<PAGE>   1




                ------------------------------------------------
                              AMENDED AND RESTATED

                AGREEMENT AND CERTIFICATE OF LIMITED PARTNERSHIP

                                       OF

                  NAHATAN STREET ASSOCIATES LIMITED PARTNERSHIP

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


                                  EXHIBIT 10.8


<PAGE>   2


                                TABLE OF CONTENTS
                                -----------------

Caption                                                                    Page
-------                                                                    ----

     RECITALS.                                                                1
     --------

ARTICLE ONE
-----------

     DEFINITIONS
     -----------

     Section 1.1   Definitions                                                1 

ARTICLE TWO
-----------

     GENERAL PROVISIONS
     ------------------

     Section 2.1   Formation                                                  6
     Section 2.2   Name and Office                                            6
     Section 2.3   Purpose and Scope                                          7
     Section 2.4   Term                                                       7
     Section 2.5   General Partners                                           7
     Section 2.6   Limited Partners                                           7
     Section 2.7   Resident Agent                                             7
     Section 2.8   Tax Matters Partner                                        7

ARTICLE THREE
-------------

     CAPITAL CONTRIBUTIONS; PARTNERSHIP INTERESTS; CAPITAL ACCOUNTS
     --------------------------------------------------------------

     Section 3.1   Initial Capital Contributions of the General Partners;   
                   Partnership Interests of the General Partners              8
     Section 3.2   Initial Capital Contributions of the Limited Partners;   
                   Partnership Interests of the Limited Partners              8
     Section 3.3   Additional Capital Requirements                            9
     Section 3.4   Capital Accounts                                          12
     Section 3.5   Special Deemed Capital Account                            13
     Section 3.6   Partnership Capital                                       14
     Section 3.7   Liability of Limited Partners                             15
                                                                           
ARTICLE FOUR
------------

     ALLOCATION OF PROFITS AND LOSSES; DISTRIBUTIONS
     -----------------------------------------------

     Section 4.1   Allocation of Profits and Losses                          15
     Section 4.2   Distributions                                             16
     Section 4.3   Distributions in Connection with Dissolution              17

ARTICLE FIVE
------------

     RIGHTS, POWERS, AND DUTIES OF THE GENERAL PARTNERS
     --------------------------------------------------

     Section 5.1   Management and Control of the Partnership                 17
     Section 5.2   Authority of the General Partners                         18
     Section 5.3   Restrictions on Authority of the General Partners         20



<PAGE>   3





     Section 5.4   Duties and Obligations of the General Partners            21
     Section 5.5   Authority of the General Partners to Deal With
                   Affiliates                                                21
     Section 5.6   Compensation of Partners                                  22
     Section 5.7   Other Interests of the General Partners
                   and Their Affiliates                                      23
     Section 5.8   Rights to Income or Profits                               23
     Section 5.9   Liability and Indemnification of the
                   General Partners                                          23

ARTICLE SIX
-----------

     TRANSFERABILITY OF A GENERAL PARTNER'S INTEREST
     -----------------------------------------------

     Section 6.1   Voluntary Retirement or Transfer by a
                   General Partner                                           23
     Section 6.2   Reconstitution of the Partnership                         25
     Section 6.3   Admission of a Person as the Substitute
                   General Partner                                           25
     Section 6.4   Restrictions on Transfer by a General Partner             26
     Section 6.5   Liability and Rights of a Retired or Transferor
                   General Partner                                           26

ARTICLE SEVEN
-------------

     TRANSFERABILITY AND ACQUISITION OF A LIMITED PARTNER'S INTEREST
     ---------------------------------------------------------------

     Section 7.1   Representations of Limited Partners                       26
     Section 7.2   Restrictions on Transfer of Interests                     26
     Section 7.3   Incapacity of a Limited Partner                           27
     Section 7.4   Transferees                                               27
     Section 7.5   Substitute Limited Partners                               28
     Section 7.6   Right of First Refusal                                    28
                                                                           
ARTICLE EIGHT
-------------

     DISSOLUTION,LIQUIDATION, AND TERMINATION OF THE PARTNERSHIP
     -----------------------------------------------------------

     Section 8.1   Events Causing Dissolution                                29
     Section 8.2   Liquidation                                               29

ARTICLE NINE
------------

     FISCAL MATTERS
     --------------

     Section 9.1   Title to Property and Bank Accounts                       30
     Section 9.2   Books and Records                                         30
     Section 9.3   Reports and Accountant                                    31
     Section 9.4   Federal Tax Elections                                     31
                                                                          


<PAGE>   4


ARTICLE TEN
-----------

     MEETINGS AND VOTING R1GHTS OF LIMITED PARTNERS
     ----------------------------------------------

     Section 10.1  Meetings                                                  32
     Section 10.2  Voting Rights of Limited Partners                         33
     Section 10.3  Conditions to Action by Limited Partners                  33
                                                                          
ARTICLE ELEVEN
--------------

     AMENDMENTS
     ----------

     Section 11.1  Adoption of Amendments                                    34
     Section 11.2  Amendments on Admission or Substitution                  
                   of Partners                                               34
                                                                           
ARTICLE TWELVE
--------------

     VALUATION AND APPRAISAL PROCEDURE
     ---------------------------------

     Section 12.1  General                                                   35
     Section 12.2  Appraisal Procedure                                       35

ARTICLE THIRTEEN
----------------

     MISCELLANEOUS PROVISIONS
     ------------------------

     Section 13.1  Appointment of Each General Partner
                   as Attorney-in-Fact                                       39
     Section 13.2  Notices, Approvals, and Consents                          41
     Section 13.3  Binding Provisions                                        41
     Section 13.4  Applicable Law                                            41
     Section 13.5  Entire Agreement                                          41
     Section 13.6  Further Assurances                                        41
     Section 13.7  Captions                                                  41
     Section 13.8  Effect on Creditors                                       42
     Section 13.9  Separability                                              42
     Section 13.10 Counterparts                                              42
     Section 13.11 Jurisdiction                                              42
     Section 13.12 Attorneys' Fees                                           42


SCHEDULE A:      Initial Capital Contributions and 
                 Initial Capital Accounts
EXHIBIT A:       Limited Partners
EXHIBIT B:       BNE Lease
EXHIBIT C:       Description of Land
EXHIBIT D:       TIAA Lease


<PAGE>   5


                  NAHATAN STREET ASSOCIATES LIMITED PARTNERSHIP

                       A Massachusetts Limited Partnership

      AMENDED AND RESTATED AGREEMENT AND CERTIFICATE OF LIMITED PARTNERSHIP
      ---------------------------------------------------------------------

     THIS AMENDED AND RESTATED AGREEMENT OF LIMITED PARTNERSHIP, made and
entered into as of the day of August, 1985, by and between JAMES F. CARLIN
("Carlin") and WILLIAM A. YETMAN ("Yetman"), as General Partners, and the
Persons listed on Exhibit A attached hereto, as Limited Partners.

                                    RECITALS:
                                    ---------

     A. Richard R. Vazza and Nahatan Street Development Corporation, as general
partners, and Telco Systems Fiber Optics Corporation ("TSFOC"), as limited
partner, created a limited partnership under the name "Nahatan Street Associates
Limited Partnership" pursuant to an Agreement of Limited Partnership dated
August 8, 1985 (the "Original Agreement"). Francis M. Vazza was; later admitted
to the Partnership as an additional general partner. (Richard R. Vazza, Francis
M. Vazza and Nahatan Street Development Corporation are! hereinafter referred to
collectively as "Vazza").

     B. The interest of TSFOC in the Partnership is, effective herewith$
assigned to its affiliate, Telco Systems, Inc. ("Telco").

     C. The interests of Vazza in the Partnership are, effective herewith,
redeemed by the Partnership.

     D. The Partnership wishes to admit certain individuals (the "Crosspoint
Group") to the Partnership as Partners.

     E. The purpose and effect of this document is to amend and restate the
Original Agreement so as to provide for the continuation of the Partnership on
the terms herein set forth and, therefore, to simultaneously (i) remove TSFOC
(the original Limited Partner) and admit Telco as a Limited Partner, (ii) remove
Vazza as General Partners and (iii) admit the Crosspoint Group as General
Partners and Limited Partners as herein set forth.

     NOW, THEREFORE, in consideration of the premises and the agreements herein
contained and intending to be legally bound hereby, the Partners hereby agree as
follows:

                                   ARTICLE ONE
                                   -----------

                                   DEFINITIONS
                                   -----------

Section 1.1  Definitions
             -----------

     For purposes of this Agreement, the following terms and phrases shall have
the meanings specified in this Article One. The singular shall include the


<PAGE>   6


plural, and the masculine gender shall include the feminine and neuter. and vice
versa, as the context requires:

          "ACCOUNTANT". Arthur Young & Co., or such other independent
     accountants as shall be designated from certified public accountant or firm
     of independent certified pubic Interest of the Partners. time to time by a
     Majority in

          "ACT ". The Massachusetts Uniform Limited Partnership Act, as; the
     same may hereafter be amended.

          "AFFILIATE". With respect to any specified Person, any other Person
     directly or indirectly controlling or controlled by or under direct or
     indirect common control with such specified Person. For the purposes of
     this definition, the term CONTROL when used with respect to any specified
     Person means the power to direct the management and policies of such
     Person, directly or indirectly, whether through the ownership of voting
     securities, by contract or otherwise; and the terms CONTROLLING and
     controlled by have the meanings correlative to the foregoing.

          "AGREEMENT". This Amended and Restated Agreement and Certificate of
     Limited Partnership of Nahatan Street Associates Limited Partnership, as
     the same may be amended from time to time.

