limitation on Use by Tenant. Tenant covenants and agrees to
use the Demised Premises only for the use or uses set forth as Permitted Uses by
Tenant in the Summary of Basic Lease Terms and for no other purposes, except
with the prior written consent of Landlord. Landlord has made no investigation
of and makes no representations or warranties whatsoever regarding the
permissibility of Tenant's Permitted Uses under applicable zoning or land use
laws, rules, regulations or approvals.

         8.2      Compliance with Laws. Tenant covenants and agrees that at all
times during the Lease Term, Tenant's use of the Demised Premises shall be in
compliance with all zoning, land use, and other applicable laws, rules, and
regulations with respect thereto, and that nothing shall be done or kept on the
Demised Premises in violation of any law, ordinance, order, rule or regulation
of any governmental authority having jurisdiction, and that the Demised Premises
shall be used, kept and maintained in compliance with any such law, ordinance,
order, rule or regulation and with the certificate of occupancy issued for the
Building and/or the Demised Premises.

         8.3      Compliance with Insurance Requirements. Tenant covenants and
agrees that nothing shall be done or kept on the Demised Premises which might
impair or increase the cost of insurance maintained with respect to the Demised
Premises or the Property, which might increase the insured risks or which might
result in cancellation of any such insurance.

         8.4      No Waste or Impairment of Value. Tenant covenants and agrees
that nothing shall be done or kept on the Demised Premises or the Property which
might impair the value of the Demised Premises or the Property, or which would
constitute excessive wear and tear or waste.

         8.5      No Overloading. Tenant covenants and agrees that nothing shall
be done or kept on the Demised Premises or the Building and that no
improvements, changes, alterations, additions, maintenance or repairs shall be
made to the Demised Premises which might impair the structural soundness of the
Building, Improvements, or Parking Area, which might result in an overload of
electrical lines serving the Building or cause excessive tripping of circuit
breakers, which might interfere with any telephone lines or equipment or any
other electric or electronic equipment in the Building or on any adjacent or
nearby property, which might place excessive demands on or exceed the capacity
of the water lines or sewer lines servicing the Building, or which might in any
other way overload any portion of the Property or Improvements or any equipment
or facilities servicing the same. In the event of violations hereof, Tenant
covenants and agrees to immediately remedy the violation at Tenant's expense and
in compliance with all requirements of governmental authorities and insurance
underwriters.

         8.6      No Nuisance. Noxious or Offensive Activity. Tenant covenants
and agrees that no noxious or offensive activity shall be carried on upon the
Demised Premises or the Property nor shall anything be done or kept on the
Demised Premises or the Property which may be or become a public or private
nuisance or which may cause embarrassment, disturbance, or annoyance to others
in the Building or on adjacent or nearby property.

         8.7      No Annoying Lights, Sounds or Odors. Tenant covenants and
agrees that no light shall be emitted from the Demised Premises which is
unreasonably bright or causes unreasonable glare; no sound shall be emitted from
the Demised Premises which is unreasonably loud or annoying; and no odor shall
be emitted from the Demised Premises which is or might be noxious or offensive
to others in the Building or on adjacent or nearby property.

         8.8      No Unsightliness. Tenant covenants and agrees that no
unsightliness shall be permitted on the Demised Premises or the Property which
is visible from any adjacent or nearby property. Without limiting the generality
of the foregoing, all unsightly conditions, equipment, objects and conditions
shall be kept enclosed within the Demised Premises; no refuse, scrap, debris,
garbage, trash, bulk materials or waste shall be kept,

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stored or allowed to accumulate on the Demised Premises or the Property except
as may be enclosed within the Demised Premises; all pipes, wires, poles,
antennas and other facilities for utilities or the transmission or reception of
audio or visual signals or electricity shall be kept and maintained underground
or enclosed within the Demised Premises or appropriately screened from view; and
no temporary structure shall be placed or permitted on the Demised Premises or
the Property without the prior written consent of Landlord.

         8.9      No Animals. Tenant covenants and agrees that no animals shall
be permitted or kept on the Demised Premises or the Property; provided, however,
that nothing herein shall be construed as prohibiting qualified service animals
which may not be legally excluded from the Demised Premises or Property pursuant
to the Americans with Disabilities Act or any similar law, rule or regulation
applicable to the Property.

         8.10     Restriction on Signs and Exterior Lighting. Tenant covenants
and agrees that no signs or advertising devices of any nature shall be erected
or maintained by Tenant on the Demised Premises or the Property and no exterior
lighting shall be permitted on the Demised Premises or the Property except as
approved in writing by Landlord.

         8.11     No Violation of Covenants. Tenant covenants and agrees not to
commit, suffer or permit any violation of any covenant, condition or restriction
affecting the Demised Premises or the Property.

         8.12     Restriction on Changes and Alterations. Tenant covenants and
agrees not to improve, change, alter, add to, remove or demolish any
improvements on the Demised Premises, ("Changes"), without the prior written
consent of Landlord which consent shall not be unreasonably withheld, and unless
Tenant complies with all conditions which may be imposed by Landlord, in its
sole discretion, in connection with such consent; and unless Tenant pays to
Landlord the reasonable costs and expenses of Landlord for architectural,
engineering, legal or other consultants which may be reasonably incurred by
Landlord in determining whether to approve any such Changes. Landlord's consent
to any Changes and the conditions imposed in connection therewith shall be
subject to all requirements and restrictions of any holder of a mortgage or deed
of trust encumbering the Property. If such consent is given, no such changes
shall be permitted unless Tenant shall have procured and paid for all necessary
permits and authorizations from any governmental authorities having
jurisdiction; unless such Changes will not reduce the value of the Property, and
will not affect or impair existing insurance on the Property; and unless Tenant,
at Tenant's sole cost and expense, shall maintain or cause to be maintained
workmen's compensation insurance covering all persons employed in connection
with the work and obtains liability insurance covering any loss or damage to
persons or property arising in connection with any such Changes and such other
insurance or bonds as Landlord may reasonably require. Tenant covenants and
agrees that any such Changes approved by Landlord shall be completed with due
diligence and in a good and workmanlike fashion and in compliance with all
conditions imposed by Landlord and all applicable permits, authorizations, laws,
ordinances, orders, rules and regulations of governmental authorities having
jurisdiction and that the costs and expenses with respect to such Changes shall
be paid promptly when due and that the Changes shall be accomplished free of
liens of mechanics and materialmen. Tenant covenants and agrees that all such
Changes shall become the property of the Landlord at the expiration of the Lease
Term or, if Landlord so requests, Tenant shall, at or prior to expiration of the
Lease Term and at its sole cost and expense, remove such Changes and restore the
Demised Premises to their condition prior to such Changes.

         8.13     No Mechanic's Liens. Tenant covenants and agrees not to permit
or suffer, and to cause to be removed and released, any mechanic's,
materialmen's or other lien on account of supplies, machinery, tools, equipment,
labor or material furnished or used in connection with the construction,
alteration, improvement, addition to or repair of the Demised Premises by,
through or under Tenant. At least fifteen (15) days prior to any Changes, Tenant
shall provide written notice to Landlord of the date of commencement of any
Changes. Prior to the commencement of any Changes, Tenant shall post in
conspicuous locations and maintain on the Demised Premises and Building Notices
of Owner's Non-Liability in the form attached hereto as Exhibit C or in such
other form as Landlord may from time to time require in writing. Tenant shall
have the right to contest, in good faith and with reasonable diligence, the
validity of any such lien or claimed lien, provided that Tenant shall give to
Landlord such security as may be reasonably requested by Landlord to insure the
payment of any amounts claimed, including interest and costs, and to prevent any
sale, foreclosure or forfeiture of any interest in the

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Property on account of any such lien, including, without limitation, bonding,
escrow or endorsement of the title insurance policy of Landlord and any holder
of a mortgage or deed of trust encumbering the Property. If Tenant so contests,
then on final determination of the lien or claim for lien, Tenant shall
immediately pay any judgment rendered, with interest and costs, and will cause
the lien to be released and any judgment satisfied.

         8.14     No Other Encumbrances. Tenant covenants and agrees not to
obtain any financing secured by Tenant's interest in the Demised Premises and
not to encumber the Demised Premises or Landlord's or Tenant's interest therein,
without the prior written consent of Landlord, and to keep the Demised Premises
free from all liens and encumbrances except liens and encumbrances existing upon
the date of commencement of the Lease Term or liens and encumbrances created by
Landlord.

         8.15     Subordination to Landlord Mortgages. Tenant covenants and
agrees that this Lease and Tenant's interest in the Demised Premises shall be
junior and subordinate to any mortgage or deed of trust now or hereafter
encumbering the Property. In the event of a foreclosure of any such mortgage or
deed of trust, Tenant shall attorn to the party acquiring title to the Property
as the result of such foreclosure. No act or further agreement by Tenant shall
be necessary to establish the subordination of this Lease to any such mortgage
or deed of trust, which is self-executing, but Tenant covenants and agrees, upon
request to Landlord, to execute such documents as may be necessary or
appropriate to confirm and establish this Lease as subordinate to any such
mortgage or deed of trust in accordance with the foregoing provisions,
including, without limitation, the form of Subordination, Non-Disturbance and
Attornment Agreement attached hereto as Exhibit D. Alternatively, Tenant
covenants and agrees that, at the option of any mortgagee or beneficiary under a
deed of trust, Tenant shall execute documents as may be necessary to establish
this Lease and Tenant's interest in the Demised Premises as superior to any such
mortgage or deed of trust. If Tenant UNREASONABLY OR IN BAD FAITH fails to
execute any documents REASONABLY required to be executed by Tenant under the
provisions hereof WITHIN FIFTEEN (15) DAYS AFTER REQUEST, Tenant hereby makes,
constitutes and irrevocably appoints Landlord as Tenant's attorney in fact and
in Tenant's name, place and stead to execute any such document. In the event
Tenant requests any changes or revisions to any such document or agreement,
Tenant shall pay to Landlord, within ten (10) days after demand by Landlord, the
reasonable costs and expenses of Landlord in connection with the negotiation,
drafting, and revision thereof, including attorneys' fees.

         8.16     Assignment or Subletting. Tenant covenants and agrees not to
make or permit a Transfer by Tenant, as hereinafter defined, without Landlord's
prior written consent, which consent shall not be unreasonably withheld. A
Transfer by Tenant shall include an assignment of this Lease, a sublease of all
or any part of the Demised Premises, any transfer of 50% or more of the voting
stock or interests of Tenant, or any assignment, sublease, license, franchise,
transfer, mortgage, pledge or encumbrance of all or any part of Tenant's
interest under this Lease or in the Demised Premises, by operation of law or
otherwise, or the use or occupancy of all or any part of the Demised Premises by
anyone other than Tenant. Any such Transfer by Tenant without Landlord's written
consent shall be void and shall constitute a default under this Lease. In the
event Landlord consents to any Transfer by Tenant, Tenant shall not be relieved
of its obligations under this Lease and Tenant shall remain liable, jointly and
severally and as a principal, and not as a guarantor or surety, under this
Lease, to the same extent as though no Transfer by Tenant had been made, unless
specifically provided to the contrary in Landlord's prior written consent. The
acceptance of rent by Landlord from any person other than Tenant shall not be
deemed to be a waiver by Landlord of the provisions of this Section or of any
other provision of this Lease and any consent by Landlord to Transfer by Tenant
shall not be deemed a consent to any subsequent Transfer by Tenant. In giving or
withholding its consent to a proposed Transfer by Tenant, Landlord shall be
entitled to consider any reasonable factor, including but not limited to the
following: (a) financial strength and credit history of the proposed
subtenant/assignee; (b) business reputation of the proposed subtenant/assignee;
(c) proposed use of the Demised Premises by the proposed subtenant/assignee; (d)
managerial and operational skills of the proposed subtenant/assignee; and (e)
compatibility of the proposed subtenant/assignee with other tenants of the
Building. UNDER NO CIRCUMSTANCES SHALL TENANT BE PERMITTED TO MAKE ANY
ASSIGNMENT, SUBLEASE OR OTHER TRANSFER OF THIS LEASE TO, NOR PERMIT ANY
OCCUPANCY OR USE OF THE DEMISED PREMISES BY, XOR NETWORK ENGINEERING, INC., RED
SHIFT, INC., OR ANY PARENT, SUBSIDIARY, OR AFFILIATE OF SUCH CORPORATIONS.

