Document:

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                                                                    Exhibit 10.8

                                                    235 Littleton Road, Westford
                                                                  EXECUTION COPY

                              AGREEMENT OF SUBLEASE

      THIS AGREEMENT OF SUBLEASE ("Sublease") is made as of the 20th day of
October, 2000, by and between Unisphere Networks, Inc., a Delaware corporation
("Landlord"), having an office at One Executive Drive, Chelmsford, MA 01824 and
Sonus Networks, Inc. ("Tenant"), a Delaware corporation, having an office at 5
Carlisle Road, Westford, MA 01886.

                                     WITNESS

      WHEREAS, by Lease dated as of December 9, 1999, as amended by that certain
Addendum to Lease dated as of June 23, 2000 (the "First Amendment")
(collectively hereinafter the "Prime Lease") by and between 235 Littleton Road
Associates, Inc. ("Prime Landlord") and Unisphere Solutions, Inc., Prime
Landlord leased to Unisphere Solutions, Inc. the premises (as hereinafter
defined) (the "Premises") which is located within the building known by the
street address of 235 Littleton Road, Westford, MA 01886 (the "Building"), which
Premises are more particularly described in the Prime Lease and include 8,418
rentable square feet consisting of Units 1, 3 & 5;

      WHEREAS, Unisphere Solutions, Inc. changed its name to Unisphere Networks,
Inc. (hereinafter referred to as "Landlord");

      WHEREAS, Landlord desires to sublease to Tenant and Tenant desires to
sublease from Landlord the Premises, and Landlord is willing to sublease the
Premises on the terms and conditions hereinafter set forth.

      NOW, THEREFORE, in consideration of the mutual covenants herein contained
and for other good and valuable consideration, the parties agree as follows:

      1. Subleasing of Premises. Subject to the written consent of the Prime
Landlord, Landlord hereby subleases to Tenant and Tenant hereby subleases from
Landlord the Premises, upon and subject to all of the terms, covenants, recitals
and conditions hereinafter set forth.

      2. Term

            a. The term (the "Term") of this Sublease shall commence on February
1, 2001 (the "Commencement Date"), with said Term to expire at midnight on
January 13, 2003 (the "Expiration Date"), unless sooner terminated as
hereinafter provided.

            b. Tenant acknowledges that Landlord is in the process of
constructing a new building into which it intends to relocate its operations
from the Premises. Notwithstanding any other provision of this Sublease to the
contrary, Landlord may deliver the Premises to Tenant at any time from February
1, 2001 to June 30, 2001 upon thirty (30)

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days notice ("Commencement Date Notice") to Tenant, provided that the
Commencement Date shall be extended to such date and the Rent, as hereinafter
defined, shall become payable on the Commencement Date.

            c. Under no circumstances shall Landlord be required to vacate the
Premises if its new building shall not be substantially complete, in Landlord's
sole judgment. In the event that Landlord is unable to deliver the Premises to
Tenant on or before June 30, 2001, then either party may terminate this Sublease
in which case this Sublease shall terminate without further recourse to either
party hereunder and shall be null and void with no further force or effect.
Tenant shall have no right to terminate this Sublease (in the event of
Landlord's failure to deliver the Premises on or before June 30, 2001) unless
Tenant terminates that certain Agreement of Sublease by and between Landlord and
Tenant dated of even date herewith relating to space lease at 5 Carlisle Road,
Westford.

            d. Tenant shall not be required to take delivery of the Premises
unless and until Landlord shall deliver possession of the Premises located at 5
Carlisle Road, Westford, Massachusetts.

            e. Tenant shall have the right to have entry and access to the
Premises commencing on the twentieth day after receipt of the Commencement Date
Notice and Tenant shall not be obligated to pay any rent due hereunder but all
other terms and conditions of this Sublease shall be in full force and effect
upon the date of entry into the Premises by Tenant for any purposes.

      3. Base Rent. During the Term, Tenant shall pay to Landlord, in lawful
money of the United States which at the time shall be legal tender in payment of
all debts and dues, public and private, an annual fixed rent (the "Base Rent")
of $145,210.88 in monthly installments of $12,100.88. All such monthly
installments shall be paid in advance, on the first (1st) day of each month
during the Term, at the office of the Landlord, or such other place as Landlord
may designate, without any setoff or deduction of any kind whatsoever.

      4. Additional Rent.

            (a) Beginning on the Commencement Date, Tenant shall pay, as
Additional Rent one hundred percent (100%) of all additional rent payments for
real estate taxes under Section 6 of the Prime Lease (as such terms are referred
to in the Prime Lease) and one hundred percent (100%) of all payments for the
use of the dumpster under Section 22 of the Prime Lease. Rental and any other
sums due hereunder not paid by the due date shall bear interest of 18% per
annum. All payments shall be made to Landlord at its address set forth in
Section 24 below, or at such other address or addresses as Landlord may from
time to time designate by written notice to Tenant.

            Tenant shall also pay, as Additional Rent, the cost of all utilities
furnished to Tenant on the Premises, including, but not limited to, electricity,
gas, oil, water and sewer.

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Tenant agrees to pay any and all such charges for the Premises to Landlord in
the event any such utilities are not separately metered to Tenant (to the extent
Landlord is assessed such charges by Prime Landlord) or directly to the utility
company if such utilities are separately metered.

            (b) Tenant's obligation to pay Additional Rent hereunder shall be on
account of the period from and after the Commencement Date and shall survive the
Expiration Date or sooner termination of the Term.

            (c) All amounts payable by Tenant to Landlord pursuant to this
Sublease, including, without limitation, Base Rent and Additional Rent, shall be
deemed and constitute rent and, in the event of any non-payment thereof,
Landlord shall have all of the rights and remedies provided herein, in the Prime
Lease or in law or at equity for non-payment of rent.

            (d) Tenant agrees to pay to Landlord Tenant's pro rata share of any
taxes attributable to leasehold improvements, furniture or equipment within the
Premises which are payable by Landlord under the Prime Lease.

      5. Care, Surrender and Restoration of the Premises.

            (a) Without limiting any other provision of this Sublease or the
Prime Lease, Tenant shall take good care of the Premises, suffer no waste or
injury thereto and shall comply with all those laws, orders and regulations
applicable to the Premises, the Building and Tenant's use or manner of use
thereof, which are imposed on Landlord, as tenant under the Prime Lease, in
connection with the Premises and the Building, including without limitation any
rules and regulations promulgated by the Prime Landlord.

            (b) At the expiration or other termination of the Term, Tenant shall
surrender the Premises and all alterations and additions thereto (including any
fixtures, panelling, railings and like installation installed at the Premises at
any time by Tenant, by Prime Landlord or by Landlord) in good order, repair and
condition, ordinary wear and tear and damage by casualty only excepted, first
removing all goods and effects of Tenant and, to the extent specified by
Landlord by notice to Tenant given at least thirty (30) days before such
expiration or termination (but only to the extent required by Prime Landlord
pursuant to the terms of the Prime Lease), all alterations and additions made by
or on behalf of Tenant. Tenant shall repair any damage caused by such removal
and restore the Premises and leave them clean and neat in compliance with the
requirements of Section 5 of this Sublease and Sections 12 and 21 of the Prime
Lease. All property permitted or required to be removed by Tenant upon the
Expiration Date or sooner termination of the Term remaining in the Premises
shall be deemed abandoned and may, at the election of Landlord, either be
retained as Landlord's property or may be removed from the Premises by Landlord,
at Tenant's expense. Any such reasonable expenses shall be paid by Tenant to
Landlord upon demand therefor and shall be deemed Additional Rent, collectible
by Landlord in the same manner and with the same remedies as though said sums
were Base Rent reserved hereunder.

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            (c) Upon the Expiration Date or sooner termination of the Term,
Tenant shall quit and surrender the Premises to Landlord, broom clean, in good
order and condition, ordinary wear and tear and damage by fire and other
casualty excepted, and Tenant shall remove all of its property. If the
Expiration Date or sooner termination of the Term of this Sublease falls on a
Sunday, this Sublease shall expire at noon on the preceding Saturday unless it
be a legal holiday, in which case it shall expire at noon on the preceding
business day. Tenant shall observe and perform the covenants herein stated and
Tenant's obligations hereunder shall survive the Expiration Date or sooner
termination of the Term.

      6. Use. Tenant shall use and occupy the Premises for the purposes
permitted under Section 8 of the Prime Lease, "Office Space", and for no other
purpose.

      7. Subordination to and Incorporation of Terms of Prime Lease.

            (a) This Sublease is in all respects subject and subordinate to the
terms and conditions of the Prime Lease and to the matters to which the Prime
Lease is or shall be subordinate. Except as otherwise expressly provided in this
Sublease, the terms, provisions, covenants, stipulations, conditions, rights,
obligations, remedies and agreements of the Prime Lease are incorporated in this
Sublease by reference and made a part hereof as if herein set forth at length,
and shall, as between Landlord and Tenant (as if they were the Landlord and
Tenant, respectively, under the Prime Lease and as if the Premises being sublet
hereby were the Prime Lease Premises demised under the Prime Lease), constitute
the terms of this Sublease, except to the extent that they do not relate to the
Premises or are inapplicable to, inconsistent with, or modified or eliminated
by, the terms of this Sublease. In particular, it is intended that Tenant shall
not be subject to duplicate monetary obligations to Landlord and Prime Landlord.
To the extent that Tenant is required by this Sublease to make monetary payments
to Landlord (such as for rent, additional rent or upon default), Tenant shall
not be obligated to the Prime Landlord for any such monetary obligations nor to
Landlord for its monetary obligations to the Prime Landlord. Landlord and Tenant
acknowledge and agree that Tenant has reviewed and is familiar with the Prime
Lease and Landlord hereby represents that the copy delivered to Tenant for such
purpose and attached hereto as Exhibit A is a true, correct and complete copy of
such Prime Lease.

            (b) In the event of a default by Landlord, as tenant under the Prime
Lease, resulting in the termination, reentry or dispossession thereunder, Prime
Landlord shall take over all of the right, title and interest of Landlord under
this Sublease and Tenant hereunder shall, at the option of the Prime Landlord,
attorn to and recognize Prime Landlord as Landlord hereunder except that Prime
Landlord shall not (i) be liable for any previous act or omission of Landlord
under this Sublease, (ii) be subject to any offset, not expressly provided for
in this Sublease, which theretofore accrued to Tenant against Landlord, or (iii)
be bound by any previous modification of this Sublease or by any previous
prepayment of more than one month's rent, and shall, promptly upon Prime
Landlord's request, execute and deliver all instruments necessary or appropriate
to confirm such attornment and recognition. Tenant hereby waives all rights
under any present or future law to elect, by reason of the termination of such
Prime Lease, to terminate this Sublease or surrender possession of the Premises.

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      8. Tenant's Obligations. Except as otherwise specifically provided herein,
during the term of this Sublease all acts to be performed and all of the terms,
provisions, covenants, stipulations, conditions, rights, obligations, remedies
and agreements to be observed by and inuring to the benefit of, Landlord, as
tenant under the Prime Lease of the Premises and arising from and after the
Commencement Date, shall be performed, and observed by, and shall inure to the
benefit of, Tenant, and Tenant's obligations shall run to Landlord or the Prime
Landlord as Landlord may determine to be appropriate or required by the
respective interests of Landlord and Prime Landlord. Tenant shall indemnify
Landlord against, and hold Landlord harmless from and against, all costs,
damages, claims, liabilities, liens and expenses (including, but not limited to,
reasonable attorneys' fees and disbursements, court costs and other expenses of
litigation or arbitration) paid, suffered, incurred by or claimed against
Landlord as a result of the nonperformance or nonobservance by Tenant, Tenant's
agents, contractors, employees, invitees or licensees of any such terms,
provisions, covenants, stipulations, conditions, obligations and agreements
contained in the Prime Lease. In furtherance of the foregoing, Tenant shall not
(i) do or permit to be done anything prohibited to Landlord, as tenant under the
Prime Lease, or (ii) take any action or do or permit anything which would result
in any additional cost or other liability to Landlord under the Prime Lease
and/or this Sublease. In the event of any inconsistency between the Prime Lease
and this Sublease, such inconsistency (i) if it relates to obligations of, or
restrictions on, Tenant, shall be resolved in favor of that obligation which is
more onerous to Tenant or that restriction which is more restrictive of Tenant,
as the case may be, or (ii) if it relates to the rights of, or benefits to be
conferred upon, Tenant, shall be resolved in favor of this Sublease.

      9. Landlord's Obligations. Anything contained in this Sublease or in the
Prime Lease to the contrary notwithstanding, Landlord shall have no
responsibility to Tenant for, and shall not be required to provide, any of the
services or make any of the repairs or restorations that Prime Landlord has
agreed to make or provide, or cause to be made or provided, under the Prime
Lease (including, without limitation, those set forth in Sections 11(B)
[Lessor's Obligations], and Section 16 [Indemnification and Liability] thereof),
and Tenant shall rely upon, and look solely to, Prime Landlord for the provision
or making thereof. If Prime Landlord shall default in the performance of any of
its obligations under the Prime Lease, or if Tenant wishes to file a protest or
to dispute any matter or thing, Landlord has the right to protest or dispute as
tenant under the Prime Lease, then Tenant shall advise Landlord of such protest
or dispute (together with all material facts and circumstances pertaining
thereto) and Landlord shall make demand on Prime Landlord and shall employ all
reasonable efforts to cause Prime Landlord to cure such default or resolve such
dispute. Except as may result from a default of Landlord from its obligations
specified in the preceding sentence, Tenant shall not make any claim against
Landlord for any damage which may arise, nor shall Tenant's obligations
hereunder be impaired or abated (except for any abatement provided to and
actually received by Landlord) by reason of (i) the failure of Prime Landlord to
keep, observe or perform its obligations pursuant to the Prime Lease, or (ii)
the acts or omissions of Prime Landlord and each of its agents, contractors,
servants, employees, invitees or licensees.

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      10. Covenants with respect to the Prime Lease. Tenant covenants and agrees
that Tenant shall not do anything that would constitute a default under the
Prime Lease or omit to do anything that Tenant is obligated to do under the
terms of this Sublease so as to cause there to be a default under the Prime
Lease.

      11. Broker. Tenant represents and warrants to Landlord that Tenant has not
dealt with any broker in connection with this Sublease. Tenant shall indemnify
Landlord against, and hold Landlord harmless from, any claim on, or liability
to, any broker or any other party with whom Tenant shall have dealt in
connection with this transaction and Sublease.

      12. Indemnification.

            12.1 Reciprocal Indemnification of Landlord and Tenant.

                  (a) Tenant shall indemnify, defend with competent and
experienced counsel and hold harmless Landlord from and against any and all
damages, liabilities, actions, causes of action, suits, claims, demands, losses,
costs and expenses (including without limitation reasonable attorneys' fees and
disbursements and court costs) to the extent arising from or in connection with
the negligence or willful misconduct of Tenant, its agents, employees,
representatives or contractors.

                  (b) Landlord shall indemnify, defend with competent and
experienced counsel and hold harmless Tenant, its subsidiaries and affiliates
and their respective officers, directors, shareholders and employees, from and
against any and all damages, liabilities, actions, causes of action, suits,
claims, demands, losses, costs and expenses (including without limitation
reasonable attorneys' fees and disbursements and court costs) to the extent
arising from or in connection with the negligence or willful misconduct of
Landlord, its agents, employees, representatives or contractors.

                  (c) The party seeking indemnification under this Section (the
"Indemnified party") shall provide prompt written notice of any third party
claim to the party from whom indemnification is sought (the "Indemnifying
Party"). The Indemnifying Party shall have the right to assume exclusive control
of the defense of such claim or at the option of the Indemnifying Party, to
settle the same. The Indemnified Party agrees to cooperate reasonably with the
Indemnifying Party in connection with the performance of the Indemnifying
Party's obligations under this Section.

                  (d) Notwithstanding anything to the contrary contained in this
Sublease, neither party hereto shall be liable to the other for any indirect,
special, consequential or incidental damages (including without limitation loss
of profits, loss of use or loss of goodwill) regardless of (i) the negligence
(either sole or concurrent) of either party' or (ii) whether either party has
been informed of the possibility of such damages. It is expressly understood and
agreed that damages payable by either party to Prime Landlord shall be deemed to
constitute direct damages of such party. This subparagraph (d) shall not be
applicable to Section 21 of this Sublease.

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            12.2 Indemnification by Tenant of Prime Landlord. Tenant agrees to
defend, save harmless and indemnify Prime Landlord to the same extent as
Landlord is required to do so under the provisions of the Prime Lease including,
but not limited to, Section 16 of the Prime Lease.

            12.3 Survival. The provisions of this Section shall survive the
expiration or earlier termination of this Sublease.

      13. Quiet Enjoyment. Subject to the terms and conditions hereof and as
long as Tenant pays all of the Base Rent and Additional Rent due hereunder and
otherwise performs and observes all of the obligations, terms and conditions
contained herein and in the Prime Lease as herein incorporated, Tenant shall
peaceably and quietly have, hold and enjoy the Premises.

      14. Termination of Prime Lease. If for any reason the term of the Prime
Lease is terminated prior to the Expiration Date of this Sublease, this Sublease
shall thereupon terminate, and Landlord shall not be liable to Tenant by reason
thereof unless such termination is due solely to an event of default on behalf
of Landlord. Notwithstanding the foregoing, if the termination of the Prime
Lease does not result in the termination of this Sublease by reason of Tenant's
attornment to, and recognition of, Prime Landlord as landlord hereunder in
accordance with the provisions of Section 7(b) hereof, Landlord shall not be
liable to Tenant hereunder for damages or otherwise, and Landlord's obligation
to Tenant shall be limited to returning to Tenant a portion of any rent paid in
advance by Tenant, if any, prorated as of the date of such termination.

      15. Modification of Prime Lease. For the purposes hereof, the terms of the
Prime Lease are subject to the following modifications:

            (a) In all provisions of the Prime Lease requiring the approval or
consent of Prime Landlord, Tenant shall be required to obtain the approval or
consent of both Prime Landlord and Landlord. In all provisions of the Prime
Lease requiring that notice be given to Prime Landlord, Tenant shall be required
to give notice to both the Prime Landlord and Landlord.

            (b) The following provisions of the Prime Lease do not apply to
Tenant and are hereby deleted in respect of this Sublease: Sections 3 (Term), 13
(Assignments -- Subleasing) (as between Landlord and Tenant only), 18 (Fire,
Casualty -- Eminent Domain) (but only with respect to any right to terminate the
Prime Lease) and 22 (Other Provisions).

      16. Consents. Landlord's refusal to consent to or approve any matter or
thing, whenever Landlord's consent or approval is required under this Sublease
or under the Prime Lease, as incorporated herein, shall be deemed reasonable if
Prime Landlord has refused or failed to give its consent or approval to such
matter or thing.

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      17. Condition of the Premises; Tenant's Changes.

            (a) Tenant represents it has made a thorough examination of the
Premises and it is familiar with the condition thereof. Tenant acknowledges that
it enters into this Sublease without any representation or warranties by
Landlord except as set forth in this Lease, or anyone acting or purporting to
act on behalf of Landlord, as to the present or future conditions of the
Premises or the appurtenances thereto or any improvements therein or of the
Building. It is further agreed that Tenant does and will accept the Premises "as
is" in their present condition and Landlord has no obligation to perform any
work therein.

            (b) Notwithstanding anything to the contrary contained in the Prime
Lease, Tenant shall not make any changes to the Premises whatsoever, including,
without limitation, structural or non-structural changes, without the prior
written consent of Landlord which consent shall not be unreasonably withheld,
conditioned or delayed but subject to prior consent of Prime Landlord in
accordance with the Prime Lease. All structural and/or non-structural changes
shall be subject to the Construction Specifications attached hereto as Exhibit
B.

      18. Assignment and Subletting.

            (a) Tenant, for itself, its successors and assigns, expressly
covenants that it shall not assign, whether by operation of law or otherwise,
mortgage or pledge or otherwise transfer or encumber this Sublease, or sublet
all or any part of the Premises without obtaining the prior written consent of
Landlord which consent may be given or withheld in Landlord's sole discretion.
Notwithstanding the foregoing, Landlord's consent shall not be unreasonably
withheld with respect to assignments or transfers to Affiliated Entities.
Affiliated Entities shall mean (i) a subsidiary of Tenant, (ii) a corporation or
other entity into or with which Tenant has merged or consolidated or to which
substantially all of Tenant's stock or assets are transferred, or (iii) any
corporation or other entity which controls, is controlled by, or is under common
control with Tenant.

            Notwithstanding the foregoing, provided there is no default
continuing beyond any applicable notice and/or cure period, Landlord also
agrees, upon the written request of Tenant, to not unreasonably withhold its
consent to a sub-sublease of the Premises by Tenant, provided and on the
condition that: (i) such sub-sublease including the subtenant shall be subject
to Prime Landlord's prior approval, which approval shall be governed by the
terms of the Prime Lease; (ii) such subtenant shall be of a business reputation
reasonably acceptable to Landlord; (iii) such subtenant shall have a financial
net worth, determined by generally acceptable accounting principles,
satisfactory to Landlord (and Tenant shall supply financial information and
documentation regarding such financial status to Landlord thirty (30) days prior
to the execution of any new sub-sublease); (iv) the terms of such new
sub-sublease shall be on the same or better terms as this Sublease (or if any
term may be less favorable to Landlord, the inclusion of such change in the new
sub-sublease shall be subject to Landlord's sole discretion); (v) the new
sub-sublease shall be unconditionally guaranteed by Tenant, which form of
guaranty shall be satisfactory to Landlord; (vi) Tenant shall reimburse Landlord
for its reasonable out-of-pocket expenses, including reasonable

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attorney's fees, incurred in connection with such surrender and sub-sublease and
Tenant shall be solely responsible for any leasing commissions, improvements
allowances or other expenses relating to the proposed sub-sublease; (vii) Tenant
shall not be in default hereunder; (viii) Tenant shall pay to Landlord 50% of
all rents received in connection with such sub-sublease in excess of the rents
set forth herein; and (ix) the new sub-sublease shall be in the form of this
Sublease. Any obligations of Tenant to reimburse Landlord hereunder shall
survive the surrender of the Sublease.

            (b) If Tenant requests Landlord's consent to a sublease as set forth
above, Tenant, together with such request for consent, shall provide Landlord
with the name of the proposed transferee and the nature of the business of the
proposed transferee, the term, use, rental rate and all other material terms and
conditions of the proposed transfer, including, without limitation, a copy of
the proposed sub-sublease or other contractual documents and evidence
satisfactory to Landlord that the proposed transferee is financially
responsible.

            With respect to any sub-sublease of fifty (50%) percent or more of
the Premises, Landlord may have the right to recapture the Premises if Tenant
proposes to sub-sublease the Premises to a third party after the one year
anniversary of the Commencement Date. Landlord must exercise (or forego) its
recapture rights within fifteen (15) days of its receipt of Tenant's
sublease/assignment notice. In order to effectuate its recapture rights,
Landlord may terminate, at its election, the sublease with respect to the entire
Premises or with respect to that portion of the Premises described in the
sub-sublease and Tenant shall have no further obligations (except as otherwise
specifically set forth in this Sublease) with respect to that portion of the
Premises which are recaptured (and there shall be a pro rata reduction in Rent
and the Security Deposit based upon the rentable square footage of the
recaptured portion of the Premises relative to the rentable square footage of
Premises prior to recapture), except as specifically set forth herein, and
Tenant shall at its expense erect, if necessary, a demising wall to separate the
remainder of the Premises from that portion of the Premises which is being
recaptured and to take such other steps as shall be necessary to make the
portion of the Premises that is not being recaptured into a self-contained,
lawfully demisable rental unit.

            (c) In the event Landlord is requested to consent to an assignment
of this Sublease or a subletting of the Premises, Tenant shall pay all costs and
expenses in connection with such assignment or subletting, including, without
limitation, any reasonable attorneys' fees of Landlord in connection with its
review of the assignment or subletting documents, any cost of renovating,
altering or decorating the Premises for a new occupancy (if Tenant desires to do
the same) and any leasing brokerage fees payable.

            (d) The listing of any name other than that of Tenant, whether on
the doors of the Premises or on the Building directory, or otherwise, shall not
operate to vest any right or interest in this Sublease or in the Premises or be
deemed to be the written consent of Landlord mentioned in this Section, it being
expressly understood that any such listing is a privilege extended by Landlord
revocable at will by written notice to Tenant.

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            (e) If this Sublease is assigned, or if the Premises or any part
thereof is sublet or occupied by anybody other than Tenant, Landlord may at any
time and from time to time, collect rent and other charges from the assignees,
subtenants or occupants, and apply the net amount collected to the Base Rent and
other charges herein reserved, but no such assignment, sublease or collection
shall be deemed a waiver of this covenant, or the acceptance of the assignee,
Tenant or occupant as a Landlord, or a release of Tenant from the further
performance of covenants on the part of Tenant herein contained, including
without limitation, Tenant's obligation to pay the Base Rent and other charges,
or a release of the Security Deposit (as hereinafter defined). The consent by
Landlord to an assignment or subletting or occupancy shall not in any way be
construed to relieve Tenant from obtaining the express consent in writing of
Landlord to any further assignment or subletting or occupancy.

            (f) Notwithstanding the immediately preceding sentences, any steps
taken by Landlord or Tenant in this regard shall be subject to all terms and
conditions of the Prime Lease.

            (g) Landlord reserves the right to transfer and assign its interest
in and to this Sublease to any entity or person who shall succeed to Landlord's
interest in and to the Prime Lease.

            (h) Consent by Landlord to any assignment, transfer or subletting to
any party shall not be construed as a waiver or release of Tenant from the terms
of any covenant or its primary responsibility under this Sublease, nor shall
consent to one assignment, transfer or sublease to any person, partnership, firm
or corporation be deemed to be a consent to any subsequent assignment, transfer
or subletting to another person, partnership, firm or corporation; Tenant shall
remain directly and primarily liable and any such sublessee or assignee agrees
directly with Landlord by written instrument reasonably satisfactory to Landlord
to be bound by all of the obligations of Tenant.

      19. Insurance.

            (a) Tenant agrees to maintain all insurance coverages specified in
and in accordance with Section 17 of the Prime Lease (including without
limitation commercial general liability and property damage insurance, casualty
insurance and, in addition, statutory workers' compensation insurance). All such
insurance shall be underwritten by a company or companies licensed to do
insurance business in the Commonwealth of Massachusetts by the Department of
Insurance and in good standing, and shall be written on an "occurrence basis."
All such insurance policies shall name Landlord and Prime Landlord as additional
insureds thereunder and, in addition, shall name as additional insureds the
holders of any mortgage of the Building, or the property on which the building
is located (the "Property"), of which Tenant is notified in writing, as their
respective interests may appear. Tenant shall furnish Landlord receipts
evidencing payment of the premiums for such insurance (if requested by Landlord)
and shall deposit with Landlord certificates for such insurance no later than
the Rent Commencement Date and at least fifteen (15) days before each insurance
renewal date thereof, bearing the endorsement that the polices will not

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be canceled nor will coverages be reduced until after ten (10) days' prior
written notice to both Landlord and Prime Landlord of such proposed action.
Tenant shall pay all premiums and charges for such insurance, and if Tenant
shall fail to obtain such insurance, Landlord may, but shall not be obligated
to, obtain the same, in which event the amount of the premium paid shall be paid
by Tenant to Landlord upon Landlord's demand therefor, shall be deemed
Additional Rent and shall be collectible by Landlord in the same manner and with
the same remedies as though said sums were Additional Rent reserved hereunder.

            (b) Tenant acknowledges that Landlord will not carry any insurance
in favor of Tenant, and that neither Prime Landlord nor Landlord will carry
insurance on Tenant's furniture and/or furnishings or any fixtures or equipment,
improvements or appurtenances of Tenant in or about the Premises.

      20. Waiver of Subrogation.

            (a) Any casualty insurance carried by the Tenant with respect to the
Premises, the Building or the Property, or property therein or occurrences
thereon shall include a clause or endorsement denying to the insurer rights of
subrogation against the other party to the extent rights have been waived by the
insured prior to occurrence of injury or loss, provided that such clause or
endorsement is obtainable without payment of an additional premium. If such
clause or endorsement is obtainable upon payment of an additional premium,
notice thereof shall be given to the Landlord and the Landlord may request the
Tenant to obtain it and shall reimburse the Tenant for the cost of such
additional premium.

            (b) Each party, notwithstanding any provisions of this Sublease to
the contrary, hereby waives any rights of recovery against the other for injury
or loss due to hazards covered by such insurance to the extent such party's
policy permits such waivers of subrogation and then only with respect to sums
which are collectible thereunder. Landlord shall be afforded the protection of
this provision notwithstanding any right which Tenant may have to self insure.

      21. End of Term. If Tenant shall remain in possession of the Premises or
any part thereof after the expiration or prior termination of the Term hereof,
as the same may be extended, the parties agree that no such holding over by
Tenant shall operate to extend or renew this Sublease, and that any such holding
over shall cause Tenant to become a month-to-month tenant and Tenant shall be
obligated to pay monthly installment of Base Rent and Additional Rent in an
amount equal to one hundred fifty percent (150%) times the sum of the
installment of Base Rent and Additional Rent payable during the last full
calendar month of the Lease Term, and such tenancy shall otherwise be subject to
all the terms, conditions, covenants and agreements of this Sublease. Tenant
further agrees to pay to Landlord all direct, indirect and consequential
damages, costs and expenses incurred by Landlord as a result of such holding
over, including without limitation, any costs and expenses that Prime Landlord
charges to Landlord on account thereof and Tenant agrees to indemnify Landlord
against, and hold Landlord harmless from, any damage, loss, claim,

<PAGE>
                                     - 12 -

liability or expenses, including without limitation, reasonable attorneys' fees
arising out of such holding over.

      22. Default.

            (a) In the event that Tenant shall default in the payment of Base
Rent, Additional Rent or any other charge payable hereunder within five (5) days
after written notice, or shall default in the performance or observance of any
of the terms, conditions and covenants of this Sublease within twenty (20) days
after written notice, or, if not curable within said twenty-day period, Tenant
does not commence to cure said default within said twenty-day period and
diligently prosecute the same to completion, and provided that there exists no
event of default under the Prime Lease, Landlord, in addition to and not in
limitation of any rights otherwise available to it, shall have the same rights
and remedies with respect to such default as are provided to Prime Landlord
under the Prime Lease with respect to defaults by Landlord as tenant thereunder,
with the same force and effect as though all such provisions relating to any
such default or defaults were set forth herein in their entirety, and Tenant
shall have all of the obligations of the tenant under the Prime Lease with
respect to such default or defaults.

            Notwithstanding anything to the contrary as contained herein the
parties acknowledge that there is not a grace period under the Prime Lease for
non-monetary default, and accordingly, should Prime Landlord notify Landlord of
a default with respect to non-monetary matters, the twenty (20) day period set
forth above shall automatically be revoked.

            (b) In the event of a default by Tenant in the performance of any of
its non-monetary obligations hereunder, including those under the Prime Lease,
Landlord may, at its option, and without waiving any other remedies for such
default herein or at law or by incorporation by reference of the Prime Lease
provided, at any time thereafter, give written notice to Tenant that if such
default is not cured, or the cure not commenced, within twenty (20) days after
notice, and if so commenced is not thereafter pursued diligently to completion,
Landlord may cure such default for the account of Tenant, and any amount paid or
incurred by Landlord in so doing shall be deemed paid or incurred for the
account of Tenant and Tenant agrees promptly to reimburse Landlord therefor and
save Landlord harmless therefrom; provided, however, that Landlord may cure any
such default as aforesaid prior to the expiration of any waiting period if
reasonably necessary to protect Landlord's interest under the Prime Lease or to
prevent injury or damage to persons or property.