          "BASE RATE". The highest annual prime rate of interest charged from
     time to time by The First National Bank of Boston to its prime commercial
     customers for 90-day unsecured loans, plus two percent (2%).

          "BNE FINANCING". The interim financing with respect to the Premises to
     be provided to the Partnership by Bank of New England pursuant to its
     commitment letter of May 6, 1985.

          "BNE LEASE". The lease of the Premises, dated 1985, between the
     Partnership, as landlord, and TSFOC, as tenant, pursuant to the terms of
     the BNE Financing, in the form attached hereto as Exhibit B. The BNE Lease
     is to commence upon the closing of the BNE Financing and is to terminate
     upon the closing of the TIAA Financing.

          "BUILDING". The former Masoneilan building situated on the Land which
     is undergoing construction/renovation and which is to be substantially
     constructed/renovated by the Partnership. Upon Building Completion, the
     Building will be a one and two-story steel frame and brick office,
     research/development and light assembly building containing approximately
     216,000 rentable square feet.

          "BUILDING COMPLETION". Substantial completion of the construction/
     renovation of the Building as certified by the architect for the Building.

          "CAPITAL ACCOUNT". The account of each Partner on the books of the
     Partnership as defined in Section 3.4.

          "CAPITAL CONTRIBUTION". The cash and/or property contributed to the
     Partnership by each Partner.

                                        2


<PAGE>   7


          "CERTIFICATE". The Certificate of Limited Partnership of the
     Partnership as provided for in the Act. as originally filed in the Office
     of the Secretary of State of the State and as amended from time to time.

          "CODE". The Internal Revenue Code of 1954, as amended.

          "CONSENT". The consent of a Person to do the act or things for which
     the consent is solicited, or the act of granting such consent.

          "CROSSPOINT GROUP". All Partners of the Partnership other than Telco.

          "DISTRIBUTABLE CASH". With respect to any Fiscal Year of the
     Partnership, the excess of the Revenues (other than Excess Rent and other
     than proceeds arising from an Excess Cash Proceeds Event) of the
     Partnership during such Fiscal Year over the sum of:

          (i) the amount of cash (other than cash withdrawn from reserves
     therefor) disbursed in such Fiscal Year (a) to make payments then due on
     accrued liabilities and obligations of the Partnership including those
     related to advances or loans to the Partnership and/or (b) to pay other
     costs and expenses incident to the redemption of the Vazza Interests and
     the construction/renovation of the Building and other improvements on the
     Land, and the development, operation and management of the Premises and the
     Partnership business; and

          (ii) amounts allocated during such Fiscal Year to reserves to pay
     costs, expenses or liabilities of the type described in clause (i) for
     which the General Partners do not expect the Partnership to receive the
     necessary cash prior to the time such payments are required to be made.

          "DISTRIBUTIONS". Payments of cash and distributions of property by the
     Partnership to the Partners, or any of them.

          "EXCESS CASH PROCEEDS". This term shall mean (i) with respect to any
     financing or refinancing (other than the BNE Financing or the TIAA
     Financing) affecting the Premises (or any portion thereof), the net amount
     of cash realized by the Partnership; and (ii) with respect to insurance
     proceeds from loss, to condemnation proceeds, and to proceeds from the
     Transfer of Partnership assets, the amount by which such proceeds exceed
     reserves for known liabilities incurred, and contingent liabilities arising
     out of the transaction giving rise to such proceeds, as reasonably
     determined by the General Partners, except that if the General Partners
     reasonably determine that any such reserve is no longer necessary, then
     such reserve shall be deemed Excess Cash Proceeds and shall be distributed
     as if included in Excess Cash Proceeds initially. "EXCESS CASH PROCEEDS
     EVENT" means an event of the type described in (i) or (ii) above, whether
     or not Excess Cash Proceeds are generated therefrom.

          "EXCESS RENT". With respect to any Fiscal Year of the Partnership, the
     difference, if any, between (i) the total amount of the debt service
     (principal, if any, and interest) required to be paid during such Fiscal
     Year with respect to the TIAA Financing and (ii) the total amount of
     absolutely net rent received by the Partnership during such FiscaL Year
     pursuant to the TIAA Lease.

                                        3


<PAGE>   8


          The term Excess Rent only has relevance with respect to the first ten
     (lo) years of the TIAA Lease. Accordingly, for example, there will be no
     Excess Rent - that is, the amount of Excess Rent will be zero --- with
     respect to any Fiscal Year or portion thereof subsequent to the occurrence
     of any one or more of the following events: (i) the commencement of the
     eleventh -year of the term of the TIAA Lease; and (ii) the sale or other
     disposition of the Premises. Furthermore, Excess Rent shall be subject to
     reduction or set-off as more particularly set forth in the TIAA Lease.

          "FISCAL YEAR". The calendar year, except that in the year the
     Partnership commences or terminates, the Fiscal Year shall begin on the
     date of such commencement or end on the date of such termination, as the
     case may be.

          "GENERAL PARTNERS". Carlin and Yetman, and any successor general
     partners admitted to the Partnership pursuant to this Agreement, in each
     such Person's capacity as a General Partner of the Partnership.

          "INCAPACITY" OR "INCAPACITATED". These terms shall meant as to any
     Person, the bankruptcy, insolvency, dissolution or termination, as the case
     may be, of such Person. With respect to any Person who is an individual,
     these terms shall mean, in addition to the foregoing, the death or
     adjudication of incompetence or insanity of such Person. "BANKRUPTCY" or
     "INSOLVENCY" shall be deemed to have occurred (i) if a Person shall become
     unable to pay his debts as they fall due, or shall make an assignment for
     the benefit of creditors, or shall file a voluntary petition in bankruptcy
     or shall be adjudicated a bankrupt or insolvent, or shall file any petition
     or answer seeking, consenting to, or acquiescing in, any reorganization,
     arrangement, composition readjustment, liquidation, 'dissolution or similar
     relief under any present or future applicable statute or law, or shall seek
     or consent to or acquiesce in the appointment of any trustee, receiver or
     liquidator of such Person or of all or any substantial part of his
     properties, or (ii) if within thirty (30) days after the commencement of
     any proceeding against a Person, seeking any reorganization, arrangement,
     composition, readjustment, liquidation, dissolution or similar relief under
     any present or future applicable statute or law, such proceeding shall not
     have been dismissed, or if, within thirty (30) days after the appointment,
     without the consent or acquiescence of such Person, of any trustee,
     receiver or liquidator of such Person or of all or any substantial part of
     his properties, such appointment shall not have been vacated or stayed on
     appeal or otherwise, or if, within thirty (30) days after the expiration of
     any such stay, such appointment shall not have been vacated.

          "INTEREST". The ownership interest (or any portion thereof) of a
     Partner in the Partnership at any particular time. A Partner's Interest in
     the Partnership shall be considered personal property for all purposes.

          "LAND". The parcel of land containing approximately twenty-five (25)
     acres and more particularly described in Exhibit C attached hereto, on
     which the Building and other improvements are situated.

          "LIMITED PARTNER". Any one of the Limited Partners listed on Exhibit A
     attached hereto, and their respective successors and assigns admitted to

                                        4


<PAGE>   9


the Partnership as Substitute Limited Partners pursuant to this Agreement, in
each such Person's capacity as a Limited Partner of the Partnership.

          "MAJORITY IN INTEREST". Partners (General Partners and/or Limited
     Partners, as the context evidences) who in the aggregate own, at the time
     in question. a majority of the particular Partnership Interests at issue,
     determined on an aggregate percentage interest basis. The term "SUBSTANTIAL
     MAJORITY IN INTEREST" means such Partners who in the aggregate own, at the
     time in question, at least seventy-five percent (75%) of the particular
     Partnership Interests at issue, determined on an aggregate percentage
     interest basis.

          "PARTNER". Any Person who is a General Partner or a Limited Partner of
     the Partnership as herein provided; and "PARTNERS" means collectively the
     Persons who are the General Partners and the Limited Partners.

          "PARTNERSHIP". The limited -partnership of Nahatan Street Associates
     Limited Partnership, as continued in accordance with this Agreement and as
     said limited partnership may from time to time be constituted.

          "PERSON". An individual, corporation. company, voluntary association,
     partnership, trust, unincorporated organization, or government or any
     agency, instrumentality, or political subdivision thereof.

          "PREMISES". The Land together with the Building and other improvements
     thereon.

          "PROFITS AND LOSSES". The net income or loss of the Partnership for a
     Fiscal Year as determined for federal income tax purposes, including all
     items of Partnership income, gain, loss, deduction, credit or the like, and
     any gain or loss from an Excess Cash Proceeds Event. The separate terms
     "Profits" and "Losses" shall mean such net income or loss respectively.

          "REVENUES". This term shall mean (i) gross receipts of the Partnership
     from whatever source, exclusive of loans or advances to the Partnership or
     Capital Contributions by the Partners and (ii) to the extent not included
     in (i) above, the amount of any reserve established by the General
     Partners, which the General Partners reasonably determine need no longer be
     retained by the Partnership.

          "SPECIAL DEEMED CAPITAL ACCOUNT". This term shall have the meaning set
     forth in Section 3.5.

          "STATE". The Commonwealth of Massachusetts.

          "SUBSTITUTE LIMITED PARTNER". A Transferee of a Limited Partner's
     Interest who has been admitted to the Partnership pursuant to Sections 7.5
     and 11.2. The rights and obligations of any Substitute Limited Partner
     shall be determined by reference to the rights and obligations of the
     Transferor Limited Partner under this Agreement.

          "TELCO". Telco Systems, Inc., a California corporation which is a
     Limited Partner of the Partnership.