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         Tenant covenants and agrees that in the event Landlord consents to a
sublease by Tenant, Tenant and Tenant's Subtenant shall enter into the form of
Sublease, Assumption and Consent Agreement attached hereto as Exhibit E, and in
the event Landlord consents to an assignment, Tenant and Tenant's assignee shall
enter into the form of Assignment, Assumption, and Consent Agreement attached
hereto as Exhibit F, or the REASONABLE standard form of agreement in each case
then being used by Landlord for subleases and assignments. In the event Tenant
or Tenant's transferee requests any changes or revisions to any such agreement,
Tenant shall pay to Landlord, within ten (10) days after demand by Landlord, the
reasonable costs and expenses of Landlord in connection with any request by
Tenant for consent to a Transfer, including REASONABLE attorneys' fees. LANDLORD
AGREES THAT SO LONG AS TENANT IS NOT IN DEFAULT, TENANT MAY COLLECT RENT ON ANY
SUBLEASES AND LANDLORD WILL NOT REQUIRE SUCH SUBTENANTS TO MAKE DIRECT PAYMENTS
TO LANDLORD.


         8.17     Annual Financial Statements. Tenant covenants and agrees to
furnish to Landlord, within fifteen (15) days after Landlord's written request,
copies of Tenant's most recent year end financial statements, and agrees that
Landlord may deliver any such financial statements to any existing or
prospective mortgagee or purchaser of the Property; PROVIDED, HOWEVER, THAT
TENANT SHALL NOT BE OBLIGATED TO PROVIDE ANT FINANCIAL STATEMENTS TO LANDLORD
THAT HAVE NOT YET BEEN RELEASED BY TENANT IN ITS FILINGS WITH THE SECURITIES AND
EXCHANGE COMMISSION. The financial statements shall include a balance sheet as
of the end of, and a statement of profit and loss for, the preceding fiscal year
of Tenant and, if regularly prepared by Tenant, a statement of sources and use
of funds for the preceding fiscal year of Tenant.

         8.18     Payment of Income and Other Taxes. Tenant covenants and agrees
to pay promptly when due all personal property taxes on personal property of
Tenant on the Demised Premises and all federal, state and local income taxes,
sales taxes, use taxes, Social Security taxes, unemployment taxes and taxes
withheld from wages or salaries paid to Tenant's employees, the nonpayment of
which might give rise to a lien on the Demised Premises or Tenant's interest
therein, and to furnish, if requested by Landlord, evidence of such payments.


         8.19     Estoppel Certificates. Tenant covenants and agrees to execute,
acknowledge and deliver to Landlord, upon Landlord's written request, a written
Estoppel Certificate certifying that this Lease is unmodified (or, if modified,
stating the modifications) and in full force and effect; stating the dates to
which Basic Rent has been paid, stating the amount of the Security Deposit held
by Landlord; stating the amount of the Monthly Deposits held by Landlord for the
then tax and insurance year; and stating whether or not Landlord is in default
under this Lease (and, if so, specifying the nature of the default); and stating
such other matters concerning this Lease as Landlord may reasonably request,
including but not limited to, the form of Estoppel Certificate attached hereto
as Exhibit G. Tenant agrees that such statement may be delivered to and relied
upon by any existing or prospective mortgagee or purchaser of the Property.
Tenant agrees that a failure to deliver such a statement within FIFTEEN (15)
days after written request from Landlord shall be conclusive upon Tenant that
this Lease is in full force and effect without modification except as may be
represented by Landlord; that there are no uncured defaults by Landlord under
this Lease; and that any representation by Landlord with respect to Basic Rent,
the Security Deposit and Monthly Deposits are true. In the event Tenant requests
any changes or revisions to any such Estoppel Certificate, OTHER THAN CHANGES
NECESSARY TO MAKE THE STATEMENTS CONTAINED IN SUCH CERTIFICATE ACCURATE, Tenant
shall pay to Landlord,


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within ten (10) days after demand by Landlord, the reasonable costs and expenses
of Landlord in connection the negotiation, drafting and revision of such
Estoppel Certificate, including REASONABLE attorneys' fees.

         8.20     Landlord Right to Inspect and Show Premises and to Install
"For Sale" Signs. Tenant covenants and agrees that Landlord and the authorized
representatives of Landlord shall have the right to enter the Demised Premises
at any reasonable time for the purposes of inspecting, repairing or maintaining
the same or performing any obligations of Tenant which Tenant has failed to
perform hereunder or for the purposes of showing the Demised Premises to any
existing or prospective mortgagee, purchaser or lessee of the Property or the
Demised Premises. Tenant covenants and agrees that Landlord may at any time and
from time to time place on the Property or the Demised Premises a sign
advertising the Property or the Demised Premises for sale or for lease.

         8.21     Landlord Right to Renovate. Expand or Modify Building. Tenant
covenants and agrees that Landlord shall have the right to renovate, expand,
reconstruct, or otherwise modify the Building and/or Common Facilities at any
time, in Landlord's sole discretion; provided, however, that no such renovation,
expansion, reconstruction, or other modification shall permanently and
materially interfere with Tenant's right to the quiet use and enjoyment of the
Demised Premises according to the terms of this Lease. In the event any
renovation, expansion, reconstruction or other modification of the Building or
Common Facilities by Landlord causes a temporary material interference with
Tenant's use and enjoyment of the Demised Premises, then during the period of
such interference, there shall be an abatement of Basic Rent and Additional Rent
proportionate to the extent of the space and period of time that Tenant is
unable to use and enjoy the Demised Premises.




WRH
WW

         8.23     Landlord Title to Fixtures. Improvements and Equipment.
Tenant covenants and agrees that all fixtures and improvements on the Demised
Premises and all equipment and personal property relating to the use and
operation of the Demised Premises (as distinguished from operations incident to
the business of Tenant), including all plumbing, heating, lighting, electrical
and air conditioning fixtures and equipment, whether or not attached to or
affixed to the Demised Premises, and whether now or hereafter located upon the
Demised Premises, shall be and remain the property of the Landlord upon
expiration of the Lease Term.

         8.24     Removal of Tenant's Equipment. Tenant covenants and agrees to
remove, at or prior to the expiration of the Lease Term, all of Tenant's
Equipment, as hereinafter defined. "Tenant's Equipment" shall mean all
equipment, apparatus, machinery, signs, furniture, furnishings and personal
property used in the operation of the business of Tenant (as distinguished from
the use and operation of the Demised Premises). If such removal shall injure or
damage the Demised Premises Tenant covenants and agrees, at its sole cost and
expense, at or prior to the expiration of the Lease Term, to repair such injury
and damage in good and workmanlike fashion and to place the Demised Premises in
the same condition as the Demised Premises would

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have been if such Tenant's Equipment had not been installed. If Tenant fails to
remove any Tenant's Equipment by the Expiration of the Lease Term, Landlord may,
at its option, AFTER TEN (10) DAYS WRITTEN NOTICE TO TENANT, keep and retain any
such Tenant's Equipment or dispose of the same and retain any proceeds
therefrom, and Landlord shall be entitled to recover from Tenant any costs or
expenses of Landlord in removing the same and in restoring the Demised Premises
in excess of the actual proceeds, if any, received by Landlord from disposition
thereof. Tenant releases and discharges Landlord from any and all claims and
liabilities of any kind arising out of Landlord's disposition of Tenant's
Equipment.

         8.25     Tenant Indemnification of Landlord. Tenant covenants and
agrees to protect, indemnify, defend, and hold Landlord harmless from and
against all liability, obligations, claims, damages, penalties, causes of
action, costs and expenses, including attorneys' fees, imposed upon, incurred by
or asserted against Landlord by reason of: (a) any accident, injury to or death
of any person or loss of or damage to any property occurring on or about the
Demised Premises or Common Facilities; (b) any act or omission of Tenant or
Tenant's officers, employees, agents, guests or invitees or of anyone claiming
by, through or under Tenant; (c) any use which may be made of, or condition
existing upon, the Demised Premises or Common Facilities; (d) any improvements,
fixtures or equipment upon the Demised Premises or Common Facilities; (e) any
failure on the part of Tenant to perform or comply with any of the provisions,
covenants or agreements of Tenant contained in this Lease; (f) any violation of
any law, ordinance, order, rule or regulation of governmental authorities having
jurisdiction by Tenant or Tenant's officers, employees, agents, guests or
invitees or by anyone claiming by, through or under Tenant; and (g) any repairs,
maintenance of Changes to the Demised Premises made or caused to be made by,
through or under Tenant. Tenant further covenants and agrees that, in case any
action, suit or proceeding is brought against Landlord by reason of any of the
foregoing, Tenant will, at Tenant's sole cost and expense, pay all costs and
expenses to defend Landlord in any such action, suit or proceeding with counsel
of Landlord's choosing.

         8.26     Liability of Landlord. Landlord shall be liable to Tenant for
Landlord's gross negligence and willful misconduct. Tenant waives and releases
any claims Tenant may have against Landlord or Landlord's officers, agents or
employees for loss, damage or injury to person or property sustained by Tenant
or Tenant's officers, agents, employees, guests, invitees, or anyone claiming
by, through or under Tenant resulting from any cause whatsoever other than gross
negligence or willful misconduct. Notwithstanding anything to the contrary
contained in this Lease, Landlord, its beneficiaries, successors and assigns,
shall not be personally liable with respect to any of the terms, covenants and
conditions of this Lease, and Tenant shall look solely to the equity of Landlord
in the Property in the event of any default or liability of Landlord under this
Lease, such exculpation of liability to be absolute and without any exception
whatsoever.

         8.27     Release upon Transfer by Landlord. In the event of a transfer
by Landlord of the Property or of Landlord's interest as Landlord under this
Lease, Landlord's successor or assignee shall take subject to and be bound by
this Lease and, in such event, Tenant covenants and agrees that Landlord shall
be released from all obligations of Landlord under this Lease, except
obligations which arose and matured prior to such transfer by Landlord; that
Tenant shall thereafter look solely to Landlord's successor or assign for
satisfaction of the obligations of Landlord under this Lease; and that, upon
demand by Landlord or Landlord's successor or assign, Tenant shall attorn to
such successor or assign.

         8.28     Rules and Regulations. Tenant shall observe and comply with
rules and regulations which may be reasonably promulgated and amended from time
to time by Landlord by providing written notice thereof to Tenant. Landlord
shall not be responsible to Tenant for the future of any other tenant of the
Building to observe or comply with any of the rules or regulations, but Landlord
shall make reasonable efforts to enforce the rules and regulations (if any) for
the benefit of all tenants of the Building.

         8.29     Monitoring Equipment. Should equipment for monitoring fire
systems and/or security systems be deemed necessary by Tenant or be required for
the Demised Premises by federal, state, or local governing agencies because of
Tenant's equipment, the nature of Tenant's business, or Tenant's modification of
the Demised Premises, Tenant shall be responsible for installation of such
monitoring system, for any required building permits, monthly monitoring fees,
and any fines, penalties or other

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charges for false alarms. Should such monitoring systems be otherwise required
by federal, state, or local governing agencies, or deemed by Landlord to be
advisable for the operation of the Building, Landlord shall be responsible for
installation of such monitoring systems, and all costs and expenses relating
thereto shall be included as Common Facilities Charges.