            (c) In addition to any other event of default under this Sublease or
the Prime Lease, it shall be an event of default under this Sublease, without
any notice or cure period, if Tenant shall be in default under that certain
Agreement of Sublease between Landlord and Tenant dated October 20, 2000
relating to space located at 5 Carlisle Road, Westford, MA continuing beyond any
applicable notice and/or cure period.

<PAGE>
                                     - 13 -

      23. Destruction, Fire and other Casualty. If the whole or any part of the
Premises or the Building shall be damaged by fire or other casualty and the
Prime Lease is not terminated on account thereof by either Landlord or Prime
Landlord in accordance with the terms thereof this Sublease shall remain in full
force and effect and Base Rent and Additional Rent, shall not abate except to
the extent Base Rent and Additional Rent for the Premises shall abate under the
terms of the Prime Lease.

      Notwithstanding the foregoing, if and only to the extent Landlord has an
opportunity under Section 18 of the Prime Lease to terminate the Prime Lease
with respect to the Premises ("Casualty Termination Option"), Landlord shall
within ten (10) days of such Casualty Termination Option notify Tenant whether
Landlord has elected to terminate or not terminate the Prime Lease. If Landlord
has decided not to terminate the Prime Lease under Section 18 of the Prime Lease
with respect to the Premises, Tenant may decide, notwithstanding such decision,
that it elects to terminate the Sublease provided (i) there is no default
hereunder, and (ii) Tenant informs Landlord within five (5) business days of
receipt of such Casualty Termination Option from Landlord that it elects to
terminate the Sublease which event the Sublease shall terminate in accordance
with Section 18 of the Prime Lease. If Tenant fails to satisfy all of the
foregoing conditions, Tenant shall be deemed to have waived any rights set forth
herein. All times set forth herein are of the essence.

      24. Notices.

            (a) Whenever, by the terms of this Sublease, notice, demand or other
communication shall or may be given to either party, the same shall be in
writing and addressed as follows:

                   If to Landlord:   Unisphere Networks, Inc.
                                     One Executive Drive
                                     Chelmsford, MA 01824
                                           Attn: Suzanne M. Zabitchuck
                                                 General Counsel

                   with a copy to:
                                     Gadsby Hannah LLP
                                     225 Franklin Street
                                     Boston, MA 02110
                                           Attn: Cynthia B. Keliher, Esq.

                   If to Tenant:     Sonus Networks, Inc.
                                     5 Carlisle Road
                                     Westford, MA 01886
                                     Attn: Stephen J. Nill, Vice President of
                                           Finance and CFO

or to such other address or addresses as shall from time to time be designated
by written notice by either party to the other as herein provided. All notices
shall be sent by registered

<PAGE>
                                     - 14 -

or certified mail, postage prepaid and return receipt requested, or by Federal
Express or other comparable courier providing proof of delivery, and shall be
deemed duly given and received (i) if mailed, on the third business day
following the mailing thereof, or (ii) if sent by courier, the date of its
receipt (or, if such day is not a business day, the next succeeding business
day). Landlord and Tenant each promptly shall deliver to the other copies of all
notices, requests, demands or other communications which relate to the Premises
or the use or occupancy thereof after receipt of the same from Prime Landlord or
others.

            (b) Each party hereunder shall promptly furnish the other with
copies of all notices under the Prime Lease or this Sublease with respect to the
Premises which such party shall receive from Prime Landlord under the Prime
Lease.

      25. Sublease Conditional Upon Certain Consents. Landlord and Tenant each
acknowledge and agree that this Sublease is subject to Landlord's obtaining the
unconditional consent of Prime Landlord in accordance with the terms of the
Prime Lease, and that if such consent shall not be obtained within forty-five
(45) days of the date hereof, then this Sublease shall be deemed cancelled and
terminated and neither of the parties hereto shall have any liability to the
other.

      26. Security Deposit. Tenant concurrently with the execution of this
Sublease has deposited with Landlord a deposit (the "Security Deposit") in the
amount of Twelve Thousand One Hundred 88/100 Dollars ($12,100.88) to be held by
Landlord without interest as security for the faithful performance and
observance by Tenant of the terms, conditions and provisions of this Sublease,
including without limitation the surrender of possession of the Premises to
Landlord as herein provided. Landlord shall not be required to maintain the
Security Deposit in a separate account. It is agreed that in the event Tenant
defaults in respect of any of the terms, provisions and conditions of this
Sublease, including, but not limited to, the payment of Base Rent and Additional
Rent, Landlord may apply or retain the whole or any part of the Security Deposit
to the extent required for the payment of any Base Rent and Additional Rent or
any other sum as to which Tenant is in default or for any sum which Landlord may
expend or may be required to expend by reason of Tenant's default in respect of
any of the terms, covenants and conditions of this Sublease, including but not
limited to, any damages or deficiency in the reletting of the Premises, whether
such damages or deficiency accrue or accrues before or after summary proceedings
or other reentry by Landlord. The Security Deposit is not to be used or applied
by Tenant as a substitute for rent due any month, but may be so applied by
Landlord at any time at Landlord's option. The use, application or retention of
the Security Deposit, or any portion thereof, by Landlord shall not prevent
Landlord from exercising any other right or remedy provided by this Sublease or
by law and shall not operate as a limitation on any recovery to which Landlord
may otherwise be entitled. If Landlord applies or retains any part of the
Security Deposit, Tenant, upon written demand therefor by Landlord, shall
deposit cash with Landlord in such amount so that Landlord shall have the full
deposit on hand at all times during the Term. If Tenant shall fully and
faithfully comply with all of the terms, provisions, covenants and conditions of
this Sublease, the balance of the Security Deposit, if any, shall be returned to
Tenant within thirty (30) days after the Expiration Date and after the delivery
of the entire possession of the Premises to Landlord.

<PAGE>
                                     - 15 -

      27. Payment of the First Month's Base Rent. Tenant shall pay to Landlord
the first monthly installment of the applicable Base Rent upon execution of this
Sublease.

      28. Signage. Any signage contemplated by the Tenant shall be subject the
consent of the Prime Landlord. Landlord shall have no obligation or
responsibility to remove any signage which exists at the Premises as of the
Commencement Date.

      29. Landlord's Representations. Landlord hereby represents and warrants
that (i) the Prime Lease is in full force and effect, (ii) the Prime Lease
attached hereto as Exhibit A is the complete Prime Lease and that, except for
the Addendum to Lease dated June 23, 2000, the Prime Lease has not been amended
or modified; (iii) to the best of Landlord's knowledge, there are no existing
setoffs, defenses or counterclaims against the Prime Landlord with respect to
the payment of rent reserved under the Prime Lease or any performance of other
terms, conditions or covenants of the Prime Lease on the part of the Tenant
under the Prime Lease to be performed; and (iv) there exists no defaults or
breaches of Prime Landlord's or Tenant's obligations under the Prime Lease nor,
to the best of Landlord's knowledge, any event which with the giving of notice
or passage of time, or both, would constitute a default under the Prime Lease.

      30. Miscellaneous.

            (a) This Sublease may not be extended, renewed, terminated, or
otherwise modified except by an instrument in writing signed by the party
against whom enforcement of any such modification is sought.

            (b) It is understood and agreed that all understandings and
agreements heretofore had between the parties hereto are merged in this
Sublease, which alone fully and completely expresses their agreement, and that
the same is entered into after full investigation, neither party relying upon
any statement, representation or warranty made by the other not embodied in this
Sublease.

            (c) The paragraph headings appearing herein are for purposes of
convenience only and are not deemed to be a part of this Sublease.

            (d) The provisions of this Sublease shall be governed by and
construed in accordance with the laws of the Commonwealth of Massachusetts
without regard to principles of conflicts of laws. Landlord and Tenant agree to
submit to jurisdiction in the Commonwealth of Massachusetts with respect to any
dispute under or arising out of this Sublease and agree that any such dispute
shall be brought either in the courts of the Commonwealth of Massachusetts or in
the applicable federal district court located in Massachusetts.

            (e) If any provision of this Sublease or the application thereof to
any person or circumstance shall to any extent be invalid or unenforceable, the
remainder of this Sublease, or the application of such provision to persons or
circumstance other than those as

<PAGE>
                                     - 16 -

to which it is invalid or unenforceable, shall not be affected thereby, and each
provision of this Sublease shall be valid and enforced to the fullest extent
permitted by law.

            (f) This Sublease may be executed in counterparts each of which
shall be deemed an original and all of which together shall constitute one and
the same document.

            (g) This Sublease (or any notice hereof) shall not be recorded.

            (h) Landlord and Tenant hereby each waive trail by jury in any
action, proceeding or counterclaim brought by either against the other, on or in
respect of any matter whatsoever arising out of or in any way connected with
this Sublease, the relationship of Landlord and Tenant or Tenant's use or
occupancy of the Premises.

            (i) This Sublease includes and incorporates all Exhibits referred to
hereby and attached hereto.

                      [SIGNATURES APPEAR ON THE NEXT PAGE]

<PAGE>
                                     - 17 -

      IN WITNESS WHEREOF, this Agreement of Sublease has been duly executed as
of the day and year first above written.

                                     LANDLORD:
                                     UNISPHERE NETWORKS, INC.

                                     By: /s/ John J. Connolly
                                         --------------------------------
                                     Name: John J. Connolly
                                           ------------------------------
                                     Title: V.P. Finance & CFO.
                                            -----------------------------

                                     TENANT:
                                     SONUS NETWORKS, INC.

                                     By: /s/ S. J. Nill
                                         --------------------------------
                                     Name: S. J. Nill
                                           ------------------------------
                                     Title: VP & CFO
                                            -----------------------------

<PAGE>
                                     - 18 -

                                    EXHIBIT A
                                   Prime Lease

                                 Attached hereto

<PAGE>
                                     - 19 -

                                    EXHIBIT B
                          TENANT IMPROVEMENTS AGREEMENT

      This Tenant Improvements Agreement (the "Agreement") is attached to and
made a part of the Sublease. The capitalized terms used in this Agreement that
are defined in the Sublease shall have the same meanings as provided in the
Sublease.

1.    General

      This Agreement sets forth the terms and conditions governing Tenant's
construction of improvements to be installed in the Premises (the "Tenant
Improvements").

2.    Intentionally Omitted.

3.    Design and Schedule.

      3.1   Tenant Plans for Tenant Improvements.

            (a)   Space Plan: The "Space Plan" as used herein shall mean a plan
                  containing, among other things, a partition layout, door
                  location and, if appropriate, some furniture located in key
                  spaces within the Premises.

            (b)   Construction Drawings and Specifications: The "Construction
                  Drawings and Specifications" as used herein shall mean the
                  construction working drawings, the mechanical, electrical and
                  other technical specifications, and the finishing details,
                  including wall finishes and colors and technical and
                  mechanical equipment installation, if any, all of which
                  details the installation of the Tenant Improvements in the
                  Premises. The Construction Drawings shall be signed by
                  Tenant's Representative:

                  (i)   be compatible with the Building shell, and with the
                        design, construction and equipment of the Building;

                  (ii)  comply with all applicable laws, codes and ordinances
                        including the Americans With Disabilities Act, and the
                        rules and regulations of all governmental authorities
                        having jurisdiction;

                  (iii) comply with all applicable insurance regulations and the
                        requirements of the Board of Underwriters for a fire
                        resistant Class A building; and

<PAGE>
                                     - 20 -

                  (iv)  include locations of all Tenant Improvements including
                        complete dimensions.

      3.2   Approvals by Landlord. The Space Plan and all Construction Drawings
            and Specifications for the Tenant Improvements shall be subject to
            Landlord's prior written approval, which shall not be unreasonably
            withheld or delayed, except that Landlord shall have complete
            discretion with regard to granting or withholding approval of
            Construction Drawings and Specifications to the extent they impact
            the Building's structure or systems, affect future marketability of
            the Building or would be visible from the common facilities or
            exterior of the Building. Any changes, additions or modifications
            that Tenant desires to make to the Tenant Plans shall also be
            subject to Landlord's prior written approval, which shall not be
            unreasonably withheld or delayed except as provided above for
            Building structure, system or appearance impact.

4.    Construction of Tenant Improvements. Following Landlord's and Landlord's
      final approval of the Tenant Plans and Tenant obtaining permits, Tenant
      shall commence and diligently proceed with the construction of the Tenant
      Improvements. Landlord and Tenant acknowledge that Tenant shall hire a
      contractor mutually acceptable to Prime Landlord, Landlord and Tenant (in
      their reasonable discretion) to complete the Tenant Improvements. The
      Tenant Improvements shall be conducted with due diligence, in a good and
      workmanlike manner befitting a first class office building, and in
      accordance with the Tenant Plans and all applicable laws, codes,
      ordinances and rules and regulations of all governmental authorities
      having jurisdiction.

      Tenant hereby agrees to indemnify Landlord and Landlord and hold Landlord
      and Landlord harmless from any and all claims for personal or bodily
      injury and property damage that may arise from the performance of the
      Tenant Improvements, whether resulting from the negligence or willful
      misconduct of its general contractors, subcontractors or otherwise. Tenant
      and its contractors and subcontractors shall execute such additional
      documents as Landlord deems reasonably appropriate to evidence said
      indemnity.

      Notwithstanding the foregoing, Tenant shall not commence the Tenant
      Improvements until the following is provided:

      (a)   Insurance. Prior to construction, Tenant shall provide Landlord with
            an original certificate of All-Risk Builder's Risk Insurance (the
            "Builder's Risk Insurance Policy"), subject to Landlord's reasonable
            approval, in the minimum amount of the replacement cost of the
            Tenant Improvements issued by a company or companies acceptable to
            Landlord and authorized to do business in the Commonwealth of
            Massachusetts, covering the Premises (including the Premises), with
            premiums prepaid, and which names the Landlord as an additional
            insured. Said policy shall insure the Tenant Improvements and all
            materials and supplies for the Tenant Improvements

<PAGE>
                                     - 21 -

            stored on the Premises (or at any other sites and including the
            Premises) against loss or damage by fire and the risks and hazards
            insured against by the standard form of extended coverage, and
            against vandalism and malicious mischief, and such other risks and
            hazards as Landlord may reasonably request. Said insurance coverage
            shall be for 100% of replacement cost, including architectural fees.
            The Builder's Risk Insurance Policy shall contain a provision that
            the insurance company waive the rights of recovery or subrogation
            against Landlord, its agents, servants, invitees, employees,
            co-tenants, co-venturers, affiliate companies, and their insurers.

      (b)   Governmental Permits. Building permits and other appropriate permits
            and licenses from the appropriate agency or office of any
            governmental or regulatory body having jurisdiction over the
            Premises and which are required for the construction of the Tenant
            Improvements.

      (c)   Additional Insurance. Additional insurance in the form of and
            meeting the requirements as Landlord and Prime Landlord may
            determine in their reasonable discretion provided it is commercially
            reasonable under the circumstances..

5.    Change Orders. If Tenant requests any change or addition to or subtraction
      from the Tenant Improvements ("Change Order") after Tenant's and
      Landlord's approval of the final and complete Construction Drawings and
      Specifications for the Tenant Improvements, Landlord shall respond to
      Tenant's request for consent as soon as possible, but in no event later
      than five (5) working days after being made. Any changes, additions or
      modifications that Tenant desires to make to the Tenant Plans shall not be
      unreasonably withheld, except that Landlord shall have complete discretion
      with regard to granting or withholding approval for Building structure,
      system or appearance as provided in Section 3.2 above.

6.    Cooperation With Other Tenants. Tenant shall promptly remove from the
      common facilities any of Tenant's vehicles, equipment, materials, supplies
      or other property deposited in the common facilities during the
      construction of the Tenant Improvements. Further, Tenant shall at no time
      disrupt or allow disruption to any existing Landlord's parking vehicles
      and pedestrian access, nor allow disruptions of mechanical, electrical,
      telephone and plumbing services. In addition, Tenant shall not interrupt
      the normal business operation of any other tenant at the Building or on
      the Lot.

7.    Inspection by Landlord. Landlord shall have the right to inspect the
      Tenant Improvements at all reasonable times. Landlord's failure to inspect
      the Tenant Improvements shall in no event constitute a waiver of any of
      Landlord's rights hereunder nor shall Landlord's inspection of the Tenant
      Improvements constitute the Landlord's approval of same.

<PAGE>
                                     - 22 -

8.    Removal of Specialized Tenant Improvements. Portions of the Tenant
      Improvements, if any, as reasonably determined by Landlord to be
      specialized improvements shall, at the election of Landlord, either be
      removed by Tenant at its expense before the expiration of the Term or
      shall remain in the Premises and be surrendered therewith at the
      expiration date or earlier termination of this Sublease as the property of
      Landlord without disturbance, molestation or injury. If Landlord requires
      the removal of all or part of said specialized Tenant Improvements,
      Landlord shall so notify Tenant at the time that Landlord renders its
      approval to the Space Plan and Construction Drawings pursuant to Section
      3.2 above, and Tenant, at the expiration or earlier termination of the
      Sublease, at its expense, shall repair any damage to the Premises or the
      Building caused by such removal and restore the Premises to its condition
      prior to the installation of such specialized Tenant Improvements. If
      Tenant fails to remove said specialized Tenant Improvements that Tenant is
      required to remove hereunder, then Landlord may (but shall not be
      obligated to) remove the same and the cost of such removal, repair and
      restoration, together with any and all damages which Landlord may suffer
      and sustain by reason of the failure of Tenant to remove the same, shall
      be charged to Tenant and paid upon demand.

9.    Completion of Tenant Improvements. Tenant shall notify Landlord in writing
      when the Tenant Improvements have been substantially completed. Landlord
      shall thereupon have the opportunity to inspect the Premises in order to
      determine if the Premises has been substantially completed in accordance
      with the Tenant Plans. If the Tenant Improvements has not been
      substantially completed in accordance with the Tenant Plans, Landlord
      shall immediately following inspection, provide Tenant with written
      notification of the items deemed incorrect or incomplete. Tenant shall
      forthwith proceed to correct the incorrect or incomplete items.
      Notwithstanding anything to the contrary, the Tenant Improvements shall
      not be considered suitable for review by Landlord until all designated or
      required governmental inspections, permits and certifications necessary
      for the Tenant Improvements, including, but not limited to a temporary or
      final certificate of occupancy, have been made, given and/or posted.

10.   Consent of Landlord. Tenant shall be solely responsible for obtaining the
      consent of Prime Landlord to the construction of the Tenant Improvements
      pursuant to the terms and conditions of the Prime Lease prior to any
      construction therein and immediately upon receipt shall deliver a copy of
      such consent to Landlord.<PAGE>

                                                                    Exhibit 10.9

                                      LEASE

                                     BETWEEN

                         SONUS NETWORKS, INC., AS TENANT

                                       AND

                   BCIA NEW ENGLAND HOLDINGS LLC, AS LANDLORD

                    25 PORTER ROAD, LITTLETON, MASSACHUSETTS

The submission of an unsigned copy of this document to Tenant for Tenant's
consideration does not constitute an offer to lease the Premises or an option to
or for the Premises. This document shall become effective and binding only upon
the execution and delivery of this Lease by both Landlord and Tenant.
<PAGE>

                                TABLE OF CONTENTS

                                                                            PAGE

      ARTICLE 1         BASIC DATA; DEFINITIONS                                1

1.1   Basic Data
1.2   Definitions
1.3   Enumeration of Exhibits

      ARTICLE 2         PREMISES AND APPURTENANT RIGHTS                        4

2.1   Lease of Premises
2.2   Appurtenant Rights and Reservations

      ARTICLE 3         BASIC RENT                                             5

3.1   Payment

      ARTICLE 4         COMMENCEMENT AND CONDITION                             6

4.1   Commencement Date
4.2   Preparation of the Premises: As Is Condition

      ARTICLE 5         USE OF PREMISES                                        6

5.1   Permitted Use
5.2   Installations and Alterations by Tenant
5.3   Extra Hazardous Use
5.4   Hazardous Materials

      ARTICLE 6         ASSIGNMENT AND SUBLETTING                              9

6.1   Prohibition
6.2   Acceptance of Rent
6.3   Excess Payments
6.4   Landlord's Recapture Right
6.5   Further Requirements
6.6   Initial Permitted Subletting

                                      -ii-
<PAGE>

      ARTICLE 7         RESPONSIBILITY FOR REPAIRS AND
                        CONDITION OF PREMISES; SERVICES TO BE
                        FURNISHED BY LANDLORD                                 11

7.1   Landlord Repairs
7.2   Tenant Repairs
7.3   Floor Loan - Heavy Machinery
7.4   Utility Services
7.5   Other Services
7.6   Interruption of Service

      ARTICLE 8         REAL ESTATE TAXIES                                    16

8.1   Payments on Account of Real Estate Taxes
8.2   Abatement

      ARTICLE 9         OPERATING AND UTILITY EXPENSES                        17

9.1   Definitions
9.2   Tenant's Payment of Operating Expenses

      ARTICLE 10        INDEMNITY AND PUBLIC LIABILITY INSURANCE              18

10.1  Tenant's Indemnity
10.2  Tenant Insurance
10.3  Tenant's Risk
10.4  Waiver of Subrogation

      ARTICLE 11        FIRE, EMINENT DOMAIN, ETC.                            19

11.1  Landlord's Right of Termination
11.2  Restoration: Tenant's Right of Termination
11.3  Landlord's Insurance
11.4  Abatement of Rent
11.5  Condemnation Award

      ARTICLE 12        HOLDING OVER; SURRENDER                               20

12.1  Holding Over
12.2  Surrender of Premises

      ARTICLE 13        RIGHTS OF MORTGAGEES; TRANSFER OF TITLE               21

13.1  Rights of Mortgagees
13.2  Assignment of Rents and Transfer of Title
13.3  Notice to Mortgagee

                                      -iii-
<PAGE>

      ARTICLE 14        DEFAULT; REMEDIES                                     22

14.1  Tenant's Default
14.2  Landlord's Remedies
14.3  Additional Rent
14.4  Remedying Defaults
14.5  Remedies Cumulative
14.6  Attorney's Fees
14.7  Waiver
14.8  Security Deposit
14.9  Landlord's Default

      ARTICLE 15        MISCELLANEOUS PROVISIONS                              27

15.1  Right of Access
15.2  Covenant of Quiet Enjoyment
15.3  Landlord's Liability
15.4  Estoppel Certificate
15.5  Intentionally Deleted
15.6  Brokerage
15.7  Rules and Regulations
15.8  Invalidity of Particular Provisions
15.9  Provisions Binding, Etc.
15.10 Recording
15.11 Notice
15.12 When Lease Becomes Binding: Entire Agreement: Modification
15.13 Paragraph Headings and Interpretation of Sections
15.14 Dispute Resolution
15.15 Financial Statements
15.16 Waiver of Jury Trial
15.17 Time is of the Essence
15.18 Multiple Counterparts
15.19 Governing Law

      EXHIBIT A Location Plan of Premises             A1

      EXHIBIT B Intentionally Omitted

      EXHIBIT C Commencement Date Letter              C1

      EXHIBIT D Operating Expenses                    1

      EXHIBIT E Rules and Regulations of Building     1

      EXHIBIT F Approved Sublease

      EXHIBIT G Consent to Sublease

                                      -iv-
<PAGE>

                                      LEASE

THIS LEASE is dated as of September 30, 2000 between the Landlord and the Tenant
named below, and is of space in the Building described below.

                                    ARTICLE 1
                             BASIC DATA: DEFINITIONS

      1.1 Basic Data. Each reference in this Lease to any of the following terms
shall be construed to incorporate the data for that term set forth in this
Section:

      Landlord: BCIA New England Holdings LLC, a Delaware limited liability
company

      Landlord's Address: c/o Boston Capital Institutional Advisors LLC, One
Boston Place, Boston, MA 02108

      Tenant: Sonus Networks, Inc.

      Tenant's Address: 5 Carlisle Road, Westford, MA 01886

      Guarantor: Not Applicable

      Property: The land parcel(s) located in Littleton, Massachusetts, together
with the Building and other improvements thereon, known as and numbered 25
Porter Road, Littleton, MA.

      Building: The building commonly known and numbered as 25 Porter Road,
Littleton, MA.

      Building Rentable Area: Agreed to be 66,805 rentable square feet.

      Premises: The portion of the Building shown on the location plan attached
hereto as Exhibit A.

      Premises Rentable Area: Agreed to be 33,194 rentable square feet.

      Basic Rent: The Basic Rent is as follows:

             Rental Period            Annual Basic Rent          Monthly Payment
             -------------            -----------------          ---------------
                                         (per annum)

      Commencement Date                  $506,490.50               $42,207.54
      through and including May    (10,613 ft @ $19.00 and
      31, 2003                        22,581 ft @ $13.50
                                          per annum)

      June 1, 2003 through May           $630,686.00               $52,557.17
      31, 2004                       (33,194 ft @ $19.00
                                          per annum)
<PAGE>

      Tenant's Proportionate Share: Forty-nine and sixty-nine one hundredths
(49.69%) percent (which is based on the ratio of (a) Premises Rentable Area to
(b) Building Rentable Area).

      Security Deposit: $50,000.00 to be held and disposed of as provided in
Section 14.8.

      Commencement Date: October 1, 2000

      Term: Commencing on the Commencement Date and expiring at the close of the
day on May 31, 2004. The Term shall include any extension thereof that is
expressly provided for by this Lease and that is effected strictly in accordance
with this Lease; if no extension of the Term is expressly provided for by this
Lease, no right to extend the Term shall be implied by this provision.

      Initial General Liability Insurance: $2,000,000.00 per
occurrence/$3,000,000.00 aggregate (combined single limit) for property damage,
bodily injury or death.

      Permitted Uses: Executive and general offices, light assembly.

      Tenant's Share of Parking Spaces: The number of parking spaces equal to
4.0 spaces for every 1,000 square foot of Premises Rentable Area.

      1.2 Definitions. When used in Lease, the capitalized terms set forth below
shall bear the meanings set forth below.

      Adequate Assurance: As defined in Section 14.1.

      Adequate Assurance of Future Performance: As defined in Section 14.1.

      Additional Rent: All charges and sums payable by Tenant as set forth in
this Lease, other than and in addition to Basic Rent.

      Agent: BCIA Property Management LLC, or such other person or entity from
time to time designated by Landlord.

      Alterations: As defined in Section 5.2.

      Bankruptcy Code: As defined in Section 14.1.

      Basic Rent: As defined in Section 1.1.

      Broker: Trammell Crow Company

      Building: As defined in Section 1.1.

      Building Rentable Area: As defined in Section 1.1.

      Business Day: All days except Saturdays, Sundays, and other days when
national banks in the Commonwealth of Massachusetts are not open for business.

      Default of Tenant: As defined in Section 14.1.

      Environmental Condition: Any disposal, release or threat of release of
Hazardous Materials on, from or about the Building or the Property or storage of
Hazardous Materials on, from or about the Building or the Property.

                                      -2-
<PAGE>

      Environmental Laws: Any federal, state and/or local statute, ordinance,
bylaw, code, rule and/or regulation now or hereafter enacted, pertaining to
any aspect of the environment or human health, including, without limitation,
Chapter 21C, Chapter 21D, and Chapter 21E of the General Laws of
Massachusetts and the regulations promulgated by the Massachusetts Department
of Environmental Protection, the Comprehensive Environmental Response,
Compensation and Liability Act of 1980, 42 U.S.C. Section 9601 et seq., the
Resource Conservation and Recovery Act of 1976, 42 U.S.C. Section 6901 et
seq., the Toxic Substances Control Act, 15 U.S.C. Section 2061 et seq., the
Federal Clean Water Act, 33 U.S.C. Section 1251, and the Federal Clean Air
Act, 42 U.S.C. Section 7401 et seq.

      Essential Services: As defined in Section 7.6.

      Event of Bankruptcy: As defined in Section 14.1.

      Force Majeure: Collectively and individually, strikes or other labor
trouble, fire or other casualty, acts of God, governmental preemption of
priorities or other controls in connection with a national or other public
emergency or shortages of fuel, supplies or labor resulting therefrom, or any
other cause, whether similar or dissimilar, beyond the reasonable control of the
party required to perform an obligation.

      Guarantor: As defined in Section 1.1.

      Holder: As defined in Section 13.1.

      Hazardous Materials: Shall mean each and every element, compound, chemical
mixture, contaminant, pollutant, material, waste or other substance which is
defined, determined or identified as hazardous or toxic under any Environmental
Law, including, without limitation, any "oil," "hazardous material," "hazardous
waste," "hazardous substance" or "chemical substance or mixture", as the
foregoing terms (in quotations) are defined in any Environmental Laws.

      Initial General Liability Insurance: As defined in Section 1.1.

      Land: The land that constitutes a portion of the Property.

      Landlord: As defined in Section 1.1.

      Mortgage: As defined in Section 13.1.

      Operating Expenses: As defined in Section 9.1.

      Operating Year: As defined in Section 9.1.

      Permitted Uses: As defined in Section 1.1.

      Premises Rentable Area: As defined in Section 1.1.

      Property: As defined in Section 1.1.

      Recapture Date: As defined in Section 6.4.

      Rules and Regulations: As defined in Section 2.2.

      Security Deposit: As defined in Section 1.1.

                                      -3-
<PAGE>

      Service Interruption: As defined in Section 7.6.

      Successor: As defined in Section 13.1.

      Taxes: As defined in Section 8.1.

      Tax Year: As defined in Section 8.1.

      Tenant: As defined in Section 1.1.

      Tenant's Address: As defined in Section 1.1.

      Tenant's Proportionate Share: As defined in Section 1.1.

      Tenant's Removable Property: As defined in Section 5.2.

      Term: As defined in Section 1.1.

      Tenant's Share of Parking Spaces: As defined is Section 1.1.

      1.3 Enumeration of Exhibits. The following Exhibits are a part of this
Lease, are incorporated herein by reference attached hereto, and are to be
treated as a part of this Lease for all purposes. Undertakings contained in such
Exhibits are agreements on the part of Landlord and Tenant, as the case may be,
to perform the obligations stated therein.

            Exhibit A - Location Plan of the Premises
            Exhibit B - Intentionally Omitted
            Exhibit C - Commencement Date Letter
            Exhibit D - Operating Expenses
            Exhibit E - Rules and Regulations
            Exhibit F - Approved Sublease
            Exhibit G - Consent to Sublease

                                    ARTICLE 2
                         PREMISES AND APPURTENANT RIGHTS

      2.1 Lease of Premises. Landlord hereby leases to Tenant and Tenant hereby
leases from Landlord the Premises for the Term and upon the terms and conditions
hereinafter set forth.

      2.2 Appurtenant Rights and Reservations.

            (a) Tenant shall have, as appurtenant to the Premises, the
non-exclusive right to use, and permit its invitees to use in common with
Landlord and others, (i) public or common lobbies, hallways, stairways,
elevators and common walkways necessary for access to the Building and the
Premises, and if the portion of the Premises on any floor includes less than the
entire floor, the common toilets, corridors and elevator lobby of such floor;
and (ii) the access roads, driveways, parking areas, loading areas, pedestrian
sidewalks, landscaped areas, trash enclosures, recreation areas and other areas
or facilities, if any, which are located in or on the Property and designated by
Landlord from time to time for the non-exclusive use of tenants and other
occupants of the Building (the "Common Facilities"); but such rights shall
always be subject to reasonable rules and regulations from time to time
established by Landlord pursuant to Section 15.7 (the "Rules and Regulations")
and to the right of Landlord to designate and change from time to time areas and
facilities so to be used.