                                        5


<PAGE>   10


          "TIAA FINANCING". The initial permanent financing with respect to the
     Premises to be provided to the Partnership by Teachers Insurance and
     Annuity Association ("TIAA) pursuant to its commitment letter of May 29,
     1985, as amended by letter of June 25, 1985.

          "TIAA LEASE". The lease of the Premises between the Partnership, as
     landlord, and TSFOC, as tenant, pursuant to the terms of the TIAA
     Financing, in substantially the form attached hereto as Exhibit 1) but
     subject to commercially reasonable changes requested by TIAA. The TIAA
     Lease is to commence upon the termination of the BNE Lease and the closing
     of the TIAA Financing.

          "TRANSFER". This term means and includes any events action, or
     transaction which is considered a sale or exchange for federal income tax
     purposes (whether or not taxable income is recognized in connection
     therewith), or any assignment , pledge, gift, or other disposition, or the
     act of effecting any of the above.

          "TRANSFEREE". The recipient of a Transfer of a Partnership Interest.

          "TRANSFEROR". The- Partner who has made a Transfer of his Partnership
     Interest.

          "TSFOC". Telco Systems Fiber Optics Corporation, a California
     corporation which is an Affiliate of Telco.

          "U.C.C." The Uniform Commercial Code as enacted in the State, as the
     same may hereafter be amended.

          "VAZZA INTERESTS". The Interests of Richard R. Vazza, Francis M. Vazza
     and Nahatan Street Development Corporation in the Partnership, the
     redemption of which Interests by the Partnership is effective herewith.,

                                   ARTICLE TWO
                                   -----------

                               GENERAL PROVISIONS
                               ------------------

Section 2.1  Formation
             --------- 

     Pursuant to the Act, the Partners hereby constitute themselves as a limited
partnership in accordance with this Agreement. The General Partners shall
promptly amend the Certificate in such form as shall be necessary under the laws
of the State to give effect to the provisions of this Agreement.

Section 2.2 Name and Office
            ---------------

     The Partnership shall be conducted solely under the name of Nahatan Street
Associates Limited Partnership. The Massachusetts office of the Partnership is
located at 235 West Central Street, Natick, Massachusetts 01760, or such other
place in the State as the General Partners may from time to time determine and
shall specify by prior notice to the Limited Partners.

                                        6


<PAGE>   11


Section 2.3 Purpose and Scope
            -----------------

     The purpose and scope of the business of the Partnership is to
construct/renovate the Building and other improvements on the Land, and to
develop, operate, lease and/or manage the Premises. Such business purpose shall
include. the doing of any and all things incident thereto or connected
therewith.

     The Partnership shall carry out the foregoing activities pursuant to the
arrangements set forth in this Agreement.

     The Partnership shall not engage in any other business or activity without
the prior Consent of all Partners.

Section 2.4 Term
            ----

     The term of the Partnership commenced on August S. 1984, and shall continue
in full force and effect until December 31. 2015, unless sooner dissolved or
terminated as provided in this Agreement.

Section 2.5 General Partners
            ----------------

     The General Partners of the Partnership and their respective addresses are
as follows:

           James F. Carlin
           99 Woodland Street
           Natick, Massachusetts 01760

           and

           William A. Yetman
           5 Bryant Lane
           Dover, Massachusetts 02030

Section 2.6 Limited Partners
            ----------------

     The Limited Partners of the Partnership and their respective addresses are
as set forth on Exhibit A attached hereto.

Section 2.7 Resident Agent
            --------------

     The Partnership's resident agent for service of process in Massachusetts
shall be:

           Crosspoint Development Corporation
           235 West Central Street
           Natick, Massachusetts 01760

Section 2.8 Tax Matters Partner
            -------------------

     Yetman shall be the tax matters partner of the Partnership.

                                        7


<PAGE>   12


                                  ARTICLE THREE
                                  -------------

          CAPITAL CONTRIBUTIONS; PARTNERSHIP INTERESTS; CAPITAL ACCOUNT
          -------------------------------------------------------------

Section 3.1 Initial Capital Contributions of the General Partners: Partnership
            ------------------------------------------------------------------
            Interests of the General Partners
            ---------------------------------

     A.   Upon the execution of this Agreement, the General Partners shall make
          Capital Contributions to the Partnership of all their right, title and
          interest, and all of the right, title and interest of their
          Affiliates, in and to the commitments for the BNE Financing and for
          the TIAA Financing which they may now own; and the Partnership (i)
          ratifies and confirms the actions of the General Partners (including
          such actions as took place prior to the date hereof) with respect to
          such commitments and (ii) shall. undertake, assume and perform the
          obligations and duties of the General Partners and their Affiliates
          with respect to such commitments.

          The Capital Accounts of the General Partners shall not be credited in
          any amount as a result of such Capital Contributions.

          Each General Partner shall make an initial Capital Contribution in the
          amount as set forth on Schedule A attached hereto.

          The Partnership Interest of each of the General Partners shall be as
          follows: Carlin -- ten and one-quarter percent (10-1/4%); Yetman ten
          and one-quarter percent (10-1/4%).

     B.   In addition to the provisions of Subsection A of this Section 3.1, the
          General Partners may from time to time, as they deem appropriate, make
          loans to the Partnership at the Base Rate, to the extent they deem
          necessary to protect and preserve Partnership assets; provided that
          the principal amount of such loan(s) outstanding at any time shall not
          exceed ten thousand dollars ($10,000) in the aggregate! and that the
          term of each such loan shall not exceed ninety (90) days.,

     C.   Except as provided in Subsection A of this Section 3.1 and in Section
          3.3, the General Partners shall not be required to make any Capital
          Contributions or loans to the Partnership.

Section 3.2 Initial Capital Contributions of the Limited Partners;
            ------------------------------------------------------
            Partnership Interests of the Limited Partners
            ---------------------------------------------

     A.   Upon the execution of this Agreement, Telco shall cause TSFOC, its
          Affiliate, to execute and deliver the BNE Lease. Upon the termination
          of the BNE Lease, Telco shall cause TSFOC to execute! and deliver the
          TIAA Lease.

          The Capital Account of Telco shall not be credited in any amount as a
          result of the foregoing transactions.

          Each Limited Partner shall make an initial Capital Contribution in the
          amount as Set forth on Schedule A attached hereto.

                                        8


<PAGE>   13


          The Partnership Interest of each of the Limited Partners shall be as
          set forth on Exhibit A attached hereto.

     B.   Except as provided in Subsection A of this Section 3.2 and in Section
          3.3, the Limited Partners shall not be required to make any Capital
          Contributions or loans to the Partnership.

Section 3.3 Additional Capital Requirements
            -------------------------------

     A.   If from time to time during the term of the Partnership the General
          Partners reasonably determine that additional funds are required to
          meet obligations of the Partnership -- including, without imitation,
          obligations in connection with the redemption of the Vazza Interests
          and/or the construction/renovation, development, operation, leasing
          and/or management of the Premises - or to protect and preserve
          Partnership assets and if the Partnership has been unable to obtain
          such funds through Partnership borrowings, then from time to time as
          so determined and upon notice from the General Partners to all the
          Partners, the Partners shall make additional Capital Contributions to
          the Partnership of such additional funds as may be so required in cash
          and in proportion to their respective Partnership Interests.

          Notwithstanding the above provisions of this Subsection A, the
          Partners are under no obligation to make additional Capital
          Contributions to the Partnership in excess of two hundred thousand
          dollars ($200,000) in the aggregate. If, from time to time, the
          aggregate capital requirements of the Partnership are in excess of
          this limitation, the General Partners shall give notice to all
          Partners of such excess capital requirements. Such excess capital
          requirements shall be funded by Capital Contributions in accordance
          herewith only upon the Consent of all Partners; and the Consent of any
          Partner may be withheld in such Partner's absolute discretion. If any
          one or more of the Partners fail to so Consent within fifteen (15)
          days after such notice, then the General Partners shall give notice of
          this fact to the Partners; and within fifteen (15) days after such
          notice is given, any one or more of the Partners may elect to loan the
          amount of such excess capital requirements to the Partnership at the
          Base Rate plus 2%. If more than one Partner elects to make such a
          loan, then the rights and obligations of such Partners under this
          Subsection A shall be allocated between or among them in proportion to
          their respective Partnership Interests.

          The respective amounts of additional Capital Contributions shall be
          credited to the Partners' respective Capital Accounts upon payment
          thereof.

     B.   In the event that any Partner (the "Defaulting Partner") fails to pay
          to the Partnership his respective portion of the funds so required
          hereby to be paid as an additional Capital Contribution within thirty
          (30)days after receipt of notice therefor from the General Partners,
          then the Defaulting Partner shall be deemed to be in default of his
          obligation hereunder as of the thirtieth day after receipt of such
          notice.

          The General Partners shall promptly notify all Partners other than the
          Defaulting Partner of such default. Within fifteen (15) days 

                                       9


<PAGE>   14


          after such notice is given, any one or more of such Partners may elect
          either to advance the sum which the Defaulting Partner failed to pay
          in accordance with paragraph (1) of this Subsection B or to purchase
          the Partnership Interest of the Defaulting Partner in accordance with
          paragraph (2) of this Subsection B -- in each case by notifying the
          Partnership of such election. If one or more of such Partners elect
          each option, then the option as' to which Partners with the greater
          aggregate Partnership Interest elect shall be the effective option; if
          each option is elected by Partners with the same aggregate Partnership
          Interest, then the General Partners shall determine the effective
          option. If more than one of such Partners elect the effective option,
          then the rights and obligations of such Partners under this Subsection
          B shall be allocated between or among them in proportion to their
          respective Partnership Interests. The General Partners shall promptly
          notify all the Partners as to the effective option and as to which
          Partners (and their respective proportions) have elected the effective
          option.