                                    ARTICLE 9
                              ENVIRONMENTAL MATTERS

         9.1      Definitions.

                  9.1.1    Hazardous Material. Hazardous Material means any
substance:

                           9.1.1.1  which is or becomes defined as a "hazardous
material," "hazardous waste," "hazardous substance," "regulated substance,"
"pollutant" or "contaminant" under any federal, state or local statute,
regulation, rule or ordinance or amendments thereto including, without
limitation, the Comprehensive Environmental Response, Compensation and Liability
Act (42 U.S.C. Section 9601 et seq.) and the Resource Conservation and Recovery
Act (42 U.S.C. Section 6901 et seq.); or

                           9.1.1.2  which is toxic, explosive, corrosive,
flammable, infectious, radioactive, carcinogenic, mutagenic, or otherwise
hazardous and is or becomes regulated by any governmental authority, agency,
department, commission, board, agency or instrumentality of the United States,
the State of Colorado or any political subdivision thereof; or

                           9.1.1.3  the presence of which on the premises causes
or threatens to cause a nuisance upon the premises or to adjacent properties or
poses or threatens to pose a hazard to the health or safety of persons on or
about the premises; or

                           9.1.1.4  which contains gasoline, diesel fuel or
other petroleum hydrocarbons; or

                           9.1.1.5  which contains polychlorinated bipheynols
(PCBs), asbestos or urea formaldehyde foam insulation; or

                           9.1.1.6  radon gas.

                  9.1.2    Environmental Requirements. Environmental
Requirements means all applicable present and future statutes, regulations,
rules, ordinances, codes, licenses, permits, orders, approvals, plans,
authorizations, concessions, franchises, and similar items, of all governmental
agencies, departments, commissions, boards, bureaus, or instrumentalities of the
United States, states and political subdivisions thereof and all applicable
judicial, administrative, and regulator decrees, judgments, and orders
relating to the protection of human health or the environment.

                  9.1.3    Environmental Damages. Environmental Damages means
all claims, judgments, damages, losses, penalties, fines, liabilities (including
strict liability), encumbrances, liens, costs, and expenses of investigation and
defense of any claim, whether or not such claim is ultimately defeated, and of
any good faith settlement or judgment, of whatever kind or nature, contingent or
otherwise, matured or unmatured, foreseeable or unforeseeable, including without
limitation reasonable attorneys' fees and disbursements and consultants' and
witnesses' fees, any of which are incurred at any time as a result of the
existence of Hazardous Material upon, about, beneath the premises or migrating
or threatening to migrate to or from the premises, or the existence of a
violation of Environmental Requirements pertaining to the premises.

         9.2      Tenant's Obligation to Indemnify. Defend and Hold Harmless.
Tenant, its successors, assigns and guarantors, agree to indemnify, defend,
reimburse and hold harmless the following persons from and against any and all
Environmental Damages ARISING FROM ACTIVITIES OF TENANT OR ITS EMPLOYEES,

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AGENTS, CONTRACTORS, SUBCONTRACTORS, OR GUESTS, LICENSEES, OR INVITEES which (1)
result in the presence of Hazardous Materials upon, about or beneath the Demised
Premises or migrating to or from the Demised Premises, or (2) result in the
violation of any Environmental Requirements pertaining to the Demised Premises
and the activities thereon:

                  9.2.1    Landlord;

                  9.2.2    any other person who acquires an interest in the
premises in any manner, including but not limited to purchase at a foreclosure
sale or otherwise; and

                  9.2.3    the directors, officers, shareholders, employees,
partners, agents, contractors, subcontractors, experts, licensees, affiliates,
lessees, mortgagees, trustees, heirs, devisees, successors, assigns, guests and
invitees of such persons.

         This obligation shall include, but not be limited to, the burden and
expense of investigating and defending all claims, suits and administrative
proceedings (with counsel reasonably approved by the indemnified parties),
including attorneys' fees and expert witness and consulting fees, even if such
claims, suits or proceedings are groundless, false or fraudulent, and conducting
all negotiations of any description, and paying and discharging, when and as the
same become due, any and all judgments, penalties or other sums due against such
indemnified persons, and all such expenses incurred in enforcing the obligation
to indemnify. Tenant, at its sole expense, may employ additional counsel of its
choice to associate with counsel representing the indemnified parties.

         9.3      Tenant's Obligation to Remediate. Notwithstanding the
obligation of Tenant to indemnify Landlord pursuant to this agreement, Tenant
shall, upon demand of Landlord, and at its sole cost and expense, promptly take
all actions to remediate the Demised Premises, Building, and Land which are
reasonably necessary to mitigate Environmental Damages or to allow full economic
use of the Building and Land, or are required by Environmental Requirements,
which remediation is necessitated by the 1) introduction of a Hazardous Material
upon, about or beneath the Demised Premises or 2) a violation of Environmental
Requirements, EITHER OF WHICH IS CAUSED BY THE ACTIONS OF TENANT, ITS EMPLOYEES,
AGENTS, CONTRACTORS, SUBCONTRACTORS, GUESTS, INVITEES OR LICENSEES. Tenant shall
promptly provide to Landlord copies of testing results and reports that are
generated in connection with the above activities, and copies of any
correspondence with any governmental entity related to such activities.

         9.4      Notification. If Tenant shall become aware of or receive
notice or other communication concerning any actual, alleged, suspected or
threatened violation of Environmental Requirements, or liability of Tenant for
Environmental Damages in connection with the Demised Premises or past or present
activities of any person thereon, or that any representation set forth in this
agreement is not or is no longer accurate, then Tenant shall deliver to
Landlord, within ten days of the receipt of such notice or communication by
Landlord, a written description of said violation, liability, correcting
information, or actual or threatened event or condition, together with copies of
any such notice or communication. Receipt of such notice shall not be deemed to
create any obligation on the part of Landlord to defend or otherwise respond to
any such notification or communication.

         9.5      Negative Covenants.

                  9.5.1    No Hazardous Material on Demised Premises. Except in
strict compliance with all Environmental Requirements, Tenant shall not cause,
permit or suffer any Hazardous Material to be brought upon, treated, kept,
stored, disposed of, discharged, released, produced, manufactured, generated,
refined or used upon, about or beneath the Demised Premises by Tenant, its
agents, employees, contractors, subcontractors, guests, licensees or invitees,
or any other person. Tenant shall deliver to Landlord copies of all documents
which Tenant provides to any governmental body in connection with compliance
with Environmental Requirements with respect to the premises, such delivery to
be contemporaneous with provision of the documents to the governmental agency.

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                  9.5.2    No Violations of Environmental Requirements. Tenant
shall not cause, permit or suffer the existence or the commission by Tenant, its
agents, employees, contractors, subcontractors or guests, licensees or invitees,
or by any other person of a violation of any Environmental Requirements upon,
about or beneath the Demised Premises or any portion of the Building or Land.

         9.6      Landlord's Right to Inspect and to Audit Tenant's Records.
Landlord shall have the right in its sole and absolute discretion, but not the
duty, to enter and conduct an inspection of the Demised Premises and to inspect
and audit Tenant's records concerning Hazardous Materials at any reasonable time
to determine whether Tenant is complying with the terms of the Lease, including
but not limited to the compliance of the Demised Premises and the activities
thereon with Environmental Requirements and the existence of Environmental
Damages. Tenant hereby grants to Landlord the right to enter the Demised
Premises UPON TWO BUSINESS DAYS' NOTICE, EXCEPT IN CASE OF EMERGENCY, IN WHICH
CASE SUCH NOTICE SHALL NOT BE REQUIRED, and to perform such tests on the Demised
Premises as are reasonably necessary in the opinion of Landlord to assist in
such audits and investigations. Landlord shall use reasonable efforts to
minimize interference with the business of Tenant by such tests inspections and
audits, but Landlord shall not be liable for any interference caused thereby.

         9.7      Landlord's Right to Remediate. Should Tenant fail to perform
or observe any of its obligations or agreements pertaining to Hazardous
Materials or Environmental Requirements, then Landlord shall have the right, but
not the duty, without limitation upon any of the rights of Landlord pursuant to
this Lease, to enter the Demised Premises personally or through its agents,
consultants or contractors and perform the same. Tenant agrees to indemnify
Landlord for the costs thereof and liabilities therefrom as set forth in Section
9.2.

         9.8      Survival of Environmental Obligations. The obligations of
Landlord and Tenant as set forth in this Article 9 and all of its sections shall
survive expiration or termination of this Lease.

                                   ARTICLE 10
                             DAMAGE OR DESTRUCTION

         10.1     Damage to Demised Premises. If any portion of the Demised
Premises shall be damaged or destroyed by fire or other casualty, Tenant shall
give prompt written notice thereof to Landlord ("Tenant's Notice of Damage").


         10.2     Options to Terminate if Damage to Demised Premises is
Substantial. Upon receipt of Tenant's Notice of Damage, Landlord shall promptly
proceed to determine the nature and extent of the damage or destruction and to
estimate the time necessary to repair or restore the Demised Premises. As soon
as reasonably possible, BUT IN NO EVENT LATER THAN THIRTY (30) DAYS, Landlord
shall give written notice to Tenant stating Landlord's estimate of the time
necessary to repair or restore the Demised Premises ("Landlord's Notice of
Repair Time"). If Landlord reasonably estimates that repair or restoration of
the Demised Premises cannot be completed within ONE HUNDRED EIGHTY (180) days
from the time of Landlord's Notice of Repair Time, Landlord and Tenant shall
each have the option to terminate this Lease. If, however, the damage or
destruction was caused by the NEGLIGENCE of Tenant or Tenant's officers,
employees, agents, guests or invitees or of anyone claiming by, through or under
Tenant, Landlord shall have the option to terminate this Lease if Landlord
reasonably estimates that the repair or restoration cannot reasonably be
completed within ONE HUNDRED EIGHTY (180) days from the time of Tenant's Notice
of Damage, but Tenant shall not have the option to terminate this Lease. Any
option granted hereunder shall be exercised by written notice to the other party
given within ten (10) days after Landlord's Notice of Repair Time. If either
Landlord or Tenant exercises its option to terminate this Lease, the Lease Term
shall expire thirty (30) days after the notice by either Landlord or Tenant
exercising such party's option to terminate this Lease. Following termination of
this Lease under the provisions hereof, Landlord shall refund to Tenant such
amounts of Basic Rent and Additional Rent theretofore paid by Tenant as may be
applicable to the period subsequent to the time of Tenant's Notice of Damage
less the reasonable value of any use or occupation of the Demised Premises by
Tenant subsequent to the time of Tenant's Notice of Damage.


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         10.3     Damage to Building. If the Building shall be damaged or
destroyed by fire or other casualty (whether or not the Demised Premises are
affected) to the extent of fifty percent (50%) or more of the replacement value
of the Building, and within thirty (30) days after the happening of such damage
Landlord shall decide not to reconstruct or rebuild the Building, then upon
written notice to Tenant within such thirty (30) days, this Lease shall
terminate and Landlord shall refund to Tenant such amounts of Basic Rent and
Additional Rent paid by Tenant for the period after such damage less the
reasonable value of any use or occupation of the Demised Premises by Tenant
during such period.


         10.4     Obligations to Repair and Restore. If repair and restoration
of the Demised Premises can be completed within the period specified in Section
10.2, in Landlord's reasonable estimation, or if neither Landlord nor Tenant
terminate this Lease as provided in Sections 10.2 or 10.3, this Lease shall
continue in full force and effect and Landlord shall proceed forthwith to cause
the Demised Premises to be repaired and restored with reasonable diligence and
there shall be abatement of Basic Rent and Additional Rent proportionate to the
extent of the space and period of time that Tenant is unable to use and enjoy
the Demised Premises.