                                      -4-
<PAGE>

            (b) Excepted and excluded from the Premises and the Common
Facilities are the ceiling, floor, perimeter walls and exterior windows (except
the inner surface of each thereof), and any space in the Premises used for
shafts, stacks, pipes, conduits, fan rooms, ducts, electric or other utilities,
sinks or other Building facilities, but the entry doors (and related glass and
finish work) to the Premises are a part thereof. Landlord shall have the right
to place in the Premises (but in such manner as to reduce to a minimum
interference with Tenant's use of the Premises) interior storm windows, sun
control devices, utility lines, equipment, stacks, pipes, conduits, ducts and
the like. In the event that Tenant shall install any hung ceilings or walls in
the Premises, Tenant shall install and maintain, as Landlord may require, proper
access panels therein to afford access to any facilities above the ceiling or
within or behind the walls. Tenant shall be entitled to install any such
ceilings or walls only in compliance with the other terms and conditions of this
Lease.

            (c) Tenant shall also have the right (subject to the Rules and
Regulations) to use, on a non-exclusive, unreserved basis, Tenant's Share of
Parking Spaces.

            (d) Landlord shall cause Tenant's name to be listed on the building
directory in the Building lobby.

                                    ARTICLE 3
                                   BASIC RENT

      3.1 Payment.

            (a) Tenant agrees to pay the Basic Rent and Additional Rent to
Landlord, or as directed by Landlord, commencing on the Commencement Date,
without offset, abatement (except as provided in Section 11.1), deduction or
demand. Basic Rent shall be payable in equal monthly installments, in advance,
on the first day of each and every calendar month during the Term of this Lease,
to Landlord at Landlord's Address or at such other place as Landlord shall from
time to time designate by notice, in lawful money of the United States. In the
event that any installment of Basic Rent or any regularly scheduled payment of
Additional Rent is not paid when due on any two occasions during any twelve
calendar month period, then, beginning with the third such occasion within such
12 calendar month period and at any time thereafter during the Term of this
Lease when a payment of Basic Rent and/or Additional Rent is not paid when due,
Tenant shall pay, in addition to any charges under Section 14.4, at Landlord's
request an administrative fee equal to 5% of the overdue payment. Landlord and
Tenant agree that all amounts due from Tenant under or in respect of this Lease,
whether labeled Basic Rent, Additional Rent or otherwise, shall be considered as
rental reserved under this Lease for all purposes, including without limitation
regulations promulgated pursuant to the Bankruptcy Code, and including further
without limitation Section 502(b) thereof.

            (b) Basic Rent for any partial month shall be pro-rated on a daily
basis, and if the first day on which Tenant must pay Basic Rent shall be other
than the first day of a calendar month, the first payment which Tenant shall
make to Landlord shall be equal to a proportionate part of the monthly
installment of Basic Rent for the partial month from the first day on which
Tenant must pay Basic Rent to the last day of the month in which such day
occurs, plus the installment of Basic Rent for the succeeding calendar month.

                                      -5-
<PAGE>

                                    ARTICLE 4
                           COMMENCEMENT AND CONDITION

      4.1 Commencement Date. The "Commencement Date" shall be October 1, 2000.

Promptly upon the occurrence of the Commencement Date, Landlord and Tenant shall
execute a letter substantially in the form attached hereto as Exhibit C, but the
failure by either party to execute such a letter shall have no effect on the
Commencement Date, as hereinabove determined.

      4.2 Preparation of the Premises: As Is Condition.

            Tenant is presently in occupancy of the Premises as a Sublessee of a
third party and the Premises are hereby demised to Tenant in their present "as
is, where is" condition with all faults and without representation or warranty
by Landlord of any kind, name or nature. In no event shall Landlord be required
to make or pay for any work, alterations or improvements in connection with
Tenant's use and occupancy of the Premises.

                                    ARTICLE 5
                                 USE OF PREMISES

      5.1 Permitted Use.

            (a) Tenant agrees that the Premises shall be used and occupied by
Tenant only for Permitted Uses and for no other use without Landlord's express
written consent.

            (b) Tenant agrees to conform to the following provisions during the
Term of this Lease:

                  (i) Tenant shall cause all freight to be delivered to or
      removed from the Building and the Premises in accordance with the Rules
      and Regulations established by Landlord therefor;

                  (ii) Tenant will not place on the exterior of the Premises
      (including both interior and exterior surfaces of doors and interior
      surfaces of windows) or on any part of the Building outside the Premises,
      any sign, symbol, advertisement or the like visible to public view outside
      of the Premises. Landlord will not withhold consent for signs or lettering
      on the entry doors to the Premises provided such signs conform to sign
      standards for the building adopted by Landlord in its sole discretion and
      Tenant has submitted to Landlord a plan or sketch in reasonable detail
      (showing, without limitation, size, color, location, materials and method
      of affixation) of the sign to be placed on such entry doors. Landlord
      agrees, however, to maintain a tenant directory in the lobby of the
      Building (and, in the case of multi-tenant floors, in that floor's
      elevator lobby) in which will be placed Tenant's name and the location of
      the Premises in the Building;

                  (iii) Tenant shall not perform any act or carry on any
      practice which may injure the Premises, or any other part of the Building,
      or cause any offensive odors or loud noise or constitute a nuisance or a
      menace to any other tenant or tenants or other persons in the Building;

                  (iv) Tenant shall, in its use of the Premises, comply with the
      requirements of all applicable governmental laws, rules and regulations,
      including, without limitation, the Americans With Disabilities Act of 1990
      and the regulations of the

                                      -6-
<PAGE>

      Massachusetts Architectural Access Board (nothing contained in this clause
      (iv) shall be deemed or construed to limit or modify Landlord's
      obligations pursuant to Section 7.1 hereof); and

                  (v) Tenant shall not abandon the Premises.

      5.2 Installations and Alterations by Tenant.

            (a) Tenant shall make no alterations, additions (including, for the
purposes hereof, wall-to-wall carpeting), or improvements (collectively,
"Alterations") in or to the Premises (including any Alterations, other than
Landlord's Work, necessary for Tenant's initial occupancy of the Premises)
without Landlord' s prior written consent, which consent shall not be
unreasonably withheld or delayed with respect to non-structural Alterations that
do not affect or involve the Building' s electrical, plumbing or mechanical
systems or any other Building systems. Any Alterations shall be in accordance
with the Rules and Regulations in effect with respect thereto and with plans and
specifications meeting the requirements set forth in the Rules and Regulations
and approved in advance by Landlord. All work shall be (i) be performed in a
good and workmanlike manner and in compliance with all applicable laws,
ordinances and regulations; (ii) be made at Tenant's sole cost and expense;
(iii) become part of the Premises and the property of Landlord unless Landlord
shall require their removal as provided in this Lease; and (iv) be coordinated
with any work being performed by Landlord in such a manner as not to damage the
Building or interfere with the construction or operation of the Building. At
Landlord's request, Tenant shall, before its work is started, secure assurances
satisfactory to Landlord in its reasonable discretion protecting Landlord
against claims arising out of the furnishing of labor and materials for the
Alterations.

      If any Alterations shall involve the removal of fixtures, equipment or
other property in the Premises which are not Tenant' s Removable Property, such
fixtures, equipment or property shall be promptly replaced by Tenant at its
expense with new fixtures, equipment or property of like utility and of at least
equal quality.

            (b) All articles of personal property and all business fixtures,
machinery and equipment and furniture owned or installed by Tenant solely at its
expense in the Premises ("Tenant's Removable Property") shall remain the
property of Tenant and may be removed by Tenant at any time prior to the
expiration or earlier termination of the Term, provided that Tenant, at its
expense, shall repair any damage to the Building caused by such removal.

            (c) Notice is hereby given that Landlord shall not be liable for any
labor or materials furnished or to be furnished to Tenant upon credit, and that
no mechanic's or other lien for any such labor or materials shall attach to or
affect the reversion or other estate or interest of Landlord in and to the
Premises, the Building or the Property. To the maximum extent permitted by law,
before such time as any contractor commences to perform work on behalf of
Tenant, such contractor (and any subcontractors) shall furnish a written
statement acknowledging the provisions set forth in the prior clause. Tenant
agrees to pay promptly when due the entire cost of any work done on behalf of
Tenant, its agents, employees or independent contractors, and not to cause or
permit any liens for labor or materials performed or furnished in connection
therewith to attach to all or any part of the Property and immediately to
discharge any such liens which may so attach. If, notwithstanding the foregoing,
any lien is filed against all or any part of the Property for work claimed to
have been done for, or materials claimed to have been furnished to, Tenant or
its agents, employees or independent contractors, Tenant, at its sole cost and
expense, shall cause such lien to be dissolved promptly after receipt of notice
that such lien has been filed, by the payment thereof or by the filing of a bond
sufficient to accomplish the foregoing. If Tenant shall fail to discharge any
such lien, Landlord may, at its option, discharge such lien and treat the cost
thereof (including reasonable attorneys fees incurred in connection therewith)
as Additional Rent payable upon demand, it being expressly agreed that such
discharge by Landlord

                                      -7-
<PAGE>

shall not be deemed to waive or release the default of Tenant in not discharging
such lien. Tenant shall indemnify and hold Landlord harmless from and against
any and all expenses, liens, claims, liabilities and damages based on or
arising, directly or indirectly, by reason of the making of any alterations,
additions or improvements by or on behalf of Tenant to the Premises under this
Section, which obligation shall survive the expiration or termination of this
Lease.

            (d) In the course of any work being performed by Tenant (including,
without limitation, the "field installation" of any Tenant's Removable
Property), Tenant agrees to use labor compatible with that being employed by
Landlord for work in the Building or on the Property or other buildings owned by
Landlord or its affiliates (which term, for purposes hereof, shall include,
without limitation, entities which control or are under common control with or
are controlled by Landlord or, if Landlord is a partnership or limited liability
company, by any partner or member of Landlord) and not to employ or permit the
use of any labor or otherwise take any action which might result in a labor
dispute involving personnel providing services in the Building or on the
Property pursuant to arrangements made by Landlord.

      5.3 Extra Hazardous Use. Tenant covenants and agrees that Tenant will not
do or permit anything to be done in or upon the Premises, or bring in anything
or keep anything therein, which shall increase the rate of property or liability
insurance on the Premises or the Property above the standard rate applicable to
Premises being occupied for the Permitted Uses. If the premium or rates payable
with respect to any policy or policies of insurance purchased by Landlord or
Agent with respect to the Property increases as a result of any act or activity
on or use of the Premises during the Term or payment by the insurer of any claim
arising from any act or neglect of Tenant, its employees, agents, contractors or
invitees, Tenant shall pay such increase, from time to time, within fifteen (15)
days after demand therefor by Landlord, as Additional Rent.

      5.4 Hazardous Materials.

            (a) Tenant may use chemicals such as adhesives, lubricants, ink,
solvents and cleaning fluids of the kind and in amounts and in the manner
customarily found and used in business offices in order to conduct its business
at the Premises and to maintain and operate the business machines located in the
Premises. Tenant shall not use, store, handle, treat, transport, release or
dispose of any other Hazardous Materials on or about the Premises or the
Property without Landlord's prior written consent, which Landlord may withhold
or condition in Landlord's sole discretion.

            (b) Any handling, treatment, transportation, storage, disposal or
use of Hazardous Materials by Tenant in or about the Premises or the Property
and Tenant's use of the Premises shall comply with all applicable Environmental
Laws.

            (c Tenant shall indemnify, defend upon demand with counsel
reasonably acceptable to Landlord, and hold Landlord harmless from and against,
any liabilities, losses claims, damages, interest, penalties, fines, attorneys'
fees, experts' fees, court costs, remediation costs, and other expenses which
result from the use, storage, handling, treatment, transportation, release,
threat of release or disposal of Hazardous Materials in or about the Premises or
the Property by Tenant or Tenant's agents, employees, contractors or invitees.

            (d) Tenant shall give written notice to Landlord as soon as
reasonably practicable of (i) any communication received by Tenant from any
governmental authority concerning Hazardous Materials which relates to the
Premises or the Property, and (ii) any Environmental Condition of which Tenant
is aware.

                                      -8-
<PAGE>

                                    ARTICLE 6
                            ASSIGNMENT AND SUBLETTING

      6.1 Prohibition.

            (a) Except as otherwise expressly provided in this Lease, Tenant
covenants and agrees that neither this Lease nor the term and estate hereby
granted, nor any interest herein or therein, will be assigned, mortgaged,
pledged, encumbered or otherwise transferred, whether voluntarily,
involuntarily, by operation of law or otherwise, and that neither the Premises
nor any part thereof will be encumbered in any manner by reason of any act or
omission on the part of Tenant, or used or occupied or permitted to be used or
occupied, by anyone other than Tenant, or for any use or purpose other than a
Permitted Use, or be sublet (which term, without limitation, shall include
granting of concessions, licenses and the like) in whole or in part, or be
offered or advertised for assignment or subletting by Tenant or any person
acting on behalf of Tenant without Landlord's prior written consent, which
consent shall not be unreasonably withheld or delayed subject to Landlord's
rights pursuant to Section 6.4 hereof and all other applicable provisions of
this Article 6. Without limiting the foregoing, any agreement pursuant to which:
(x) Tenant is relieved from the obligation to pay, or a third party agrees to
pay on Tenant's behalf, all or any portion of the Basic Rent or Additional Rent
under this Lease; and/or (y) a third party undertakes or is granted by or on
behalf of Tenant the right to assign or attempt to assign this Lease or sublet
or attempt to sublet all or any portion of the Premises, shall for all purposes
hereof be deemed to be an assignment of this Lease and subject to the provisions
of this Article 6. The provisions of this paragraph (a) shall apply to a
transfer (by one or more transfers) of a controlling portion of or interest in
the stock or partnership or membership interests or other evidences of equity
interests of Tenant as if such transfer were an assignment of this Lease;
provided that if equity interests in Tenant at any time are or become traded on
a public stock exchange, the transfer of equity interests in Tenant on a public
stock exchange shall not be deemed an assignment within the meaning of this
Article.

            (b) The provisions of paragraph (a) shall not apply to either (x)
transactions with an entity into or with which Tenant is merged or consolidated,
or to which all or substantially all of Tenant's assets are transferred, or (y)
transactions with any entity which controls or is controlled by Tenant or is
under common control with Tenant; provided that in any such event:

                  (i) the successor to Tenant has a net worth, computed in
      accordance with generally accepted accounting principles consistently
      applied, at least equal to the net worth of Tenant immediately prior to
      such merger, consolidation or transfer,

                  (ii) proof satisfactory to Landlord of such net worth shall
      have been delivered to Landlord at least ten (10) days prior to the
      effective date of any such transaction, and

                  (iii) the assignee agrees directly with Landlord, by written
      instrument in form satisfactory to Landlord in its reasonable discretion,
      to be bound by all the obligations of Tenant hereunder, including, without
      limitation, the covenant against further assignment and subletting.

      6.2 Acceptance of Rent. If this Lease be assigned, or if the Premises or
any part thereof be sublet or occupied by anyone other than Tenant, whether or
not in violation of the terms and conditions of the Lease, Landlord may, at any
time and from time to time, collect rent and other charges from the assignee,
subtenant or occupant, and apply the net amount collected to the rent and other
charges herein reserved, but no such assignment, subletting, occupancy,
collection or modification of any provisions of this Lease shall be deemed a
waiver of this covenant, or the acceptance of the assignee, subtenant or
occupant as a tenant or a release of Tenant from the further performance of
covenants on the part of Tenant to be performed

                                      -9-
<PAGE>

hereunder. Any consent by Landlord to a particular assignment, subletting or
occupancy or other act for which Landlord's consent is required under paragraph
(a) of Section 6.1 shall not in any way diminish the prohibition stated in
paragraph (a) of Section 6.1 as to any further such assignment, subletting or
occupancy or other act or the continuing liability of the original named Tenant.
No assignment or subletting hereunder shall relieve Tenant from its obligations
hereunder, and Tenant shall remain fully and primarily liable therefor. Landlord
may revoke any consent by Landlord to a particular assignment, subletting or
occupancy if the assignment or sublease does not provide that the assignee,
subtenant or other occupant agrees to be independently bound by and upon all of
the covenants, agreements, terms, provisions and conditions set forth in this
Lease on the part of Tenant to be kept and performed.

      6.3 Excess Payments. If Tenant assigns this Lease or sublets the Premises
or any portion thereof, Tenant shall pay to Landlord as Additional Rent 50% of
the amount, if any, by which (a) any and all compensation received by Tenant as
a result of such assignment or subletting, exceeds (b) in the case of an
assignment, the Basic Rent and Additional Rent under this Lease, and in the case
of a subletting, the portion of the Basic Rent and Additional Rent allocable to
the portion of the Premises subject to such subletting. Such payments shall be
made on the date the corresponding payments under this Lease are due.
Notwithstanding the foregoing, the provisions of this Section shall impose no
obligation on Landlord to consent to an assignment of this Lease or a subletting
of all or a portion of the Premises.

      6.4 Landlord's Recapture Right. Notwithstanding anything herein to the
contrary, in addition to withholding or granting consent with respect to any
proposed assignment of this Lease or proposed sublease of all or a portion of
the Premises, Landlord shall have the right (the "Recapture Right") to be
exercised in writing (a "Recapture Notice") within thirty (30) days after
written notice from Tenant seeking Landlord's consent to assign this Lease or
sublease all or any portion of the Premises (a "Consent Request"), to terminate
this Lease (in the event of a proposed assignment) or recapture that portion of
the Premises to be subleased (in the event of a proposed sublease).

      In any case where Landlord shall give Tenant a Recapture Notice, Tenant
shall have the right, exercisable by Tenant by written notice to Landlord (a
"Revocation Notice") within five (5) Business Days after Tenant's receipt of the
Recapture Notice to rescind and revoke Tenant's Consent Request with respect to
the applicable transaction. In the event Tenant shall give Landlord a Revocation
Notice within the time and manner hereinabove set forth, time being of the
essence, Tenant shall be deemed to have rescinded and revoked its Consent
Request and Landlord's exercise of the Recapture Right with respect to the
proposed transaction shall be deemed cancelled and Tenant shall not enter into
nor effect the proposed assignment or subletting.

      In the case of a proposed assignment where Landlord shall give Tenant a
Recapture Notice and Tenant shall not give Landlord a Revocation Notice within
the time and manner provided hereunder, time being of the essence, this Lease
shall terminate as of the date (the "Recapture Date") which is the later of (a)
sixty (60) days after the date of Landlord' s election, and (b) the proposed
effective date of such assignment or sublease, as if such date were the last day
of the Term of this Lease. If Landlord gives Tenant a Recapture Notice
exercising Landlord's rights under this Section in connection with a proposed
sublease and Tenant shall not give Landlord a Revocation Notice within the time
and manner herein provided, time being of the essence, this Lease shall be
deemed amended to eliminate the proposed sublease premises from the Premises as
of the Recapture Date, and thereafter all Basic Rent and Additional Rent and,
provided that no Default of Tenant shall then exist and be continuing, the
amount of the Security Deposit shall each be appropriately prorated to reflect
the reduction of the Premises as of the Recapture Date (or, in the case of a
proposed subletting of the entire Premises, this Lease shall expire on the
Recapture Date as if such date were the last date of the Term of this Lease). In
the event Landlord gives Tenant a Recapture Notice exercising Landlord's
Recapture Right with

                                      -10-
<PAGE>

respect to only a portion of the Premises, Tenant shall be responsible for all
costs and expenses sustained by Landlord in connection with separately demising
the space which is the subject of the Recapture Right from the then remaining
balance of the Premises (including, without limitation, demising walls, means of
access, utility services and HVAC separation).

      6.5 Further Requirements. Tenant shall reimburse Landlord on demand, as
Additional Rent, for any out-of-pocket costs (including reasonable attorneys'
fees and expenses) incurred by Landlord in connection with any actual or
proposed assignment or sublease or other act described in paragraph (a) of
Section 6.1, whether or not consummated, including the costs of making
investigations as to the acceptability of the proposed assignee or subtenant.
Any sublease to which Landlord gives its consent shall not be valid or binding
on Landlord unless and until Tenant and the sublessee execute a consent
agreement in form and substance satisfactory to Landlord in its reasonable
discretion and a fully executed counterpart of such sublease has been delivered
to Landlord. Landlord may condition its consent to any partial subletting upon a
condition that the portion of the space so sublet shall be in compliance with
applicable statutes, building laws, ordinances and codes. In the event that
Landlord consents to any sublease under the provisions of this Article, the
sublease shall provide that: (i) the term of the sublease must end no later than
one day before the last day of the Term of this Lease; (ii) such sublease is
subject and subordinate to this Lease; (iii) Landlord may enforce the provisions
of the sublease, including collection of rents; and (iv) in the event of
termination of this Lease or reentry or repossession of the Premises by
Landlord, Landlord may, at its sole discretion and option, take over all of the
right, title and interest of Tenant, as sublessor, under such sublease, and such
subtenant shall, at Landlord's option, attorn to Landlord, but nevertheless
Landlord shall not (A) be liable for any previous act or omission of Tenant
under such sublease; (B) be subject to any defense or offset previously accrued
in favor of the subtenant against Tenant; or (C) be bound by any previous
modification of such sublease made without Landlord's written consent or by any
previous prepayment of more than one month's rent.

       6.6 Initial Permitted Subletting Subject to the conditions and
limitations hereafter set forth and all other applicable provisions of this
Lease (including, without limitation, Section 6.3 hereof but excluding Section
6.4 hereof), Landlord hereby consents to Tenant subletting approximately 3,000
rentable square feet of the Premises (the "X-Rite Space") to X-Rite Corporation
("X-Rite") provided that (i) Tenant and X-Rite enter into and deliver a Sublease
Agreement for the X-Rite Space in the form attached to this Lease as Exhibit F
and (ii) Tenant, X-Rite and Landlord enter into a Consent to Sublease in
Landlord's usual form as attached as Exhibit G to this Lease. In no event shall
Tenant be relieved from any of its obligations under this Lease as the result of
Landlord's consent to the subletting to X-Rite as contemplated in this Section
6.6

                                    ARTICLE 7
                    RESPONSIBILITY FOR REPAIRS AND CONDITION
                OF PREMISES. SERVICES TO BE FURNISHED BY LANDLORD

      7.1 Landlord Repairs.

            (a) Except as otherwise provided in this Lease, Landlord agrees to
keep in good order, condition and repair the roof, public areas, exterior walls
(including exterior glass) and structure of the Building (including all
plumbing, mechanical and electrical systems installed by Landlord and which
serve all tenants of the Building generally, but specifically excluding any such
systems or components thereof within and which serve the Premises exclusively,
other than components of the Building fire suppression and/or heating,
ventillation and air conditioning system, any existing independent supplemental
heating, ventilation or air conditioning equipment or systems not tied to the
main Building heating ventillation and air conditioning system or any such
systems that are installed by or at Tenant's request or as a result of Tenant's
requirements in excess of building standard design criteria), all insofar as
they affect the Premises, except that

                                      -11-
<PAGE>

Landlord shall in no event be responsible to Tenant for the repair of glass in
the Premises, the doors (or related glass and finish work) leading to the
Premises, or any condition in the Premises or the Building caused by any act or
neglect of Tenant, its employees, agents, invitees or contractors. Landlord
shall also keep and maintain all Common Facilities in a good and clean order,
condition and repair, free of snow and ice and accumulation of dirt and rubbish,
and shall keep and maintain all landscaped areas on the Property in a neat and
orderly condition. Landlord shall not be responsible to make any improvements or
repairs to the Building other than as expressly in this Section 7.1 provided,
unless expressly provided otherwise in this Lease.

      In the event that a court or other governmental authority having
jurisdiction over the Property shall issue a final non-appealable order or
judgment requiring that alterations or modifications be made to the structure of
the Building and/or to any interior or exterior common area of the Building
and/or to any Building system or component of the Building (such as by way of
example, the Building's fire suppression system) which serves all tenants of the
Building generally (as opposed to serving the Premises exclusively) and such
alterations or modifications are required in order to bring such system or
component of the Building into compliance with applicable laws, codes, statutes
or ordinances, Landlord shall cause such alteration or improvement to be made
unless the requirement for the making of such alterations or improvements
results or arises from (i) any alteration or improvement made by or on behalf of
the Tenant or (ii) Tenant's particular use of the Premises for other than
general office purposes or (iii) the acts or omissions of Tenant and/or Tenant's
agents, servants, employees or contractors. All costs and expenses sustained by
Landlord in performing any such alterations, modifications, work or repairs
pursuant to this Section 7.1 shall be included in Operating Expenses.

            (b) Landlord shall never be liable for any failure to make repairs
which Landlord has undertaken to make under the provisions of this Section 7.1
or elsewhere in this Lease, unless Tenant has given notice to Landlord of the
need to make such repairs, and Landlord has failed to commence to make such
repairs within a reasonable time after receipt of such notice, or fails to
proceed with reasonable diligence to complete such repairs.

      7.2 Tenant Repairs.

            (a) Tenant will keep the Premises and every part thereof neat and
clean, and will maintain the same in good order, condition and repair, excepting
only those repairs for which Landlord is responsible under the terms of this
Lease, reasonable wear and tear of the Premises, and damage by fire or other
casualty or as a consequence of the exercise of the power of eminent domain; and
Tenant shall surrender the Premises, at the end of the Term, in such condition.
Except for those matters which are the Landlord's obligations pursuant to
Section 7.1(a) hereof, Tenant shall comply with all laws, codes and ordinances
from time to time in effect and all directions, rules and regulations of
governmental agencies having jurisdiction, and the standards recommended by the
local Board of Fire Underwriters applicable to Tenant's use and occupancy of the
Premises, and shall, at Tenant's expense, obtain all permits, licenses and the
like required thereby. Subject to Section 10.4 regarding waiver of subrogation
and except and to the extent actually covered by insurance proceeds, Tenant
shall be responsible for the cost of repairs which may be made necessary by
reason of damage to the Building caused by any act or neglect of Tenant, or its
contractors or invitees (including any damage by fire or other casualty arising
therefrom).

            (b) If repairs are required to be made by Tenant pursuant to the
terms hereof, and Tenant fails to make the repairs, upon not less than ten (10)
days' prior written notice (except that no notice shall be required in the event
of an emergency), Landlord may make or cause such repairs to be made (but shall
not be required to do so), and the provisions of Section 14.4 shall be
applicable to the costs thereof. Landlord shall not be responsible to Tenant for
any loss or damage whatsoever that may accrue to Tenant's stock or business by
reason of Landlord's making such repairs.

                                      -12-
<PAGE>

      7.3 Floor Load - Heavy Machinery.

            (a) Tenant shall not place a load upon any floor in the Premises
exceeding the floor load per square foot of area which such floor was designed
to carry and which is allowed by law. Landlord reserves the right to prescribe
the weight and position of all business machines and mechanical equipment,
including safes, which shall be placed so as to distribute the weight. Business
machines and mechanical equipment shall be placed and maintained by Tenant at
Tenant's expense in settings sufficient, in Landlord's judgment, to absorb and
prevent vibration, noise and annoyance. Tenant shall not move any safe, heavy
machinery, heavy equipment, freight, bulky matter or fixtures into or out of the
Building without Landlord's prior consent, which consent may include a
requirement to provide insurance, naming Landlord as an insured, in such amounts
as Landlord may deem reasonable.

            (b) If any such safe, machinery, equipment, freight, bulky matter or
fixtures requires special handling, Tenant agrees to employ only persons holding
a Master Rigger's License to do such work, and that all work in connection
therewith shall comply with applicable laws and regulations. Any such moving
shall be at the sole risk and hazard of Tenant, and Tenant will exonerate,
indemnify and save Landlord harmless against and from any liability, loss,
injury, claim or suit resulting directly or indirectly from such moving.

      7.4 Utility Services.

            (a) Landlord shall, on Business Days from 8:00 a.m. to 6:00 p.m. and
Saturdays from 8:00 a.m. to 1:00 p.m., furnish heating and cooling as normal
seasonal changes may require to provide reasonably comfortable space temperature
and ventilation for occupants of the Premises under normal business operation
and an electrical load not exceeding 3.0 watts per square foot of Premises
Rentable Area. If Tenant shall require air conditioning, heating or ventilation
outside the hours and days above specified, Landlord may furnish such service
and Tenant shall pay therefor such charges as may from time to time be in effect
for the Building upon demand as Additional Rent. In the event Tenant introduces
into the Premises personnel or equipment which overloads the capacity of the
Building system or in any other way interferes with the system's ability to
perform adequately its proper functions, supplementary systems may, if and as
needed, at Landlord's option, be provided by Landlord, and the cost of such
supplementary systems shall be payable by Tenant to Landlord upon demand as
Additional Rent.

            (b) Tenant shall be responsible for the payment of all utilities
used and consumed in the Premises. Tenant shall pay for all separately metered
utilities used and consumed in the Premises directly to the provider thereof.
Landlord shall charge Tenant, Tenant's Proportionate Share of the electricity
and natural gas used in connection with the HVAC system for the Building.
Electricity for lights and plugs in the Premises shall be charged back to Tenant
by Landlord based on the Tenant's use and consumption thereof. From time to
time, but not more than once per calendar month, Landlord shall invoice Tenant
for electricity used and consumed in the Premises as measured by the applicable
method described above. Tenant shall pay Landlord such amounts as Additional
Rent hereunder within thirty (30) days after receipt of each such invoice. The
obligation to pay for electricity used and consumed in the Premises during the
last month of the Term hereof shall survive expiration of the Term.

Landlord shall purchase and install, at Tenant's expense, all lamps, tubes,
bulbs, starters and ballasts. In order to assure that the foregoing requirements
are not exceeded and to avert possible adverse effect on the Building's electric
system, Tenant shall not, without Landlord's prior consent, connect any
fixtures, appliances or equipment to the Building' s electric distribution
system other than personal computers, facsimile transceivers, typewriters,
pencil sharpeners, adding machines, photocopiers, word and data processors,
clocks, radios, hand-held or desk top

                                      -13-
<PAGE>

calculators, dictaphones, desktop computers and other similar small electrical
equipment normally found in business offices and not drawing more than 15 amps
at 120/208 volts.

            (c) From time to time during the Term of this Lease, Landlord shall
have the right to have an electrical consultant selected by Landlord make a
survey of Tenant' s electric usage, the result of which survey shall be
conclusively binding upon Landlord and Tenant. In the event that such survey
shows that Tenant has exceeded the requirements set forth in paragraph (b), in
addition to any other rights Landlord may have hereunder, Tenant shall, upon
demand, reimburse Landlord for the cost of such survey and the cost, as
determined by such consultant, of electricity usage in excess of such
requirements as Additional Rent.

      7.5 Other Services.

            Landlord shall also provide:

            (a) Passenger elevator service from the existing passenger elevator
system in common with Landlord and others entitled thereto.

            (b) Warm water for lavatory purposes and cold water (at temperatures
supplied by the city in which the Property is located) for drinking, lavatory
and toilet purposes. If Tenant uses water for any purpose other than for
ordinary lavatory and drinking purposes, Landlord may assess a reasonable charge
for the additional water so used, or install a water meter and thereby measure
Tenant' s water consumption for all purposes. In the latter event, Tenant shall
pay the cost of the meter and the cost of installation thereof as Additional
Rent upon demand and shall keep such meter and installation equipment in good
working order and repair. Tenant agrees to pay for water consumed, as shown on
such meter, together with the sewer charge based on such meter charges, as and
when bills are rendered, and in the event Tenant fails timely to make any such
payment, Landlord may pay such charges and collect the same from Tenant upon
demand as Additional Rent.

            (c) Cleaning and janitorial services to the Premises, provided the
same are kept in order by Tenant, substantially in accordance with the cleaning
standards from time to time in effect for the Building (the "Cleaning
Services"). Landlord shall provide (or shall engage a cleaning company selected
by Landlord to provide) such Cleaning Services and Tenant shall directly pay
Landlord the actual cost to Landlord for providing or causing such Cleaning
Services to be provided to Tenant as Additional Rent under this Lese from time
to time within thirty (30) days after written demand therefor,.