          If no such Partner elects either option, then the Partnership may
          enforce the obligations of the Defaulting Partner at law and/or in
          equity; all fees and expenses incurred by the Partnership with respect
          to such enforcement, including reasonable attorneys' fees, shall be
          paid by the Defaulting Partner.

          For purposes of this Subsection B, such Partners electing to advance
          the sum which the Defaulting Partner failed to pay shall be
          collectively referred to as the "Advancing Partner", and such Partners
          electing to purchase the Partnership Interest of the Defaulting
          Partner shall be collectively referred to as the "Acquiring Partner".

          The options to advance or to purchase shall be upon the following
          terms and conditions:

          (1)  The Advancing Partner shall, within thirty (30) days after notice
               of default is given by the General Partners, advance! the sum
               which the Defaulting Partner failed to pay and thereupon the
               Defaulting Partner shall be obligated to repay said stun
               immediately to the Advancing Partner with interest from the date
               of said default until such sum is paid at the lesser of WI the
               highest rate of interest allowed by law or (ii) the Base Rate
               PLUS 4%.

               Each Partner hereby covenants and agrees that the Advancing
               Partner, in addition to such other rights as may be available in
               law or in equity, shall have and is hereby granted a security
               interest and lien upon the Partnership Interest of the Defaulting
               Partner to secure the payment of such indebtedness in accordance
               with the following provisions, and that the Advancing Partner
               shall have and is hereby granted all of the rights and remedies
               available to a secured party under the U.C.C. If the full amounts
               of principal and interest due the Advancing Partner are not paid
               by the Defaulting Partner within ninety (90) days after written
               demand therefor -- or, if the U.C.C. specifies a longer period,
               such longer period prior to the related action

                                       10


<PAGE>   15


               after notice of default has been given to the Defaulting Partner
               -- the Advancing Partner having such lien on the Interest of the
               Defaulting Partner shall be entitled to foreclose upon the entire
               Partnership Interest of such Defaulting Partner and enforce such
               lien by causing the Defaulting Partner,s Interest to be sold at
               public or private sale (in the manner specified in the U.C.C.) to
               satisfy such obligation.

               Without limiting the foregoing, any such lien on the Partnership
               Interest of the Defaulting Partner and the obligations secured
               thereby may be enforced by the Advancing Partner, including
               enforcement through judicial proceedings, and the Defaulting
               Partner shall execute a financing statement evidencing such lien.
               and, upon foreclosure thereof, appropriate instruments of
               transfer of the Partnership Interest subject thereto.

          (2)  The purchase price to be paid by the Acquiring Partner to the
               Defaulting Partner for the latter's Partnership Interest shall be
               an amount equal to (A) seventy-five percent (75%) of the then net
               fair market value of such Partnership Interest as determined as
               set forth in Article Twelve; less (B) the sum which the
               Defaulting Partner failed to pay and all direct expenses actually
               incurred by the Partnership in effectuating the process set forth
               in this Subsection B.

               The purchase price for such Partnership Interest shall be
               determined within five (5) business days from the date the
               General Partners receive notice of the decision of the Appraiser
               as set forth in Article Twelve, and the General Partners shall
               promptly notify all the Partners of such purchase price. The
               purchase price for such Partnership Interest shall be payable,
               without interest thereon, to the Defaulting Partner within two
               (2) months from the date the General Partners notify all the
               Partners of such purchase price.

               The Acquiring Partner, as a condition to the exercise of his
               right to purchase the Defaulting Partner's Partnership Interest
               pursuant to this Subsection B and as a condition to receiving
               such Partnership Interest, shall agree in writing to pay to the
               Partnership the sum which the Defaulting Partner failed to pay.

               The Acquiring Partner purchasing the Defaulting Partner's
               Partnership Interest pursuant to this paragraph (2) of Subsection
               B shall become the owner thereof upon payment of the purchase
               price therefor. The Acquiring Partner shall pay to the
               Partnership, within thirty (30) days from the date he acquires
               such Partnership Interest, the sum which the Defaulting Partner
               failed to pay and all direct expenses actually incurred by the
               Partnership with respect to such default.

               Notwithstanding the provisions of this paragraph (2) of
               Subsection B, the obligation of the Defaulting Partner to pay the
               sum which the Defaulting Partner failed to pay shall be
               extinguished only by, and only to the extent 'of, the actual

                                       11
<PAGE>   16


               amount of the monies received by the Partnership from the
               Acquiring Partner who has purchased the Partnership Interest of
               the Defaulting Partner hereunder.

               The Partnership Interest subject to purchase pursuant to this
               paragraph (2) of Subsection B shall include the right to
               Distributions and to the allocation of Profits and Losses
               attributable to such Interest from and after the date of default
               of the Defaulting Partner's obligation hereunder. From and after
               the date of default of the Defaulting Partner's obligation
               hereunder, the Defaulting Partner shall have no right to receive
               Distributions or to be allocated Profits and Losses of the
               Partnership.

               The Transfer of such Partnership interest pursuant to this
               paragraph (2) of Subsection B shall be effective as of the date
               of payment of the purchase price therefor, without the necessity
               of any action on the part of the Defaulting Partner. Each Partner
               agrees that if his Partnership Interest is purchased pursuant to
               this paragraph (2) of Subsection B, he will execute, acknowledge
               and deliver all instruments requested by the Partnership or the
               Acquiring Partner for the purpose Of confirming or evidencing the
               Transfer of such Partnership Interest.

               The Acquiring Partner who shall acquire the Defaulting Partner's
               Partnership Interest pursuant to this paragraph (2) of Subsection
               B shall, with respect to and Lo the extent of the Partnership
               Interest so transferred to him, be deemed to be a Limited
               Partner, with the same interest in Profits, Losses; and
               Distributions, etc., as the Defaulting Partner had prior to the
               time of default.

     C.   The Defaulting Partner may cure any default which he is deemed to have
          made pursuant' to Subsection B of this Section 3.3 by paying, (i) the
          sum which he previously failed to pay with interest from the date such
          payment was due at the lesser of (A) the highest rate of interest
          allowed by law or (B) the Base Rate PLUS 4%, and (ii) all direct
          expenses actually incurred by the Partnership with respect to such
          default; PROVIDED that no prior election has been made pursuant; to
          Subsection B of this Section 3.3.

Section 3.4 Capital Accounts
            ----------------

     A separate Capital Account shall be maintained for each Partner. There
shall be credited to each Partner's Capital, Account the amount of any cash, and
the agreed value of other property actually contributed by such Partner to the
capital of the Partnership and such Partner's share of Partnership Profits and
there shall be charged against such Partner's Capital Account the amount of all
Distributions to such Partner and such Partner's share of the Losses of the
Partnership.

     All Partners confirm that the initial Capital Account of each Partner is as
set forth on Schedule A attached hereto.

                                       12


<PAGE>   17


Section 3.5 Special Deemed Capital Account
            ------------------------------

A.   Telco shall be credited with a Special Deemed Capital Account in the amount
     of $1,500,000. This Special Deemed Capital Account (i) shall be separate
     and distinct from and shall not be considered part of the Capital Account
     of Telco; and (ii) shall not be increased or decreased and shall not be
     payable to Telco except in connection with an Excess Cash Proceeds Event
     and except in the manner set forth in Subsections B and C of this Section
     3.5.

B.   Upon the occurrence of the first Excess Cash Proceeds Event (not including
     Excess Cash Proceeds Events, if any, occurring on or before the date
     hereof) with respect to the Partnership which will result in Distributions
     to the Partners in accordance with Section 4.2.C hereof, the then fair
     market value of the Premises shall he determined as set forth in Article
     Twelve. The Special Deemed Capital Account of Telco shall then be increased
     (but not decreased) to an amount equal to $1,500,000 multiplied by a
     fraction, the numerator of which is such fair market value and the
     denominator of which is $16,500,000, which fraction shall in no case be
     less than one. Distribution to Telco pursuant to clause (1) of Section
     4.2.C of Excess Cash Proceeds in connection with such Excess Cash Proceeds
     Event shall thereupon be made in accordance with and credited against the
     Special Deemed Capital Account as so increased.

     In the event that the Special Deemed Capital Account of Telco has not
     theretofore been reduced to zero, upon the occurrence of each subsequent
     Excess Cash Proceeds Event which will result in Distributions to the
     Partners in accordance with Section 4.2.C hereof, the then remaining
     balance of the Special Deemed Capital Account of Telco shall be increased
     or decreased to an amount equal to the greater of (A) such then remaining
     balance multiplied by a fraction, the numerator of which is the then fair
     market value of the Premises (as determined as set forth in Article Twelve)
     and the denominator of which is the fair market value of the Premises as
     last determined in connection with an Excess Cash Proceeds Event and (B)
     $1,500,000 minus all previous Distributions pursuant to clause (1) of
     Section 4.2.C. Distribution to Telco pursuant to clause! (1) of Section
     4.2-C of Excess Cash Proceeds in connection with each such subsequent
     Excess Cash Proceeds Event shall be made in accordance with and credited
     against such then remaining balance of the Special Deemed Capital Account
     as so increased or decreased until the Special Deemed Capital. Account has
     been reduced to zero.

C.   The foregoing provisions of this Section 3.5 may be illustrated by the
     following examples:

          (1)  Example l:
               ---------

               The first Excess Cash Proceeds Event of the Partnership occurs on
               January 1, 1996 when the Partnership refinances the Premises for
               $25,000,000. The fair market value of the Premises is then
               $33,000,000. The Special Deemed Capital Account of Telco is then
               increased to $3,000,000: $1,500,000 x $33,000,000/ $16,500,000.
               If there are Excess Cash Proceeds of $8,000,000 in connection
               with the refinancing, then $3,000,000 will be

                                       13


<PAGE>   18


               distributed to Telco pursuant to clause (1) of Section 4.2.C, and
               the remaining $5,000,000 will be distributed to the Partners
               pursuant to clauses (2) and (3) of Section 4.2.C. Thereafter, the
               Special Deemed Capital Account of Telco will be zero and,
               accordingly, will not be a factor in any subsequent Distribution
               of Excess Cash Proceeds.