         10.5     Application of Insurance Proceeds. The proceeds of any
Casualty Insurance maintained on the Demised Premises, other than casualty
insurance maintained by Tenant on fixtures and personal property of Tenant,
shall be paid to and become the property of Landlord, subject to any obligation
of Landlord to cause the Demised Premises to be repaired and restored and
further subject to any rights of a holder of a mortgage or deed of trust
encumbering the Property to such proceeds. Landlord's obligation to repair and
restore the Demised Premises provided in this Article 10 is limited to the
repair and restoration that can be accomplished with the proceeds of any
Casualty Insurance maintained on the Demised Premises. The amount of any such
insurance proceeds is subject to any right of a holder of a mortgage or deed of
trust encumbering the Property to apply such proceeds to its secured debt. IF
INSURANCE PROCEEDS ARE INADEQUATE TO PERMIT RESTORATION OF THE DEMISED PREMISES
AS REQUIRED HEREIN, TENANT SHALL HAVE THE RIGHT TO TERMINATE THIS LEASE UPON
WRITTEN NOTICE TO LANDLORD.

                                   ARTICLE 11
                                  CONDEMNATION

         11.1     Taking - Substantial Taking - Insubstantial Taking. A "Taking"
shall mean the taking of all or any portion of the Demised Premises as a result
of the exercise of the power of eminent domain or condemnation for public or
quasi-public use or the sale of all or part of the Demised Premises under the
threat of condemnation. A "Substantial Taking" shall mean a Taking of twenty
five percent (25%) or more of the area (in square feet) of either the Demised
Premises or Hie Building. An "Insubstantial Taking" shall mean a Taking which
does not constitute a Substantial Taking.

         11.2     Termination on Substantial Taking. If there is a Substantial
Taking with respect to the Demised Premises or the Building, the Lease Term
shall expire on the date of vesting of title pursuant to such Taking. In the
event of termination of this Lease under the provisions hereof, Landlord shall
refund to Tenant such amounts of Basic Rent and Additional Rent theretofore paid
by Tenant as may be applicable to the period subsequent to the time of
termination of this Lease.


         11.3     Restoration on Insubstantial Taking. In the event of an
Insubstantial Taking, this Lease shall continue in full force and effect,
Landlord shall proceed forthwith to cause the Demised Premises, less such
Taking, to be restored as near as may be to the original condition thereof and
there shall be abatement of Basic Rent and Additional Rent proportionate to the
extent of the space so taken.


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         11.4     Right to Award. The total award, compensation, damages or
consideration received or receivable as a result of a Taking ("Award") shall be
paid to and be the property of Landlord, including, without limitation, any part
of the Award made as compensation for diminution of the value of the leasehold
or the fee of the Demised Premises. Tenant hereby assigns to Landlord, all of
Tenant's right, title and interest in and to any such Award. Tenant covenants
and agrees to execute, immediately upon demand by Landlord, such documents as
may be necessary to facilitate collection by Landlord of any such Award.
Notwithstanding Landlord's right to the entire Award, Tenant shall be entitled
to any separate award, if any, for the loss of Tenant's personal property or the
loss of Tenant's business and profits AND LANDLORD SHALL REASONABLY COOPERATE
WITH TENANT IN ITS EFFORTS TO PURSUE SUCH A SEPARATE AWARD

                                   ARTICLE 12
                               DEFAULTS BY TENANT

         12.1     Defaults Generally. Each of the following shall constitute a
"Default by Tenant" under this Lease.


         12.2     Failure to Pay Rent or Other Amounts. A Default by Tenant
shall exist if Tenant fails to pay Basic Rent, Additional Rent, Monthly
Deposits, or any other amounts payable by Tenant under the terms of this Lease,
within FIVE (5) days after such rental or amount is due.


         12.3     Violation of Lease Terms. A Default by Tenant shall exist if
Tenant breaches or fails to comply with any agreement, term, covenant or
condition in this Lease applicable to Tenant, and Tenant does not cure such
breach or failure within thirty (30) days after WRITTEN notice thereof by
Landlord to Tenant, or, if such breach or failure to comply cannot be reasonably
cured within such 30-day period, if Tenant shall not in good faith commence to
cure such breach or failure to comply with such 30-day period or shall not
diligently proceed therewith to completion with sixty (60) days following the
occurrence of the breach or failure.


         12.4     Nonoccupancy of Demised Premises. A Default by Tenant shall
exist if Tenant shall LEAVE THE DEMISED PREMISES CONTINUOUSLY VACANT FOR SIXTY
(60) DAYS AND abandon the Demised Premises.


         12.5     Transfer of Interest Without Consent. A Default by Tenant
shall exist if Tenant's interest under this Lease or in the Demised Premises
shall be transferred to or pass to or devolve upon any other party without
Landlord's prior written consent.

         12.6     Execution and Attachment Against. A Default by Tenant shall
exist if Tenant's interest under this Lease or in the Demised Premises shall be
taken upon execution or by other process of law directed against Tenant, or
shall be subject to any attachment at the instance of any creditor or claimant
against Tenant and said attachment shall not be discharged or disposed of within
thirty (30) days after the levy thereof.

         12.7     Bankruptcy or Related Proceedings. A Default by Tenant shall
exist if Tenant shall file a petition in bankruptcy or insolvency or for
reorganization or arrangement under the bankruptcy laws of the United States or
under any similar act of any state, or shall voluntarily take advantage of any
such law or act by answer or otherwise, or shall be dissolved or shall make an
assignment for the benefit of creditors or if involuntary proceedings under any
such bankruptcy or insolvency law or for the dissolution of Tenant shall be
instituted against Tenant or a receiver or trustee shall be appointed for the
Demised Premises or for all or substantially all of the property of Tenant, and
such proceedings shall not be dismissed or such receivership or trustee-ship
vacated within sixty (60) days after such institution or appointment.

                                   ARTICLE 13

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                               LANDLORD'S REMEDIES

         13.1     Remedies Generally. Upon the occurrence of any Default by
Tenant, Landlord shall have the right, at Landlord's election, then or at
anytime thereafter, to exercise any one or more of the following remedies.

         13.2     Cure by Landlord. In the event of a Default by Tenant,
Landlord may, at Landlord's option, but without obligation to do so, and without
releasing Tenant from any obligations under this Lease, make any payment or take
any action as Landlord may deem necessary or desirable to cure any such Default
by Tenant in such manner and to such extent as Landlord may deem necessary or
desirable. LANDLORD SHALL GIVE TENANT NOTICE AND OPPORTUNITY TO CURE SUCH
DEFAULT WITHIN THE TIME PERIODS SPECIFIED IN THIS LEASE, EXCEPT IN CASE OF
EMERGENCY, IN WHICH CASE Landlord may do so without demand on, or written notice
to, Tenant and without giving Tenant any opportunity to cure such Default by
Tenant. Tenant covenants and agrees to pay to Landlord, within ten (10) days
after demand, all advances, costs and expenses of Landlord in connection with
the making of any such payment or the taking of any such action, including
reasonable attorneys' fees, together with interest as hereinafter provided from
the day of payment of any such advances, costs and expenses by Landlord. Action
taken by Landlord may include commencing, appearing in, defending or otherwise
participating in any action or proceedings and paying, purchasing, contesting or
compromising any claim, right, encumbrance, charge or lien with respect to the
Demised Premises which Landlord, in its discretion, may deem necessary or
desirable to protect its interest in the Demised Premises and under this Lease.

         13.3     Termination of Lease and Damages. In the event of a Default by
Tenant THAT IS NOT CURED WITHIN THE APPLICABLE CURE PERIOD(S) PROVIDED IN THIS
LEASE, Landlord may terminate this Lease, effective at such time as may be
specified by written notice to Tenant, and demand (and, if such demand is
refused, recover) possession of the Demised Premises from Tenant. Tenant shall
remain liable to Landlord for damages in an amount equal to the Basic Rent,
Additional Rent and other sums which would have been owing by Tenant hereunder
for the balance of the term, had this Lease not been terminated, less the net
proceeds, if any, of reletting of the Demised Premises by Landlord subsequent to
such termination, after deducting all Landlord's REASONABLE expenses in
connection with such recovery of possession or reletting. Landlord shall be
entitled to collect and receive such damages from Tenant on the days on which
the Basic Rent, Additional Rent and other amounts would have been payable if
this Lease had not been terminated. Alternatively, at the option of Landlord,
Landlord shall be entitled to recover forthwith from Tenant, as damages for loss
of the bargain and not as a penalty, an aggregate sum which, at the time of such
termination of this Lease, represents the excess, if any, of (a) the aggregate
of the Basic Rent, Additional Rent and all other sums payable by Tenant
hereunder that would have accrued for the balance of the Lease Term, over (b)
the aggregate rental value of the Demised Premises for the balance of the Lease
Term, both discounted to present worth at the then applicable federal rate.


         13.4     Repossession and Reletting. In the event of Default by Tenant
THAT IS NOT CURED WITHIN THE APPLICABLE CURE PERIOD(S) PROVIDED IN THIS LEASE,
Landlord may reenter and take possession of the Demised Premises or any part
thereof, WITH SUCH DEMAND OR NOTICE AS MAY BE REQUIRED BY APPLICABLE LAW, and
repossess the same and expel Tenant and any party claiming by, under or through
Tenant, and remove the effects of both, without breach of the peace, without
being liable for prosecution on account thereof or being deemed guilty of any
manner of trespass, and without prejudice to any remedies for arrears of rent or
right to bring any proceeding for breach of covenants or conditions. No such
reentry or taking possession of the Demised Premises by Landlord shall be
construed as an election by Landlord to terminate this Lease unless a written
notice of such intention is given to Tenant. No notice from Landlord hereunder
or under a forcible entry and detainer statute or similar law shall constitute
an election by Landlord to terminate this Lease unless such notice specifically
so states. Landlord reserves the right, following any reentry or reletting, to
exercise its right to terminate this Lease by giving Tenant such written notice,
in which even the Lease will terminate as specified in said notice. After
recovering possession of the Demised Premises, Landlord may, from time to time,
but shall not be obligated to, relet the Demised Premises, or any part thereof,
for the account of Tenant, for such term or terms and on such conditions and
upon such other terms as Landlord, in its uncontrolled discretion, may
determine. Landlord may make such


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<PAGE>

repairs, alterations or improvements as Landlord may consider appropriate to
accomplish such reletting, and Tenant shall reimburse Landlord upon demand for
all REASONABLE costs and expenses, including brokers' commissions and attorneys'
fees, which Landlord may incur in connection with such reletting. Landlord may
collect and receive the rents for such reletting but Landlord shall in no way be
responsible or liable for any failure to relet the Demised Premises, or any part
thereof, or for any failure to collect any rent due upon such reletting.
Notwithstanding Landlord's recovery of possession of the Demised Premises,
Tenant shall continue to pay on the dates herein specified, the Basic Rent,
Additional Rent and other amounts which would be payable hereunder if such
repossession had not occurred. Upon the expiration or earlier termination of
this Lease, Landlord shall refund to Tenant any amount, without interest, by
which the amounts paid by Tenant, when added to the net amount, if any,
recovered by Landlord through any reletting of the Demised Premises, exceeds the
amounts payable by Tenant under this Lease. If, in connection with any
reletting, the new lease term extends beyond the existing term, or the premises
covered thereby include other premises not part of the Demised Premises, a fair
apportionment of the rent received from such reletting and the expenses incurred
in connection therewith will be made in determining the net amount recovered
from such reletting. NOTWITHSTANDING ANYTHING TO THE CONTRARY HEREIN, LANDLORD
SHALL MAKE COMMERCIALLY REASONABLE EFFORTS TO MITIGATE ITS DAMAGES.


         13.5     Security Interest.


         13.6     Suits by Landlord. Actions or suits for the recovery of
amounts and damages payable under this Lease may be brought by Landlord from
time to time, at Landlord's election, and Landlord shall not be required to
await the date upon which the Lease Term would have expired to bring any such
action or suit.