            (d) Access to the Premises at all times, subject to security
precautions from time to time in effect, if any, and subject always to
restrictions based on emergency conditions.

If and to the extent that Tenant desires to provide security for the Premises or
for such persons or their property, Tenant shall be responsible for so doing,
after having first consulted with Landlord and after obtaining Landlord's
consent, which shall not be unreasonably withheld. Landlord expressly disclaims
any and all responsibility and/or liability for the physical safety of Tenant's
property, and for that of Tenant's employees, agents, contractors and invitees,
and, without in any way limiting the operation of Article 10 hereof, Tenant, for
itself and its agents, contractors, invitees and employees, hereby expressly
waives any claim, action, cause of action or other right which may accrue or
arise as a result of any damage or injury to the person or property of Tenant or
any such agent, invitee, contractor or employee. Tenant agrees that, as between
Landlord and Tenant, it is Tenant's responsibility to advise its employees,
agents, contractors and invitees as to necessary and appropriate safety
precautions.

                                      -14-
<PAGE>

      7.6 Interruption of Service.

            (a) Landlord reserves the right to curtail, suspend, interrupt
and/or stop the supply of water, sewage, electrical current, cleaning, and other
services, and to curtail, suspend, interrupt and/or stop use of entrances and/or
lobbies serving access to the Building, or other portions of the Property,
without thereby incurring any liability to Tenant, when necessary by reason of
accident or emergency, or for repairs, alterations, replacements or improvements
in the judgment of Landlord reasonably exercised desirable or necessary, or when
prevented from supplying such services or use due to any act or neglect of
Tenant or Tenant's agents employees, contractors or invitees or any person
claiming by, through or under Tenant or by Force Majeure, including, but not
limited to, strikes, lockouts, difficulty in obtaining materials, accidents,
laws or orders, or inability, by exercise of reasonable diligence, to obtain
electricity, water, gas, steam, coal, oil or other suitable fuel or power.
Except as set forth in paragraph (b) below, no diminution or abatement of rent
or other compensation, nor any direct, indirect or consequential damages shall
or will be claimed by Tenant as a result of, nor shall this Lease or any of the
obligations of Tenant be affected or reduced by reason of, any such
interruption, curtailment, suspension or stoppage in the furnishing of the
foregoing services or use, irrespective of the cause thereof. Except as set
forth in paragraph (b) below, failure or omission on the part of Landlord to
furnish any of the foregoing services or use as provided in this paragraph shall
not be construed as an eviction of Tenant, actual or constructive, nor entitle
Tenant to an abatement of rent, nor to render the Landlord liable in damages,
nor release Tenant from prompt fulfillment of any of its covenants under this
Lease.

            (b) Notwithstanding anything contained in this Lease to the
contrary, if (i) an interruption or curtailment, suspension or stoppage of an
Essential Service (as said term is hereinafter defined) shall occur, except any
of the same due to any act or neglect of Tenant or Tenant's agents employees,
contractors or invitees or any person claiming by, through or under Tenant (any
such interruption of an Essential Service being hereinafter referred to as a
"Service Interruption"), and (ii) such Service Interruption occurs or continues
as a result of the negligence or a wrongful conduct of the Landlord or
Landlord's agents, servants, employees or contractors, and (iii) such Service
Interruption continues for more than fifteen (15) Business Days after Landlord
shall have received notice thereof from Tenant, and (iv) as a result of such
Service Interruption, the conduct of Tenant's normal operations in the Premises
are materially and adversely affected, then there shall be an abatement of one
day's Basic Rent and Additional Rent on account of Operating Expenses and Taxes
for each day during which such Service Interruption continues after such fifteen
(15) Business Day period; provided, however, that if any part of the Premises is
reasonably useable for Tenant's normal business operations or if Tenant conducts
all or any part of its operations in any portion of the Premises notwithstanding
such Service Interruption, then the amount of each daily abatement of Basic Rent
and Additional Rent on account of Operating Expenses and Taxes shall only be
proportionate to the nature and extent of the interruption of Tenant's normal
operations or ability to use the Premises. The rights granted to Tenant under
this paragraph (b) shall be Tenant's sole and exclusive remedy resulting from a
failure of Landlord to provide services, and Landlord shall not otherwise be
liable for any loss or damage suffered or sustained by Tenant resulting from any
failure or cessation of services. For purposes hereof, the term "Essential
Services" shall mean the following services: access to the Premises, water and
sewer/septic service and electricity, but only to the extent that Landlord has
an obligation to provide same to Tenant under this Lease. Any abatement of Basic
Rent and Additional Rent on account of Operating Expenses and Taxes under this
paragraph shall apply only with respect to Basic Rent and Additional Rent on
account of Operating Expenses and Taxes allocable to the period after each of
the conditions set forth in subsections (i) through (iv) hereof shall have been
satisfied and only during such times as each of such conditions shall exist.

                                      -15-
<PAGE>

                                    ARTICLE 8
                                REAL ESTATE TAXES

      8.1 Payments on Account of Real Estate Taxes.

            (a) "Tax Year" shall mean a twelve-month period commencing on July 1
and falling wholly or partially within the Term, and "Taxes" shall mean (i) all
taxes, assessments (special or otherwise), levies, fees and all other government
levies, exactions and charges of every kind and nature, general and special,
ordinary and extraordinary, foreseen and unforeseen, which are, at any time
prior to or during the Term, imposed or levied upon or assessed against the
Property or any portion thereof, or against any Basic Rent, Additional Rent or
other rent of any kind or nature payable to Landlord by anyone on account of the
ownership, leasing or operation of the Property, or which arise on account of or
in respect of the ownership, development, leasing, operation or use of the
Property or any portion thereof; (ii) all gross receipts taxes or similar taxes
imposed or levied upon, assessed against or measured by any Basic Rent,
Additional Rent or other rent of any kind or nature or other sum payable to
Landlord by anyone on account of the ownership, development, leasing, operation,
or use of the Property or any portion thereof; (iii) all value added, use and
similar taxes at any time levied, assessed or payable on account of the
ownership, development, leasing, operation, or use of the Property or any
portion thereof; and (iv) reasonable expenses of any proceeding for abatement of
any of the foregoing items included in Taxes, provided Landlord prevails in such
abatement proceeding; but the amount of special taxes or special assessments
included in Taxes shall be limited to the amount of the installment (plus any
interest, other than penalty interest, payable thereon) of such special tax or
special assessment required to be paid during the year in respect of which such
Taxes are being determined. There shall be excluded from Taxes all income,
estate, succession, inheritance and transfer taxes of Landlord; provided,
however, that if at any time during the Term the present system of ad valorem
taxation of real property shall be changed so that a capital levy, franchise,
income, profits, sales, rental, use and occupancy, or other tax or charge shall
in whole or in part be substituted for, or added to, such ad valorem tax and
levied against, or be payable by, Landlord with respect to the Property or any
portion thereof, such tax or charge shall be included in the term "Taxes" for
the purposes of this Article.

            (b) Tenant shall pay to Landlord, as Additional Rent, an amount
equal to (i) the Taxes for each Tax Year (or portion thereof falling within the
Term), multiplied by (ii) Tenant's Proportionate Share, such amount to be
apportioned for any portion of a Tax Year in which the Commencement Date falls
or the Term expires.

            (c) Estimated payments by Tenant on account of Taxes shall be made
on the first day of each and every calendar month during the Term of this Lease,
in the fashion herein provided for the payment of Basic Rent. The monthly amount
so to be paid to Landlord shall be sufficient to provide Landlord by the time
real estate tax payments are due with a sum equal to Tenant's required payment,
as reasonably estimated by Landlord from time to time, on account of Taxes for
the then current Tax Year. Promptly after receipt by Landlord of bills for such
Taxes, Landlord shall advise Tenant of the amount thereof and the computation
of Tenant's payment on account thereof. If estimated payments theretofore made
by Tenant for the Tax Year covered by such bills exceed the required payment on
account thereof for such Tax Year, Landlord shall credit the amount of
overpayment against subsequent obligations of Tenant on account of Taxes (or
promptly refund such overpayment if the Term of this Lease has ended and Tenant
has no further obligation to Landlord); but if the required payments on account
thereof for such Tax Year are greater than estimated payments theretofore made
on account thereof for such Tax Year, Tenant shall pay the difference to
Landlord as Additional Rent within thirty (30) days after being so advised by
Landlord, and the obligation to make such payment for any period within the Term
shall survive expiration of the Term.

                                      -16-
<PAGE>

      8.2 Abatement. If Landlord shall receive any tax refund or reimbursement
of Taxes or sum in lieu thereof with respect to any Tax Year all or any portion
of which falls within the Term, then out of any balance remaining thereof after
deducting Landlord's reasonable expenses in obtaining such refund, Landlord
shall pay to Tenant, provided there does not then exist a Default of Tenant, an
amount equal to such refund or reimbursement or sum in lieu thereof (exclusive
of any interest, and apportioned if such refund is for a Tax Year a portion of
which falls outside the Term,) multiplied by Tenant's Proportionate Share;
provided, that in no event shall Tenant be entitled to receive more than the
payments made by Tenant on account of Taxes for such Tax Year pursuant to
paragraph (b) of Section 8.1.

                                    ARTICLE 9
                         OPERATING AND UTILITY EXPENSES

       9.1 Definitions. "Operating Year" shall mean each calendar year all or
any part of which falls within the Term, and "Operating Expenses" shall mean the
aggregate costs and expenses incurred by Landlord with respect to the operation,
administration, cleaning, repair, maintenance and management of the Property,
all as set forth in Exhibit D attached hereto, provided that if during any
portion of the Operating Year for which Operating Expenses are being computed,
less than all of the Building was occupied by tenants or Landlord was not
supplying all tenants with the services being supplied under this Lease, actual
Operating Expenses incurred shall be extrapolated reasonably by Landlord on an
item by item basis to the estimated Operating Expenses that would have been
incurred if the Building were fully occupied for such Operating Year and such
services were being supplied to all tenants, and such extrapolated amount shall,
for the purposes hereof, be deemed to be the Operating Expenses for such
Operating Year.

      9.2 Tenant's Payment of Operating Expenses.

            (a) Tenant shall pay to Landlord, as Additional Rent, an amount
equal to (i) Operating Expenses for each Operating Year (or portion thereof
falling within the Term) multiplied by (ii) Tenant's Proportionate Share, such
amount to be apportioned for any portion of an Operating Year in which the
Commencement Date falls or the Term of this Lease ends.

            (b) Estimated payments by Tenant on account of Operating Expenses
shall be made on the first day of each and every calendar month during the Term
of this Lease, in the fashion herein provided for the payment of Basic Rent. The
monthly amount so to be paid to Landlord shall be sufficient to provide Landlord
by the end of each Operating Year a sum equal to Tenant's required payment, as
reasonably estimated by Landlord from time to time during each Operating Year,
on account of Operating Expenses for such Operating Year. After the end of each
Operating Year, Landlord shall submit to Tenant a reasonably detailed accounting
of Operating Expenses for such Operating Year, and Landlord shall certify to the
accuracy thereof. If estimated payments theretofore made for such Operating Year
by Tenant exceed Tenant' s required payment on account thereof for such
Operating Year according to such statement, Landlord shall credit the amount of
overpayment against subsequent obligations of Tenant with respect to Operating
Expenses (or promptly refund such overpayment if the Term of this Lease has
ended and Tenant has no further obligation to Landlord); but if the required
payments on account thereof for such Operating Year are greater than the
estimated payments (if any) theretofore made on account thereof for such
Operating Year, Tenant shall make payment to Landlord as Additional Rent within
thirty (30) days after being so advised by Landlord, and the obligation to make
such payment for any period within the Term shall survive expiration of the
Term.

                                      -17-
<PAGE>

                                   ARTICLE 10
                    INDEMNITY AND PUBLIC LIABILITY INSURANCE

      10.1 Tenant's Indemnity. Except to the extent arising from the negligence
or willful misconduct of Landlord or its agents or employees, Tenant agrees to
indemnify and save harmless Landlord and Landlord's partners, members,
shareholders, officers, directors, managers, employees, agents and contractors
from and against all claims, losses, cost, damages, liability or expenses of
whatever nature arising: (i) from any accident, injury or damage whatsoever to
any person, or to the property of any person, occurring in or about the
Premises; (ii) from any accident, injury or damage whatsoever to any person, or
to property of any person, occurring outside of the Premises but on or about the
Property, where such accident, damage or injury results or is claimed to have
resulted from any act or omission on the part of Tenant or Tenant's agents,
employees, contractors, invitees or sublessees; or (iii) the use or occupancy of
the Premises or of any business conducted therein, and, in any case, occurring
after the Commencement Date until the expiration of the Term of this Lease and
thereafter so long as Tenant is in occupancy of any part of the Premises. This
indemnity and hold harmless agreement shall include indemnity against all
losses, costs, damages, expenses and liabilities incurred in or in connection
with any such claim or any proceeding brought thereon, and the defense thereof,
including, without limitation, reasonable attorneys' fees and costs at both the
trial and appellate levels.

      10.2 Tenant Insurance. Tenant agrees to maintain in full force from the
date upon which Tenant first enters the Premises for any reason, throughout the
Term of this Lease, and thereafter so long as Tenant is in occupancy of any part
of the Premises, a policy of commercial general liability and property damage
insurance (including broad form contractual liability, independent contractor's
hazard and completed operations coverage) under which Tenant is named as an
insured and Landlord, Agent (and such other persons as are in privity of estate
with Landlord as may be set out in a notice from time to time) are named as
additional insureds, and under which the insurer agrees to indemnify and hold
Landlord, Agent and those in privity of estate with Landlord, harmless from and
against all cost, expense and/or liability arising out of or based upon any and
all claims, accidents, injuries and damages set forth in Section 10.1. Tenant
may satisfy such insurance requirements by including the Premises in a so-called
"blanket" and/or "umbrella" insurance policy, provided that the amount of
coverage allocated to the Premises shall fulfill the requirements set forth
herein. Each policy required hereunder shall be non-cancelable and non-amendable
with respect to Landlord, Agent and Landlord's said designees without thirty
(30) days' prior notice, shall be written on an "occurrence" basis, and shall be
in at least the amounts of the Initial General Liability Insurance specified in
Section 1.1 or such greater amounts as Landlord in its reasonable discretion
shall from time to time request, and a duplicate original or certificates
thereof satisfactory to Landlord, together with a photocopy of the entire
policy, shall be delivered to Landlord.

      10.3 Tenant's Risk. Tenant agrees to use and occupy the Premises and to
use such other portions of the Property as Tenant is herein given the right to
use at Tenant's own risk. Landlord shall not be liable to Tenant, its employees,
agents, invitees or contractors for any damage, injury, loss, compensation, or
claim (including, but not limited to, claims for the interruption of or loss to
Tenant's business) based on, arising out of or resulting from any cause
whatsoever, including, but not limited to, repairs to any portion of the
Premises or the Property, any fire, robbery, theft, mysterious disappearance
and/or any other crime or casualty, the actions of any other tenants of the
Building or of any other person or persons, or any leakage in any part or
portion of the Premises or the Building, or from water, rain or snow that may
leak into, or flow from any part of the Premises or the Building, or from
drains, pipes or plumbing fixtures in the Building, unless due to the negligence
or willful misconduct of Landlord or Landlord's agents, contractors or
employees. Any goods, property or personal effects stored or placed in or about
the Premises shall be at the sole risk of Tenant, and neither Landlord nor
Landlord's insurers shall in any manner be held responsible therefor.
Notwithstanding the foregoing,

                                      -18-
<PAGE>

Landlord shall not be released from liability for any injury, loss, damages or
liability to the extent arising from any negligence or willful misconduct of
Landlord, its servants, employees or agents acting within the scope of their
authority on or about the Premises; provided, however, that in no event shall
Landlord, its servants, employees or agents have any liability to Tenant based
on any loss with respect to or interruption in the operation of Tenant's
business. Tenant shall carry "all-risk" property insurance on a "replacement
cost" basis, insuring Tenant's Removable Property and any Alterations made by
Tenant pursuant to Section 5.2, to the extent that the same have not become the
property of Landlord.

      10.4 Waiver of Subrogation. The parties hereto shall each procure an
appropriate clause in, or endorsement on, any property insurance policy on the
Premises or any personal property, fixtures or equipment located thereon or
therein, pursuant to which the insurer waives subrogation or consents to a
waiver of right of recovery in favor of either party, its respective agents or
employees. Having obtained such clauses and/or endorsements, each party hereby
agrees that it will not make any claim against or seek to recover from the other
or its agents or employees for any loss or damage to its property or the
property of others resulting from fire or other perils covered by such property
insurance.

                                   ARTICLE 11
                           FIRE, EMINENT DOMAIN, ETC.

      11.1 Landlord's Right of Termination. If the Premises or the Building are
substantially damaged by fire or casualty (the term "substantially damaged"
meaning damage of such a character that the same cannot, in the ordinary course,
reasonably be expected to be repaired within sixty (60) days from the time that
repair work would commence), or if any part of the Building is taken by any
exercise of the right of eminent domain, then Landlord shall have the right to
terminate this Lease (even if Landlord's entire interest in the Premises may
have been divested) by giving notice of Landlord's election so to do within
ninety (90) days after the occurrence of such casualty or the effective date of
such taking, whereupon this Lease shall terminate thirty (30) days after the
date of such notice with the same force and effect as if such date were the date
originally established as the expiration date hereof.

      11.2 Restoration: Tenant's Right of Termination. If the Premises or the
Building are damaged by fire or other casualty, and this Lease is not terminated
pursuant to Section 12.1, Landlord shall thereafter use reasonable efforts to
restore the Building and the Premises (excluding any Alterations made by Tenant
pursuant to Section 5.2) to proper condition for Tenant's use and occupation,
provided that Landlord's obligation shall be limited to the amount of insurance
proceeds available therefor. If, for any reason, such restoration shall not be
substantially completed within six months after the expiration of the ninety-day
period referred to in Section 11.1 (which six-month period may be extended for
such periods of time as Landlord is prevented from proceeding with or completing
such restoration due to Force Majeure, but in no event for more than an
additional three months), Tenant shall have the right to terminate this Lease by
giving notice to Landlord thereof within thirty (30) days after the expiration
of such period (as so extended) provided that such restoration is not completed
within such period. This Lease shall cease and come to an end without further
liability or obligation on the part of either party thirty (30) days after such
giving of notice by Tenant unless, within such thirty-day period, Landlord
substantially completes such restoration. Such right of termination shall be
Tenant's sole and exclusive remedy at law or in equity for Landlord's failure so
to complete such restoration, and time shall be of the essence with respect
thereto.

      11.3 Landlord's Insurance. Landlord agrees to maintain in full force and
effect, during the Term of this Lease, property damage insurance with such
deductibles and in such amounts as may from time to time be carried by
reasonably prudent owners of similar buildings in the area in which the Property
is located, provided that in no event shall Landlord be required

                                      -19-
<PAGE>

to carry other than fire and extended coverage insurance or insurance in amounts
greater than 80% of the actual insurable cash value of the Building (excluding
footings and foundations). Landlord may satisfy such insurance requirements by
including the Property in a so-called "blanket" insurance policy, provided that
the amount of coverage allocated to the Property shall fulfill the foregoing
requirements.

      11.4 Abatement of Rent. If the Premises or the Building are damaged by
fire or other casualty, Basic Rent and Additional Rent payable by Tenant shall
abate proportionately for the period during which, by reason of such damage,
there is substantial interference with Tenant's use of the Premises, having
regard for the extent to which Tenant may be required to discontinue Tenant' s
use of all or an undamaged portion of the Premises due to such damage, but such
abatement or reduction shall end if and when Landlord shall have substantially
completed sufficient restoration that Tenant is reasonably able to use the
Premises and the Premises are in substantially the condition in which they were
prior to such damage (excluding any Alterations made by Tenant pursuant to
Section 5.2). If the Premises shall be affected by any exercise of the power of
eminent domain, Basic Rent and Additional Rent payable by Tenant shall be justly
and equitably abated and reduced according to the nature and extent of the loss
of use thereof suffered by Tenant. In no event shall Landlord have any liability
for damages to Tenant for inconvenience, annoyance, or interruption of business
arising from any fire or other casualty or eminent domain.

      11.5 Condemnation Award. Landlord shall have and hereby reserves and
excepts, and Tenant hereby grants and assigns to Landlord, all rights to recover
for damages to the Property and the leasehold interest hereby created, and to
compensation accrued or hereafter to accrue by reason of any taking, by exercise
of the right of eminent domain, and by way of confirming the foregoing, Tenant
hereby grants and assigns, and covenants with Landlord to grant and assign to
Landlord, all rights to such damages or compensation, and covenants to deliver
such further assignments and assurances thereof as Landlord may from time to
time request, and Tenant hereby irrevocably appoints Landlord its
attorney-in-fact to execute and deliver in Tenant's name all such assignments
and assurances. Nothing contained herein shall be construed to prevent Tenant
from prosecuting in any condemnation proceedings a claim for the value of any of
Tenant's Removable Property installed in the Premises by Tenant at Tenant's
expense and for relocation expenses, provided that such action shall not affect
the amount of compensation otherwise recoverable by Landlord from the taking
authority.

                                   ARTICLE 12
                             HOLDING OVER: SURRENDER

      12.1 Holding Over. Any holding over by Tenant after the expiration of the
Term of this Lease shall be treated as a daily tenancy at sufferance at a equal
to two (2) times the Basic Rent then in effect plus the Additional Rent herein
provided (prorated on a daily basis). Tenant shall also pay to Landlord all
damages, direct and/or indirect, sustained by reason of any such holding over.
In all other respects, such holding over shall be on the terms and conditions
set forth in this Lease as far as applicable.

      12.2 Surrender of Premises. Upon the expiration or earlier termination of
the Term of this Lease, Tenant shall peaceably quit and surrender to Landlord
the Premises in neat and clean condition and in good order, condition and
repair, together with all alterations, additions and improvements which may have
been made or installed in, on or to the Premises prior to or during the Term of
this Lease (except as hereinafter provided), excepting only ordinary wear and
use and damage by fire or other casualty for which, under other provisions of
this Lease, Tenant has no responsibility to repair or restore. Tenant shall
remove all of Tenant's Removable Property and, to the extent specified by
Landlord, all alterations and additions made by Tenant and all partitions wholly
within the Premises unless installed initially by Landlord in preparing the

                                      -20-
<PAGE>

Premises for Tenant's occupancy; and shall repair any damages to the Premises or
the Building caused by such removal. Any Tenant's Removable Property which shall
remain in the Building or on the Premises after the expiration or termination of
the Term of this Lease shall be deemed conclusively to have been abandoned, and
either may be retained by Landlord as its property or may be disposed of in such
manner as Landlord may see fit, at Tenant's sole cost and expense.

                                   ARTICLE 13
                     RIGHTS OF MORTGAGEES: TRANSFER OF TITLE

      13.1 Rights of Mortgagees. This Lease shall be subject and subordinate to
the lien and terms of any mortgage, deed of trust or ground lease or similar
encumbrance (collectively, a "Mortgage", and the holder thereof from time to
time the "Holder") from time to time encumbering the Premises, whether executed
and delivered prior to or subsequent to the date of this Lease, unless the
Holder shall elect otherwise. If this Lease is subordinate to any Mortgage and
the Holder or any other party shall succeed to the interest of Landlord pursuant
to the Mortgage (such Holder or other party, a "Successor"), at the election of
the Holder or Successor, Tenant shall attorn to the or Successor and this Lease
shall continue in full force and effect between the Holder or Successor and
Tenant. Tenant agrees to execute such instruments of subordination or attornment
in confirmation of the foregoing agreement as the Holder or Successor reasonably
may request.

      Notwithstanding the foregoing to the contrary, upon the written request of
Tenant, Landlord shall request that any present or future Holder enter into an
agreement with Tenant in such Holder's usual and customary form of
subordination, non-disturbance and attornment agreement and in form and
substance reasonably satisfactory to such Holder to the effect that such Holder
shall recognize this Lease and Tenant's occupancy of the Premises and agrees to
not disturb Tenant's possession of the Premises in the event of a foreclosure of
such Holder's mortgage. Upon Tenant's written request, Landlord shall use good
faith efforts to obtain such an agreement from each Holder now or hereafter
holding a mortgage on the Property but failure of any such Holder to execute and
deliver such an agreement with Tenant shall not affect the validity of this
Lease nor entitle the Tenant to any claim, rights or causes of action against
Landlord of any kind, type or nature.

      13.2 Assignment of Rents and Transfer of Title.

            (a) With reference to any assignment by Landlord of Landlord's
interest in this Lease, or the rents payable hereunder, conditional in nature or
otherwise, which assignment is made to the holder of a mortgage on property
which includes the Premises, Tenant agrees that the execution thereof by
Landlord, and the acceptance thereof by the holder of such mortgage shall never
be treated as an assumption by such holder of any of the obligations of Landlord
hereunder unless such holder shall, by notice sent to Tenant, specifically
otherwise elect and, except as aforesaid, such holder shall be treated as having
assumed Landlord's obligations hereunder only upon foreclosure of such holder's
mortgage and the taking of possession of the Premises.

(b In no event shall the acquisition of Landlord's interest in the Property by a
purchaser which, simultaneously therewith, leases Landlord's entire interest in
the Property back to the seller thereof be treated as an assumption by operation
of law or otherwise, of Landlord's obligations hereunder, but Tenant shall look
solely to such seller-lessee, and its successors from time to time in title, for
performance of Landlord's obligations hereunder. In any such event, this Lease
shall be subject and subordinate to the lease to such purchaser. For all
purposes, such seller-lessee, and its successors in title, shall be the Landlord
hereunder unless and until Landlord's position shall have been assumed by such
purchaser-lessor.

                                      -21-
<PAGE>

(c Except as provided in paragraph (b)of this Section, in the event of any
transfer of title to the Property by Landlord, Landlord shall thereafter be
entirely freed and relieved from the performance and observance of all covenants
and obligations hereunder.

      13.3 Notice to Mortgagee. After receiving written notice from Landlord of
any Holder of a Mortgage which includes the Premises, no notice from Tenant to
Landlord alleging any default by Landlord shall be effective unless and until a
copy of the same is given to such Holder (provided Tenant shall have been
furnished with the name and address of such Holder by written notice from
Landlord), and the curing of any of Landlord's defaults by such Holder shall be
treated as performance by Landlord.

                                   ARTICLE 14
                                DEFAULT: REMEDIES

      14.1 Tenant's Default.

            (a) If at any time subsequent to the date of this Lease any one or
more of the following events (herein referred to as a "Default of Tenant") shall
happen:

                  (i) Tenant shall fail to pay the Basic Rent or Additional Rent
      hereunder when due and such failure shall continue for three (3) Business
      Days after written notice to Tenant from Landlord; or

                  (ii) Tenant shall neglect or fail to perform or observe any
      other covenant herein contained on Tenant's part to be performed or
      observed and Tenant shall fail to remedy the same within thirty (30) days
      after written notice to Tenant specifying such neglect or failure, or if
      such failure is of such a nature that Tenant cannot reasonably remedy the
      same within such thirty (30) day period, Tenant shall fail to commence
      promptly (and in any event within such thirty (30) day period) to remedy
      the same and to prosecute such remedy to completion with diligence and
      continuity (and in any event, within ninety (90) days after the notice
      described in this subparagraph (ii)); or

                  (iii) Tenant's leasehold interest in the Premises shall be
      taken on execution or by other process of law directed against Tenant; or

                  (iv) Tenant shall make an assignment for the benefit of
      creditors or shall be adjudicated insolvent, or shall file any petition or
      answer seeking any reorganization, arrangement, composition, readjustment,
      liquidation, dissolution or similar relief for itself under any present or
      future Federal, State or other statute, law or regulation for the relief
      of debtors (other than the Bankruptcy Code, as hereinafter defined), or
      shall seek or consent to or acquiesce in the appointment of any trustee,
      receiver or liquidator of Tenant or of all or any substantial part of its
      properties, or shall admit in writing its inability to pay its debts
      generally as they become due; or

                  (v) An Event of Bankruptcy (as hereinafter defined) shall
      occur with respect to Tenant; or

                  (vi) A petition shall be filed against Tenant under any law
      (other than the Bankruptcy Code) seeking any reorganization, arrangement,
      composition, readjustment, liquidation, dissolution, or similar relief
      under any present or future Federal, State or other statute, law or
      regulation and shall remain undismissed or unstayed for an aggregate of
      sixty (60) days (whether or not consecutive), or if any trustee,
      conservator, receiver or liquidator of Tenant or of all or any substantial
      part of its properties shall be appointed without the consent or
      acquiescence of Tenant and such

                                      -22-
<PAGE>

      appointment shall remain unvacated or unstayed for an aggregate of sixty
      (60) days (whether or not consecutive);

                  (vii) If: (x) Tenant shall fail to pay the Basic Rent or
      Additional Rent hereunder when due or shall fail to perform or observe any
      other covenant herein contained on Tenant's part to be performed or
      observed and Tenant shall cure any such failure within the applicable
      grace period set forth in clauses (i) or (ii) above; or (y) a Default of
      Tenant of the kind set forth in clauses (i) or (ii) above shall occur and
      Landlord shall, in its sole discretion, permit Tenant to cure such Default
      of Tenant after the applicable grace period has expired; and the same or a
      similar failure shall occur more than twice within the next 365 days
      (whether or not such similar failure is cured within the applicable grace
      period); or

                  (viii) The occurrence of any of the events described in
      paragraphs (a)(iv)-(a)(vi) with respect to any guarantor of all or any
      portions of Tenant's obligations under this Lease;

then in any such case Landlord may terminate this Lease as hereinafter provided.

            (b) For purposes of clause (a)(v) above, an "Event of Bankruptcy"
means the filing of a voluntary petition by Tenant, or the entry of an order
for relief against Tenant, under Chapter 7, 11, or 13 of the Bankruptcy Code,
and the term "Bankruptcy Code" means 11 U.S.C. Section 101, et seq.. If an
Event of Bankruptcy occurs, then the trustee of Tenant's bankruptcy estate or
Tenant as debtor-in-possession may (subject to final approval of the court)
assume this Lease, and may subsequently assign it, only if it does the
following within sixty (60) days after the date of the filing of the
voluntary petition, the entry of the order for relief (or such additional
time as a court of competent jurisdiction may grant, for cause, upon a motion
made within the original sixty-day period):

                  (i) file a motion to assume the Lease with the appropriate
court;

                  (ii) satisfy all of the following conditions, which Landlord
and Tenant acknowledge to be commercially reasonable:

            (A)   cure all Defaults of Tenant under this Lease or provide
                  Landlord with Adequate Assurance (as defined below) that it
                  will (x) cure all monetary Defaults of Tenant hereunder within
                  ten (10) days from the date of the assumption; and (y) cure
                  all nonmonetary Defaults of Tenant hereunder within thirty
                  (30) days from the date of the assumption;

            (B)   compensate Landlord and any other person or entity, or provide
                  Landlord with Adequate Assurance that within ten (10) days
                  after the date of the assumption, it will compensate Landlord
                  and such other person or entity, for any pecuniary loss that
                  Landlord and such other person or entity incurred as a result
                  of any Default of Tenant, the trustee, or the
                  debtor-in-possession;

            (C)   provide Landlord with Adequate Assurance of Future Performance
                  (as defined below) of all of Tenant's obligations under this
                  Lease; and

            (D)   deliver to Landlord a written statement that the conditions
                  herein have been satisfied.