          (2)  Example 2:
               ----------

               The first Excess Cash Proceeds Event of the Partnership occurs on
               January 1, 1992 when the Partnership refinances the Premises for
               $18,000,000 and when the fair market value thereof is
               $22,000.000. The Special Deemed Capital Account of Telco is then
               increased to $2,000,000: $1,500,000 x $22,000,000/ $16,500,000.
               If there are Excess Cash Proceeds of $1,500,000 in connection
               with the refinancing, then the entire $1,500,000 will be
               distributed to Telco pursuant to clause (1) of Section 4.2-C. The
               remaining balance of the Special Deemed Capital Account of Telco
               will then be $500,000.

               The next Excess Cash Proceeds Event occurs on January 1, 1997
               when the Partnership refinances the Premises for $25,000,000 and
               when the fair market value thereof is $33,000,000. The remaining
               balance of the Special Deemed Capital Account of Telco is then
               increased to $750,000: $500,000 x $33,000,000/ $22,000,000. If
               there are Excess Cash Proceeds of $6,000,000 in connection with
               the refinancing, then $750,000 will be distributed to Telco
               pursuant to clause (1) of Section 4.2.C, and the remaining
               $5,250,000 will be distributed to the Partners pursuant to
               clauses (2) and (3) of Section 4.2.C. Thereafter, the Special
               Deemed Capital Account of Telco will be zero and, accordingly,
               will not be a factor in any subsequent Distribution of Excess
               Cash Proceeds.

          (3)  Example 3:
               ---------

               The facts are the same as in Example 2 above, except that on
               January 1, 1997 the Partnership sells the entire Premises for
               $19,800,000, representing the then fair market value thereof. The
               remaining balance of the Special Deemed Capital Account of Telco
               is then reduced to $450,000: $500,000 x $19,800,000/ $22,000,000.
               If there are Excess Cash Proceeds of $1,500,000 in connection
               with the sale, then $450,000 will be distributed to Telco
               pursuant to clause (1) of Section 4.2.C, and the remaining
               $1,050.000 will be distributed to the Partners pursuant to
               clauses (2) and (3) of Section 4.2.C.

Section 3.6 Partnership Capital
            -------------------

     A.   No Partner shall be paid interest on his Capital Contribution to the
          Partnership, on his Capital Account or on his Special Deemed Capital
          Account, as the case may be.

                                       14


<PAGE>   19


     B    No Partner shall have the right to withdraw his Capital Contribution
          or to receive any return of any portion of his Capital Contribution,
          except as provided for herein or in the Act.

     C.   Under circumstances requiring a, return of any Capital Contribution,
          no Partner shall have the right to receive property other than cash,
          except as may be specifically provided for in this Agreement.

Section 3.7 Liability of Limited Partners
            -----------------------------

     A.   No Limited Partner in his capacity as a Limited Partner shall be
          liable for the debts, liabilities, contracts, or any other obligations
          of the Partnership, except to the extent of his obligations set forth
          in Section 3.2 and Section 3.3.

     B.   No Limited Partner shall be required to lend funds to the Partnership,
          but may do so in his discretion.

                                  ARTICLE FOUR
                                  ------------

                        ALLOCATION OF PROFITS AND LOSSES:
                        ---------------------------------
                                  DISTRIBUTIONS
                                  -------------

Section 4.1 Allocation of Profits and Losses
            --------------------------------

     A.   The Profits and Losses of the Partnership shall be determined and
          allocated with respect to each Fiscal Year of the Partnership its of,
          and within ninety (90) days after, the end of such Fiscal Year.

     B.   Subject to Subsection C of this Section 4.1. Profits and Losses
          (including all items of Partnership income, gain, loss, deduction,
          credit, or the like) for any Fiscal Year shall be allocated (and
          credited or borne, as the case may be) as follows:

          (1)  Profits shall be allocated as follows:

               (a)  FIRST, to the Partners, to eliminate and in proportion to
                    any deficit balances in their respective Capital Accounts;

               (b)  THEN, to the Partners pro rata in accordance with their
                    respective Partnership Interests.

          (2)  Losses shall be allocated to the Partners pro rata in accordance
               with their respective Partnership Interests.

     C.   All gain or loss from an Excess Cash Proceeds Event, whether or not
          such event causes or is in connection with the dissolution or
          termination of the Partnership, shall be allocated (and credited or
          borne, as the case may be) as follows:

          (1)  Gain from an Excess Cash Proceeds Event shall be allocated as
               follows:

                                       15


<PAGE>   20


               (a)  FIRST, to Telco to the extent of Excess Cash Proceeds
                    distributed to Telco pursuant to clause (1) Of Section
                    4.2.C;

               (b)  THEN, to the Partners, to eliminate and in proportion to any
                    deficit balances in their respective Capital Accounts;

               (c)  THEN, to the Partners in proportion to and to the extent of
                    the respective amounts of Excess Cash Proceeds distributed
                    to the Partners pursuant to clause (2) of Section 4.2.C;

               (d)  THEN, to the Partners pro rata. in accordance with their
                    respective Partnership Interests.

          (2)  Loss from an Excess Cash Proceeds Event shall be allocated as
               follows:

               (a)  FIRST, to the Partners, to eliminate and in proportion to
                    any positive balances in their respective Capital Accounts;

               (b)  THEN, to the Partners pro rata in accordance with their
                    respective Partnership Interests.

Section 4.2 Distributions
            -------------

     A.   All Distributable Cash of the Partnership shall be distributed to the
          Partners not later than one hundred twenty (120) days after the end of
          each Fiscal Year. All Excess Cash Proceeds arising out of an Excess
          Cash Proceeds Event, which does not cause or is not in connection with
          the dissolution, or termination of the Partnership, shall be
          distributed to the Partners within ninety (90) days after the receipt
          thereof.

     B.   Subject to Section 4.2.D and Section 8.2, Distributable Cash shall be
          distributed to the Partners pro rata in accordance with their
          respective Partnership Interests.

     C.   Subject to Section 4.2.1) and Section 8.29 Excess Cash Proceeds
          arising from an Excess Cash Proceeds Event, whether or not such event
          causes or is in connection with the dissolution or termination of the
          Partnership, shall be distributed as follows:

          (1)  FIRST, to Telco up to an amount equal to the then remaining
               balance of the Special Deemed Capital Account of Telco, as; such
               remaining balance shall be determined as set forth in Section
               3.5;

          (2)  THEN, to the Partners in proportion to, and up to an amount equal
               to, any positive balances in their respective Capital Accounts;

          (3)  THEN, to the Partners pro rata in accordance with their
               respective Partnership Interests.

                                       16


<PAGE>   21


     D.   Distributable Cash and Excess Cash Proceeds arising from an Excess
          Cash Proceeds Event, whether or not such event causes or is in
          connection with the dissolution or termination of the Partnership,
          shall be paid out in the following order:

          (1)  to any Partner in repayment of loans or advances of -cash to or
               on behalf of the Partnership pursuant to Section 3.1.B, Section
               3.3.A or Section 3.7.B, including accrued interest thereon;

          (2)  the balance, if any, in the manner provided in Section 4.2.B or
               Section 4.2.C, as the case may be.

Section 4.3 Distributions in Connection with Dissolution
            --------------------------------------------

     Upon dissolution of the Partnership, all funds and assets of the
Partnership shall be distributed, subject to the prior payment of all
Partnership fees and obligations in accordance with Section 8.2.B, to and among
the Partners in accordance with Section 4.2.

                                  ARTICLE FIVE
                                  ------------

                           RIGHTS, POWERS, AND DUTIES
                           --------------------------
                             OF THE GENERAL PARTNERS
                             -----------------------

Section 5.1 Management and Control of the Partnership
            -----------------------------------------

     A.   Subject to the Consent of the Limited Partners where required by this
          Agreement, the General Partners, or any one or more of them, shall
          have the full and exclusive rights, powers, and obligations required
          or appropriate to manage and control the business and affairs of the
          Partnership in good faith and to make all decisions regarding the
          business of the Partnership and shall have all of the rights, powers,
          and obligations of general partners of a limited partnership under the
          laws of the State.

     B.   In order to expedite the handling of the Partnership's business; and
          affairs, it is understood that any document executed by the General
          Partners, or any one or more of them, while acting in the name and on
          behalf of the Partnership shall be deemed to be the action of the
          Partnership as to any third parties.

     C.   The Limited Partners shall not participate in the management of, or
          have any control over, the Partnership's business, nor shall the
          Limited Partners have the power to represent, act for, sign for. or
          bind the General Partners or the Partnership, but the Limited Partners
          shall nevertheless have the rights provided herein.

          The Limited Partners hereby Consent to the exercise by the General
          Partners, or any one or more of them, of the rights and powers
          conferred art the General Partners by this Agreement.