         13.7     Recovery of Landlord Enforcement Costs. All costs and expenses
incurred by Landlord in connection with collecting any amounts and damages owing
by Tenant pursuant to the provisions of this Lease or to enforce any provision
of this Lease, including reasonable attorneys' fees, whether or not any action
is commenced by Landlord, shall be paid by Tenant to Landlord upon demand.


         13.8     Administrative Late Charge. Other remedies for nonpayment of
rent notwithstanding, if the monthly rental payment is not received by Landlord
on or before the FIFTH day of the month for which the rent is due, or if
any other payment due Landlord by Tenant is not received by Landlord on or
before the last day of the month next following the month in which Tenant was
invoiced, an Administrative Late Charge of FOUR PERCENT (4%) of such past due
amount shall be come due and payable in addition to such amounts owed under this
Lease to help defray the additional cost to Landlord for processing such late
payments.



         13.9     Interest on Past-Due Payments and Advances. Tenant covenants
and agrees to pay to Landlord interest on demand at the rate of EIGHTEEN PERCENT
(18%) per annum, compounded on a monthly basis, on the amount of any Monthly
Rent, Monthly Deposit or other charges not paid when due, from the date due and
payable, and on the amount of any payment made by Landlord required to have been
made by Tenant under this Lease and on the amount of any costs and expenses,
including reasonable attorneys' fees, paid by Landlord in connection with the
taking of any action to cure any Default by Tenant, from the date of making any
such payment or the advancement of such costs and expenses by Landlord.


         13.10    Landlord's Bankruptcy. Nothing contained in this Lease shall
limit or prejudice the right of Landlord to prove and obtain as liquidated
damages in any bankruptcy, insolvency, receivership, reorganization or
dissolution proceeding, an amount equal to the maximum allowable by any statute
or rule of law governing such proceeding in effect at the time when such damages
are to be proved, whether or not such amount be greater, equal or less than the
amounts recoverable, either as damages or rent, under this Lease.

Copyright(C)1999 Flatiron Park Company

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         13.11    Remedies Cumulative. Exercise of any of the remedies of
Landlord under this Lease shall not prevent the concurrent or subsequent
exercise of any other remedy provided for in this Lease or otherwise available
to Landlord at law or in equity.

                                   ARTICLE 14
                           SURRENDER AND HOLDING OVER

         14.1     Surrender upon Lease. Upon the expiration or earlier
termination of this Lease, or on the date specified in any demand for possession
by Landlord after any UNCURED Default by Tenant, Tenant covenants and agrees to
surrender possession of the Demised Premises to Landlord broom clean, with all
lighting, doors, and electrical and mechanical systems (including, without
limitation, all HVAC facilities) in good working order and condition, all walls
in clean condition and holes or punctures in the walls repaired, and otherwise
in the same condition as when Tenant first occupied the Demised Premises,
ordinary wear and tear excepted.


         14.2     Holding Over. If Tenant shall hold over after the expiration
of the Lease Term, without written agreement providing otherwise, Tenant shall
be deemed to be a Tenant at sufferance, at a monthly rental, payable in advance,
equal to ONE HUNDRED FIFTY PERCENT (150%) of the Monthly Rental, and Tenant
shall be bound by all of the other terms, covenants and agreements of this
Lease. Nothing contained herein shall be construed to give Tenant the right to
hold over at any time, and Landlord may exercise any and all remedies at law or
in equity to recover possession of the Demised Premises, as well as any damages
incurred by Landlord, due to Tenant's failure to vacate the Demised Premises and
deliver possession to Landlord as herein provided.


                                   ARTICLE 15
                                 MISCELLANEOUS

         15.1     No Implied Waiver. No failure by Landlord to insist upon the
strict performance of any term, covenant or agreement contained in this Lease,
no failure by Landlord to exercise any right or remedy under this Lease, and no
acceptance of full or partial payment during the continuance of any Default by
Tenant, shall constitute a waiver of any such term, covenant or agreement, or a
waiver of any such right or remedy, or a waiver of any such Default by Tenant.

         15.2     Survival of Provisions. Notwithstanding any termination of
this Lease, the same shall continue in force and effect as to any provisions
hereof which require observance or performance by Landlord or Tenant subsequent
to termination.

         15.3     Covenants Independent. This Lease shall be construed as if the
Covenants herein between Landlord and Tenant are independent, and not dependent,
and Tenant shall not be entitled to any offset against Landlord if Landlord
fails to perform its obligations under this Lease.

         15.4     Covenants as Conditions. Each provision of this Lease
performable by Tenant shall be deemed both a covenant and a condition.

         15.5     Tenant's Remedies. Tenant may bring a separate action against
Landlord for any claim Tenant may have against Landlord under this Lease,
provided Tenant shall first give written notice thereof to Landlord and shall
afford Landlord a reasonable opportunity to cure any such default. In addition,
Tenant shall send notice of such default by certified or registered mail,
postage prepaid, to the holder of any mortgage or deed of trust covering the
Demised Premises, the Property or any portion thereof of whose address Tenant
has been notified in writing, and shall afford such holder a reasonable
opportunity to cure any default on Landlord's behalf. In no event will Landlord
be responsible for any incidental, consequential or special damages incurred by
Tenant, including, but not limited to, loss of profits or interruption of
business as a result of any default by Landlord hereunder.

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<PAGE>

         15.6     Binding Effect. This Lease shall extend to and be binding upon
the heirs, executors, legal representatives, successors and assigns of the
respective parties hereto. The terms, covenants, agreements and conditions in
this Lease shall be construed as covenants running with the Land.

         15.7     Short Form Lease. This Lease shall not be recorded, but Tenant
agrees, at the request of Landlord, to execute a short form lease for recording,
containing the names of the parties, a description of the Demised Premises and
the Lease Term.

         15.8     Notices and Demands. All notices, demands or billings under
this Lease shall be in writing, signed by the party giving the same and shall be
deemed properly given and received when actually given and received or three (3)
business days after mailing, if sent by registered or certified United States
mail, postage prepaid, addressed to the party to receive the notice at the
address set forth for such party in the first paragraph of this Lease or at such
other address as either party may notify the other of in writing. Any notice by
Tenant to Landlord shall not be effective until a copy thereof shall have been
received by or transmitted in the same manner to Landlord's counsel at the
address set forth in the Summary of Basic Lease Terms or such other address as
Landlord may from time to time notify Tenant in writing.

         15.9     Force Majeure. In the event that Landlord shall be delayed or
hindered in, or prevented from, the performance of any act required hereunder by
reason of strikes, lock-outs, labor troubles, inability to procure materials,
the inability to obtain building inspections, approvals, or permits, stop work
orders, the inability to obtain a certificate of occupancy, failure of power or
unavailability of utilities, riots, insurrection, war or other reason of like
nature not the fault of Landlord, or not within its reasonable control, the
performance of such acts shall be excused for the period of delay, and the
period for the performance of any such act shall be extended for a period
equivalent to the period of such delay (including extension of both the
commencement and expiration dates of this Lease); provided, however, that if
Tenant is not in any way responsible for the delay and does not have use or
occupancy of the Demised Premises during the period of delay, the rent and other
charges payable hereunder shall be abated for such period of delay.

         15.10    Time of the Essence. Time is of the essence under this Lease,
and all provisions herein relating thereto shall be strictly construed.

         15.11    Captions for Convenience. The headings and captions hereof are
for convenience only and shall not be considered in interpreting the provisions
hereof.

         15.12    Severability. If any provision of this Lease shall be held
invalid or unenforceable, the remainder of this Lease shall not be affected
thereby, and there shall be deemed substituted for the affected provision a
valid and enforceable provision as similar as possible to the affected
provision.

         15.13    Governing Law and Venue. This Lease shall be interpreted and
enforced according to the laws of the State of Colorado. Any action or
proceeding arising out of this Lease, its modification or termination, or the
performance or breach of either party hereto, shall be brought exclusively in
courts of the state and county in which the Property is located. The parties
agree that such courts are a convenient forum and waive any right to alter or
change venue, including removal.

         15.14    Entire Agreement/Further Assurances. This Lease and any
exhibits and addenda referred to herein, constitute the final and complete
expression of the parties' agreement with respect to the Demised Premises and
Tenant's occupancy thereof. Each party agrees that it has not relied upon or
regarded as binding any prior agreements, negotiations, representations, or
understandings, whether oral or written, except as expressly set forth herein.
The parties agree that if there should be any clerical or typographical errors
in this Lease, the Summary of Basic Lease Terms, any exhibit or addendum hereto,
the party requested to do so will use its reasonable, good faith efforts to
execute such corrective instruments or do all things necessary or appropriate to
correct such errors. Further, the parties agree that if it becomes necessary or
desirable to execute further instruments or to

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<PAGE>

make other assurances, the party requested to do so will use its reasonable,
good faith efforts to provide such executed instruments or do all things
reasonably necessary or appropriate to carry out this Lease.

         15.15    No Oral Amendment or Modifications. No amendment or
modification of this Lease, and no approvals, consents or waivers by Landlord
under this Lease, shall be valid and binding unless in writing and executed by
the party to be bound.

         15.16    Real Estate Brokers. Tenant covenants to pay, hold harmless
and indemnify the Landlord from and against any and all cost, expense or
liability for any compensation, commissions, charges or claims by any broker or
other agent with respect to this Lease or the negotiation thereof other than the
broker(s) listed as the Brokers), if any, on the Summary of Basic Lease Terms.

         15.17    Relationship of Landlord and Tenant. Nothing contained herein
shall be deemed or construed as creating the relationship of principal and agent
or of partnership, or of joint venture by the parties hereto, it being
understood and agreed that no provision contained in this Lease nor any acts of
the parties hereto shall be deemed to create any relationship other than the
relationship of Landlord and Tenant.

         15.18    Authority of Tenant. Each individual executing this Lease on
behalf of Tenant represents and warrants that he is duly authorized to deliver
this Lease on behalf of Tenant and that this Lease is binding upon Tenant in
accordance with its terms.

         15.19    REASONABLE COSTS AND EXPENSES. WHENEVER ANY PROVISON OF THIS
LEASE REQUIRES THE REIMBURSEMENT OF COSTS OR EXPENSES BY TENANT, SUCH PROVISION
SHALL BE INTERPRETED TO MEAN REASONABLE COSTS AND EXPENSES.

                                     * * *

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<PAGE>

         IN WITNESS WHEREOF, the parties hereto have caused this Lease to be
executed the day and year first above written.

LANDLORD:                                   TENANT:

2545 Central, LLC.                          Carrier Access Corporation

By: /s/ Richard L. Hedges                   By: /s/ Nancy Pierce
   ------------------------                    -------------------------------
      Richard L. Hedges                           Nancy Pierce
      Vice President                              Chief Financial Officer
      Authorized Agent for Landlord

STATE OF COLORADO  )
                   )ss
COUNTY OF BOULDER  )

         The foregoing instrument was acknowledged before me this 15th day of
December, 1999 by Richard L. Hedges, as Vice President and Authorized Agent of
FLATIRON PARK COMPANY.

   Witness my hand and official seal.
   My commission expires: FEB 11, 2002
        CHARISSE J. KOLISH
         NOTARY PUBLIC
        STATE OF COLORADO                          /s/ CHARISSE J. KOLISH
                                                   ---------------------------
    My commission expires: FEB 11, 2002            Notary Public

STATE OF COLORADO   )
                    )ss
COUNTY OF BOULDER   )

         The foregoing instrument was acknowledged before me this 15th day of
December, 1999 by Nancy Pierce, as Chief Financial Officer of Carrier Access
Corporation.