                                      -23-
<PAGE>

            (c) For purposes only of the foregoing paragraph (b), and in
addition to any other requirements under the Bankruptcy Code, any future federal
bankruptcy law and applicable case law, "Adequate Assurance" means at least
meeting the following conditions, which Landlord and Tenant acknowledge to be
commercially reasonable:

                  (i) entering an order segregating sufficient cash to pay
      Landlord and any other person or entity under paragraph (b) above, and

                  (ii) granting to Landlord a valid first lien and security
      interest (in form acceptable to Landlord) in all property comprising the
      Tenant's "property of the estate," as that term is defined in Section 541
      of the Bankruptcy Code, which lien and security interest secures the
      trustee's or debtor-in-possession's obligation to cure the monetary and
      nonmonetary defaults under the Lease within the periods set forth in
      paragraph (b) above.

            (d) For purposes only of paragraph (b) above, and in addition to any
other requirements under the Bankruptcy Code, any future federal bankruptcy law
and applicable case law, "Adequate Assurance of Future Performance" means at
least meeting the following conditions, which Landlord and Tenant acknowledge to
be commercially reasonable:

                  (i) the trustee or debtor-in-possession depositing with
      Landlord, as security for the timely payment of rent and other monetary
      obligations, an amount equal to the sum of two (2) months' Basic Rent plus
      an amount equal to two (2) months' installments on account of Operating
      Expenses and Taxes;

                  (ii) the trustee or the debtor-in-possession agreeing to pay
      in advance, on each day that the Basic Rent is payable, the monthly
      installments on account of Operating Expenses and Taxes;

                  (iii) the trustee or debtor-in-possession providing adequate
      assurance of the source of the rent and other consideration due under this
      Lease;

                  (iv) Tenant's bankruptcy estate and the trustee or
      debtor-in-possession providing Adequate Assurance that the bankruptcy
      estate (and any successor after the conclusion of the Tenant's bankruptcy
      proceedings) will continue to have sufficient unencumbered assets after
      the payment of all secured obligations and administrative expenses to
      assure Landlord that the bankruptcy estate (and any successor after the
      conclusion of the Tenant's bankruptcy proceedings) will have sufficient
      funds to fulfill Tenant's obligations hereunder.

            (e) If the trustee or the debtor-in-possession assumes the Lease
under paragraph (b) above and applicable bankruptcy law, it may assign its
interest in this Lease only if the proposed assignee first provides Landlord
with Adequate Assurance of Future Performance of all of Tenant's obligations
under the Lease, and if Landlord determines, in the exercise of its reasonable
business judgment, that the assignment of this Lease will not breach any other
lease, or any mortgage, financing agreement, or other agreement relating to the
Property by which Landlord or the Property is then bound (and Landlord shall not
be required to obtain consents or waivers from any third party required under
any lease, mortgage, financing agreement, or other such agreement by which
Landlord is then bound).

            (f) For purposes only of paragraph (e) above, and in addition to any
other requirements under the Bankruptcy Code, any future federal bankruptcy law
and applicable case law, "Adequate Assurance of Future Performance" means at
least the satisfaction of the following conditions, which Landlord and Tenant
acknowledge to be commercially reasonable:

                                      -24-
<PAGE>

                  (i) the proposed assignee submitting a current financial
      statement, audited by a certified public accountant, that allows a net
      worth and working capital in amounts determined in the reasonable business
      judgment of Landlord to be sufficient to assure the future performance by
      the assignee of Tenant's obligation under this Lease; and

                  (ii) if requested by Landlord in the exercise of its
      reasonable business judgment, the proposed assignee obtaining a guarantee
      (in form and substance satisfactory to Landlord) from one or more persons
      who satisfy Landlord's standards of creditworthiness.

      14.2 Landlord's Remedies.

            (a) Upon the occurrence of a Default of Tenant, Landlord may
terminate this Lease by notice to Tenant, specifying a date not less than five
(5) days after the giving of such notice on which this Lease shall terminate and
this Lease shall come to an end on the date specified therein as fully and
completely as if such date were the date herein originally fixed for the
expiration of the Term of this Lease, and Tenant will then quit and surrender
the Premises to Landlord, but Tenant shall remain liable as hereinafter
provided..

            (b) If this Lease shall have been terminated as provided in this
Article, then Landlord may re-enter the Premises, either by summary proceedings,
ejectment or otherwise, and remove and dispossess Tenant and all other persons
and any and all property from the same, as if this Lease had not been made.

            (c) If this Lease shall have been terminated as provided in this
Article, Tenant shall pay the Basic Rent and Additional Rent up to the time of
such termination, and thereafter Tenant, until the end of what would have been
the Term of this Lease in the absence of such termination, and whether or not
the Premises shall have been relet, shall be liable to Landlord for, and shall
pay to Landlord, as liquidated current damages: (x) the Basic Rent and
Additional Rent payable hereunder as if such termination had not occurred, less
the net proceeds, if any, of any reletting of the Premises, after deducting all
actual and reasonable expenses in connection with such reletting, including,
without limitation, all repossession costs, brokerage commissions, legal
expenses, attorneys' fees, advertising, expenses of employees, alteration costs
and expenses of preparation for such reletting; and (y) if this Lease provides
that Tenant was entitled to occupy the Premises for any period of time without
paying Basic Rent, the amount of Basic Rent that Tenant would have paid for any
such period. Tenant shall pay the portion of such current damages referred to in
clause (x) above to Landlord monthly on the days which the Basic Rent would have
been payable hereunder if this Lease had not been terminated, and Tenant shall
pay the portion of such current damages referred to in clause (y) above to
Landlord upon such termination.

            (d) At any time after termination of this Lease as provided in this
Article, whether or not Landlord shall have collected any such current damages,
as liquidated final damages and in lieu of all such current damages beyond the
date of such demand, at Landlord' s election Tenant shall pay to Landlord an
amount (discounted to present value using a discount factor reasonably
determined by Landlord in its sole but reasonable judgment) equal to the excess,
if any, of the Basic Rent and Additional Rent which would be payable hereunder
from the date of such demand assuming that, for the purposes of this paragraph,
annual payments by Tenant on account of Taxes and Operating Expenses would be
the same as the payments required for the immediately preceding Operating or Tax
Year for what would be the then unexpired Term of this Lease if the same
remained in effect, over the then fair net rental value of the Premises for the
same period.

                                      -25-
<PAGE>

            (e) In case of any Default of Tenant, re-entry, expiration and
dispossession by summary proceedings or otherwise, Landlord may (i) re-let the
Premises or any part or parts thereof, either in the name of Landlord or
otherwise, for a term or terms which may at Landlord's option be equal to or
less than or exceed the period which would otherwise have constituted the
balance of the Term of this Lease and may grant concessions or free rent to the
extent that Landlord considers advisable and necessary to re-let the same and
(ii) make such alterations, repairs and decorations in the Premises as Landlord
considers advisable and necessary for the purpose of reletting the Premises; and
the making of such alterations, repairs and decorations shall not operate or be
construed to release Tenant from liability hereunder as aforesaid. Tenant hereby
expressly waives any and all rights of redemption granted by or under any
present or future laws in the event of Tenant being evicted or dispossessed, or
in the event of Landlord obtaining possession of the Premises, by reason of the
violation by Tenant of any of the covenants and conditions of this Lease.

      14.3 Additional Rent. If Tenant shall fail to pay when due any sums under
this Lease designated as Additional Rent, Landlord shall have the same rights
and remedies as Landlord has hereunder for failure to pay Basic Rent.

      14.4 Remedying Defaults. Landlord shall have the right, but shall not be
required, to pay such sums or do any act which requires the expenditure of
monies which may be necessary or appropriate by reason of the failure or neglect
of Tenant to perform any of the provisions of this Lease, and in the event of
the exercise of such right by Landlord, Tenant agrees to pay to Landlord
forthwith upon demand all such sums, together with interest thereon at a rate
equal to 3% over the base rate in effect from time to time at The First National
Bank of Boston or its successor(but in no event less than 18% per annum), as
Additional Rent. Any payment of Basic Rent and Additional Rent payable hereunder
not paid when due shall, at the option of Landlord, bear interest at a rate
equal to 3% over the base rate in effect from time to time at The First National
Bank of Boston or its successor (but in no event less than 18% per annum) from
the due date thereof and shall be payable forthwith on demand by Landlord, as
Additional Rent.

      14.5 Remedies Cumulative. The specified remedies to which Landlord may
resort hereunder are not intended to be exclusive of any remedies or means of
redress to which Landlord may at any time be entitled lawfully, and Landlord may
invoke any remedy (including the remedy of specific performance) allowed at law
or in equity as if specific remedies were not herein provided for.

      14.6 Attorneys' Fees. Reasonable attorneys' fees and expenses incurred by
or on behalf of Landlord in enforcing its rights hereunder or occasioned by any
Default of Tenant shall be paid by Tenant.

      14.7 Waiver.

            (a) Failure on the part of Landlord or Tenant to complain of any
action or non-action on the part of the other, no matter how long the same may
continue, shall never be a waiver by Tenant or Landlord, respectively, of any of
the other's rights hereunder. Further, no waiver at any time of any of the
provisions hereof by Landlord or Tenant shall be construed as a waiver of any of
the other provisions hereof, and a waiver at any time of any of the provisions
hereof shall not be construed as a waiver at any subsequent time of the same
provisions. The consent or approval of Landlord or Tenant to or of any action by
the other requiring such consent or approval shall not be construed to waive or
render unnecessary Landlord's or Tenant' s consent or approval to or of any
subsequent similar act by the other.

            (b) No payment by Tenant, or acceptance by Landlord, of a lesser
amount than shall be due from Tenant to Landlord shall be treated otherwise than
as a payment on account of the earliest installment of any payment due from
Tenant under the provisions hereof.

                                      -26-
<PAGE>

The acceptance by Landlord of a check for a lesser amount with an endorsement or
statement thereon, or upon any letter accompanying such check, that such lesser
amount is payment in full, shall be given no effect, and Landlord may accept
such check without prejudice to any other rights or remedies which Landlord may
have against Tenant.

      14.8 Security Deposit. If a security deposit is specified in Section 1.1
hereof, Tenant agrees that the same will be paid upon execution and delivery of
this Lease, and that Landlord shall hold the same throughout the Term of this
Lease as security for the performance by Tenant of all obligations on the part
of Tenant hereunder. Landlord shall have the right from time to time, without
prejudice to any other remedy Landlord may have on account thereof, to apply
such deposit, or any part thereof, to Landlord' s damages arising from, or to
cure, any Default of Tenant. If Landlord shall so apply any or all of such
deposit, Tenant shall immediately upon demand deposit with Landlord the amount
so applied to be held as security hereunder. Landlord shall return the deposit,
or so much thereof as shall not have theretofore been applied in accordance with
the terms of this Section, to Tenant on the expiration or earlier termination of
the Term of this Lease and surrender of possession of the Premises by Tenant to
Landlord at such time, provided that there is then existing no Default of Tenant
(nor any circumstance which, with the passage of time or the giving of notice,
or both, would constitute a Default of Tenant). While Landlord holds such
deposit, Landlord shall have no obligation to pay interest on the same and shall
have the right to commingle the same with Landlord's other funds. If Landlord
conveys Landlord's interest under this Lease, the deposit, or any part thereof
not previously applied, may be turned over by Landlord to Landlord' s grantee,
and, if so turned over, Tenant agrees to look solely to such grantee for proper
application of the deposit in accordance with the terms of this Section, and the
return thereof in accordance herewith. The holder of a mortgage shall not be
responsible to Tenant for the return or application of any such deposit, whether
or not it succeeds to the position of Landlord hereunder, unless such deposit
shall have been received in hand by such holder.

      14.9 Landlord's Default. Landlord shall in no event be in default under
this Lease unless Landlord shall neglect or fail to perform any of its
obligations hereunder and shall fail to remedy the same within thirty (30) days
after notice to Landlord specifying such neglect or failure, or if such failure
is of such a nature that Landlord cannot reasonably remedy the same within such
thirty (30) day period, Landlord shall fail to commence promptly (and in any
event within such thirty (30) day period) to remedy the same and to prosecute
such remedy to completion with diligence and continuity.

                                   ARTICLE 15
                            MISCELLANEOUS PROVISIONS

      15.1 Rights of Access. Landlord and Agent shall have the right upon
reasonable advance notice to Tenant (except in the case of emergency when no
advance notice shall be required) to enter the Premises at all reasonable hours
for the purpose of inspecting the Premises, doing maintenance or making repairs
or otherwise exercising its rights or fulfilling its obligations under this
Lease, and Landlord and Agent also shall have the right to make access available
at all reasonable hours to prospective or existing mortgagees, purchasers or
tenants of any part of the Property. In exercising is rights pursuant to this
Section 15.1, Landlord shall use good faith efforts to avoid unreasonable
interference with Tenant's use of the Premises.

      15.2 Covenant of Quiet Enjoyment. Subject to the terms and conditions of
this Lease, on payment of the Basic Rent and Additional Rent and observing,
keeping and performing all of the other terms and conditions of this Lease on
Tenant' s part to be observed, kept and performed, Tenant shall lawfully,
peaceably and quietly enjoy the Premises during the term hereof, without
hindrance or ejection by any persons lawfully claiming under Landlord to have
title to the Premises superior to Tenant. The foregoing covenant of quiet
enjoyment is in lieu of any other covenant, express or implied.

                                      -27-
<PAGE>

      15.3 Landlord's Liability.

            (a) Tenant agrees to look solely to Landlord's equity interest in
the Property at the time of recovery for recovery of any judgment against
Landlord, and agrees that neither Landlord nor any successor of Landlord shall
be personally liable for any such judgment, or for the payment of any monetary
obligation to Tenant. The provision contained in the foregoing sentence is not
intended to, and shall not, limit any right that Tenant might otherwise have to
obtain injunctive relief against Landlord or any successor of Landlord, or to
take any action not involving the personal liability of Landlord or any
successor of Landlord to respond in monetary damages from Landlord's assets
other than Landlord's equity interest in the Property.

            (b) In no event shall Landlord ever be liable to Tenant for any loss
of business or any other indirect or consequential damages suffered by Tenant
from whatever cause.

            (c) Where provision is made in this Lease for Landlord's consent,
and Tenant shall request such consent, and Landlord shall fail or refuse to give
such consent, Tenant shall not be entitled to any damages for any withholding by
Landlord of its consent, it being intended that Tenant's sole remedy shall be an
action for specific performance or injunction, and that such remedy shall be
available only in those cases where Landlord has expressly agreed in writing not
to unreasonably withhold its consent. Furthermore, whenever Tenant requests
Landlord's consent or approval (whether or not provided for herein), Tenant
shall pay to Landlord, on demand, as Additional Rent, any reasonable expenses
incurred by Landlord (including without limitation reasonable attorneys' fees
and costs, if any) in connection therewith.

            (d) Any repairs or restoration required or permitted to be made by
Landlord under this Lease may be made during normal business hours, and Landlord
shall have no liability for damages to Tenant for inconvenience, annoyance or
interruption of business arising therefrom; provided, however, that Landlord
will use good faith efforts to avoid unreasonable interference with Tenant's use
of the Premises.

      15.4 Estoppel Certificate. Tenant shall, at any time and from time to
time, upon not less than ten (10) business days prior written notice by
Landlord, execute, acknowledge and deliver to Landlord an estoppel certificate
containing such statements of fact as Landlord reasonably requests.

      15.5 Relocation. Intentionally Deleted.

      15.6 Brokerage. Tenant warrants and represents that Tenant has dealt with
no broker in connection with the consummation of this Lease other than Broker,
and, in the event of any brokerage claims against Landlord predicated upon prior
dealings with Tenant, Tenant agrees to defend the same and indemnify Landlord
against any such claim (except any claim by Broker which shall be paid by
Landlord pursuant to its direct agreements with Broker).

      15.7 Rules and Regulations. Tenant shall abide by the Rules and
Regulations from time to time established by Landlord, it being agreed that such
Rules and Regulations will be established and applied by Landlord in a
non-discriminatory fashion, such that all Rules and Regulations shall be
generally applicable to other tenants of the Building of similar nature to the
Tenant named herein. Landlord agrees to use reasonable efforts to insure that
any such Rules and Regulations are uniformly enforced, but Landlord shall not be
liable to Tenant for violation of the same by any other tenant or occupant of
the Building, or persons having business with them. In the event that there
shall be a conflict between such Rules and Regulations and the provisions of
this Lease, the provisions of this Lease shall control. The Rules and
Regulations currently in effect are set forth in Exhibit E.

                                      -28-
<PAGE>

      15.8 Invalidity of Particular Provisions. If any term or provision of this
Lease, or the application thereof to any person or circumstance shall, to any
extent, be invalid or unenforceable, the remainder of this Lease, or the
application of such term or provision to persons or circumstances other than
those as to which it is held invalid or unenforceable, shall not be affected
thereby, and each term and provision of this Lease shall be valid and be
enforced to the fullest extent permitted by law.

      15.9 Provisions Binding. Etc. Except as herein otherwise provided, the
terms hereof shall be binding upon and shall inure to the benefit of the
successors and assigns, respectively, of Landlord and Tenant (except in the case
of Tenant, only such successors and assigns as may be permitted hereunder) and,
if Tenant shall be an individual, upon and to his heirs, executors,
administrators, successors and permitted assigns. Each term and each provision
of this Lease to be performed by Tenant shall be construed to be both a covenant
and a condition. Any reference in this Lease to successors and assigns of Tenant
shall not be construed to constitute a consent to assignment by Tenant.

      15.10 Recording, Tenant agrees not to record this Lease, but, if the Term
of this Lease (including any extended term) is seven (7) years or longer, each
party hereto agrees, on the request of the other, to execute a notice of lease
in recordable form and complying with applicable law. In no event shall such
document set forth the rent or other charges payable by Tenant under this Lease;
and any such document shall expressly state that it is executed pursuant to the
provisions contained in this Lease, and is not intended to vary the terms and
conditions of this Lease. At Landlord' s request, promptly upon expiration of or
earlier termination of the Term, Tenant shall execute and deliver to Landlord a
release of any document recorded in the real property records for the location
of the Property evidencing this Lease, and Tenant hereby appoints Landlord
Tenant's attorney-in-fact, coupled with an interest, to execute any such
document if Tenant fails to respond to Landlord's request to do so within
fifteen (15) days. The obligations of Tenant under this Section shall survive
the expiration or any earlier termination of the Term.

      15.11 Notice. All notices or other communications required hereunder shall
be in writing and shall be deemed duly given if delivered in person (with
receipt therefor), if sent by reputable overnight delivery or courier service
(e.g., Federal Express) providing for receipted delivery, or if sent by
certified or registered mail, return receipt requested, postage prepaid, to the
following address:

      (a) if to Landlord, at Landlord s Address, to the attention of Karl W.
Weller

      (b) if to Tenant, at Tenant's Address.

      Receipt of notice or other communication shall be conclusively established
by either (i) return of a return receipt indicating that the notice has been
delivered; or (ii) return of the letter containing the notice with an indication
from the courier or postal service that the addressee has refused to accept
delivery of the notice. Either party may change its address for the giving of
notices by notice given in accordance with this Section.

      15.12 When Lease Becomes Binding: Entire Agreement: Modification. The
submission of this document for examination and negotiation does not constitute
an offer to lease, or a reservation of, or option for, the Premises, and this
document shall become effective and binding only upon the execution and delivery
hereof by both Landlord and Tenant. This Lease is the entire agreement between
Landlord and Tenant, and this Lease expressly supersedes any negotiations,
considerations, representations and understandings and proposals or other
written documents relating hereto. This Lease may be modified or altered only by
written agreement between Landlord and Tenant, and no act or omission of any
employee or agent of Landlord shall alter, change or modify any of the
provisions hereof.

                                      -29-
<PAGE>

      15.13 Paragraph Headings and Interpretation of Sections. The paragraph
headings throughout this instrument are for convenience and reference only, and
the words contained therein shall in no way be held to explain, modify, amplify
or aid in the interpretation, construction or meaning of the provisions of this
Lease. The provisions of this Lease shall be construed as a whole, according to
their common meaning (except where a precise legal interpretation is clearly
evidenced), and not for or against either party. Use in this Lease of the words
"including," "such as" or words of similar import, when followed by any general
term, statement or matter, shall not be construed to limit such term, statement
or matter to the specified item(s), whether or not language of non-limitation,
such as "without limitation" or "including, but not limited to," or words of
similar import, are used with reference thereto, but rather shall be deemed to
refer to all other terms or matters that could fall within a reasonably broad
scope of such term, statement or matter.

      15.14 Dispute Resolution. In the event of a dispute between Landlord and
Tenant pursuant to this Lease (other than a dispute relating to the payment of
Basic Rent and Additional Rent the parties agree that prior to pursuing other
available remedies (excluding giving notices of default), they will attempt to
directly negotiate resolution of their dispute. If negotiation is unsuccessful,
then they agree to participate in at least three hours of mediation to be
facilitated by a mediator mutually acceptable to them under the mediation
procedures set by the mediator. The mediation session shall be conducted within
thirty (30) days of the date on which the mediator receives the request to
mediate. The costs of such mediation shall be shared equally by the parties.

      15.15 Financial Statements. Tenant shall, without charge therefor, at any
time, within ten (1 0) days following a request by Landlord, deliver to
Landlord, or to any other party designated by Landlord, a true and accurate copy
of Tenant's most recent financial statements. All requests made by Tenant
regarding subleases or assignments must be accompanied by the most recent
financial statement of Tenant's prospective subtenant or prospective assignee.
The provisions of this Section 15.15 shall not apply during such periods as
Tenant's stock is publicly traded on a nationally recognized public stock
exchange and such information is otherwise readily available through
governmental filings which are available to Landlord.

      15.16 Waiver of Jury Trial. Landlord and Tenant hereby each waive trial by
jury in any action, proceeding or counterclaim brought by either against the
other, on or in respect of any matter whatsoever arising out of or in any way
connected with this Lease, the relationship of Landlord and Tenant or Tenant' s
use or occupancy of the Premises.

      15.17 Time Is of the Essence. Time is of the essence of each provision of
this Lease.

      15.18 Multiple Counterparts. This Lease may be executed in multiple
counterparts, each of which shall be deemed an original and all of which
together shall constitute one and the same document.

      15.19 Governing Law. This Lease shall be governed by the laws of the state
in which the Property is located.

                                      -30-
<PAGE>

      IN WITNESS WHEREOF, Landlord and Tenant have caused this Lease to be duly
executed, under seal, by persons hereunto duly authorized, as of the date first
set forth above.

                      LANDLORD:

                      BCIA NEW ENGLAND HOLDINGS LLC, a Delaware limited
                      liability company

                            By:   BCIA NEW ENGLAND HOLDINGS MASTER
                                  LLC, a Delaware limited liability company, its
                                  Manager

                                  By:   BCIA NEW ENGLAND HOLDINGS
                                        MANAGER LLC, a Delaware limited
                                        liability company, its Manager

                                        By:   BCIA NEW ENGLAND
                                              HOLDINGS MANAGER CORP., a
                                              Delaware corporation, its Manager

                            By:   /s/ Karl W. Weller
                                  -------------------------------
                                  Name:       KARL W. WELLER
                                  Title: EXECUTIVE VICE PRESIDENT

                      TENANT:

                      SONUS NETWORKS, INC

                            By:     /s/ S.J. Nill
                                    -----------------------------
                            Name:   S.J. Nill
                                    -----------------------------
                            Title:  VP & CFO
                                    -----------------------------

BCIA15

                                      -31-
<PAGE>

                                    EXHIBIT A
                           Location Plan of Premises

                                      -32-
<PAGE>

                                    EXHIBIT A
                                 SONUS PREMISES

                                [GRAPHIC OMITTED]
<PAGE>

                                    EXHIBIT B
                              Site Plan of Building

                                      -33-
<PAGE>

                                    EXHIBIT C
                            Commencement Date Letter

[Name of Contact
[Name of Tenant]
[Address of Tenant]

      RE:   [Name of Tenant]
            [Premises Rentable Area and Floor]

Dear [Name of Contact]:

      Reference is made to that certain Lease, dated as of ______________, 2000,
between [Landlord], as Landlord and [Tenant] as Tenant, with respect to Premises
on the _______floor of the above-referenced building. In accordance with Section
4.1 of the Lease, this is to confirm that the Commencement Date of the Term of
the Lease occurred on ____________, and that the Term of the Lease shall expire
on _______________

      If the foregoing is in accordance with your understanding, kindly execute
the enclosed duplicate of this letter, and return the same to us.

                                   Very truly yours,

                                   [Landlord]

                                   By:    __________________________________
                                          Name: ____________________________
                                          Title ____________________________

Accepted and Agreed:

[Tenant]

By:
      Name:  ________________________
      Title: ________________________
      Date:  ________________________

                                      -34-
<PAGE>

                                    EXHIBIT D
                               Operating Expenses

Operating Expenses shall include the following, without limitation:

      All expenses incurred by Landlord or Landlord's agents which shall be
            directly related to employment of personnel, including amounts
            incurred for wages, salaries and other compensation for services,
            payroll, social security, unemployment and similar taxes, workmen's
            compensation insurance, disability benefits, pensions,
            hospitalization, retirement plans and group insurance, uniforms and
            working clothes and the cleaning thereof, and expenses imposed on
            Landlord or Landlord's agents pursuant to any collective bargaining
            agreement for the services of employees of Landlord or Landlord's
            agents in connection with the operation, repair, maintenance,
            cleaning, management and protection of the Property, including,
            without limitation, day and night supervisors, manager, accountants,
            bookkeepers, janitors, carpenters, engineers, mechanics,
            electricians and plumbers and personnel engaged in supervision of
            any of the persons mentioned above; provided that, if any such
            employee is also employed on other property of Landlord, such
            compensation shall be suitably prorated among the Property and such
            other properties.

      The cost of services, utilities, materials and supplies furnished or used
            in the operation, repair, maintenance, cleaning, management and
            protection of the Property.

      The cost of replacements for tools and other similar equipment used in the
            repair, maintenance, cleaning and protection of the Property,
            provided that, in the case of any such equipment used jointly on
            other property of Landlord, such costs shall be suitably prorated
            among the Property and such other properties.

      Where the Property is managed by Landlord or an affiliate of Landlord, a
            sum equal to the amounts customarily charged by management firms in
            the Greater Boston area for similar properties, whether or not
            actually paid, or where managed by other than Landlord or an
            affiliate thereof, the amounts accrued for management, together
            with, in either case, amounts accrued for legal and other
            professional fees relating to the Property, but excluding such fees
            and commissions paid in connection with services rendered for
            securing or renewing or enforcing leases and for matters not related
            to the normal administration and operation of the Property.

      Premiums for insurance against damage or loss to the Property from such
            hazards as Landlord shall determine, including, but not by way of
            limitation, insurance covering loss of rent attributable to any such
            hazards, and public liability insurance.

      If, during the Term of this Lease, Landlord shall make a capital
            expenditure, the total cost of which is not properly includable in
            Operating Expenses for the Operating Year in which it was made,
            there shall nevertheless be included in such Operating Expenses for
            the Operating Year in which it was made and in Operating Expenses
            for each succeeding Operating Year the annual charge-off of such
            capital expenditure. Annual charge-off shall be determined by
            dividing the original capital expenditure plus an interest factor,
            reasonably determined by Landlord, as being the interest rate then
            being charged for long-term mortgages by institutional lenders on
            like properties within the locality in which the Property is
            located, by the number of years of useful life of the capital
            expenditure; and the useful life

                                      -35-
<PAGE>

            shall be determined reasonably by Landlord in accordance with
            generally accepted accounting principles and practices in effect at
            the time of making such expenditure.

      Costs for electricity, water and sewer use charges, gas and other
            utilities supplied to the Property and not paid for directly by
            tenants.

      Betterment assessments, provided the same are apportioned equally over the
            longest period permitted by law, and to the extent, if any, not
            included in Taxes.

      Amounts paid to independent contractors for services, materials and
            supplies furnished for the operation, repair, maintenance, cleaning
            and protection of the Property.

Operating Expenses shall not include:

      1.    Taxes;

      2.    Cost of leasing space to other tenants or occupants including
            brokers commissions, attorneys fees, advertising expenses,
            improvements costs or other rental concessions;

      3.    Depreciation on the Building;

      4.    Ground lease rentals or debt service on any Mortgage;

      5.    Interest or amortization of debt except as otherwise expressly
            provided above in connection with capital expenditures or capital
            repairs;

      6.    Fines and penalties resulting from the acts or omissions of Landlord
            or other tenants or occupants of the Building;

      7.    Expenses for which and to the extent Landlord is actually reimbursed
            by net insurance proceeds; and

      8.    Expenses paid directly by or separately billed to individual
            tenants.

                                      -36-
<PAGE>

                                    EXHIBIT E

                        Rules and Regulation of Building

The following regulations are generally applicable:

If the Building is occupied by more than one tenant, the public sidewalks,
      entrances, passages, courts, elevators, vestibules, stairways, corridors
      or halls shall not be obstructed or encumbered by Tenant (except as
      necessary for deliveries) or used for any purpose other than ingress and
      egress to and from the Premises.

If the Building is occupied by more than one tenant, no awnings, curtains,
      blinds, shades, screens or other projections shall be attached to or hung
      in, or used in connection with, any window of the Premises or any outside
      wall of the Building. Such awnings, curtains. blinds, shades, screens or
      other projections must be of a quality, type, design and color, and
      attached in the manner, approved by Landlord, which approval shall not be
      unreasonably withheld or delayed but may be conditioned upon a requirement
      that Tenant remove same (and repair any damage) upon expiration or earlier
      termination of the term of this Lease.

No show cases or other articles shall be put in front of or affixed to any part
      of the exterior of the Building, nor, if the Building is occupied by more
      than one tenant, displayed through interior windows into the atrium of the
      Building, nor placed in the halls, corridors or vestibules, provided that
      show cases or articles may be displayed through interior windows into the
      atrium of the Building (if any) with Landlord's prior written approval,
      such approval not to be unreasonably withheld or delayed so long as such
      display does not adverse affect the aesthetic integrity of the Building.

The water and wash closets and other plumbing fixtures shall not be used for any
      purposes other than those for which they were designed and constructed,
      and no sweepings, rubbish, rags, acids or like substances shall be
      deposited therein. All damages resulting from any misuse of the fixtures
      shall be borne by the Tenant.

Tenant shall not use the Premises or any part thereof or permit the Premises or
      any part thereof to be used as a public employment bureau or for the sale
      of property of any kind at auction, except in connection with Tenant's
      business.

Tenant must, upon the termination of its tenancy, return to the Landlord all
      locks, cylinders and keys to offices and toilet rooms of the Premises.

Landlord reserves the right to exclude from the Building after business hours
      and at all hours on days other than Business Days all persons connected
      with or calling upon the Tenant who are not escorted in the Building by an
      employee of Tenant. Tenant shall be responsible for all persons to whom it
      allows access and shall be liable to the Landlord for all wrongful acts of
      such persons.

The requirements of Tenant will be attended to only upon application at the
      Building Management Office. Employees of Landlord shall not perform any
      work or do anything outside of their regular duties, unless under special
      instructions from the office of the Landlord.

There shall not be used in any space in the Building, or in the public halls of
      the Building, either by Tenant or by jobbers or others, in the delivery or
      receipt of merchandise, any hand trucks, except those equipped with rubber
      tires and side guards.

                                      -37-
<PAGE>

No vehicles or animals of any kind shall be brought into or kept in or about the
      Premises. No bicycles may be brought into any portion of the Building or
      property other than the Premises

If the Building is occupied by more than one tenant, no tenant shall make, or
      permit to be made, any unseemly or disturbing noises or disturb or
      interfere with occupants of this or any neighboring building or premises
      or those having business with them whether by use of any musical
      instrument, radio, talking machine, unmusical noise, whistling, singing,
      or in any other way. No tenant shall throw anything out of the doors,
      windows or skylights or down the passageways.