                                       17


<PAGE>   22



Section 5.2 Authority of the General Partners
            ---------------------------------

     A.   In addition to any other rights and powers which the General Partners
          may possess under this Agreement and the Act, the General Partners, or
          any one or more of them, shall., except to the extent otherwise
          provided herein, have all specific rights and powers required or
          appropriate to the management of the Partnership business which, by
          way of illustration but not by way of limitation, may include the
          following rights and powers:

          (1)  to redeem the VaZza Interests;

          (2)  to admit Telco and the Crosspoint Croup as Partners;

          (3)  to close the BNE Financing;

          (4)  to enter into the BNE Lease;

          (5)  to construct/renovate the Building and other improvements on the
               Land, and to develop, operate, lease and/or manage the Premises;

          (6)  to close the TIAA Financing;

          (7)  to enter into the TIAA Lease;

          (8)  to pay the Development/Construction Management Fee as set forth
               in Section 5.5;

          (9)  to pay the Excess Rent as set forth in Section 5.5;

          (10) to execute, acknowledge, and deliver, in furtherance of any and
               all of the purposes of the Partnership, any and all agreements$
               contracts, documents, certifications, bills of sale, deeds, and
               other instruments deemed by the General Partners in good faith to
               be necessary or appropriate in connection with the business of
               the Partnership;

          (11) to protect and preserve the title and interest of the Partnership
               in its assets, and to collect all amounts due to the Partnership
               and otherwise to enforce all rights of the Partnership, and in
               that connection to retain counsel and institute suits or
               proceedings in the name and on behalf of the Partnership;

          (12) to the extent that funds of the Partnership are available, to pay
               all debts and obligations of the Partnership and to make all
               Distributions periodically to the Partners in accordance with the
               provisions of this Agreement;

          (13) to open separate bank accounts for the Partnership with such bank
               or banks as the General Partners may from time to time select,
               and to designate and change signatories on such accounts;

          (14) to obtain governmental or other approvals, licenses, permits, and
               authorizations, if any, which may be required for the

                                       18


<PAGE>   23


               construction, development, operation, leasing and/or management
               of the Premises;

          (15) to negotiate, execute and/or modify leases, options, concessions,
               licenses, and other occupancy and operating agreements with
               respect to the Premises;

          (16) to employ on behalf of the Partnership such Persons as the
               General Partners in good faith shall deem advisable in the
               operation and management of the Partnership business, including,
               without limitations accountants, architects, the Accountant,
               attorneys, engineers, appraisers, advisers, and other experts, on
               such terms and for such reasonable compensation as prevail for
               such services in the geographical area in question;

          (17) to borrow funds on behalf of the Partnership and/or to make loans
               to the Partnership pursuant to the provisions of Section 3.1.B,
               Section 3.3.A and Section 3.7.B;

          (18) to adjust, in the event of a casualty with respect to the
               Premises resulting in an insurance claim in favor of the
               Partnership, any claim or retain the services of an independent
               professional adjuster to settle such claim, the COST Of SUCH an
               adjuster to be an expense of the Partnership;

          (19) to grant any covenant, restriction, or similar lien or
               encumbrance affecting the Premises; provided that the same is in
               the best interest of the Partnership in each. instance;

          (20) to execute and deliver all federal, state, and local tax returns
               on behalf of the Partnership and to retain counsel and institute,
               prosecute, defend, and compromise in good faith any suits or
               proceedings, whether administrative or judicial., in connection
               with such returns.

     B.   Any person dealing with the Partnership or the General Partners may
          rely upon a certificate signed by the General Partners, or any one or
          more of them, thereunto duly authorized, as to:

          (1)  the identity of the General Partners or the Limited Partners;

          (2)  the existence or non-existence of any fact or facts which
               constitute conditions precedent to acts by the General Partners
               or are in any other manner germane to the affairs of the
               Partnership;

          (3)  the Person who is authorized to execute, acknowledge and deliver
               any instrument or document of or on behalf of the Partnership; or

          (4)  any act or failure to act by the Partnership or as to any other
               matter whatsoever involving the Partnership or any Partner.





                                       19


<PAGE>   24


Section 5-3 Restrictions on Authority of the General Partners
            -------------------------------------------------

     A.   Without the Consent of all the Limited Partners, the General Partners
          shall not have the authority to:

          (1)  do any act in contravention of this Agreement;

          (2)  do any act which would make it impossible or impracticable to
               carry on the ordinary business of the Partnership;

          (3)  confess a judgment against the Partnership;

          (4)  possess Partnership assets, or assign its rights in specific
               Partnership assets, for other than a Partnership purpose;

          (5)  admit a Person as a General Partner, except as provided in this
               Agreement; or

          (6)  knowingly perform any act that would subject any Limited Partner
               to liability as a general partner in any jurisdiction.

     B.   Without the Consent of a Majority in Interest of the Limited Partners,
          the General Partners shall not have the authority to:

          (1)  voluntarily dissolve the Partnership, except as set forth in
               Article Six;

          (2)  voluntarily sell or otherwise dispose of the Premises, except
               with respect to a lease or leases for a term or terms of riot
               more than five (5) years (including renewals) with respect to
               portions of the Premises not exceeding twenty thousand (20,000)
               square feet in the aggregate;

          (3)  voluntarily grant a mortgage or other security interest with
               respect to the Premises, except for such mortgages and other
               security interests as are necessary or required in connection
               with the BNE Financing and the TIAA Financing;

          (4)  construct any building or other improvement on the Land, except
               for the Building and the improvements contemplated by the TIAA
               Financing;

          (5)  enter into any agreement with any Partner or any Affiliate of any
               Partner, except as set forth in Section 5.5;

          (6)  borrow funds on behalf of the Partnership, except with respect to
               the BNE Financing or the TIAA Financing or pursuant 'to the
               provisions of Section 3.1.B, Section 3.3.A or Section 3.7.B; or

          (7)  except pursuant to the provisions of Section 3.1.B, Section.
               3.3.A or Section 3.7.B, voluntarily incur and pay ordinary and
               necessary expenses with respect to the partnership business other
               than debt service (with respect to the BNE Financing and/or the
               TIAA Financing) and other than expenses which are

                                       20


<PAGE>   25


               payable by a tenant under the BNE Lease, under the TIAA Lease
               and/or under any other lease of the Premises or any portion
               thereof - in excess of (i) twenty thousand dollars ($20,000) in
               any of the first three Fiscal Years of the Partnership after the
               date hereof; (ii) twenty-five thousand dollars ($25,000) in any
               of Fiscal Years four through six of the Partnership after the
               date hereof; (iii) thirty thousand dollars ($30,000) in any of
               Fiscal Years seven through nine of the Partnership after the date
               hereof; and (iv) thirty thousand dollars ($30,000) as adjusted
               upward as reasonably determined by the General. Partners with the
               Consent of a Majority in Interest of the Limited Partners in any
               Fiscal Year subsequent to the ninth Fiscal. Year of the
               Partnership after the date hereof.

Section 5.4 Duties and Obligations of the General Partners
            ----------------------------------------------

     A.   The General Partners shall take all action which may be necessary or
          appropriate (i) for the formation and continuation of the
          Partnership's valid existence as a limited partnership under the: laws
          of the State and (ii) for the redemption of the Vazza Interests, the
          removal of TSFOC as a Limited Partner, the admission of Telco and the
          Crosspoint Group as Partners, the construction/renovation of the
          Building, and the development, operation, leasing and/or management of
          the Premises, in accordance with the provisions of this Agreement and
          applicable laws and regulations and to the extent that Partnership
          funds are available to carry out such duties and obligations.

     B.   The General Partners shall devote to the Partnership such time as may
          be necessary for the proper performance of their duties hereunder

     C.   The General Partners shall take such action as may be necessary or
          appropriate in order to form or qualify the Partnership under the laws
          of any jurisdiction in which the Partnership is doing business or in
          which such formation or qualification is necessary in order to protect
          the limited liability of the Limited Partners or. in order to continue
          in effect such formation or qualification. The General Partners. shall
          file or cause to be filed for recordation in the office of the
          appropriate authorities of the State and in the proper office or
          offices in each other jurisdiction in which the Partnership is formed
          or qualified, the Certificate and such certificates (including limited
          partnership and fictitious name certificates) and other documents as
          are required by the applicable statutes, rules or regulations of any
          such jurisdiction or are required to reflect the identity of the'
          Partners and the amounts of their respective Capital Contributions.

Section 5.5 Authority of the General Partners to Deal With Affiliates
            ---------------------------------------------------------

     A.   The General Partners may for, in the name of, and on behalf of the
          Partnership enter into' such agreements, contracts or the like with a
          General Partner or any Affiliate of a General Partner to undertake

                                       21


<PAGE>   26


          and carry out the business of the Partnership as if such General
          Partner or Affiliate were an independent contractor. The General
          Partners may obligate the Partnership to pay reasonable compensation
          for and on account of any such services and accept terms which are no
          less favorable to the Partnership than are available from others on an
          arm's-length basis in the same geographical area.

     B.   All Partners are aware that the Partnership has entered or may enter
          into the following arrangements with Affiliates of the Partners. which
          arrangements were not or will not be determined by arm's-length
          negotiations:

          (1)  the payment to Crosspoint Development Corporation, a
               Massachusetts corporation which is an Affiliate of that General
               Partners and of certain of the Limited Partners, of a, fee
               ("Development/Construction Management Fee") equal to $450,000,
               payable as follows:

               (a)  $225,000 upon the closing of the BNE Financing;

               (b)  $225,000.upon Building Completion;

          (2)  the payment to TSFOC of Excess Rent, payable in monthly
               installments, but subject to the provisions of the TIAA Lease;

          (3)  the BNE Lease!, and

          (4)  the TIAA Lease.

All Partners ratify, confirm and assent to the foregoing arrangements and the
terms and provisions thereof.