         Witness my hand and official seal.
         My commission expires: FEB 11, 2002

      CHARISSE J. KOLISH                         /s/ CHARISSE J. KOLISH
        NOTARY PUBLIC                            ------------------------------
     STATE OF COLORADO                           Notary Public

    My Commission Expires: Feb. 11, 2002

 Copyright (C) 1999 Flatiron Park Company

                                       24
<PAGE>

                                    EXHIBIT A

                           LEGAL DESCRIPTION OF LAND

LOT 5, FLATIRON INDUSTRIAL PARK FILING N0.4
COUNTY OF BOULDER, STATE OF COLORADO

Copyright (C) 1999 Flatiron Park Company

<PAGE>

                                    EXHIBIT B

                  LOCATION OF DEMISED PREMISES WITHIN BUILDING

[ENTIRE BUILDING]

Copyright (C) 1999 Flatiron Park Company

<PAGE>

                                   EXHIBIT B

                                  [FLOOR PLAN]

                              5765 CENTRAL AVENUE

                                   1ST FLOOR

<PAGE>

                                   EXHIBIT B

                                  (CONTINUED)

                               [FLOORFLOOR PLAN]

                                5766 CENTRAL AV.

                                   2ND FLOOR
<PAGE>

                                    EXHIBIT C

                  NOTICE OF NON-LIABILITY FOR MECHANICS' LIENS

Pursuant to C.R.S. Section 38-22-105, [Landlord], the owner of these premises,
located at [Building address], Boulder, Colorado, hereby gives notice to all
persons performing labor or furnishing skill, materials, machinery, or other
fixtures in connection with any construction, alteration, removal, addition,
repair or other improvement on or to these premises, that the owner shall not be
liable therefor and the interests of said owner shall not be subject to any lien
for the same.

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                                    EXHIBIT D

                                     FORM OF

                         SUBORDINATION, NON-DISTURBANCE
                            AND ATTORNMENT AGREEMENT

         THIS AGREEMENT is entered into as of the__________ day of ___________,
________, among _________________________________ ("Landlord"), whose address is
c/o Flatiron Park Company, 5540 Central Avenue, Boulder, CO 80301,
_________________________ ("Tenant"), whose address is ________________________,
and ____________________ ("Lender"), whose address is _________________________.

                                    RECITALS

         A.       Landlord is the owner or the ground lessee of the real
property described on Exhibit A attached hereto (the "Property").

         B.       Pursuant to a certain Lease dated _____________________,
_______________ (the "Lease"), Landlord has leased to Tenant all or a portion of
the Property.

         C.       Financing for the Property is to be provided by a loan to be
made by Lender to Borrower (the "Loan"). The Loan will be secured, in part, by a
Deed of Trust (the "Deed of Trust") from Landlord to the Public Trustee of
Boulder County, Colorado, for the use and benefit of Lender.

         D.       The parties wish to provide for subordination of the Lease to
the Deed of Trust, for the continuation of Tenant's right to occupy the Property
so long as no default exists under the Lease, notwithstanding any foreclosure of
the Deed of Trust, and for Tenant's attornment to any person or entity who may
acquire title to the Property upon or in lieu of foreclosure of the Deed of
Trust.

         NOW, THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which is hereby acknowledged, the parties agree as follows:

                              TERMS AND CONDITIONS

         1.       Status of Lease. Tenant represents and warrants to Lender that
the Lease has been duly authorized, executed and delivered by Tenant. Landlord
and Tenant each represent and warrant to Lender that the Lease is in full force
and effect and has not been modified or amended in any way, and neither party to
the Lease is in default with respect to such party's obligations under the Lease
as of the date of this Agreement.

         2.       Assignment of Landlord's Interest in Lease. Tenant
acknowledges that, pursuant to the Deed of Trust, Landlord has assigned all of
the rights and benefits (but none of the obligations) of Landlord under the
Lease to Lender. Upon notice from Lender that Lender has revoked its revocable
waiver of Lender's rights under the Deed of Trust, and until subsequent notice
from Lender to the contrary, Tenant shall pay all rent and other sums coming due
under the Lease directly to Lender or in accordance with Lender's instructions,
notwithstanding any contrary instruction which Tenant may receive from Landlord.
Landlord hereby expressly authorizes Tenant to make such payments directly to
Lender and agrees that the rights of Tenant under the Lease will in no way be
prejudiced or impaired by reason of Tenant's compliance with any such notice
from Lender.

         3.       Subordination of Lease. Tenant hereby subordinates the Lease,
and all of Tenant's right, title and interest in and to the Property, to the
Deed of Trust and to any and all increases, renewals,

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<PAGE>

modifications, extensions, substitutions, replacements and/or consolidations of
the Deed of Trust. The lien of the Deed of Trust shall, with respect to all
amounts now or at any time hereafter secured by such lien (including amounts in
excess of the principal face amount of the Note referred to in the Deed of
Trust) be senior and superior in all respects to any interest of Tenant in the
Property.

         4.       Non-Disturbance. Lender agrees that so long as Tenant is not
in default under the Lease and no right exists under the terms of the Lease
whereby the owner of the Property is entitled to terminate the Lease, the Lease
will not be terminated, and Tenant will not be disturbed in its possession of
the Property, by or as a result of any foreclosure of the Deed of Trust or any
conveyance in lieu of any such foreclosure. Nothing in this paragraph shall
prevent Lender from giving any notice to Tenant required by law in connection
with any such foreclosure, or joining Tenant as a party in any judicial
foreclosure action, but no such notice and no such joinder shall have any effect
inconsistent with the first sentence of this paragraph.

         5.       Attornment. Tenant shall attorn to, and recognize as Tenant's
landlord under the Lease, Lender or any other person who may acquire title to
the Property upon foreclosure of the Deed of Trust or by conveyance in lieu of
such foreclosure. The provisions of this paragraph shall be self-executing and
no further writing or other formal act of attornment shall be required, but
Tenant shall, upon the request of any person so acquiring title to the Property,
execute and deliver to such person an instrument in recordable form
acknowledging such attornment, but not otherwise modifying or amending Tenant's
obligations under the Lease. From and after any such attornment, Lender or any
other person who may acquire title to the Property upon or in lieu of a
foreclosure of the Deed of Trust shall be bound to Tenant under all of the
terms, covenants and conditions of the Lease; provided, however, that Lender or
such other person shall not be (a) liable for any act or omission of any prior
landlord (including Landlord); (b) bound by Tenant's payment to any prior
landlord (including Landlord) under the Lease of any rents beyond that due for
the then-current rent period; (c) liable for the return or application of any
security deposits unless Landlord delivers such deposits to Lender or such other
person; (d) bound by any amendment or modification to the Lease made without
Lender's written consent, which consent shall not be unreasonably withheld; or
(e) subject to any offsets or deficiencies which Tenant might be entitled to
assert against any prior landlord (including Landlord).

         6.       Notice and Cure Rights. Notwithstanding anything to the
contrary in the Lease, Tenant agrees that it shall not commence any action
against Landlord or otherwise pursue any right or remedy against Landlord in
consequence of a default by Landlord under the terms and provisions of the Lease
unless written notice of such default is given to Lender. Tenant further agrees
that Lender shall have the right, but shall not be obligated, to cure such
default on behalf of Landlord within thirty (30) days after receipt of such
notice. Tenant further agrees not to invoke any of its remedies under the Lease
(except in the case of emergency repairs) unless such default shall remain
uncured at the expiration of the thirty (30) day period after such notice of
default is given to Lender, or if such default cannot reasonably be cured within
such thirty (30) day period, unless the cure of such default is not commenced
within such thirty (30) day period and thereafter prosecuted diligently to
completion. In addition to such notice and cure rights, Tenant agrees that if
the Event of Default is one that Lender cannot reasonably cure, such Event of
Default shall be considered excused.

         7.       Casualty. Notwithstanding anything to the contrary that may be
contained in the Lease, Lender shall have the right, in its sole discretion, to
apply any insurance proceeds received as a result of any casualty to the
Property to reduce the mortgage or debt owed to Lender.

         8.       Responsibility. Neither this Agreement nor the Deed of Trust
shall, prior to Lender's succession to Landlord's interest in the Property,
through foreclosure, assignment in lieu of foreclosure, or a possessory action,
operate to place responsibility for the control, care, management or repair of
the Property upon Lender, or impose upon Lender any responsibility for the
performance of the terms and conditions of the Lease.

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<PAGE>

         9.       Notices. Any notice required or permitted to be given under
this Agreement must be in writing and will be deemed given upon personal
delivery, or on the third business day after mailing by registered or certified
United States mail, postage prepaid, to the appropriate party at such party's
address set forth on the first page of this Agreement. Any party may change such
party's address for future notices by notice to the other parties in accordance
with this paragraph.

         10.      Real Covenants; Successors and Assigns. The provisions of this
Agreement shall be real covenants running with title to the Property and to the
leasehold estate created by the Lease, and shall bind and benefit the parties
hereto and their respective successors and assigns.

         11.      Governing Law. This Agreement shall be governed by and
construed in accordance with the laws of the State of Colorado.

         IN WITNESS WHEREOF, the parties have executed this Agreement as of the
date first set forth above.

                                                  LANDLORD:

                                            By:_________________________________
                                            Title:________________________

                                            TENANT:

                                            By:_________________________________
                                            Title:________________________

                                            LENDER:

                                            By:_________________________________
                                            Title:________________________
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<PAGE>

STATE OF COLORADO       )
                        )ss.
COUNTY OF ___________   )

         The foregoing instrument was acknowledged before me this_________ day
of ______________, by _____________, as _____________ of ______________________.

         Witness my hand and official seal.
         My commission expires:___________________

                                            _______________________________
                                            Notary Public

STATE OF COLORADO       )
                        )ss.
COUNTY OF ___________   )

         The foregoing instrument was acknowledged before me this_________ day
of ______________, by _____________, as _____________ of ______________________.

         Witness my hand and official seal.
         My commission expires:___________________

                                            _______________________________
                                            Notary Public

STATE OF COLORADO       )
                        )ss.
COUNTY OF __________    )

         The foregoing instrument was acknowledged before me this_________ day
of ______________, by _____________, as _____________ of ______________________.

         Witness my hand and official seal.
         My commission expires:___________________

                                            _______________________________
                                            Notary Public

Copyright (C) 1999 Flatiron Park Company

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<PAGE>

                                    EXHIBIT E

                                     FORM OF

                   SUBLEASE, ASSUMPTION AND CONSENT AGREEMENT
                        (Sublease of Portion of Premises)

         This Sublease, Assumption and Consent Agreement is entered into this
_________ day of ____________, 199____, by and between ________________________,
a Colorado __________________ ("Landlord"), ______________________________
("Sublandlord") and ______________________________________ ("Subtenant").

                                    RECITALS

         A.       Sublandlord is a tenant in ____________________, located at
___________________________, Boulder, Colorado (the "Premises").

         B.       Landlord and Sublandlord have entered into a Lease Agreement
dated_____________, 199_____, attached hereto as Exhibit A and incorporated
herein by reference (the "Lease"). The term of the Lease extends
through___________________, 199____.

         C.       Subtenant desires to sublease from Sublandlord and Sublandlord
desires to sublease to Subtenant that portion of the leased Premises described
on Exhibit B attached hereto (the "Subleased Premises") for the term to commence
on __________________, 199_____ and continue through ________________________,
199____ (the "Sublease Term").

         D.       Sublandlord and Subtenant have entered into a Sublease
Agreement for the Subleased Premises, dated as of ________________, 199____(the
"Sublease"), which is attached hereto as Exhibit C.

         E.       In order to induce Landlord to consent to the Sublease,
Subtenant is willing to assume the obligations of Sublandlord and to be bound by
the terms of the Lease with respect to the Subleased Premises.

         F.       Landlord is willing to accept and consent to such sublease and
assumption upon the terms and conditions of this Agreement.

         NOW THEREFORE, in consideration of the payment of rent and the
performance of the covenants and agreements by the parties as hereinafter set
forth, the parties agree as follows:

         1.       Sublease and Delivery of the Subleased Premises. Sublandlord
subleases to Subtenant, effective as of the _____ day of _________________,
199____ (the "Effective Date"), all of Sublandlord's right, title and interest
in the Subleased Premises during the Sublease Term. Sublandlord will deliver
possession of the Subleased Premises to Subtenant on the Effective Date.