The Premises shall not be used for lodging or sleeping or for any immoral or
      illegal purpose.

No smoking shall be permitted in the Premises or the Building. Smoking shall
      only be permitted in smoking areas outside of the Building which have been
      designated by the Landlord.

Landlord shall have the right, exercisable without notice and without liability
      to any tenant, to change the name and street address of the Building.

The rules and regulations set forth in Attachment I to this Exhibit, which is by
      this reference made a part hereof ,are applicable to any Alterations being
      undertaken by or for Tenant in the Premises pursuant to Section 5.2 of the
      Lease:

                                      -38-
<PAGE>

                            Attachment I to Exhibit E

                  Rules and Regulations for Tenant Alterations

      1. General

      1. All Alterations made by Tenant in, to or about the Premises shall be
made in accordance with the requirements of this Exhibit and by contractors or
mechanics approved by Landlord, which approval of contractors or mechanics shall
not be unreasonably withheld or delayed.

      2. Tenant shall, prior to the commencement of any work, submit for
Landlord's written approval, complete plans for the Alterations, with full
details and specifications for all of the Alterations, in compliance with
Section D below.

      3. Alterations must comply with the Building Code applicable to the
Property and the requirements, rules and regulations and any other governmental
agencies having jurisdiction.

      4. No work shall be permitted to commence before Tenant obtains and
furnishes to Landlord copies of all necessary licenses and permits from all
governmental authorities having jurisdiction.

      5. All demolition, removals or other categories of work that may
inconvenience other tenants or disturb Building operations, must be scheduled
and performed before or after normal business hours, and Tenant shall provide
Agent with at least 24 hours' notice prior to proceeding with such work.

      6. All inquiries, submissions, approvals and all other matters shall be
processed through Agent.

      7. All work, if performed by a contractor or subcontractor, shall be
subject to reasonable supervision and inspection by Landlord's representative.
Such supervision and inspection shall be at Tenant's sole expense and Tenant
shall pay Landlord's reasonable charges for such supervision and inspection.

      2. Prior to Commencement of Work

      1. Tenant shall submit to the Building manager a request to perform the
work. The request shall include the following enclosures:

            (1)   A list of Tenant's contractors and/or subcontractors for
                  Landlord's approval.

            (2)   Four complete sets of plans and specifications properly
                  stamped by a registered architect or professional engineer.

            (3)   A properly executed building permit application form.

            (4)   Four executed copies of the Insurance Requirements Agreement
                  in the form attached to this Exhibit as Attachment II and made
                  a part hereof from Tenant's contractor and, if requested by
                  Landlord, from the contractor's subcontractors.

                                      -39-
<PAGE>

            (5)   Contractor's and subcontractor's insurance certificates,
                  including an indemnity in accordance with the Insurance
                  Requirements Agreement.

      2. Landlord will return the following to Tenant:

            (1)   Two sets of plans approved or a disapproved with specific
                  comments as to the reasons therefor (such approval or comments
                  shall not constitute a waiver of approval of governmental
                  authorities).

            (2)   Two fully executed copies of the Insurance Requirements
                  Agreement.

      3. Landlord's approval of the plans, drawings, specifications or other
submissions in respect of any Alterations shall create no liability or
responsibility on the part of Landlord for their completeness, design
sufficiency or compliance with requirements of any applicable laws, rules or
regulations of any governmental or quasi-governmental agency, board or
authority.

      4. Tenant shall obtain a building permit from the Building Department and
necessary permits from other governmental agencies. Tenant shall be responsible
for keeping current all permits. Tenant shall submit copies of all approved
plans and permits to Landlord and shall post the original permit on the Premises
prior to the commencement of any work.

      3. Requirements and Procedures

      1. All structural and floor loading requirements shall be subject to the
prior approval of Landlord's structural engineer.

      2. All mechanical (HVAC, plumbing and sprinkler), electrical and voice and
data telecommunication system installation and requirements shall be subject to
the approval of Landlord's mechanical and electrical engineers and all
mechanical and electrical work and voice and data telecommunications system
installation and requirements shall be performed by contractors who are first
approved by Landlord, which approval shall not be unreasonably withheld or
delayed. When necessary, Landlord will require engineering and shop drawings,
which drawings must be approved by Landlord before work is started. Drawings are
to be prepared by Tenant and all approvals shall be obtained by Tenant.

      3. Elevator service for construction work shall be charged to Tenant at
standard Building rates. Prior arrangements for elevator use shall be made with
Building manager by Tenant. No material or equipment shall be carried under or
on top of elevators. If an operating engineer is required by any union
regulations, such engineer shall be paid for by Tenant.

      4. If shutdown of risers and mains for electrical, HVAC, sprinkler and
plumbing work is required, such work shall be supervised by Landlord's
representative. No work will be performed in Building mechanical equipment rooms
without Landlord's approval and under Landlord's supervision.

      5. Tenant's contractor shall:

            (1)   have a superintendent or foreman on the Premises at all times;

            (2)   police the job at all times, continually keeping the Premises
                  orderly;

            (3    maintain cleanliness and protection of all areas, including
                  elevators and lobbies.

                                      -40-
<PAGE>

            (4)   protect the front and top of all peripheral HVAC units and
                  thoroughly clean them at the completion of work;

            (5)   block off supply and return grills, diffusers and ducts to
                  keep dust from entering into the Building air conditioning
                  system; and

            (6)   avoid the disturbance of other tenants.

      6. If Tenant's contractor is negligent in any of its responsibilities,
Tenant shall be charged for corrective work.

      7. All equipment and installations must be equal to the standards
generally in effect with respect to the remainder of the Building. Any deviation
from such standards will be permitted only if indicated or specified on the
plans and specifications and approved by Landlord.

      8. A properly executed air balancing report signed by a professional
engineer shall be submitted to Landlord upon the completion of all HVAC work.

      9. Upon completion of the Alterations, Tenant shall submit to Landlord a
permanent certificate of occupancy and final approval by the other governmental
agencies having jurisdiction.

      10. Tenant shall submit to Landlord a final "as-built" set of drawings
showing all items of the Alterations in full detail.

      11. Additional and differing provisions in the Lease, if any, will be
applicable and will take precedence.

D. Standards for Plans and Specifications.

      Whenever Tenant shall be required by the terms of the Lease (including
this Exhibit) to submit plans to Landlord in connection with any Alterations,
such plans shall include at least the following:

      12. Floor plan indicating location of partitions and doors (details
required of partition and door types).

      13. Location of standard electrical convenience outlets and telephone
outlets.

      14. Location and details of special electrical outlets; e.g.,
photocopiers, etc.

      15. Reflected ceiling plan showing layout of standard ceiling and lighting
fixtures. Partitions to be shown lightly with switches located indicating
fixtures to be controlled.

      16. Locations and details of special ceiling conditions, lighting
fixtures, speakers, etc.

      17. Location and specifications of floor covering, paint or paneling with
paint colors referenced to standard color system.

      18. Finish schedule plan indicating wall covering, paint, or paneling with
paint colors referenced to standard color system.

      19. Details and specifications of special millwork, glass partitions,
rolling doors and grilles, blackboards, shelves, etc.

                                      -41-
<PAGE>

      20. Hardware schedule indicating door number keyed to plan, size, hardware
required including butts, latchsets or locksets, closures, stops, and any
special items such as thresholds, soundproofing, etc. Keying schedule is
required.

      21. Verified dimensions of all built-in equipment (file cabinets, lockers,
plan files,

      22. Location and weights of storage files.

      23. Location of any special soundproofing requirements.

      24. Location and details of special floor areas exceeding 50 pounds of
live load per square foot.

      25. All structural, mechanical, plumbing and electrical drawings necessary
to complete the Premises in accordance with Tenant's Plans.

      26. All drawings to be uniform size (30" x 46") and shall incorporate the
standard project electrical and plumbing symbols and be at a scale of 1/8" = 1'
or larger.

      27. All drawings shall be stamped by an architect (or, where applicable,
an engineer) licensed in the jurisdiction in which the Property is located and
without limiting the foregoing, shall be sufficient in all respects for
submission to applicable authorization in connection with a building permit
application.

                                      -42-
<PAGE>

                           Attachment II to Exhibit E

                       Contractor's Insurance Requirements

Building:

Landlord:

Tenant:

Premises:

The undersigned contractor or subcontractor ("Contractor") has been hired by the
tenant named above (hereinafter called "Tenant") of the Building named above (or
by Tenant's contractor) to perform certain work ("Work") for Tenant in the
Premises identified above. Contractor and Tenant have requested the landlord
named above ("Landlord") to grant Contractor access to the Building and its
facilities in connection with the performance of the Work, and Landlord agrees
to grant such access to Contractor upon and subject to the following terms and
conditions:

      28. Contractor agrees to indemnify and save harmless Landlord and its
respective officers, employees and agents and their affiliates, subsidiaries and
partners, and each of them, from and with respect to any claims, demands, suits,
liabilities, losses and expenses, including reasonable attorneys' fees, arising
out of or in connection with the Work (and/or imposed by law upon any or all of
them) because of personal injuries, bodily injury (including death at any time
resulting therefrom) and loss of or damage to property, including consequential
damages, whether such injuries to person or property are claimed to be due to
negligence of the Contractor or Tenant except to the extent specifically
prohibited by law (and any such prohibition shall not void this Agreement but
shall be applied only to the minimum extent required by law).

      29. Contractor shall provide and maintain at its own expense, until
completion of the Work, the following insurance:

            (1) Workmen's Compensation and Employers, Liability Insurance
covering each and every workman employed in, about or upon the Work, as provided
for in each and every statute applicable to Workmen's Compensation and
Employers' Liability Insurance.

            (2) Comprehensive General Liability Insurance including coverages
for Protective and Contractual Liability (to specifically include coverage for
the indemnification clause of this Agreement) for not less than the following
limits:

                        Personal Injury:

                        $1,000,000 per person $3,000,000 per occurrence

                        Property Damage:
                        $1,000,000 per occurrence $3,000,000 aggregate

                                      -43-
<PAGE>

            (3) Comprehensive Automobile Liability Insurance (covering all
owned, non-owned and/or hired motor vehicles to be used in connection with the
Work) for not less than the following limits:

                        Bodily Injury:
                        $1,000,000 per person
                        $1,000,000 per occurrence

                        Property Damage:
                        $1,000,000 per occurrence

      Contractor shall furnish a certificate from its insurance carrier or
carriers to the Building office before commencing the Work, showing that it has
complied with the above requirements regarding insurance and providing that the
insurer will give Landlord ten (10) days' prior written notice of the
cancellation of any of the foregoing policies.

      30. Contractor shall require all of its subcontractors engaged in the Work
to provide the following insurance:

            (1) Comprehensive General Liability Insurance including Protective
and Contractual Liability coverages with limits of liability at least equal to
the limits stated in paragraph 2(b).

            (2) Comprehensive Automobile Liability Insurance (covering all
owned, non-owned and/or hired motor vehicles to be used in connection with the
Work) with limits of liability at least equal to the limits stated in paragraph
2(c).

      Upon the request of Landlord, Contractor shall require all of its
subcontractors engaged in the Work to execute an Insurance Requirements
agreement in the same form as this Agreement.

      Agreed to and executed this day of __________ , 2000

                                       Contractor:

                                       By: _________________________________

                                       By: _________________________________

                                       By: _________________________________

                                      -44-
<PAGE>

EXHIBIT F                                                                 X-RITE

                              AGREEMENT OF SUBLEASE

      THIS AGREEMENT OF SUBLEASE is made as of the 30th day of September, 2000,
by and between Sonus Networks, Inc. ("Landlord"), having an office at 5 Carlisle
Road, Westford, MA 01886 and X-Rite Incorporated ("Tenant"), a Michigan
corporation, having an office at 25 Porter Road, Littleton, MA 01460.

                                     WITNESS

      WHEREAS, by Lease dated as of September 30, 2000 (hereinafter the "Prime
Lease") by and between BCIA New England Holdings, LLC ("Prime Landlord") and
Landlord, Prime Landlord has leased to Landlord certain premises (the "Prime
Premises") which is located within the building known by the street address of
25 Porter Road, Littleton, MA 01460 (the "Building"), which Prime Premises are
more particularly described in the Prime Lease and include 33,194 rentable
square feet on the second floor (2nd) floor of the Building as indicated by
crosshatching on the floor plan attached to the Prime Lease as Exhibit A (a copy
of such Prime Lease is attached hereto as Exhibit A and made a part hereof);

      WHEREAS, Landlord desires to sublease to Tenant and Tenant desires to
sublease from Landlord that portion of the Prime Premises comprised of
approximately 3,000 rentable square feet and marked on Exhibit B to this
Sublease as the "Premises" (the "Premises"), and Landlord is willing to sublease
the Premises on the terms and conditions hereinafter set forth.

      NOW, THEREFORE, in consideration of the mutual covenants herein contained
and for other good and valuable consideration, the parties agree as follows:

      1. Subleasing of Premises. Subject to the written consent of the Prime
Landlord, Landlord hereby subleases to Tenant and Tenant hereby subleases from
Landlord the Premises, upon and subject to all of the terms, covenants, recitals
and conditions hereinafter set forth.

      2. Term The term (the "Term") of this Sublease shall commence on October
1, 2000 (the "Commencement Date"), with said Term to expire at midnight on
December 31, 2002, (the "Expiration Date"), unless sooner terminated as
hereinafter provided.

      3. Base Rent. During the Term, Tenant shall pay to Landlord, in lawful
money of the United States which at the time shall be legal tender in payment of
all debts and dues, public and private, an annual fixed rent (the "Base Rent")
in the amount of $28,500.00 per annum ($9.50 per rentable square foot per annum)
payable in equal monthly installments of $2,375.00. All such monthly
installments shall be paid in advance, on the first (1st) day of each month
during the Term, at the address of Landlord set forth above, or such other place
as Landlord may designate, without any setoff or deduction of any kind
whatsoever.

      4. Additional Rent.

            (a) Beginning on the Commencement Date, Tenant shall pay, as
Additional Rent, without notice or demand, Tenant's Proportionate Share (as
hereafter defined) of Taxes and Operating Expenses (as such terms are defined in
the Prime Lease) in accordance with Article 8 and Article 9 of the Prime Lease.
As used in this Sublease, the term "Tenant's Proportionate Share" shall mean
4.49%. Base Rent and Additional Rent and any other sums due hereunder by Tenant
not paid by the due date shall bear interest and be subject to late payment
and/or administrative fees, all in accordance with the provisions of Article 3
and Section 14.4 of the Prime Lease. All payments shall be made to Landlord at
its address set forth above, or at such
<PAGE>

other address or addresses as Landlord may from time to time designate by
written notice to Tenant.

            Tenant shall also pay, as Additional Rent, the cost of all utilities
furnished to Tenant on the Premises, including, but not limited to, electricity,
gas, oil, water and sewer. Tenant agrees to pay any and all such charges for the
Premises to Landlord in the event any such utilities are not separately metered
to Tenant or directly to the utility company if such utilities are separately
metered. Electricity usage within the Premises may, at Landlord's option, be
measured by the use of a check-meter, and Tenant shall pay to Landlord monthly
the amount invoiced by Landlord for electricity used in the Premises as
indicated by such check-meter, at the rate then being charged by the local
electrical utility company or by Prime Landlord. If any of such utilities are
not separately metered, Tenant shall pay its proportionate share of such
utilities for the Prime Premises based upon its relative square footage to that
of Landlord.

            (b) Tenant's obligation to pay Additional Rent hereunder shall be on
account of the period from and after the Commencement Date and shall survive the
Expiration Date or sooner termination of the Term.

            (c) All amounts payable by Tenant to Landlord pursuant to this
Sublease, including, without limitation, Base Rent and Additional Rent, shall be
deemed and constitute rent and, in the event of any non-payment thereof,
Landlord shall have all of the rights and remedies provided herein, in the Prime
Lease or in law or at equity for non-payment of rent.

            (d) Tenant agrees to pay to Landlord Tenant's Proportionate Share of
any real estate taxes attributable to leasehold improvements within the Premises
which are payable by Landlord under the Prime Lease.

      5. Care, Surrender and Restoration of the Premises.

            (a) Without limiting any other provision of this Sublease or the
Prime Lease, Tenant shall take good care of the Premises, suffer no waste or
injury thereto and shall comply with all those laws, orders and regulations
applicable to the Premises, the Building and Tenant's use or manner of use
thereof, which are imposed on Landlord, as tenant under the Prime Lease, in
connection with the Premises and the Building, including without limitation the
Rules and Regulations which are attached to the Prime Lease as Exhibit E.

            (b) At the expiration or other termination of the Term, Tenant shall
surrender the Premises and all alterations and additions thereto (including any
fixtures, panelling, railings and like installation installed at the Premises at
any time by Tenant, by Prime Landlord or by Landlord) in good order, repair and
condition, ordinary wear and tear and damage by casualty only excepted, first
removing all goods and effects of Tenant and, to the extent specified by
Landlord by notice to Tenant, all alterations and additions made by or on behalf
of Tenant. Tenant shall repair any damage caused by such removal and restore the
Premises and leave them clean and neat in compliance with the requirements of
Section 5 of this Sublease and Section 12.2 of the Prime Lease. All property
permitted or required to be removed by Tenant upon the Expiration Date or sooner
termination of the Term remaining in the Premises shall be deemed abandoned and
may, at the election of Landlord, either be retained as Landlord's property or
may be removed from the Premises by Landlord, at Tenant's expense. Any such
reasonable expenses shall be paid by Tenant to Landlord upon demand therefor and
shall be deemed Additional Rent, collectible by Landlord in the same manner and
with the same remedies as though said sums were Base Rent reserved hereunder.

            (c) Upon the Expiration Date or sooner termination of the Term,
Tenant shall quit and surrender the Premises to Landlord, broom clean, in good
order and condition, ordinary wear and tear and damage by fire and other
casualty excepted, and Tenant shall remove all of its

                                      -2-
<PAGE>

property. If the Expiration Date or sooner termination of the Term of this
Sublease falls on a Sunday, this Sublease shall expire at noon on the preceding
Saturday unless it be a legal holiday, in which case it shall expire at noon on
the preceding business day. Tenant shall observe and perform the covenants
herein stated and Tenant's obligations hereunder shall survive the Expiration
Date or sooner termination of the Term.

      6. Use. Tenant shall use and occupy the Premises for the purposes
permitted under Section 5.1 of the Prime Lease including light assembly and for
no other purpose.

      7. Subordination to and Incorporation of Terms of Prime Lease.

            (a) This Sublease is in all respects subject and subordinate to the
terms and conditions of the Prime Lease and to the matters to which the Prime
Lease is or shall be subordinate. Except as otherwise expressly provided in this
Sublease, the terms, provisions, covenants, stipulations, conditions, rights,
obligations, remedies and agreements of the Prime Lease are incorporated in this
Sublease by reference and made a part hereof as if herein set forth at length,
and shall, as between Landlord and Tenant (as if they were the Landlord and
Tenant, respectively, under the Prime Lease and as if the Premises being sublet
hereby were the Prime Premises demised under the Prime Lease), constitute the
terms of this Sublease, except to the extent that they do not relate to the
Premises or are inapplicable to, inconsistent with, or modified or eliminated
by, the terms of this Sublease.

In particular, it is intended that Tenant shall not be subject to duplicate
monetary obligations to Landlord and Prime Landlord. Except as otherwise
expressly provided in this Sublease, to the extent that Tenant is required by
this Sublease to make monetary payments to Landlord (such as for rent,
additional rent or upon default) Tenant shall not be obligated to the Prime
Landlord for any such monetary obligations nor to Landlord for its monetary
obligations to the Prime Landlord. Landlord and Tenant acknowledge and agree
that Tenant has reviewed and is familiar with the Prime Lease and Landlord
hereby represents that the copy delivered to Tenant for such purpose and
attached hereto as Exhibit A is a true, correct and complete copy of such Prime
Lease.

            (b) In the event of Prime Lease Termination (as hereinafter defined)
prior to December 31, 2002 and provided that the Sublease has not theretofore
been terminated, Prime Landlord shall recognize Tenant as Prime Landlord's
direct Tenant pursuant to the terms and provisions of the Sublease for the then
remainder of the Term of the Sublease (through December 31, 2002) and Tenant
hereby agrees to attorn to Prime Landlord and perform Tenant's obligations under
this Sublease with respect to the Subleased Premises (and only as to the
Subleased Premises) to and for the benefit of Prime Landlord as if Prime
Landlord were the "Landlord" under this Sublease as a direct Lease between Prime
Landlord and Tenant. Such arrangement between Prime Landlord and Tenant shall
entitle the Tenant to occupy the Subleased Premises under the terms and
provisions of this Sublease after Prime Lease Termination for the then remainder
of the Term of the Sublease (through December 31, 2002) but shall not relieve
Landlord from any liability to Prime Landlord under the Prime Lease. Tenant
hereby agrees to execute and deliver at any time and from time to time, upon
request of Prime Landlord, any instruments which may be necessary or appropriate
to evidence such assumption and Tenant hereby irrevocably appoints Prime
Landlord as its attorney in fact, coupled with an interest to execute on behalf
of Tenant any documents or instruments necessary to evidence such assumption.
Prime Landlord shall not (i) be liable to Tenant for any act, omission or breach
of the Sublease by Landlord, (ii) be subject to any offsets or defenses which
Tenant might have against Landlord, (iii) be bound by any rent or additional
rent which Tenant might have paid in advance to Landlord, (iv) be bound to honor
any rights of Tenant in any security deposit or advance rent made with or paid
to Landlord by Tenant except to the extent Landlord has specifically assigned
and turned over such security deposits and advance rent to Prime Landlord and
Prime Landlord shall actually have the same in its possession and control.

                                      -3-
<PAGE>

      Landlord and Tenant hereby agree that in the event of Prime Lease
Termination, Landlord shall immediately pay or transfer to Prime Landlord any
security deposits, rent or other sums then held by Landlord in connection with
the subleasing of the Subleased Premises and, notwithstanding anything contained
herein to the contrary, this shall satisfy Landlord's obligations to Tenant
under this Sublease with respect to any such sums paid over or transferred to
Prime Landlord. Such security deposit may be applied by Prime Landlord pursuant
to the terms of the Sublease in the event of any holding over or other default
by the Tenant after Prime Lease Termination. Tenant hereby agrees that under no
circumstances whatsoever shall Prime Landlord be held in any way responsible or
accountable for any security deposit or any sums paid by Tenant to Landlord
unless and until and to the extent that Prime Landlord has actually received
such sums from Landlord and has acknowledged their source, and Tenant shall have
no claim to any security or other deposit made by Landlord under the Prime
Lease.

      "Prime Lease Termination" means the termination or cancellation of the
Prime Lease prior to December 31, 2002 due to: (1) a default beyond expiration
of applicable notice and/or cure periods by Landlord under the Prime Lease or
any of the terms and provisions hereof; (2) foreclosure proceedings brought by
the holder of any mortgage or trust deed to which the Prime Lease is subject;
and (3) the termination of Landlord's leasehold estate by dispossession
proceedings. Provided, however, that notwithstanding the foregoing to the
contrary, termination of the Prime Lease in accordance with its terms prior to
December 31, 2002 as the result of a fire, casualty, the exercise of the power
of eminent domain or actions taken in lieu thereof or pursuant thereto or any
other reason or cause not enumerated in (1), (2), o (3) above shall not be
deemed a "Prime Lease Termination" for purposes of this paragraph 7.

       In addition, in the event Landlord is in default under any of the terms
and provisions of the Prime Lease beyond expiration of applicable notice and/or
cure periods, Prime Landlord may elect to receive directly from Tenant all sums
due or payable to Landlord by Tenant pursuant to the Sublease, and upon receipt
of Prime Landlord's notice, Tenant shall thereafter pay to Prime Landlord any
and all sums becoming due or payable under this Sublease and Landlord shall
receive from Prime Landlord a credit for such sums actually received by Prime
Landlord against any and all payments then owing from Landlord under the Prime
Lease. Neither the mere service of such written notice nor the receipt of such
direct payments shall cause Prime Landlord to assume any of Landlord's duties,
obligations and/or liabilities under the Sublease, nor shall such event impose
upon Prime Landlord the duty or obligation to honor this Sublease, nor
subsequently to accept any purported attornment by Tenant except and to the
extent of the occurrence of a Prime Lease Termination as aforesaid. Prime
Landlord shall credit payments actually received pursuant to this conditional
assignment to Landlord's obligations under the Prime Lease. Without limitation
of the foregoing, acceptance of rent or other payments from Landlord and/or
Tenant by Prime Landlord shall not: (i) constitute a waiver of any default or
breach of the Prime Lease or (ii) cause nor result in a reinstatement of the
Prime Lease after Prime Lease Termination or (iii) be deemed or construed to
mean that Prime Landlord has accepted the Tenant as its "Tenant" under the Prime
Lease or (iv) be deemed to mean that Tenant is entitled to any rights under the
Sublease (except in the case of a Prime Lease Termination as provided above) or
the Prime Lease.

      8 Tenant's Obligations. Except as otherwise specifically provided herein,
during the term of this Sublease all acts to be performed and all of the terms,
provisions, covenants, stipulations, conditions, rights, obligations, remedies
and agreements to be observed by and inuring to the benefit of, Landlord, as
tenant under the Prime Lease of the Premises and arising from and after the
Commencement Date, shall be performed, and observed by, and shall inure to the
benefit of, Tenant, and Tenant's obligations shall run to Landlord or the Prime
Landlord as Landlord may determine to be appropriate or required by the
respective interests of Landlord and Prime Landlord. Tenant shall indemnify
Landlord and Prime Landlord against, and hold Landlord and Prime Landlord
harmless from and against, all costs, damages, claims, liabilities,

                                      -4-
<PAGE>

liens and expenses (including, but not limited to, reasonable attorneys' fees
and disbursements, court costs and other expenses of litigation or arbitration)
paid, suffered, incurred by or claimed against Landlord and/or Prime Landlord as
a result of the nonperformance or nonobservance by Tenant, Tenant's agents,
contractors, employees, invitees or licensees of any such terms, provisions,
covenants, stipulations, conditions, obligations and agreements contained in the
Prime Lease. In furtherance of the foregoing, Tenant shall not (i) do or permit
to be done anything prohibited to Landlord, as tenant under the Prime Lease, or
(ii) take any action or do or permit anything which would result in any
additional cost or other liability to Landlord and/or Prime Landlord under the
Prime Lease and/or this Sublease. In the event of any inconsistency between the
Prime Lease and this Sublease, such inconsistency (i) if it relates to
obligations of, or restrictions on, Tenant, shall be resolved in favor of that
obligation which is more onerous to Tenant or that restriction which is more
restrictive of Tenant, as the case may be, or (ii) if it relates to the rights
of, or benefits to be conferred upon, Tenant, shall be resolved in favor of this
Sublease.

      9. Landlord's Obligations. Anything contained in this Sublease or in the
Prime Lease to the contrary notwithstanding, Landlord shall have no
responsibility to Tenant for, and shall not be required to provide, any of the
services or make any of the repairs or restorations that Prime Landlord has
agreed to make or provide, or cause to be made or provided, under the Prime
Lease (including, without limitation, those set forth in Sections 7.1, 7.4 and
Section 7.5). If Prime Landlord shall default in the of any of its obligations
under the Prime Lease, or if Tenant wishes to file a protest or to dispute any
matter or thing, Landlord has the right to protest or dispute as tenant under
the Prime Lease, then Tenant shall advise Landlord of such protest or dispute
(together with all material facts and circumstances pertaining thereto) and
Landlord shall make demand on Prime Landlord and shall employ reasonable efforts
to cause Prime Landlord to cure such default or resolve such dispute. Except as
may result from a default of Landlord from its obligations specified in the
preceding sentence, Tenant shall not make any claim against Landlord and/or
Prime Landlord for any damage which may arise, nor shall Tenant's obligations
hereunder be impaired or abated by reason of (i) the failure of Prime Landlord
to keep, observe or perform its obligations pursuant to the Prime Lease, or (ii)
the acts or omissions of Prime Landlord and each of its agents, contractors,
servants, employees, invitees or licensees.

      10 Covenants with respect to the Prime Lease. Tenant covenants and agrees
that Tenant shall not do anything that would constitute a default under the
Prime Lease or omit to do anything that Tenant is obligated to do under the
terms of this Sublease so as to cause there to be a default under the Prime
Lease.

      11. Broker. Tenant represents and warrants to Landlord and Prime Landlord
that Tenant has not dealt with any broker in connection with this Sublease.
Tenant shall indemnify Landlord and Prime Landlord against, and hold Landlord
and Prime Landlord harmless from, any claim of, or liability to, any broker or
any other party with whom Tenant shall have dealt in connection with this
transaction and Sublease.

      12. Indemnification.

            12.1 Reciprocal Indemnification of Landlord and Tenant.

                  (a) Tenant shall indemnify, defend with competent and
experienced counsel and hold harmless Landlord, its subsidiaries and affiliates
and their respective officers, directors, shareholders and employees from and
against any and all damages, liabilities, actions, causes of action, suits,
claims, demands, losses, costs and expenses (including without limitation
reasonable attorneys' fees and disbursements and court costs) to the extent
arising from or in connection with the negligence or willful misconduct of
Tenant, its agents, employees, representatives or contractors.

                                      -5-
<PAGE>

                  (b) Landlord shall indemnify, defend with competent and
experienced counsel and hold harmless Tenant, its subsidiaries and affiliates
and their respective officers, directors, shareholders and employees, from and
against any and all damages, liabilities, actions, causes of action, suits,
claims, demands, losses, costs and expenses (including without limitation
reasonable attorneys' fees and disbursements and court costs) to the extent
arising from or in connection with the negligence or willful misconduct of
Landlord, its agents, employees, representatives or contractors.

                  (c) The party seeking indemnification under this Section (the
"Indemnified party") shall provide prompt written notice of any third party
claim to the party from whom indemnification is sought (the "Indemnifying
Party"). The Indemnifying Party shall have the right to assume exclusive control
of the defense of such claim or at the option of the Indemnifying Party, to
settle the same. The Indemnified Party agrees to cooperate reasonably with the
Indemnifying Party in connection with the performance of the Indemnifying
Party's obligations under this Section.

                  (d) Notwithstanding anything to the contrary contained in this
Sublease, neither party hereto shall be liable to the other for any indirect,
special, consequential or incidental damages (including without limitation loss
of profits, loss of use or loss of goodwill) regardless of (i) the negligence
(either sole or concurrent) of either party or (ii) whether either party has
been informed of the possibility of such damages. It is expressly understood and
agreed that damages payable by either party to Prime Landlord shall be deemed to
constitute direct damages of such party.

            12.2 Indemnification by Tenant of Prime Landlord. Without limitation
of and in addition to any obligation of Tenant under this Sublease, Tenant
agrees to defend, save harmless and indemnify Prime Landlord to the same extent
as Landlord is required to do so under the provisions of Section 10.1 of the
Prime Lease.

            12.3 Survival. The provisions of this Section 12 shall survive the
expiration or earlier termination of this Sublease.

      13. Quiet Enjoyment. Subject to the terms and conditions hereof and as
long as Tenant pays all of the Base Rent and Additional Rent due hereunder and
otherwise performs and observes all of the obligations, terms and conditions
contained herein and in the Prime Lease as herein incorporated, Tenant shall
peaceably and quietly have, hold and enjoy the Premises.