Section 5.6 Compensation of Partners
            ------------------------

     A.   Subject to the provisions of Section 5.3.B(7), the General Partners
          shall be reimbursed by the Partnership for their reasonable
          out-of-pocket expenses incurred and paid in connection with
          Partnership business -- including, without limitation, all, legal.,
          accounting, travel and other expenditures incurred in connection
          therewith and the costs of direct labor, materials and supplies used
          for and in respect of the development, operation, leasing and/or
          management of the Premises and other Partnership assets and for fees,,
          commissions, and other amounts paid to brokers and similar parties in
          connection with the acquisition of leases with respect to the Premises
          or portions thereof; provided that, subject to the provisions
          of the TIAA Lease, the Excess Rent shall be paid by the Partnership to
          TSFOC before reimbursement of the General Partners pursuant to this
          Subsection A.

     B.   Except as expressly provided for in this Agreement, no payment shall
          be made by the Partnership to any Partner for the services; or,
          out-of-pocket expenses of such Partner or of any employee, agent or,
          representative of any Partner.

                                       22


<PAGE>   27


Section 5.7 Other Interests of the General Partners and Their Affiliates
            ------------------------------------------------------------

     Any General Partner and any Affiliate of a General Partner may engage IN or
possess an interest in other business ventures of every nature and description,
independently or with others -- including, without limitation, the real estate
business in all of its phases, which shall include, without limitation, the
ownership, construction, operation, management, sale, syndication, and
development of real property for his own account or for the account of others.

Section 5.8 Rights to Income or Profits
            ---------------------------

     Neither the Partnership nor any other Partner shall have any rights in or
to any income or profits derived by or from any Person and any arrangements,
agreements and ventures described in or authorized by Section 5.5.A, Section
5.5.B(l) and (2), Section 5.6 or Section 5.7 by reason of this Agreement.

Section 5.9 Liability and Indemnification of the General Partners
            -----------------------------------------------------

     A.   The General Partners shall be obligated to undertake and perform the
          duties, responsibilities and obligations of the General Partners set
          forth in this Agreement only to the extent that adequate funds of the
          Partnership are available therefor.

     B.   The General Partners shall not be liable. responsible, or accountable
          in damages or otherwise to any of the Partners or the Partnership for,
          and the Partnership shall indemnify the General Partners against and
          save each of them harmless from, any damage or expense (including
          reasonable attorneys' fees) incurred by reason of any act or omission
          performed or made by the General Partners on behalf of the Partnership
          or the Limited Partners in good faith and in a manner reasonably
          believed by the General Partners to be both within the scope of the
          authority granted to them by this Agreement and in the best interests
          of the Partnership or the Limited Partners; provided that the
          satisfaction of any indemnification shall be from, and limited to,
          Partnership assets. The Limited Partners shall not have any personal
          liability whatsoever on account of the provisions of this Section 5.9.

     C.   The General Partners shall have the right and authority to require in
          all Partnership contracts that the General Partners will not be
          personally liable thereon and that the Person contracting with the
          Partnership is to look solely to the Partnership and its assets; for
          satisfaction.

                                   ARTICLE SIX
                                   -----------

                              TRANSFERABILITY OF A
                              --------------------
                           GENERAL PARTNER'S INTEREST
                           --------------------------

Section 6.1 Voluntary Retirement or Transfer by a General Partner
            -----------------------------------------------------

     A.   No General Partner shall have the right to retire as a General Partner
          of the Partnership or to Transfer, assign or encumber his

                                       23


<PAGE>   28


          Interest (or any part thereof) as a General Partner, without the
          Consent Of a Majority in Interest of the Limited Partners in each
          instance.

     B.   Notwithstanding the provisions of Section 6.1.A:

          (1)  any General Partner may Transfer or assign his Interest (or any
               part thereof) as a General Partner to an Affiliate with the
               Consent of a Majority in Interest of the Limited Partners;

          (2)  at any time after the tenth (10th) anniversary of the date of
               this Agreement, any General Partner may retire or Transfer,
               assign or encumber his Interest (or any part thereof) as a
               General Partner without the Consent of any of the Limited
               Partners;

          PROVIDED in each case that the characteristics (including, without
          limitation, the net worth) of the remaining General Partner, are
          sufficient and of such quality so as to meet all then applicable
          requirements set by statute, the Internal Revenue Service or the
          courts to insure that the Partnership will not fail to be classified
          for federal income tax purposes as a partnership, rather than as an
          association taxable as a corporation.

          Notice of any such retirement, Transfer, assignment or encumbrance
          shall be given to all Partners; and, subject to the provisions of
          Subsection D of this Section 6.1, such retirement, Transfer,
          assignment or encumbrance shall be effective on the sixtieth (60th)
          day after the date of such notice.

     C.   Subject to the provisions of Subsection D of this Section 6.1, upon
          the retirement of a General Partner, the retiring General Partner
          shall be entitled to receive (i) the then net fair market value of his
          Interest as a General Partner as determined as set forth in Article
          Twelve and (ii) any amounts due and owing to him by the Partnership
          less any amounts due and owing by him to the Partnership.

          The right of a retired General Partner to payment under this
          Subsection C shall be subject to any claim for damages the Partnership
          or any Partner may have against the General Partner if such retirement
          is in contravention of this Agreement.

          Any payments by the Partnership to a retiring General Partner pursuant
          to this Subsection C may be paid, at the option, of the Partnership,
          by a promissory note of the Partnership (which promissory note shall
          be secured by Partnership assets and by security interests in the
          Partnership Interests of the Partners but which promissory note shall
          not impose personal liability on any Partner of the Partnership)
          payable in three (3) equal, consecutive annual installments of
          principal, the first such installment being payable one year after the
          effective date of retirement, with interest on the unpaid principal
          balance thereof at the rate of ten percent (10%) per annum and payable
          annually on. the principal installment payment date.

                                       24

                        

<PAGE>   29


     D.   Upon the notice of the retirement of a General Partner, the remaining
          Partners shall decide whether to reconstitute the Partnership in
          accordance with the provisions of Section 6.2. If the remaining
          Partners do not reconstitute the Partnership in accordance with the
          provisions of Section 6.2, then the retirement of the retiring General
          Partner shall be effective only for the purposes of Section 6.2.A and
          Section 8.1.C; for all other purposes, the retiring General Partner
          shall remain a General Partner of the Partnership until the
          Partnership and his Interest are liquidated in accordance with the
          provisions of Section 8.2.

Section 6.2 Reconstitution of the Partnership
            ---------------------------------

     A.   In the event of the retirement or Incapacity of a General Partner, the
          Partnership shall be dissolved.

     B.   Notwithstanding the provisions of Subsection A of this Section 6.2,
          the Partnership shall be continued on the terms and conditions of this
          Agreement after the retirement or Incapacity of a General Partner (the
          "Former General Partner") if, within sixty (60) days after such
          dissolution of the Partnership:

          (1)  if there is a remaining General Partner or General Partners, each
               such remaining General Partner and a Majority in Interest of the
               Limited Partners Consent to continue the Partnership; or

          (2)  if there is no remaining General Partner, all the Limited
               Partners Consent to continue the Partnership, designate in
               writing one or more substituted General Partners, and at least
               one such designee consents in writing to become a substitute
               General Partner (collectively, the "Substitute General
               Partner":).

     C.   If the business of the Partnership is continued pursuant to clause (2)
          of Subsection B of this Section 6.2 with the Substitute, General
          Partner, then, subject to the provisions of Section 6.3. the
          Substitute General Partner shall succeed to all of the powers;,
          privileges and obligations of the Former General Partner hereunder.

     D.   If the business of the Partnership is continued pursuant to Subsection
          B of this Section 6.2, then the Interest of an Incapacitated Former
          General Partner shall become a Limited Partner Interest (with the same
          interest in Profits, Losses and Distributions, etc., as the
          Incapacitated Former General Partner had prior to his Incapacity), and
          such Incapacitated Former General Partner (or his legal
          representative) shall be deemed a Limited Partner of the Partnership.

Section 6.3 Admission of a Person as the Substitute General Partner
            -------------------------------------------------------

     The admission of a Person as the Substitute General Partner pursuant to
Section 6.2 shall be effective only if and after the following conditions are
satisfied: 

          (1)  the Interests of the Limited Partners shall not be adversely
               affected by the admission of the Substitute General Partner;

                                       25


<PAGE>   30


          (2)  any Person designated as a Substitute General Partner pursuant to
               Section 6.2 shall have satisfied the requirements of Section 11.2
               hereof; and

          (3)  all of the provisions of Section 6.2 and Section 10.3 shall. have
               been complied with.

Section 6.4 Restrictions on Transfer by a General Partner
            ---------------------------------------------

     Notwithstanding anything to the contrary contained in this Agreement, tile
Interests of the General Partners shall at all times be subject to tile
restrictions on Transfer set forth in Subsections A and B of Section 7.2.

Section 6.5 Liability and Rights of a Retired or Transferor General Partner
            ---------------------------------------------------------------

     Any General Partner who shall duly retire or Transfer his entire Interest
as a General Partner shall remain liable for his portion of any obligations and
liabilities incurred as General Partner prior to the time such retirement or
Transfer shall have become effective, but any such duly retired or Transferor
General Partner shall be free of any obligation or liability incurred on account
of the activities of the Partnership from and after such time of retirement or
Transfer. Except as may be provided herein, such retirement or Transfer shall
not affect any rights of a retired or Transferor General Partner which shall
mature or become vested prior to the effective date of his retirement or
Transfer.

                                  ARTICLE SEVEN
                                  -------------

                         TRANSFERABILITY AND ACQUISITION
                         -------------------------------
                         OF A LIMITED PARTNER'S INTEREST
                         -------------------------------

Section 7.1 Representations of Limited Partners
            -----------------------------------

     Each Limited Partner hereby represents and warrants to the General Partners
and to the Partnership that his acquisition of his Interest is made as principal
for his own account for investment purposes only and not with a view to, or for,
the resale or distribution of such Interest or any portion thereof.