         2.       Assumption and Acceptance of the Subleased Premises. Subtenant
assumes and agrees to perform each and every obligation of Sublandlord under the
Lease that arises on or after the Effective Date as to the Subleased Premises.
Subtenant will accept the Subleased Premises in its condition as of the
Effective Date and acknowledges that it shall have no claim against Landlord for
any matters arising prior to the Effective Date.

         3.       Sublandlord's Representations and Warranties. Sublandlord
represents and warrants that:

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<PAGE>

                  a.       The Lease is in full force and effect, and
         unmodified, except as provided in this Sublease, Assumption and Consent
         Agreement;

                  b.       Sublandlord's interest in the Lease is free and clear
         of any liens, encumbrances, or adverse interests of third-parties; and

                  c.       Sublandlord possesses the requisite legal authority
         to assign its interest in the Lease.

         4.       Sublandlord's and Subtenant's Responsibility for Payment of
Rent and Other Charges. Although Sublandlord shall be responsible to bill
Subtenant for rent and other charges associated with the Subleased Premises,
Subtenant agrees to make all payments directly to Landlord for any rent and all
other charges, fees and expenses payable to Landlord pursuant to the Lease for
or attributable to the Subleased Premises. Sublandlord agrees to make all
payments to Landlord for the rent and all other charges, fees and expenses
payable to Landlord pursuant to the Lease for or attributable to the remaining
portion of the leased Premises.

         5.       Subsequent Amendment of Lease or Sublease. During the Sublease
Term, neither the Lease nor the Sublease may be subsequently amended or modified
by without the express written consent of Landlord, Sublandlord, and Subtenant.

         6.       Tenant Improvements. Subtenant shall not make any alterations
to the Subleased Premises or undertake any tenant improvements without obtaining
a prior written approval of Landlord and Sublandlord, pursuant to the Lease.
Subtenant shall be solely responsible for the cost of any modification to the
Subleased Premises and/or restoring the Subleased Premises to its original
condition at the expiration or earlier termination of the Lease or Sublease.

         7.       Sublandlord's Responsibility for Obligations Under Lease.
Notwithstanding Subtenant's assumption of Sublandlord's obligations under the
Lease (including obligations relating to the Subleased Premises), Sublandlord
shall remain fully liable, jointly and severally, to Landlord for the
performance of each and every obligation under the Lease, and such assumption
shall in no way release Sublandlord from said obligations.

         8.       Enforceability. The provisions of this Sublease, Assumption
and Consent Agreement shall be binding upon and inure to the benefit of the
parties and their respective successors and permitted assigns.

         9.       Landlord's Consent. Landlord consents to this Sublease,
Assumption and Consent Agreement on the express conditions that such consent
will not be deemed a consent to any subsequent sublease or assignment but,
rather, any subsequent sublease or assignment will require the consent of
Landlord pursuant to the Lease.

         10.      Entire Agreement. This Sublease, Assumption and Consent
Agreement embodies the entire agreement of Landlord, Sublandlord, and Subtenant
with respect to the subject matter contained herein and supersedes any prior
agreements, whether written or oral, with respect to the subject matter
contained herein. This Sublease, Assumption and Consent Agreement may be
modified only by written instrument duly executed by Landlord, Sublandlord and
Subtenant.

         11.      Notices. All notices required to be given or desired to be
given hereunder shall be in writing and shall be deemed duly served for all
purposes by delivery in person or by mailing a copy thereof, postage prepaid,
addressed to:

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<PAGE>

         Landlord:
                        __________________________
                        __________________________
                        __________________________

         Sublandlord:

                        __________________________
                        __________________________
                        __________________________

         Subtenant:
                        __________________________
                        __________________________
                        __________________________

or at such address as such party shall subsequently designate by notice given in
accordance with this paragraph.

         IN WITNESS WHEREOF, the parties have executed this Sublease, Assumption
and Consent Agreement on the day and year first above written.

LANDLORD:                                   SUBLANDLORD:

______________________________              ______________________________

By:___________________________              By:___________________________

Name:_________________________              Name:_________________________

Title:________________________              Title:________________________

SUBTENANT:

______________________________

By:___________________________

Name:_________________________

Title:________________________

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<PAGE>

                                   EXHIBIT F

                                    FORM OF

                  ASSIGNMENT, ASSUMPTION AND CONSENT AGREEMENT
                        (ASSIGNMENT OF ENTIRE PREMISES)

         This Assignment, Assumption and Consent Agreement is entered into this
_______ day of __________, 199____, by and between __________________________
("Landlord"), [TENANT], a ________________ ("Assignor"), and [NEW TENANT],
a____________ (" Assignee").

                                    RECITALS

         A.       Assignor is a tenant in the building located at
__________________________, Boulder, Colorado (the "'Premises").

         B.       Landlord and Assignor have entered into a lease
dated_____________________________, attached hereto as Exhibit A and
incorporated herein by reference (the "Lease"). The term of the Lease extends
through_______________________.

         C.       Assignor desires to assign to Assignee and Assignee desires to
assume from Assignor the Lease for the remainder of the term.

         D.       Landlord is willing to accept and consent to such assignment
and assumption upon the terms and conditions set forth herein.

         NOW THEREFORE, in consideration of the payment of rent and the
performance of the covenants and agreements by the parties as hereinafter set
forth, the parties agree as follows:

         1.       Assignment and Delivery of the Premises. Assignor assigns to
Assignee, effective as of the ________________________ (the "Effective Date"),
all of Assignor's right, title and interest in the Lease. Assignor shall deliver
possession of the Premises to Assignee on the Effective Date. Any adjustments or
prorations in rent or other charges due under the Lease shall be made between
Assignor and Assignee, and under no circumstances shall Landlord have any
obligation to refund any amounts paid by either Assignor or Assignee as a result
of this Agreement.

         2.       Assumption and Acceptance of the Premises. Assignee assumes
and agrees to perform each and every obligation of Assignor under the Lease that
arises on or after the Effective Date. Assignee will accept the Premises in its
condition as of the Effective Date and acknowledges that it shall have no claim
against Landlord for any matters arising prior to the Effective Date.

         3.       Assignor's Representations and Warranties. Assignor represents
and warrants that:

                  a.       The Lease is in full force and effect, and
         unmodified, except as provided in this Assignment, Assumption and
         Consent Agreement;

                  b.       Assignor has not sold, conveyed, transferred,
         assigned, encumbered, or granted any lien or interest in the Lease; and

                  c.       Assignor possesses the requisite legal authority to
         assign its interest in the Lease.

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<PAGE>

         4.       Subsequent Amendment of Lease. The Lease may not be
subsequently amended or modified by Landlord and/or Assignee without the express
written consent of Assignor. Assignor hereby consents to any subsequent
amendment of the Lease provided Assignor is given fifteen (15) days notice of
such amendment and does not object thereto within said fifteen-day period.

         5.       Assignor's Responsibility for Obligations Under Lease.
Notwithstanding Assignee's assumption of Assignor's obligations under the Lease,
Assignor shall remain fully liable, jointly and severally, to Landlord for the
performance of each and every obligation under the Lease, and such assumption
shall in no way release Assignor from said obligations. Assignee shall indemnify
and hold harmless Assignor from and against any and all claims of Landlord
pursuant to this Section 5 and pursuant to any obligations under the Lease which
shall accrue from and after the Effective Date.

         6.       Enforceability by Landlord and Assignor. The provisions of
this Assignment, Assumption and Consent Agreement inure to the benefit of
Landlord and Assignor and shall be enforceable by Landlord and Assignor.

         7.       Landlord's Consent to Assignment. Landlord consents to this
Assignment, Assumption and Consent Agreement on the express condition that such
consent will not be deemed a consent to any subsequent assignment but, rather,
any subsequent assignment or sublease will require the consent of Landlord
pursuant to the Lease. Any subsequent assignment or sublease of the Lease shall
also require the consent of Assignor, which consent shall not be unreasonably
withheld. Assignor hereby consents to any subsequent assignment or sublease of
the Lease provided Assignor is given fifteen (15) days notice of such assignment
or sublease and does not object thereto within said fifteen-day period.

         8.       Security Deposit. Pursuant to the Lease, Assignor has
deposited with Landlord a security deposit in the amount of $__________.
Assignor hereby assigns all right, title, interest, and claim in and to said
security deposit to Assignee, and Landlord shall have no further liability to
Assignor with respect to said security deposit. Landlord shall continue to hold
the security deposit pursuant to the Lease, and at the end of the term of the
Lease, shall refund said security deposit or any portion thereof to Assignee as
provided therein.

         9.       Additional Rent Reconciliation. Assignee acknowledges that
additional rent payments (triple net charges) paid to Landlord pursuant to the
Lease are estimates only, and are subject to reconciliation by Landlord.
Landlord's annual reconciliation for 199 _ will be completed in approximately
April 199____, and a copy of said reconciliation transmitted to Assignee. Any
shortfall in additional rent which is owing to Landlord shall be paid by
Assignee within fifteen (15) days after such reconciliation is transmitted to
Assignee, and any overpayment which is owing by Landlord shall be paid to
Assignee at the time such reconciliation is transmitted. Any adjustment or
proration between Assignor and Assignee with respect to said additional rent
reconciliation shall be the responsibility of Assignor and Assignee, not
Landlord.

         10.      Entire Agreement. This Assignment, Assumption and Consent
Agreement embodies the entire agreement of Landlord, Assignor, and Assignee with
respect to the subject matter contained herein, and this Agreement supersedes
any prior agreements, whether written or oral, with respect to the subject
matter contained herein. This Assignment, Assumption and Consent Agreement may
be modified only by written instrument duly executed by Landlord, Assignor, and
Assignee.

         11.      Notices. All notices required to be given or desired to be
given hereunder shall be in writing and shall be deemed duly served for all
purposes by delivery in person or by mailing a copy thereof, postage prepaid,
addressed to:

         Landlord:    c/o Flatiron Park Company
                      5540 Central Avenue
                      Boulder, Colorado 80301

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<PAGE>

         Assignor:      __________________________
                        __________________________
                        __________________________

         Assignee:      __________________________
                        __________________________
                        Boulder, CO 80301

or at such address as such party shall subsequently designate in writing.

         IN WITNESS WHEREOF, the parties have executed this Assignment,
Assumption and Consent Agreement on the day and year first above written.

LANDLORD:                                   ASSIGNOR:

______________________________              ______________________________

By:___________________________              By:___________________________

Name:_________________________              Name:_________________________

Title:________________________              Title:________________________

ASSIGNEE:

______________________________

By:___________________________

Name:_________________________

Title:________________________

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<PAGE>

                                    EXHIBIT G

                                     FORM OF

                              ESTOPPEL CERTIFICATE

TO:         ________________________________
            ________________________________
            ________________________________

FROM:       ________________________________
            ________________________________
            ________________________________

RE:         ________________________________("Tenant")
            ________________________________("the Premises")

Ladies and Gentlemen:

         The undersigned is the (check one) Tenant (__) or Guarantor (__) under
that certain Lease of the Premises consisting of approximately _______________
rentable square feet in the building located at __________________, between
Tenant and the Landlord. The undersigned hereby certifies, at the date hereof,
as follows:

         1.        The Lease identified above is the Lease with
_________________________ as Landlord. A true, correct and complete copy of the
Lease and all amendments, guaranties, security agreements, subleases and other
related documents are attached hereto as Schedule "1" and incorporated herein by
this reference. Said Schedule "1" consists of the
following:______________________________________________________________
(describe documents and set forth number of pages). There are no other
agreements or understandings between such Landlord and Tenant and/or Guarantor
which related to the Property.