      14. Termination of Prime Lease. Except as otherwise expressly set forth in
paragraph 7 hereof and paragraph 3 of the Consent to Sublease by and between
Prime Landlord, Landlord and Tenant, if for any reason the term of the Prime
Lease is terminated prior to the Expiration Date of this Sublease, this Sublease
shall thereupon terminate, and Landlord shall not be liable to Tenant by reason
thereof unless such termination is due solely to an event of default on behalf
of Landlord. Notwithstanding the foregoing, if the termination of the Prime
Lease does not result in the termination of this Sublease or otherwise does not
result in the loss of possession of the Premises by Tenant, Landlord shall not
be liable to Tenant hereunder for damages or otherwise, and Landlord's
obligation to Tenant shall be limited to returning to Tenant a portion of any
rent paid in advance by Tenant, if any, prorated as of the date of such
termination.

      15. Modification of Prime Lease. For the purposes hereof, the terms of the
Prime Lease are subject to the following modifications:

            (a) In all provisions of the Prime Lease requiring the approval or
consent of Prime Landlord, Tenant shall be required to obtain the approval or
consent of both Prime Landlord and Landlord. In all provisions of the Prime
Lease requiring that notice be given to

                                      -6-
<PAGE>

Prime Landlord, Tenant shall be required to give notice to both the Prime
Landlord and Landlord.

      16. Consents. Landlord's refusal to consent to or approve any matter or
thing, whenever Landlord's consent or approval is required under this Sublease
or under the Prime Lease, as incorporated herein, shall be deemed reasonable if
Prime Landlord has refused or failed to give its consent or approval to such
matter or thing.

      17. Condition of the Premises; Tenant's Changes.

            (a) Tenant represents it has made a thorough examination of the
Premises and it is familiar with the condition thereof. Tenant acknowledges that
it enters into this Sublease without any representation or warranties by
Landlord except as set forth in this Lease, or anyone acting or purporting to
act on behalf of Landlord, as to the present or future conditions of the
Premises or the appurtenances thereto or any improvements therein or of the
Building. It is further agreed that Tenant does and will accept the Premises "as
is" in their present condition and Landlord has no obligation to perform any
work therein.

            (b) Notwithstanding anything to the contrary contained in the Prime
Lease, Tenant shall not make any changes to the Premises whatsoever, including,
without limitation, structural or non-structural changes, without the prior
written consent of Landlord which consent shall not be unreasonably withheld,
conditioned-or delayed but subject to prior consent of Prime Landlord in
accordance with the Prime Lease.

      18. Assignment and Subletting.

            (a) Tenant, for itself, its successors and assigns, expressly
covenants that it shall not assign, whether by operation of law or otherwise,
mortgage or pledge or otherwise transfer or encumber this Sublease, or sublet
all or any part of the Premises. The parties acknowledge that Tenant may become
a public company during the Term hereof and further acknowledge that the same
will not constitute an assignment, transfer or encumbrance of this Sublease.
Landlord reserves the right to transfer and assign its interest in and to this
Sublease to any entity or person who shall succeed to Landlord's interest in and
to the Prime Lease.

            (b) Consent by Landlord to any assignment, transfer or subletting to
any party shall not be construed as a waiver or release of Tenant from the terms
of any covenant or its primary responsibility under this Sublease, nor shall
consent to one assignment, transfer or sublease to any person, partnership, firm
or corporation be deemed to be a consent to any subsequent assignment, transfer
or subletting to another person, partnership, firm or corporation.

      19. Insurance.

            (a) Tenant agrees to maintain all insurance coverages specified in
Section 10.2 of the Prime Lease (including without limitation commercial general
liability and property damage insurance, casualty insurance and workers'
compensation insurance) in accordance with Section 10.2 of the Prime Lease). All
such insurance shall be underwritten by a company or companies licensed to do
insurance business in the Commonwealth of Massachusetts by the Department of
Insurance and in good standing, and shall be written on an "occurrence basis."
All such insurance policies shall name Landlord and Prime Landlord as additional
insureds thereunder and, in addition, shall name as additional insureds the
holders of any Mortgage of the Property of which Tenant is notified in writing,
as their respective interests may appear. Tenant shall furnish Landlord receipts
evidencing payment of the premiums for such insurance (if requested by Landlord)
and shall deposit with Landlord certificates for such insurance no later than
the Commencement Date and at least fifteen (15) days before each insurance
renewal date thereof, bearing the endorsement that the polices will not be
canceled nor will coverages be

                                      -7-
<PAGE>

reduced until after ten (10) days' prior written notice to both Landlord and
Prime Landlord of such proposed action. Tenant shall pay all premiums and
charges for such insurance, and if Tenant shall fail to obtain such insurance,
Landlord may, but shall not be obligated to, obtain the same, in which event the
amount of the premium paid shall be paid by Tenant to Landlord upon Landlord's
demand therefor, shall be deemed Additional Rent and shall be collectible by
Landlord in the same manner and with the same remedies as though said sums were
Additional Rent reserved hereunder.

            (b) Tenant acknowledges that neither Landlord nor Prime Landlord
will carry any insurance in favor of Tenant, and that neither Prime Landlord nor
Landlord will carry insurance on Tenant's furniture and/or furnishings or any
fixtures or equipment, improvements or appurtenances of Tenant in or about the
Premises.

      20. Waiver of Subrogation.

            (a) Any casualty insurance carried by the Tenant with respect to the
Premises, the Building or the Property, or property therein or occurrences
thereon shall include a clause or endorsement denying to the insurer rights of
subrogation against the other party to the extent rights have been waived by the
insured prior to occurrence of injury or loss, provided that such clause or
endorsement is obtainable without payment of an additional premium. If such
clause or endorsement is obtainable upon payment of an additional premium,
notice thereof shall be given to the Landlord and the Landlord may request the
Tenant to obtain it and shall reimburse the Tenant for the cost of such
additional premium.

            (b) Each party, notwithstanding any provisions of this Sublease to
the contrary, hereby waives any rights of recovery against the other for injury
or loss due to hazards covered by such insurance to the extent such party's
policy permits such waivers of subrogation and then only with respect to sums
which are collectible thereunder. Landlord shall be afforded the protection of
this provision notwithstanding any right which Tenant may have to self insure.

      21. End of Term. If Tenant shall remain in possession of the Premises or
any part thereof after the expiration or prior termination of the Term hereof,
as the same may be extended, the parties agree that no such holding over by
Tenant shall operate to extend or renew this Sublease, and that any such holding
over shall cause Tenant to become a daily tenant at sufferance and Tenant shall
be obligated to pay monthly installment of Base Rent and Additional Rent in an
amount equal to two hundred percent (200%) of the sum of the installment of Base
Rent and Estimated Additional Rent Payments payable during the last full
calendar month of the Lease Term, and such tenancy shall otherwise be subject to
all the terms, conditions, covenants and agreements of this Sublease. Tenant
further agrees to pay to Landlord any additional amounts payable by Landlord to
Prime Landlord under the Prime Lease by reason of any such holding over by
Tenant.

      22. Default.

            (a) In the event that Tenant shall default in the payment of Base
Rent, Additional Rent or any other charge payable hereunder within one (1)
Business Day after written notice, or shall default in the performance or
observance of any of the terms, conditions and covenants of this Sublease within
twenty (20) days after written notice, or, if not curable within said twenty day
period, Tenant does not commence to cure said default within said twenty day
period and diligently prosecute the same to completion, and provided that there
exists no event of default under the Prime Lease, Landlord, in addition to and
not in limitation of any rights otherwise available to it, shall have the same
rights and remedies with respect to such default as are provided to Prime
Landlord under the Prime Lease with respect to defaults by Landlord as tenant
thereunder, with the same force and effect as though all such provisions
relating to any

                                      -8-
<PAGE>

such default or defaults were set forth herein in their entirety, and Tenant
shall have all of the obligations of the tenant under the Prime Lease with
respect to such default or defaults.

            (b) In the event of a default by Tenant in the performance of any of
its non-monetary obligations hereunder, including those under the Prime Lease,
Landlord may, at its option, and without waiving any other remedies for such
default herein or at law or by incorporation by reference of the Prime Lease
provided, at any time thereafter, give written notice to Tenant that if such
default is not cured, or the cure not commenced, within ten (10) days after
notice, and if so commenced is not thereafter pursued diligently to completion,
Landlord may cure such default for the account of Tenant, and any amount paid or
incurred by Landlord in so doing shall be deemed paid or incurred for the
account of Tenant and Tenant agrees promptly to reimburse Landlord therefor and
save Landlord harmless therefrom; provided, however, that Landlord may cure any
such default as aforesaid prior to the expiration of any waiting period if
reasonably necessary to protect Landlord's interest under the Prime Lease or to
prevent injury or damage to persons or property.

      23. Destruction. Fire and other Casualty. If the whole or any part of the
Premises or the Building shall be damaged by fire or other casualty and the
Prime Lease is not terminated on account thereof by either Landlord or Prime
Landlord in accordance with the terms thereof, this Sublease shall remain in
full force and effect and Base Rent and Additional Rent shall not abate except
to the extent Base Rent and Additional Rent for the Premises shall abate under
the terms of the Prime Lease.

      24. Notices.

            (a) Whenever, by the terms of this Sublease, notice, demand or other
communication shall or may be given to either party, the same shall be in
writing and addressed as follows:

                  If to Landlord:   At the Address of Landlord set forth
                                    above in the preamble to this Lease

                  If to Tenant:     At the Premises

or to such other address or addresses as shall from time to time be designated
by written notice by either party to the other as herein provided. All notices
shall be sent by registered or certified mail, postage prepaid and return
receipt requested, or by Federal Express or other comparable courier providing
proof of delivery, and shall be deemed duly given and received (i) if mailed, on
the third business day following the mailing thereof, or (ii) if sent by
courier, the date of its receipt (or, if such day is not a business day, the
next succeeding business day). Landlord and Tenant each promptly shall deliver
to the other copies of all notices, requests, demands or other communications
which relate to the Premises or the use or occupancy thereof after receipt of
the same from Prime Landlord or others.

            (b) Each party hereunder shall promptly furnish the other with
copies of all notices under the Prime Lease or this Sublease with respect to the
Premises which such party shall receive from Prime Landlord under the Prime
Lease.

      25. Sublease Conditional Upon Certain Consents. Landlord and Tenant each
acknowledge and agree that this Sublease is subject to Landlord's obtaining the
consent of Prime Landlord in accordance with the terms of the Prime Lease, and
that if such consent shall not be obtained within fifteen (15) days of the date
hereof, then this Sublease shall be deemed cancelled and terminated and neither
of the parties hereto shall have any liability to the other.

                                      -9-
<PAGE>

      26. Security Deposit. Tenant concurrently with the execution of this
Sublease has deposited with Landlord a deposit (the "Security Deposit") in the
amount of Sixteen Thousand and No/100ths ($16,000.00) Dollars to be held by
Landlord without interest as security for the faithful performance and
observance by Tenant of the terms, conditions and provisions of this Sublease,
including without limitation the surrender of possession of the Premises to
Landlord as herein provided. Landlord shall not be required to maintain the
Security Deposit in a separate account. It is agreed that in the event Tenant
defaults in respect of any of the terms, provisions and conditions of this
Sublease, including, but not limited to, the payment of Base Rent and Additional
Rent, Landlord may apply or retain the whole or any part of the Security Deposit
to the extent required for the payment of any Base Rent and Additional Rent or
any other sum as to which Tenant is in default or for any sum which Landlord may
expend or may be required to expend by reason of Tenant's default in respect of
any of the terms, covenants and conditions of this Sublease, including but not
limited to, any damages or deficiency in the reletting of the Premises, whether
such damages or deficiency accrue or accrues before or after summary proceedings
or other reentry by Landlord. The Security Deposit is not to be used or applied
by Tenant as a substitute for rent due any month, but may be so applied by
Landlord at any time at Landlord's option. The use, application or retention of
the Security Deposit, or any portion thereof, by Landlord shall not prevent
Landlord from exercising any other right or remedy provided by this Sublease or
by law and shall not operate as a limitation on any recovery to which Landlord
may otherwise be entitled. If Landlord applies or retains any part of the
Security Deposit, Tenant, upon written demand therefor by Landlord, shall
deposit cash with Landlord in such amount so that Landlord shall have the full
deposit on hand at all times during the Term. If Tenant shall fully and
faithfully comply with all of the terms, provisions, covenants and conditions of
this Sublease, the balance of the Security Deposit, if any, shall be returned to
Tenant within thirty (30) days after the Expiration Date and after the delivery
of the entire possession of the Premises to Landlord.

      27. Payment of the First Month's Base Rent. Tenant shall pay to Landlord
the first monthly installment of the applicable Base Rent ($2,375.00) upon
execution of this Sublease.

      28. Signage. Any signage contemplated by the Tenant shall be subject to
and in accordance with the requirements set forth in the Prime Lease. Landlord
shall have no obligation or responsibility to remove any signage which exists at
the Premises as of the Commencement Date.

      29. Landlord's Representations. Landlord hereby represents and warrants
that (i) the Prime Lease is in full force and effect, (ii) the Prime Lease
attached hereto as Exhibit A is the complete Prime Lease, the Prime Lease has
not been amended or modified; (iii) to the best of Landlord's knowledge, there
are no existing setoffs, defenses or counterclaims against the Prime Landlord
with respect to the payment of rent reserved under the Prime Lease or any
performance of other terms, conditions or covenants of the Prime Lease on the
part of the Tenant under the Prime Lease to be performed; and (iv) there exists
no defaults or breaches of Prime Landlord's or Landlord's obligations under the
Prime Lease nor, to the best of Landlord's knowledge, any event which with the
giving of notice or passage of time, or both, would constitute a default under
the Prime Lease.

      30. Miscellaneous.

            (a) This Sublease may not be extended, renewed, terminated, or
otherwise modified except by an instrument in writing signed by the party
against whom enforcement of any such modification is sought and only upon the
express written consent of Prime Landlord.

            (b) It is understood and agreed that all understandings and
agreements heretofore had between the parties hereto are merged in this
Sublease, which alone fully and completely expresses their agreement, and that
the same is entered into after full investigation,

                                      -10-
<PAGE>

neither party relying upon any statement, representation or warranty made by the
other not embodied in this Sublease.

            (c) The paragraph headings appearing herein are for purposes of
convenience only and are not deemed to be a part of this Sublease.

            (d) The provisions of this Sublease shall be governed by and
construed in accordance with the laws of the Commonwealth of Massachusetts
without regard to principles of conflicts of laws. Landlord and Tenant agree to
submit to jurisdiction in the Commonwealth of Massachusetts with respect to any
dispute under or arising out of this Sublease and agree that any such dispute
shall be brought either in the courts of the Commonwealth of Massachusetts or in
the applicable federal district court located in Massachusetts.

            (e) If any provision of this Sublease or the application thereof to
any person or circumstance shall to any extent be invalid or unenforceable, the
remainder of this Sublease, or the application of such provision to persons or
circumstance other than those as to which it is invalid or unenforceable, shall
not be affected-thereby, and each provision of this Sublease shall be valid and
enforced to the fullest extent permitted by law.

            (f) This Sublease may be executed in counterparts each of which
shall be deemed an original and all of which together shall constitute one and
the same document.

            (g) This Sublease (or any notice hereof) shall not be recorded.

            (h) Landlord and Tenant hereby each waive trail by jury in any
action, proceeding or counterclaim brought by either against the other, on or in
respect of any matter whatsoever arising out of or in any way connected with
this Sublease, the relationship of Landlord and Tenant or Tenant's use or
occupancy of the Premises.

            (i) This Sublease includes and incorporates all Exhibits referred to
hereby and attached hereto.

      IN WITNESS WHEREOF, this Agreement of Sublease has been duly executed as
of the day and year first above written.

                                    LANDLORD:
                                    SONUS NETWORKS, INC.

                                    By:    ________________________________
                                    Name:  ________________________________
                                    Title: ________________________________

                                    TENANT:
                                    X-RITE INCORPORATED
                                    By:    ________________________________
                                    Name:  ________________________________
                                    Title: ________________________________

BCIA 15

                                      -11-
<PAGE>

                                    EXHIBIT A
                                   Prime Lease

Attached hereto

                                      -12-
<PAGE>

EXHIBIT G                                                                 X-RITE

                               CONSENT TO SUBLEASE

                                    PREAMBLE

      THIS CONSENT TO SUBLEASE ("Consent") dated as of September 30, 2000, is
made with reference to that certain Sublease dated September 30, 2000 (the
"Sublease") by and between Sonus Networks, Inc. having an address of 5 Carlisle
Road, Westford, MA 01886 ("Sublandlord") and X-Rite Incorporated having an
original address of 25 Porter Road, Littleton, MA 01460 ("Subtenant"), and is
entered into by and among BCIA New England Holdings LLC, having an address do
Boston Capital Institutional Advisors LLC, One Boston Place, Suite 21000,
Boston, MA 02108 ("Overlandlord"), Sublandlord, and Subtenant, with respect to
the following facts:

      A.    Overlandlord and Sublandlord are the parties to that certain Lease
            dated as of September 30, 2000 (the "Overlease") pertaining to
            certain space (the "Master Premises") in a Building known as and
            numbered 25 Porter Road, Littleton, Massachusetts (the "Building");

      B.    Sublandlord and Subtenant wish to enter into the Sublease pursuant
            to which Sublandlord will lease to Subtenant a portion of the Master
            Premises comprised of approximately 3,000 rentable square feet (the
            "Sublease Premises");

      C.    The Overlease provides, inter alia, that Sublandlord may not enter
            into any sublease without Overlandlord's prior written approval; and

      D.    Sublandlord and Subtenant have presented the fully executed Sublease
            (a true copy of which is attached hereto as Exhibit A) to
            Overlandlord for Overlandlord's review and approval.

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

            1.    Overlandlord hereby consents to the execution and delivery of
                  the Sublease upon the terms and conditions set forth in the
                  General Conditions of Consent to Sublease ("General
                  Conditions") attached hereto and made an integral part hereof.

            2.    Sublandlord and Subtenant hereby acknowledge receipt of the
                  General Conditions and further acknowledge that Overlandlord's
                  consent is subject to such General Conditions, and that in the
                  event of a conflict between this Consent and the General
                  Conditions and the Sublease, this Consent and the General
                  Conditions shall control.
<PAGE>

EXECUTED under seal as of the date first written above.

                            OVERLANDLORD:

                            BCIA NEW ENGLAND HOLDINGS LLC, a Delaware
                            limited liability company

                            By:   BCIA NEW ENGLAND HOLDINGS MASTER
                                  LLC, a Delaware limited liability company, its
                                  Manager

                                  By:  BCIA NEW ENGLAND HOLDINGS
                                       MANAGER LLC, a Delaware limited
                                       liability company, its Manager

                                       By:   BCIA NEW ENGLAND
                                             HOLDINGS MANAGER CORP., a
                                             Delaware corporation, its Manager

                            By:   ______________________________________________

                            Its:  ______________________________________________

                            SUBLANDLORD:

                            SONUS NETWORKS, INC.

                            By:   ______________________________________________

                            Its:  ______________________________________________

                            SUBTENANT:

                            X-RITE INCORPORATED

                            By:   ______________________________________________

                            Its:  ______________________________________________

                                       -2-
<PAGE>

                    GENERAL CONDITIONS OF CONSENT TO SUBLEASE

      The following General Conditions are an integral part of and are hereby
incorporated into the foregoing Consent to Sublease:

      1.    Neither the Overlease, the Sublease nor this Consent shall be
            deemed, nor are such documents intended to grant to Subtenant, any
            rights whatsoever against Overlandlord under the Overlease or
            (except as otherwise expressly provided in paragraph 3 of these
            General Conditions) under the Sublease or otherwise. Notwithstanding
            anything contained in the Sublease to the contrary, Subtenant hereby
            acknowledges and agrees that its sole remedy for any alleged or
            actual breach of its rights in connection with the Sublease shall be
            solely against Sublandlord, if, as and to the extent any such remedy
            may exist. Subtenant acknowledges and agrees that it is not a third
            party beneficiary under the Overlease and is not entitled to assert
            any of Sublandlord's rights thereunder against Overlandlord, whether
            in its own right or on behalf of Sublandlord.

      2.    This Consent and the Sublease shall not (i) constitute a consent or
            approval by Overlandlord of any of the terms, covenants or
            conditions of the Sublease and (except as otherwise expressly
            provided in paragraph 3 of these General Conditions), Overlandlord
            shall not be bound thereby or (ii) release Sublandlord from any
            existing or future duty, obligation or liability to Overlandlord
            pursuant to the Overlease (and Sublandlord shall be and remain
            liable for the full payment, performance and observance of all of
            the terms, covenants and conditions contained in the Overlease to be
            paid, performed and observed by the "Tenant" thereunder as if the
            Sublease and this Consent had never been made), or (iii) change,
            modify or amend the Overlease in any manner, except insofar as it
            constitutes Overlandlord's consent to the execution and delivery of
            the Sublease. Notwithstanding the generality of the foregoing, this
            Consent expressly shall not absolve Sublandlord from any requirement
            set forth in the Overlease that Sublandlord obtain Overlandlord's
            prior written approval of any additional subleases, assignments or
            other dispositions of its interest in the Overlease or the Premises
            (as defined in the Overlease).

      3.    (a) In the event of Overlease Termination (as hereinafter defined)
            prior to December 31, 2002 and provided that the Sublease has not
            theretofore been terminated, Overlandlord shall recognize Subtenant
            as Overlandlord's direct Tenant pursuant to the terms and provisions
            of the Sublease for the then remainder of the Term of the Sublease
            (through December 31, 2002) and Tenant hereby agrees to attorn to
            Overlandlord and perform Subtenant's obligations under the Sublease
            with respect to the Subleased Premises (and only as to the Subleased
            Premises) to and for the benefit of Overlandlord as the "Landlord"
            under the Sublease as a direct Lease between Overlandlord and
            Subtenant. Such agreement by Subtenant to perform each and every one
            of its obligations under the Sublease with respect to the Subleased
            Premises to and for the benefit of Overlandlord as the "Landlord"
            under the Sublease shall entitle the Subtenant to occupy the
            Subleased Premises after Overlease Termination

                                       -3-
<PAGE>

            for the then remainder of the Term of the Sublease (through December
            31, 2002) as if it were leased by Overlandlord directly to
            Subtenant, but shall not relieve Sublandlord from any liability to
            Overlandlord under the Overlease. Subtenant agrees to execute and
            deliver at any time and from time to time, upon request of
            Overlandlord, any instruments which may be necessary or appropriate
            to evidence such required assumption and Subtenant hereby
            irrevocably appoints Overlandlord as its attorney in fact, coupled
            with an interest to execute on behalf of Subtenant any documents or
            instruments necessary to evidence such assumption. Overlandlord
            shall not (i) be liable to Subtenant for any act, omission or breach
            of the Sublease by Sublandlord, (ii) be subject to any offsets or
            defenses which Subtenant might have against Sublandlord, (iii) be
            bound by any rent or additional rent which Subtenant might have paid
            in advance to Sublandlord, (iv) be bound to honor any rights of
            Subtenant in any security deposit or advance rent made with or paid
            to Sublandlord by Subtenant except to the extent Sublandlord has
            specifically assigned and turned over such security deposits and
            advance rent to Overlandlord and Overlandlord has actually received
            the same, (v) be bound by any provision of the Sublease except and
            to the extent hereinabove provided or (vi) be bound to honor any
            exercise of any Option to Extend or renew the term of the Overlease
            set forth in the Overlease, which Options to Extend or renew shall
            be deemed deleted from the Overlease effective as of the date of
            this Consent.

            Sublandlord and Subtenant hereby agree that in the event of
            Overlease Termination, Sublandlord shall immediately pay or transfer
            to Overlandlord any security deposits, rent or other sums then held
            by Sublandlord in connection with the subleasing of the Subleased
            Premises and, notwithstanding anything contained in the Sublease to
            the contrary, this shall satisfy Sublandlord's obligations to
            Subtenant under this Sublease with respect to any such sums paid
            over or transferred to Overlandlord. Such security deposit may be
            applied by Overlandlord pursuant to the terms of the Overlease in
            the event of any holding over or other default by the Subtenant
            after an Overlease Termination. Subtenant hereby agrees that under
            no circumstances whatsoever shall Overlandlord be held in any way
            responsible or accountable for any security deposit or any sums paid
            by Subtenant to Sublandlord unless and until and to the extent that
            Overlandlord has actually received such sums from Sublandlord and
            has acknowledged their source, and Subtenant shall have no claim to
            any security or other deposit made by Sublandlord under the
            Overlease.

            (b) "Overlease Termination" means the termination or cancellation of
            the Overlease prior to December 31, 2002 due to: (1) a default
            continuing beyond any applicable notice and/or cure periods by
            Sublandlord under the Overlease or any of the terms and provisions
            hereof; (2) foreclosure proceedings brought by the holder of any
            mortgage or trust deed to which the Overlease is subject; and (3)
            the termination of Sublandlord's leasehold estate by dispossession
            proceedings. Provided, however, that notwithstanding the foregoing
            to the contrary, termination of the Overlease in accordance with its
            terms prior to December 31, 2002 as the

                                      -4-
<PAGE>

            result of fire, casualty, the exercise of the power of eminent
            domain or actions taken in lieu thereof or pursuant thereto or any
            other reason or cause not enumerated in (1), (2), or (3) above shall
            not be deemed an "Overlease Termination" for purposes of this
            paragraph 3 of this Consent.

      4.    In addition to Overlandlord's rights under Section 3 hereof, in the
            event Sublandlord is in default under any of the terms and
            provisions of the Overlease continuing beyond any applicable notice
            and/or cure periods, Overlandlord may elect to receive directly from
            Subtenant all sums due or payable to Sublandlord by Subtenant
            pursuant to the Sublease, and upon receipt of Overlandlord's notice,
            Subtenant shall thereafter pay to Overlandlord any and all sums
            becoming due or payable under the Sublease and Sublandlord shall
            receive from Overlandlord a credit for such sums actually received
            by Overlandlord against any and all payments then owing from
            Sublandlord under the Overlease. Except as otherwise expressly
            provided in paragraph 3 of this Consent with respect to an Overlease
            Termination, neither the mere service of such written notice nor the
            receipt of such direct payments shall cause Overlandlord to assume
            any of Sublandlord's duties, obligations and/or liabilities under
            the Sublease, nor shall such event impose upon Overlandlord the duty
            or obligation to honor the Sublease, nor subsequently to accept any
            purported attornment by Subtenant except and to the extent of the
            occurrence of an Overlease Termination as aforesaid. Sublandlord
            grants Overlandlord a security interest in all such payments due to
            Sublandlord from Subtenant, which security interest Overlandlord may
            perfect by filing a UCC-1 (which Sublandlord shall sign within three
            (3) days of Overlandlord's request). Overlandlord shall credit
            payments actually received pursuant to this conditional assignment
            to Sublandlord's obligations under the Overlease. Without limitation
            of the foregoing, acceptance of rent or other payments from
            Sublandlord and/or Subtenant by Overlandlord shall not: (i)
            constitute a waiver of any default or breach of the Overlease or
            (ii) cause nor result in a reinstatement of the Overlease after
            Overlease Termination or (iii) absent the occurrence of an Overlease
            Termination, be deemed or construed to mean that Overlandlord has
            accepted the Subtenant as its "Tenant" under the Overlease or (iv)
            absent the occurrence of an Overlease Termination, be deemed to mean
            that Subtenant is entitled to any rights under the Sublease or the
            Overlease.

      5.    Subtenant hereby acknowledges that it has read and has knowledge of
            all of the terms, provisions, rules and regulations of the Overlease
            and agrees not to do or omit to do anything which would cause
            Sublandlord to be in breach of the Overlease. Any such act or
            omission by Subtenant also shall constitute a breach of the
            Overlease and this Consent by Sublandlord shall entitle Overlandlord
            to recover any damage, loss, cost, or expense which it thereby
            suffers, from Sublandlord and/or Subtenant, who shall be jointly and
            severally liable to Overlandlord in this regard.

      6.    In the event of the commencement of an action at law or in equity by
            the filing of a complaint or other similar action involving a
            request for relief from a judicial body between or involving the
            parties hereto with respect to the Sublease, the Overlease, this
            Consent or the rights of the parties

                                      -5-
<PAGE>

            hereto, hereunder or thereunder, the Sublandlord and Subtenant,
            jointly and severally, hereby agree to pay the Overlandlord on
            demand all reasonable costs, expense and attorneys' fees incurred
            therein by Overlandlord, which amounts may be included as a part of
            a judgment rendered therein.

      7.    The parties acknowledge that the Sublease constitutes the entire
            agreement between Sublandlord and Subtenant with respect to the
            subject matter thereof, and that no amendment, termination,
            modification or change therein will be binding upon Overlandlord
            unless Overlandlord shall have given its prior written consent
            thereto, which consent may be granted or denied by Overlandlord in
            its sole and absolute discretion.

      8.    This Consent shall be binding upon and shall inure to the benefit of
            the parties' respective successors in interest and assigns, subject
            at all times, nevertheless, to all agreements and restrictions
            contained in the Overlease, the Sublease, and herein, with respect
            to subleasing, assignment or other transfer and the foregoing shall
            not be deemed to limit or negate Overlandlord's rights to prohibit
            or condition its consent to a future dispossession of Sublandlord's
            or Subtenant's interests. The agreements contained herein constitute
            the entire understanding between parties with respect to the subject
            matter hereof and supersede all prior agreements.

      9.    This Consent shall not be assignable and shall only apply with
            respect to the Sublease by and between Sublandlord and Subtenant.

      10.   The consent by Overlandlord to the use and occupancy of the
            Subleased Premises by Subtenant shall not be construed as a consent
            by Overlandlord to the use and occupancy of the Subleased Premises
            by anyone other than Subtenant or Sublandlord or as a consent to
            further subletting by Sublandlord or by Subtenant of the Subleased
            Premises, or any part thereof. Neither the Sublease nor any of the
            rights, privileges or obligations thereunder shall be assigned,
            modified, renewed or extended, nor shall the Subleased Premises, or
            any part thereof, be further sublet or occupied by others (except by
            Sublandlord, in accordance with and subject to the terms and
            provisions of the Overlease).

      11.   Subject to the provisions of General Condition numbered 3 of this
            Consent to Sublease, unless previously terminated, on or before the
            day immediately preceding the date of expiration of the Overlease or
            upon the date of any earlier termination of the term of the
            Overlease, the Sublease and its term shall expire, terminate and
            come to an end and Sublandlord shall cause Subtenant to vacate and
            surrender the Subleased Premises on or before such date in
            accordance with the applicable provisions of the Overlease regarding
            surrender and delivery of the Premises to Overlandlord.

      12.   Sublandlord and Subtenant hereby acknowledge and agree that
            Overlandlord shall not be responsible for any brokers commissions or
            fees of any kind or nature in connection with the Sublease or the
            subject matter thereof (except for any commissions or fees due and
            payable to Trammell

                                      -6-
<PAGE>

            Crow Company ("TCC"), if any, pursuant to Overlandlord's direct
            agreements with TCC which shall be paid by Overlandlord pursuant to
            its direct agreements, if any, with TCC and they each hereby agree
            to indemnify and hold Overlandlord harmless from and against any
            such claims including all reasonable attorneys fees sustained or
            incurred by Overlandlord as a result of any such claim against
            Overlandlord. Except for Overlandlord's obligation, if any, to pay
            commissions or fees to TCC pursuant to Landlord's direct agreements
            with TCC, Sublandlord and Subtenant hereby jointly and severally
            agree to indemnify and hold Overlandlord harmless from and against
            any and all claims, costs or damages sustained or incurred by
            Overlandlord as the result of any claim by any party that they are
            entitled to a commission or broker's fee in connection with this
            Consent or the Sublease. The indemnity contained herein shall
            include, without limitation, all reasonable attorneys' fees and
            expenses incurred by Overlandlord in connection with any such claim.
            This paragraph 12 shall survive expiration or earlier termination of
            the Sublease.

      13.   Sublandlord and Subtenant, jointly and severally, hereby agree to
            indemnify and hold Overlandlord harmless with respect to any and all
            liability to and claims by Subtenant in connection with the
            Sublease, Subtenant's use and occupancy of the Subleased Premises,
            or the subject matter hereof, unless due to the Overlandlord's
            negligence or willful misconduct. The within indemnity shall be
            joint and several and shall include all losses, costs, damages or
            expenses including, without limitation, reasonable attorneys fees
            sustained or incurred by Overlandlord arising out of the matters
            contained herein. The provisions of this paragraph 13 shall survive
            any expiration or earlier termination of the Sublease or the
            Overlease.

      14.   In the event that there shall be any conflict between the terms,
            covenants and conditions of this Consent to Sublease and the terms,
            covenants and, conditions of the Sublease, then the terms, covenants
            and conditions of this Consent to Sublease shall prevail in each
            instance and any conflicting terms, covenants or conditions of the
            Sublease shall be deemed modified to conform with the terms,
            covenants and conditions of this Consent to Sublease.

      15.   Notwithstanding anything contained in the Sublease to the contrary,
            Sublandlord and Subtenant represent to and agree with Overlandlord
            that no changes, additions or improvements including, without
            limitation, electrical, HVAC or other construction work shall be
            performed in the Subleased Premises unless detailed plans and
            specifications for such work are first submitted to Overlandlord for
            its approval and Overlandlord shall have granted such approval in
            writing. Such approval shall be given or withheld in accordance with
            the applicable terms of the Overlease. In accordance with the
            provisions of the Overlease, all such work, if approved by
            Overlandlord, shall be subject to the requirements contained in the
            Overlease applicable to construction within or alterations of the
            Subleased Premises and shall be performed in accordance with the
            Overlease.

                                      -7-
<PAGE>

      16.   No signs shall be placed upon or within the Building and/or the
            Subleased Premises without the express written consent of
            Overlandlord, which consent may be granted or withheld by
            Overlandlord in its sole and absolute discretion.

      17.   Subtenant shall, within 10 days of written request from Overlandlord
            therefor, execute and deliver to Overlandlord and/or the holder of
            any mortgage upon or proposed purchasers of the Building, a
            so-called "Estoppel Letter" in form satisfactory to Overlandlord or
            such holder of a Mortgage or proposed purchaser which shall include,
            among other things, if so requested, a statement (i) certifying that
            the Sublease is in full force and effect and has not been assigned,
            modified or amended, (ii) that Sublandlord is not in default
            thereunder, (iii) the date through which rent has been paid and (iv)
            that there are no defenses or set-offs against enforcement of the
            Sublease or this Agreement against Subtenant and/or Sublandlord.

      18.   Subtenant hereby further agrees that upon the written request of
            Overlandlord, Subtenant shall subordinate its interest in the
            Sublease to the lien of any mortgage, security agreement or lease
            now or hereafter affecting the Building or the land upon which the
            Building is constructed.

      19.   As a condition to the effectiveness of the within Consent, as
            additional rent under the Overlease, Sublandlord shall, within ten
            (10) days after invoice, reimburse Overlandlord for all costs and
            expenses including without limitation, attorneys fees sustained or
            incurred by Overlandlord in connection with Sublandlord's request
            for Overlandlord's Consent to the execution and delivery of the
            Sublease including, without limitation, review of the Sublease and
            preparation and negotiation of this Consent.

      20.   All notices and demands which may or are to be required or permitted
            to be given by any party hereunder shall be in writing. All notices
            and demands to Subtenant shall be sent by United States Mail,
            certified mail return receipt requested, postage prepaid, addressed
            to Subtenant at the Subleased Premises or to such other place as
            Subtenant may from time to time designate in a notice to the other
            parties hereto given in the manner herein provided.

            All notices and demands to Sublandlord shall be sent by United
            States Mail, certified mail return receipt requested, postage
            prepaid, addressed to the Sublandlord at the address set forth
            herein, and to such other person or place as the Sublandlord may
            from time to time designate in a notice to the other parties hereto
            given in the manner herein provided.

            All notices and demands to Overlandlord shall be sent by United
            States Mail, certified mail return receipt requested, postage
            prepaid, addressed to the Overlandlord at the address set forth
            herein, and to such other person or place as the Overlandlord may
            from time to time designate in a notice to the other parties hereto
            given in the manner herein provided.

                                      -8-
<PAGE>

EXHIBIT G                                                                 X-RITE

                              CONSENT TO SUBLEASE

                                    PREAMBLE

      THIS CONSENT TO SUBLEASE ("Consent") dated as of September 30, 2000, is
made with reference to that certain Sublease dated September 30, 2000 (the
"Sublease") by and between Sonus Networks, Inc. having an address of 5 Carlisle
Road, Westford, MA 01886 ("Sublandlord") and X-Rite Incorporated having an
original address of 25 Porter Road, Littleton, MA 01460 ("Subtenant"), and is
entered into by and among BCIA New England Holdings LLC, having an address c/o
Boston Capital Institutional Advisors LLC, One Boston Place, Suite 21000,
Boston, MA 02108 ("Overlandlord"), Sublandlord, and Subtenant, with respect to
the following facts:

      A.    Overlandlord and Sublandlord are the parties to that certain Lease
            dated as of September 30, 2000 (the "Overlease") pertaining to
            certain space (the "Master Premises") in a Building known as and
            numbered 25 Porter Road, Littleton, Massachusetts (the "Building");

      B.    Sublandlord and Subtenant wish to enter into the Sublease pursuant
            to which Sublandlord will lease to Subtenant a portion of the Master
            Premises comprised of approximately 3,000 rentable square feet (the
            "Sublease Premises");

      C.    The Overlease provides, inter alia, that Sublandlord may not enter
            into any sublease without Overlandlord's prior written approval; and

      D.    Sublandlord and Subtenant have presented the fully executed Sublease
            (a true copy of which is attached hereto as Exhibit A) to
            Overlandlord for Overlandlord's review and approval.

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

            1.    Overlandlord hereby consents to the execution and delivery of
                  the Sublease upon the terms and conditions set forth in the
                  General Conditions of Consent to Sublease ("General
                  Conditions") attached hereto and made an integral part hereof.

            2.    Sublandlord and Subtenant hereby acknowledge receipt of the
                  General Conditions and further acknowledge that Overlandlord's
                  consent is subject to such General Conditions, and that in the
                  event of a conflict between this Consent and the General
                  Conditions and the Sublease, this Consent and the General
                  Conditions shall control.
<PAGE>

      EXECUTED under seal as of the date first written above.

                              OVERLANDLORD:

                              BCIA NEW ENGLAND HOLDINGS LLC, a Delaware
                              limited liability company

                              By: BCIA NEW ENGLAND HOLDINGS MASTER
                                  LLC, a Delaware limited liability company, its
                                  Manager

                                  By: BCIA NEW ENGLAND HOLDINGS MANAGER LLC, a
                                      Delaware limited liability company,
                                      its Manager

                                      By: BCIA NEW ENGLAND HOLDINGS MANAGER
                                          CORP., a Delaware corporation, its
                                          Manager

                              By: ______________________________________________

                              Its: _____________________________________________

                              SUBLANDLORD:

                              SONUS NETWORKS, INC.

                              By: ______________________________________________

                              Its: _____________________________________________

                              SUBTENANT:

                              X-RITE INCORPORATED

                              By: ______________________________________________

                              Its: _____________________________________________

                                      -2-
<PAGE>

                   GENERAL CONDITIONS OF CONSENT TO SUBLEASE

      The following General Conditions are an integral part of and are hereby
incorporated into the foregoing Consent to Sublease:

      1.    Neither the Overlease, the Sublease nor this Consent shall be
            deemed, nor are such documents intended to grant to Subtenant, any
            rights whatsoever against Overlandlord under the Overlease or
            (except as otherwise expressly provided in paragraph 3 of these
            General Conditions) under the Sublease or otherwise. Notwithstanding
            anything contained in the Sublease to the contrary, Subtenant hereby
            acknowledges and agrees that its sole remedy for any alleged or
            actual breach of its rights in connection with the Sublease shall be
            solely against Sublandlord, if, as and to the extent any such remedy
            may exist. Subtenant acknowledges and agrees that it is not a third
            party beneficiary under the Overlease and is not entitled to assert
            any of Sublandlord's rights thereunder against Overlandlord, whether
            in its own right or on behalf of Sublandlord.

      2.    This Consent and the Sublease shall not (i) constitute a consent or
            approval by Overlandlord of any of the terms, covenants or
            conditions of the Sublease and (except as otherwise expressly
            provided in paragraph 3 of these General Conditions), Overlandlord
            shall not be bound thereby or (ii) release Sublandlord from any
            existing or future duty, obligation or liability to Overlandlord
            pursuant to the Overlease (and Sublandlord shall be and remain
            liable for the full payment, performance and observance of all of
            the terms, covenants and conditions contained in the Overlease to be
            paid, performed and observed by the "Tenant" thereunder as if the
            Sublease and this Consent had never been made), or (iii) change,
            modify or amend the Overlease in any manner, except insofar as it
            constitutes Overlandlord's consent to the execution and delivery of
            the Sublease. Notwithstanding the generality of the foregoing, this
            Consent expressly shall not absolve Sublandlord from any requirement
            set forth in the Overlease that Sublandlord obtain Overlandlord's
            prior written approval of any additional subleases, assignments or
            other dispositions of its interest in the Overlease or the Premises
            (as defined in the Overlease).

      3.    (a) In the event of Overlease Termination (as hereinafter defined)
            prior to December 31, 2002 and provided that the Sublease has not
            theretofore been terminated, Overlandlord shall recognize Subtenant
            as Overlandlord's direct Tenant pursuant to the terms and provisions
            of the Sublease for the then remainder of the Term of the Sublease
            (through December 31, 2002) and Tenant hereby agrees to attorn to
            Overlandlord and perform Subtenant's obligations under the Sublease
            with respect to the Subleased Premises (and only as to the Subleased
            Premises) to and for the benefit of Overlandlord as the "Landlord"
            under the Sublease as a direct Lease between Overlandlord and
            Subtenant. Such agreement by Subtenant to perform each and every one
            of its obligations under the Sublease with respect to the Subleased
            Premises to and for the benefit of Overlandlord as the "Landlord"
            under the Sublease shall entitle the Subtenant to occupy the
            Subleased Premises after Overlease Termination

                                      -3-
<PAGE>

            for the then remainder of the Term of the Sublease (through December
            31, 2002) as if it were leased by Overlandlord directly to
            Subtenant, but shall not relieve Sublandlord from any liability to
            Overlandlord under the Overlease. Subtenant agrees to execute and
            deliver at any time and from time to time, upon request of
            Overlandlord, any instruments which may be necessary or appropriate
            to evidence such required assumption and Subtenant hereby
            irrevocably appoints Overlandlord as its attorney in fact, coupled
            with an interest to execute on behalf of Subtenant any documents or
            instruments necessary to evidence such assumption. Overlandlord
            shall not (i) be liable to Subtenant for any act, omission or breach
            of the Sublease by Sublandlord, (ii) be subject to any offsets or
            defenses which Subtenant might have against Sublandlord, (iii) be
            bound by any rent or additional rent which Subtenant might have paid
            in advance to Sublandlord, (iv) be bound to honor any rights of
            Subtenant in any security deposit or advance rent made with or paid
            to Sublandlord by Subtenant except to the extent Sublandlord has
            specifically assigned and turned over such security deposits and
            advance rent to Overlandlord and Overlandlord has actually received
            the same, (v) be bound by any provision of the Sublease except and
            to the extent hereinabove provided or (vi) be bound to honor any
            exercise of any Option to Extend or renew the term of the Overlease
            set forth in the Overlease, which Options to Extend or renew shall
            be deemed deleted from the Overlease effective as of the date of
            this Consent.

            Sublandlord and Subtenant hereby agree that in the event of
            Overlease Termination, Sublandlord shall immediately pay or transfer
            to Overlandlord any security deposits, rent or other sums then held
            by Sublandlord in connection with the subleasing of the Subleased
            Premises and, notwithstanding anything contained in the Sublease to
            the contrary, this shall satisfy Sublandlord's obligations to
            Subtenant under this Sublease with respect to any such sums paid
            over or transferred to Overlandlord. Such security deposit may be
            applied by Overlandlord pursuant to the terms of the Overlease in
            the event of any holding over or other default by the Subtenant
            after an Overlease Termination. Subtenant hereby agrees that under
            no circumstances whatsoever shall Overlandlord be held in any way
            responsible or accountable for any security deposit or any sums paid
            by Subtenant to Sublandlord unless and until and to the extent that
            Overlandlord has actually received such sums from Sublandlord and
            has acknowledged their source, and Subtenant shall have no claim to
            any security or other deposit made by Sublandlord under the
            Overlease.

            (b) "Overlease Termination" means the termination or cancellation of
            the Overlease prior to December 31, 2002 due to: (1) a default
            continuing beyond any applicable notice and/or cure periods by
            Sublandlord under the Overlease or any of the terms and provisions
            hereof; (2) foreclosure proceedings brought by the holder of any
            mortgage or trust deed to which the Overlease is subject; and (3)
            the termination of Sublandlord's leasehold estate by dispossession
            proceedings. Provided, however, that notwithstanding the foregoing
            to the contrary, termination of the Overlease in accordance with its
            terms prior to December 31, 2002 as the

                                      -4-
<PAGE>

            result of fire, casualty, the exercise of the power of eminent
            domain or actions taken in lieu thereof or pursuant thereto or any
            other reason or cause not enumerated in (1), (2), or (3) above shall
            not be deemed an "Overlease Termination" for purposes of this
            paragraph 3 of this Consent.

      4.    In addition to Overlandlord's rights under Section 3 hereof, in the
            event Sublandlord is in default under any of the terms and
            provisions of the Overlease continuing beyond any applicable notice
            and/or cure periods, Overlandlord may elect to receive directly from
            Subtenant all sums due or payable to Sublandlord by Subtenant
            pursuant to the Sublease, and upon receipt of Overlandlord's notice,
            Subtenant shall thereafter pay to Overlandlord any and all sums
            becoming due or payable under the Sublease and Sublandlord shall
            receive from Overlandlord a credit for such sums actually received
            by Overlandlord against any and all payments then owing from
            Sublandlord under the Overlease. Except as otherwise expressly
            provided in paragraph 3 of this Consent with respect to an Overlease
            Termination, neither the mere service of such written notice nor the
            receipt of such direct payments shall cause Overlandlord to assume
            any of Sublandlord's duties, obligations and/or liabilities under
            the Sublease, nor shall such event impose upon Overlandlord the duty
            or obligation to honor the Sublease, nor subsequently to accept any
            purported attornment by Subtenant except and to the extent of the
            occurrence of an Overlease Termination as aforesaid. Sublandlord
            grants Overlandlord a security interest in all such payments due to
            Sublandlord from Subtenant, which security interest Overlandlord may
            perfect by filing a UCC-1 (which Sublandlord shall sign within three
            (3) days of Overlandlord's request). Overlandlord shall credit
            payments actually received pursuant to this conditional assignment
            to Sublandlord's obligations under the Overlease. Without limitation
            of the foregoing, acceptance of rent or other payments from
            Sublandlord and/or Subtenant by Overlandlord shall not: (i)
            constitute a waiver of any default or breach of the Overlease or
            (ii) cause nor result in a reinstatement of the Overlease after
            Overlease Termination or (iii) absent the occurrence of an Overlease
            Termination, be deemed or construed to mean that Overlandlord has
            accepted the Subtenant as its "Tenant" under the Overlease or (iv)
            absent the occurrence of an Overlease Termination, be deemed to mean
            that Subtenant is entitled to any rights under the Sublease or the
            Overlease.

      5.    Subtenant hereby acknowledges that it has read and has knowledge of
            all of the terms, provisions, rules and regulations of the Overlease
            and agrees not to do or omit to do anything which would cause
            Sublandlord to be in breach of the Overlease. Any such act or
            omission by Subtenant also shall constitute a breach of the
            Overlease and this Consent by Sublandlord shall entitle Overlandlord
            to recover any damage, loss, cost, or expense which it thereby
            suffers, from Sublandlord and/or Subtenant, who shall be jointly and
            severally liable to Overlandlord in this regard.

      6.    In the event of the commencement of an action at law or in equity by
            the filing of a complaint or other similar action involving a
            request for relief from a judicial body between or involving the
            parties hereto with respect to the Sublease, the Overlease, this
            Consent or the rights of the parties

                                      -5-
<PAGE>

            hereto, hereunder or thereunder, the Sublandlord and Subtenant,
            jointly and severally, hereby agree to pay the Overlandlord on
            demand all reasonable costs, expense and attorneys' fees incurred
            therein by Overlandlord, which amounts may be included as a part of
            a judgment rendered therein.

      7.    The parties acknowledge that the Sublease constitutes the entire
            agreement between Sublandlord and Subtenant with respect to the
            subject matter thereof, and that no amendment, termination,
            modification or change therein will be binding upon Overlandlord
            unless Overlandlord shall have given its prior written consent
            thereto, which consent may be granted or denied by Overlandlord in
            its sole and absolute discretion.

      8.    This Consent shall be binding upon and shall inure to the benefit of
            the parties' respective successors in interest and assigns, subject
            at all times, nevertheless, to all agreements and restrictions
            contained in the Overlease, the Sublease, and herein, with respect
            to subleasing, assignment or other transfer and the foregoing shall
            not be deemed to limit or negate Overlandlord's rights to prohibit
            or condition its consent to a future dispossession of Sublandlord's
            or Subtenant's interests. The agreements contained herein constitute
            the entire understanding between parties with respect to the subject
            matter hereof and supersede all prior agreements.

      9.    This Consent shall not be assignable and shall only apply with
            respect to the Sublease by and between Sublandlord and Subtenant.

      10.   The consent by Overlandlord to the use and occupancy of the
            Subleased Premises by Subtenant shall not be construed as a consent
            by Overlandlord to the use and occupancy of the Subleased Premises
            by anyone other than Subtenant or Sublandlord or as a consent to
            further subletting by Sublandlord or by Subtenant of the Subleased
            Premises, or any part thereof. Neither the Sublease nor any of the
            rights, privileges or obligations thereunder shall be assigned,
            modified, renewed or extended, nor shall the Subleased Premises, or
            any part thereof, be further sublet or occupied by others (except by
            Sublandlord, in accordance with and subject to the terms and
            provisions of the Overlease).

      11.   Subject to the provisions of General Condition numbered 3 of this
            Consent to Sublease, unless previously terminated, on or before the
            day immediately preceding the date of expiration of the Overlease or
            upon the date of any earlier termination of the term of the
            Overlease, the Sublease and its term shall expire, terminate and
            come to an end and Sublandlord shall cause Subtenant to vacate and
            surrender the Subleased Premises on or before such date in
            accordance with the applicable provisions of the Overlease regarding
            surrender and delivery of the Premises to Overlandlord.

      12.   Sublandlord and Subtenant hereby acknowledge and agree that
            Overlandlord shall not be responsible for any brokers commissions or
            fees of any kind or nature in connection with the Sublease or the
            subject matter thereof (except for any commissions or fees due and
            payable to Trammell

                                      -6-
<PAGE>

                          FIRST AMENDMENT TO LEASE AND
                         TEMPORARY EXPANSION AGREEMENT

      This First Amendment to Lease and Temporary Expansion Agreement (the
"First Amendment") is dated as of November 21, 2000 by and between BCIA New
England Holdings LLC, a Delaware limited liability company ("Landlord") and
Sonus Networks, Inc. ("Tenant").

                                   RECITALS:

      WHEREAS, Landlord and Tenant are the Landlord and Tenant, respectively
under and pursuant to that certain Lease, dated as of September 30, 2000 (the
"Lease") demising approximately 33,194 square feet of rentable area (the
"Original Premises") in the building (the "Building") known as 25 Porter Road,
Littleton, Massachusetts; and

      WHEREAS, Landlord and Tenant (subject to entering into this First
Amendment) desire to (a) expand the Premises demised under the Lease to include
an additional 9,073 rentable square feet of space located on the first (1st)
floor of the Building and marked on Exhibit A to this First Amendment as the
"Expansion Space" (the "Expansion Space") beginning as of the Expansion Date (as
hereafter defined) and ending on September 30, 2003 (the period of time
beginning on the Expansion Date and expiring on September 30, 2003 being
hereafter the "Expansion Space Term") and (b) to make certain other
modifications to the Lease;

      NOW THEREFORE, in consideration of the mutual covenants herein contained,
and for other good and valuable consideration, the receipt and legal sufficiency
of which are hereby acknowledged, Landlord and Tenant hereby agree as follows:

      1. Capitalized Terms. All capitalized terms not otherwise modified or
defined herein shall have the same meanings as are ascribed to them in the
Lease.

      2. Expansion: Condition of the Premises. Tenant acknowledges and agrees
that Tenant is presently in occupancy of the Original Premises and that Tenant
is accepting the Original Premises in its "as is" condition as of the date
hereof and is accepting the Expansion Space in its then "AS IS" condition, as of
the Expansion Date without representation or warranty of any kind by Landlord
(express or implied). Except as otherwise expressly provided herein, Landlord
shall not be required to make nor pay for any alterations or improvements to the
Original Premises and/or the Expansion Space in order to prepare same for
Tenant's use or occupancy.

      The "Expansion Date" shall be the last to occur of (i) December 1, 2000 or
(ii) that date upon which Landlord delivers possession and control of the
Expansion Space to Tenant regardless, in either of such cases, of whether or not
all or any portion of Tenant's Work (as hereafter defined) is completed. Tenant
acknowledges and agrees that Tenant shall have no right to enter, nor any rights
of any kind with respect to the Expansion Space unless and until the occurrence
of the Expansion Date. (Provided, however, in the event the Existing Tenant (as
hereafter defined) shall vacate the Expansion Space prior to November 30, 2000
and shall give Tenant and Landlord its express written consent to permit Tenant
to enter the Expansion Space prior to December 1, 2000 in order to perform
Tenant's Work, Tenant shall be Permitted to enter the Expansion Space as of the
earlier date consented to by the Existing Tenant solely for the
<PAGE>

limited purposes of performing Tenant's Work approved in advance by Landlord in
accordance with this First Amendment. Tenant shall deliver to Landlord a copy of
the Existing Tenant's consent prior to entering the Expansion Space for the
limited purposes herein provided). Tenant acknowledges and agrees that the
Expansion Space is presently leased to a third party (the "Existing Tenant") and
Landlord shall have no obligation to deliver the Expansion Space to Tenant
hereunder unless and until Landlord and the Existing Tenant have entered into
and delivered a mutually agreeable Amendment to the Existing Tenant's Lease
whereby the Expansion Space is excluded from the Existing Tenant's premises and
the Existing Tenant shall vacate and deliver the Expansion Space to Landlord.
Landlord has entered into negotiations with the Existing Tenant pursuant to
which Landlord believes (but does not warrant or represent to Tenant) that the
existing Tenant will vacate and deliver up the Expansion Space to Landlord on or
before November 30, 2000.

      Except for Landlord's obligation to fund the "Allowance" (as hereafter
defined) as that obligation is limited and conditioned by the terms hereof,
Landlord shall not be required to make or pay for any improvements to the
Original Premises nor to the Expansion Space in order to prepare same for
Tenant's use and occupancy.

      As and to the extent that Tenant wishes to make alterations or
improvements in and to the Original Premises and/or the Expansion Space,
Landlord has agreed, subject to the conditions and limitations hereafter set
forth, to provide Tenant with an allowance (the "Allowance") in an amount not to
exceed $27,219.00 ($3.00 per rentable square foot contained in the Expansion
Space) in order to help defray the costs of such improvements desired by Tenant
in and to the Original Premises and/or the Expansion Space (such work being the
"Tenant's Work"). The Allowance shall be paid and released to Tenant from time
to time (but not more often than once in any 30 day period) as Tenant's Work is
completed and in place but only upon satisfaction of the Allowance Release
Conditions (as hereafter defined) for and with respect to Tenant's Work
completed and for which Tenant has satisfied the Allowance Release Conditions on
or before March 31, 2001. It is agreed and understood that Landlord shall be
entitled to retain any portion of the Allowance not required to reimburse Tenant
for Tenant's Work completed within the time and manner herein provided.

      Any and all Tenant's Work shall be performed by Tenant, at Tenant's sole
cost and expense in accordance with the provisions of Article V and all other
provisions of this Lease applicable to "Alterations" as if the Tenant's Work
were "Alterations" as defined in Section 5.2 and all other applicable provisions
of the Lease relating to work, alterations or improvements made by or at the
request of Tenant. Prior to commencing any aspect of Tenant's Work, Tenant shall
first submit to Landlord detailed plans and specifications describing the
Tenant's Work to be performed for Landlord's approval.

      No portion of the Allowance may be used for moving expenses, data and
telecommunications systems, wiring, or furniture. A portion of the Allowance may
be used for architectural and engineering fees sustained in connection with the
planning and design of the Premises (including the Expansion Space) for Tenant's
use. As used herein, the term "Allowance Release Conditions" shall mean (i) that
no default by Tenant shall exist and be continuing (ii) that the applicable
Tenant's Work for which reimbursement is sought has been completed in accordance
with the plans and specifications so approved by Landlord in advance and Tenant
shall have provided Landlord with a written request for payment for such
completed Tenant's

                                      -2-
<PAGE>

Work and (iii) Tenant shall have provided Landlord with true and accurate copies
of all permits and/or approvals (if any) required for the performance and
completion of the applicable Tenant's Work (including, without limitation, if
applicable, building permits and demolition permits) or other governmental
approvals, (iv) Tenant shall deliver to Landlord lien waivers from Tenant's
contractors or workmen performing such work, (v) copies of all relevant invoices
for such work with detailed breakdown of all work performed, accompanied by
copies of Tenant's cancelled checks indicating that all such work evidenced by
such invoices has been paid in full and (vi) a certificate from Tenant or
Tenant's architect (if any) certifying that such work has been completed on or
before March 31, 2001 in compliance with the Plans and specifications so
approved by Landlord.

      Upon satisfaction of all of the Allowance Release Conditions with respect
to Tenant's Work and upon the written request of Tenant (but not more often than
once in any thirty day period), Landlord shall advance corresponding portions of
the Allowance based upon the paid invoices for Tenant's Work then completed;
provided, however, that in no event shall Landlord be required to advance any
portion of the Allowance for which the Allowance Release Conditions are not
satisfied on or before March 31, 2001.

      3, Amendments Effective as of Expansion Date. Effective as of the
Expansion Date, the Lease shall be deemed further amended in the following
respects for the period of the Expansion Space Term (and only during the
Expansion Space Term):

      (a) Premises. The definition of the term "Premises" shall be deemed
      amended to include the approximately 9,073 rentable square feet of space
      on the first (1st) floor of the Building and contained in the Expansion
      Space. During the Expansion Space Term (and only during the Expansion
      Space Term) the Premises shall contain approximately 42,267 rentable
      square feet of space and shall be comprised of the Original Premises
      (33,194 rsf) and the Expansion Space (9,073 rsf). Upon expiration of the
      Expansion Space Term, the Premises shall revert back to consisting merely
      of the Original Premises.

      (b) Basic Rent. The Basic Rent payable under the Lease during the
      Expansion Space Term shall be increased and adjusted by the amount of the
      Expansion Rent (as hereafter defined). The Expansion Rent shall be paid in
      addition to the portion of the Basic Rent set forth in Section 1.1 of the
      Lease. The Expansion Rent shall be payable beginning on the Expansion Date
      (pro-rated for any partial calendar month) and shall thereafter be paid as
      and when all other payments of Basic Rent are payable under this Lease
      without offset, deduction, set-off, abatement or demand.

      As used herein, the term "Expansion Rent" shall mean $199,606.00 per annum
      payable in equal monthly installments of $16,633.83 (pro rated and
      adjusted for any partial month). The Expansion Rent shall not be payable
      with respect to the period following expiration of the Expansion Space
      Term and the Basic Rent set forth in Section 1.1 of the Lease alone shall
      thereafter comprise the Basic Rent payable under this Lease.

      (c) Tenant's Proportionate Share. The Tenant's Proportionate Share shall
      be increased and adjusted to be 63.27% during the Expansion Space Term.
      Upon expiration of the Expansion Space Term, the term "Tenant's
      Proportionate Share" shall revert back to 49.69%.

                                      -3-
<PAGE>

      Unless this Lease is sooner terminated in accordance with its terms, upon
      expiration of the Expansion Space Term, Tenant shall remove its property
      and vacate, surrender and deliver up the Expansion Space to Landlord in
      the condition and manner required by Section 12.2 of the Lease with
      respect to surrender and delivery of the Premises to Landlord as if the
      last day of the Expansion Space term were the last day of the Term of this
      Lease with respect to the Expansion Space (and only as to the Expansion
      Space). The provisions of Section 12.1 and 12.2 of the Lease shall apply
      in the event Tenant shall fail to comply with the requirements of the
      immediately preceding sentence.

      4. Brokerage. Each party hereto represents and warrants to the other party
that it has not dealt with any real estate broker or agent in connection with
this First Amendment, except for Trammell Crow Company (the "Broker"). Each
party hereto shall indemnify the other party and hold the other party harmless
from any cost, expense or liability (including costs of suit and reasonable
attorney's' fees) for any compensation, commission or fees claimed by any other
real estate broker or agent in connection with this First Amendment or the
Amended Lease or the negotiation thereof by reason of any of their acts.
Landlord shall be responsible for any brokerage commission due the Broker in
connection with this First Amendment or the amended Lease solely pursuant to
Landlord's direct agreements with Broker.

      5. Governing Law. This First Amendment and the rights and obligations of
both parties hereunder shall be governed by the laws of The Commonwealth of
Massachusetts.

      6. Authority. Tenant warrants that the person or persons executing this
First Amendment on behalf of Tenant has the authority to do so and that such
execution has fully obligated and bound Tenant to all terms and provisions of
this First Amendment.

      7. Ratification. Except as modified by this First Amendment, the Lease is
in full force and effect and Landlord and Tenant ratify and confirm the same.

      8. Interpretation and Partial Invalidity. If any term of this First
Amendment, or the application thereof to any person or circumstances, shall to
any extent be invalid or unenforceable, the remainder of this First Amendment,
or the application of such term to persons or circumstances other than those as
to which it is invalid or unenforceable, shall not be affected thereby, and each
term of this First Amendment shall be valid and enforceable to the fullest
extent permitted by law. The titles for the paragraphs are for convenience only
and not to be considered in construing this First Amendment.

                           [Signatures on next page]

                                      -4-
<PAGE>

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

                               LANDLORD:

                               BCIA NEW ENGLAND HOLDINGS LLC, a Delaware limited
                               liability company

                               By: BCIA NEW ENGLAND HOLDINGS MASTER LLC, a
                                   Delaware limited liability company, its
                                   Manager

                                   By: BCIA NEW ENGLAND HOLDINGS MANAGER LLC,
                                       a Delaware limited liability company, its
                                       Manager

                                       By: BCIA NEW ENGLAND HOLDINGS MANAGER
                                           CORP., a Delaware corporation, its
                                           Manager

                                           By: /s/ Karl W. Weller
                                               ---------------------------------
                                              Name:  KARL W. WELLER
                                              Title: EXECUTIVE VICE PRESIDENT

                               TENANT:

                               Sonus Networks, Inc.

                               By:   /s/ S.J. Nill
                                   ---------------------------------------------
                                   Name:

                               Its:  VP & CFO
                                   ---------------------------------------------

BCIA 21

                                      -5-

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