         2.       The Lease sets forth the entire agreement between the
undersigned Tenant and Landlord with respect to the leasing of the Premises,
including but not limited to all understandings and agreements relating to the
construction or installation of any leasehold improvements by the Landlord and
to the conditions precedent to occupancy of the Premises by the undersigned.

         3.       Tenant entered into occupancy of the Premises described in the
Lease on _____________________, 19____, and is in possession of and occupies
those Leased Premises for purposes permitted under the Lease.

         4.       The commencement date under the Lease was __________, 19_____.

         5.       The Lease Term will expires on _____________________, ______.
Tenant has no rights to renew or extend the Term of the Lease or any expansion
rights under the Lease, except those (if any) set forth in the Lease.

         6.       Tenant has deposited with Landlord the sum of _______________
Dollars ($_________) in cash as security deposit or for other purposes stated in
the Lease.

         7.       No rents or charges have been paid in advance, except for the
following rents or charges which have been paid to the date specified:
________________ Dollars ($________) paid to ___________________, 19_______.

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<PAGE>

         8.       The current Basic Rent is $____________ per month and the
current total payment for Basic Rent and Monthly Deposits of Additional Rent is
$__________ per month.

         9.       Landlord has not, as an inducement, assumed any of Tenant's
Lease obligations and has made no agreements with Tenant covering free rent,
partial rent, rebate of rental payments or any other type of rental concession,
except as follows:
________________________________________________________________________________
_______________________________________________________________.

         10.      The undersigned certifies that Tenant is required to pay the
pro rata share of operating expenses as set forth in the lease. The undersigned
certifies that this pro rata share is _________%. In 19____, the Tenant paid to
Landlord ____________________________ Dollars ($_________) for real property
taxes, and ________________________ Dollars ($_________) for operating expenses.
Moreover, Tenant is required to pay for all utilities including water and sewer
used in and upon the Premises, and is responsible for all repairs and
maintenance to the HVAC/mechanical systems.

         11.      All Minimum Rent and other rentals under the Lease including
the payment of any taxes, utilities, common area maintenance payments or other
charges that are currently due have been paid, except
__________________________________________; all such rentals are being paid on a
current basis without any claims for offsets or deductions.

         12.      The Lease (including all exhibits) and all related agreements
and documents listed above are duly authorized, executed and delivered by Tenant
and/or Guarantor and are in full force and effect and have not been assigned,
modified, supplemented or amended except as indicated in paragraph 1 above; nor
have the undersigned Tenant's rights in or under such Lease been assigned.

         13.      The Lease and the other agreements listed above represent the
entire agreement between the parties as to the Premises.

         14.      No person or firm other than the undersigned is in possession
of the Premises, and to the best of the undersigned's knowledge, no person or
firm other than the Landlord has a future right to the Premises.

         15.      The undersigned is not the subject of any pending bankruptcy,
insolvency, debtor's relief, reorganization, receivership or similar
proceedings, nor is the subject of a ruling with respect to any of the
foregoing.

         16.      Except as may be specifically set forth in the Lease, Tenant
does not have any right to renew or extend the Lease Term nor any option or
preferential right to purchase all or any part of the Property or all or any
part of the building of which the Premises is a part, nor any right, title or
interest with respect to the Property other than as Tenant under the Lease.

         17.      There are no uncured defaults by Landlord under the Lease or
any of the related agreements described above, and Tenant knows of no event or
conditions which if uncured shall with the passage of time or notice or both,
would constitute a default by Landlord under the Lease or any of the related
agreements described above. There are no existing defenses or offsets which the
undersigned has against the enforcement of the Lease by Landlord.

         18.      The undersigned represents that the improvements and space
required to be furnished according to the Lease have been duly delivered by the
Landlord land accepted by the Tenant, and the Premises is in good condition and
not in need of repair as of the date of this Certificate.

         19.      All conditions of the Lease to be performed by Landlord and
necessary to the enforceability of the Lease have, to the undersigned Tenant's
knowledge, been satisfied.

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<PAGE>

         20.      As of the date hereof, the condition of the Premises is
satisfactory and adequate.

         21.      The undersigned represents that the Landlord has not
guaranteed the Lease or any of Tenant's obligations thereunder or otherwise
provided Tenant with inducement that the Landlord will pay for Tenant's
obligation(s) in the event that Tenant fails to pay any obligation that Tenant
is required to pay under the terms of the Lease.

         22.      The undersigned has been advised that _____________________
intends to sell the Property, including the building in which the Premises is
located to __________________________ or its assigns ("Purchaser"), and that in
connection with such sale transaction, Purchaser intends to enter into a
mortgage loan with ____________________________________ ("Lender"), or another
reputable lending institution, which loan will be secured by the Property,
including the building, all associated real estate and all tenant leases in the
building. Accordingly, Tenant understands that this Certificate shall be relied
upon by Purchaser and by Lender, or by such other lending institution as may be
involved in the mortgage loan transaction.

         23.      The undersigned has not dumped, spilled or in any other manner
discharged or deposited any hazardous waste substances on the Property. The
undersigned has received no notice of, and has no knowledge of, any violation or
claimed violation of any law, rule or regulation relating to hazardous waste
substances. The undersigned has not used, and the undersigned has no knowledge
of any use of petroleum distillation or other hazardous material.

         It is understood that you require this Certificate from the undersigned
as a condition to the purchase of the Property from the Landlord, and that you
are relying on this Certificate. After receipt of notice from Landlord that the
sale has been completed, the undersigned will honor the assignment of Landlord's
interest in the Lease.

          Dated this __________ day of ______________, 19_______.

TENANT____GUARANTOR____                ________________________________
       (Check one)
                                       By:_________________________
                                       Title:______________________

STATE OF COLORADO       )
                        )ss.
COUNTY OF___________    )

         The foregoing instrument was acknowledged before me this________ day of
____________, by ________________, as ______________ of ______________________.

         Witness my hand and official seal.
         My commission expires:___________________

                                            ____________________________
                                            Notary Public

Copyright (C) 1999 Flatiron Park Company

                                       3

<PAGE>

                                    EXHIBIT H

                       DECLARATION OF PROTECTIVE COVENANTS

                                   [Attached]

Copyright (C) 1999 Flatiron Park Company

<PAGE>

                               AMENDMENT TO LEASE
                               September 26, 2001

         THIS AMENDMENT TO LEASE ("Amendment") amends and modifies that certain
Lease dated December 13, 1999, between 2545 CENTRAL, LLC, a Colorado limited
liability company, as Landlord, and CARRIER ACCESS CORPORATION, a Delaware
corporation, as Tenant (the "Lease"), regarding certain premises located at 5766
Central Avenue, Boulder, Colorado 80301 (the "Premises").

         The following additional and/or modified provisions shall be added to
the Lease, and to the extent of any inconsistency or conflict between the terms
of this Amendment and the terms of the Lease, the terms of this Amendment shall
control.

         For good and valuable consideration, the receipt and sufficiency of
which is hereby acknowledged, Landlord and Tenant agree that the Lease shall
have the following additional and/or modified terms:

         1.       Reduction in Space. Effective as of October 1, 2001 (the
"Effective Date"), Tenant's Premises shall be reduced in size by 7,483 square
feet (from approximately 14,966 rentable square feet to approximately 7,483
rentable square feet), as depicted on Exhibit A attached hereto. The portion of
the Premises being deleted from the Lease is the entire first floor of the
Building, such that following the Effective Date, the Premises shall consist of
only the second floor of the Building. In addition, the telephone room located
on the second floor of the Building, as depicted on Exhibit B attached hereto,
shall be treated as a part of the Common Facilities under the Lease for the
common use of Tenant and other users of space in the Building. Tenant agrees
that it will provide reasonable access to other occupants in the Building to
such telephone room. Tenant shall vacate and return possession of the portion of
the Premises being deleted from Tenant's Lease on or before the Effective Date.

         2.       Rent. Landlord shall retain all Rent and Additional Rent paid
by Tenant for the month of September, 2001. Beginning October 1, 2001, Tenant's
new Rent Schedule shall be as follows:

<TABLE>
<S>                <C>  <C> <C>           <C>
October 1, 2001    to   June 30, 2002     $9,822 per month
July 1, 2002       to   June 30, 2003     $10,313 per month
July 1, 2003       to   June 30, 2004     $10,828 per month
July 1, 2004       to   June 30, 2005     $11,370 per month
July 1, 2005       to   June 30, 2006     $11,938 per month
July 1, 2006       to   June 30, 2007     $12,535 per month
</TABLE>

         3.       Additional Rent. Landlord shall retain all Additional Rent
paid by Tenant during 2001. Beginning October 1, 2001, Tenant's Pro Rata Share
for Additional Rent shall be reduced from 100% to 50%.

         4.       Work to be Performed by Tenant. Prior to the Effective Date,
Tenant shall, at its sole cost and expense, cause the following work to be
completed in the portion of the Premises being deleted from Tenant's Lease (the
"Released Space"):

                  (a)      The Released Space in its current condition is
                           acceptable to Landlord and meets the conditions
                           required under the Lease.

         5.       Payment of Expenses. Tenant shall pay all brokerage
commissions and any other expenses due or incurred by Tenant in connection with
the reletting of the Released Space.

<PAGE>

         6.       Commencing on the Effective Date, the place for notices shall
be:

2545 Central, LLC.                with a copy to: Hutchinson Black and Cook, LLC
c/o Flatiron Park Company                         921 Walnut Street, Suite 200
5540 Central Avenue                               P.O. Box 1170
Boulder, CO 80301                                 Boulder, CO 80306
                                                  Attn: Brigette M. Paige

Carrier Access Corporation
Attention: Legal Department
5395 Pearl Parkway
Boulder, CO 80301

         7.       Utilities: Gas will be billed directly to each tenant. There
is currently one electric meter for the Building. Electric will be reapportioned
to Tenant until such time the electrical service to the building is restored to
a multi-metered building and the first floor has its own electrical meters. Once
separate electric meters are in place, to service the first floor, electrical
utilities will be billed direct to Tenant. It is anticipated the new meters for
the first floor will be in place on or about November 30, 2001.

         8.       Ongoing Litigation with XOR, Inc. Tenant acknowledges and
confirms that it is involved in ongoing litigation with XOR, Inc., concerning
the Premises and that any replacement tenant for the Released Space is assuming
no responsibility or liability with respect to such litigation. Tenant further
confirms that in agreeing to delete the Released Space from the Lease and
entering into this Lease Amendment, Landlord is not assuming any responsibility
or liability with respect to such litigation. Tenant fully releases Landlord and
any replacement tenant for the Released Space from any and all claims initiated
by Tenant in connection with such litigation. This foregoing release is with a
full and complete reservation of all rights of Tenant against XOR, Inc. and does
not affect those rights in any way.

         9.       Condition Precedent This Amendment to Lease is conditioned
upon Landlord's entering into a new lease for the space being deleted from the
Lease with a replacement tenant and upon terms and conditions satisfactory to
Landlord in its sole discretion.

         10.      Remainder in Force and Effect. Except as expressly modified
herein, all terms and provisions of the Lease shall remain in full force and
effect Capitalized terms not defined herein shall have the meanings given such
terms in the Lease.

         IN WITNESS WHEREOF, Landlord and Tenant have executed this Amendment as
of the day and year first above written.

LANDLORD:                                   TENANT:

2545 CENTRAL, LLC                           CARRIER ACCESS CORPORATION

By: /s/ Richard L. Hedges                   By: /s/ William White
    ---------------------------                 ----------------------------
    Richard L. Hedges                       Name: WILLIAM WHITE

    Vice President                          Title: CIO

                                       2

<PAGE>

                                    EXHIBIT A

                                  ENTIRE FLOOR

                                  [FLOOR PLAN]

                         5756 CENTRAL AVENUE 2ND FLOOR

<PAGE>

                                   EXHIBIT B

                                  [FLOOR PLAN]

                         5766 CENTRAL AVENUE 2ND FLOOR