Section 7.2 Restrictions on Transfer of Interests
            -------------------------------------

     A.   Notwithstanding anything to the contrary contained in this Agreement,
          no Transfer of a Partner's Interest may be made unless an opinion,
          satisfactory in form and substance to the Partnership, is rendered by
          qualified, independent counsel to the Transferor directly to the
          Partnership, that

          (1)  such Transfer when added to the total of all other Transfers of
               Interests within the preceding twelve (12) months, would not
               result in the Partnership being considered to have terminated
               within the meaning of Section 708 of the Code; and

                                       26


<PAGE>   31


          (2)  such Transfer would not violate the Securities Act of 1933, or
               any state securities ("blue sky") laws (including any investor
               suitability standards) applicable to the Partnership or the
               Interest to be transferred.

     B.   In no event shall a Partner Transfer all or any part of his Interest
          to a minor or an incompetent except by will or intestate succession.

Section 7.3 Incapacity of a Limited Partner
            -------------------------------

     If a Limited Partner dies, his executor, administrator or trustee, or, if
he is adjudicated incompetent, his committee, guardian or conservator or, if he
becomes bankrupt the trustee or receiver of his estate, shall have all tile
rights of the Limited Partner for the purpose of settling or managing his estate
and such power as the Incapacitated Limited Partner possessed to Transfer all or
any part of his Interest and to join with such Transferee in satisfying
conditions precedent to such Transferee becoming a Substitute Limited Partner.

     The Incapacity of a Limited Partner shall not dissolve the Partnership.

Section 7.4 Transferees
            -----------

     A.   The Partnership need not recognize for any purpose any purported
          Transfer of all or any part of the Interest of a Partner unless the
          pertinent provisions of Section 7.2 shall have been complied with and
          there shall have been filed with the Partnership a written and dated
          notice of such Transfer, executed and acknowledged both by the
          Transferor and by the Transferee, which notice shall (i) contain all
          of the terms and provisions of the agreement relating to such Transfer
          and (ii) represent that such Transfer was made in accordance with all
          applicable laws and regulations (including any investor suitability
          standards). Any Transfer shall be recognized by the Partnership as
          effective on the date of such notice if the date of such notice is
          within thirty (30) days of the date on which such notice is filed with
          the Partnership, and otherwise shall be recognized as effective on the
          date such notice is filed with the Partnership.

     B.   If a Limited Partner shall Transfer all of his Interest, he shall
          cease to be a Limited Partner, except that, unless and until a
          Substitute Limited Partner is admitted in his stead, such Transferor
          Limited Partner shall retain the statutory rights of the assignor of a
          limited partner's interest under the Act.

     C.   A Person who is the Transferee of all or any part of the Interest of'
          a Limited Partner, but does not become a Substitute Limited Partner,
          and desires to make a further Transfer of such Interest, shall. be
          subject to all the provisions of this Article Seven to the same extent
          and in the same manner as if such Person were a Limited Partner
          desiring to make a Transfer of his Interest.

                                       27


<PAGE>   32


Section 7.5 Substitute Limited Partners
            ---------------------------

     A.   No Limited Partner shall have the right to substitute a Transferee as
          a Limited Partner in his place. Any Transferee of an Interest of a
          Limited Partner shall be admitted to the Partnership as a Substitute
          Limited Partner (i) if the Transferee is an Affiliate of the
          Transferor Limited Partner; (ii) if the Transferor Limited Partner
          first offered his Interest to the other Partners in accordance with
          the provisions of Section 7.6; or (iii) otherwise, only with the
          Consent of the General Partners which Consent may, in the absolute
          discretion of the General Partners, be withheld. Any such Consent by
          the General Partners shall be binding and conclusive without the
          Consent of any Limited Partner.

     B.   No Person shall become a Substitute Limited Partner until such Person
          shall have satisfied the requirements of Section 11.2; PROVIDED that
          for the purposes of Article Four, a Person shall be treated as having
          become, and as appearing in the records of the Partnership as, a
          Limited Partner on such date as the Transfer to such Person was
          recognized by the Partnership pursuant to Section 7.4.A.

Section 7.6 Right of First Refusal
            ----------------------

     A.   No Limited Partner shall Transfer his Interest for value unless and
          until he has first offered it to the other Partners as follows:

          (1)  The Limited Partner shall give notice to the General Partners
               that he desires to Transfer his Interest for value. He shall
               attach to such notice the written offer of a prospective
               purchaser to buy such Interest. Such offer shall be complete in
               all details as to purchase price and terms of payment. Such
               notice shall include the representation and warranty of the
               Limited Partner that such offer is genuine and in all respects
               what it purports to be.

          (2)  The General Partners shall promptly notify all the other Partners
               of such offer and the details thereof. Within twenty (20) days
               after such notice from the General Partners is given, any one or
               more of such Partners (including the General Partners) may elect
               to purchase the Interest of the Limited Partner at the price and
               on the terms contained in such offer. If more than one of such
               Partners elect to so purchase, then such electing Partners shall
               be entitled to purchase such Interest pro rata in accordance with
               their respective Partnership Interests.

          (3)  If no such Partner elects to purchase such Interest, the Limited
               Partner shall be free to Transfer such Interest to the Person,
               for the price, and on the terms contained in such offer within
               sixty (60) days after the expiration of the twenty (20) day
               election period, in which event such Person shall become a
               Transferee of such Interest under this Article Seven. If such
               Interest is not so transferred to such Person. such Interest
               shall become again subject to the terms and conditions of this
               Section 7.6.

                                       28


<PAGE>   33


     B.   Any such Partner who elects to purchase such Interest shall hold such
          Interest as a Limited Partner.

                                  ARTICLE EIGHT
                                  -------------

                          DISSOLUTION, LIQUIDATION AND
                          ----------------------------
                         TERMINATION OF THE PARTNERSHIP
                         ------------------------------

Section 8.1 Events Causing Dissolution
            --------------------------

     The Partnership shall dissolve upon the happening of any of the following
events:

     A.   the expiration of its term;

     B.   the election to dissolve the Partnership made in writing by a
          Substantial Majority in Interest of the Limited Partners pursuant to
          Section 10.2.B;

     C.   the retirement or Incapacity of a General Partner, SUBJECT, HOWEVER, 
          to reconstitution as provided for in Section 6.2;

     D.   the Transfer of all of the Partnership assets; or

     E.   the happening of any other event causing the dissolution of the
          Partnership under the laws of the State.

Dissolution of the Partnership shall be effective on the day on which the event
occurs giving rise to the dissolution, but the Partnership shall not terminate
until the Partnership's Certificate has been cancelled and the assets of the
Partnership have been distributed as provided in Section 8.2.

Section 8.2 Liquidation
            -----------

     A.   Upon dissolution of the Partnership, its liabilities shall be paid in
          the order provided hereinafter. The General Partners shall cause the
          assets of the Partnership to be sold in accordance with reasonable
          business judgment, in an effort to obtain the best prices for, the
          assets, and the General Partners shall cause the cancellation of the
          Certificate. Pending such actions, the General Partners shall have the
          right to continue to operate and otherwise deal with the assets of the
          Partnership. In the event the General Partners are not able to
          function or in the event the General Partners are not performing their
          responsibilities under this Section 8.2.A in accordance with
          reasonable business judgment, the Partnership shall elect, by Consent
          of a Majority in Interest of the Limited Partners, a Person to perform
          the functions of the General Partners in liquidating the assets of the
          Partnership and winding up its affairs.

     B.   In settling accounts after dissolution, the remaining assets of the
          Partnership shall, subject to applicable laws, be paid out in the
          following order:

                                       29


<PAGE>   34

          (1)  FIRST, to pay the expenses of liquidation;

          (2)  THEN, to third party creditors (including, without limitation,
               and Affiliates as such creditors, if and to the extent or
               advances made by them to the Partnership), in the priority
               provided for by law;

          (3)  THEN, to set up a reserve for contingencies such as the General
               consider necessary;

          (4)  THEN, the balance, if any, to the Partners in the manner provided
               in Section 4.3.

     C.   The foregoing provisions of this Section 8.2 shall not apply in the
          event that the Partnership is reconstituted as provided for in Section
          6.2.

                                  ARTICLE NINE
                                  ------------

                                 FISCAL MATTERS
                                 --------------

Section 9.1 Title to Property and Bank Accounts 
            ----------------------------------- 

     The assets of the Partnership shall be held in the name of the Partnership.

     The funds of the Partnership shall be deposited in the name of the
Partnership in such bank account or accounts in Massachusetts as shall be
designated by the General Partners, and withdrawals therefrom shall be made upon
the signature of the General Partners or of such Persons as shall be so
designated by the General Partners.

     All funds not needed in the operation of the Partnership business may be
deposited in interest-bearing accounts or invested in short-term United States
Government obligations maturing within one year or otherwise invested in such
manner as the General Partners in their discretion deem advisable.

Section 9.2 Books and Records
            -----------------

     The books and records of the Partnership, a list of the names; and
addresses and Interests of all Partners, and a certified copy of the Certificate
shall be maintained by the General Partners at the principal office of the
Partnership and shall be available to the Limited Partners and their duly
authorized representatives for inspection at any and all reasonable times upon
two business days' prior notice.

     The books and records of the Partnership will be kept on the cash basis.
Reports of the Partnership for tax purposes will be prepared on such method of
accounting as will, in the opinion of the Accountant, be most advantageous to a
Substantial Majority in Interest of the Partners. Financial statements for the
Partnership will be prepared in conformity with generally accepted accounting
principles applied on a consistent basis and in respect of an annual period
ending on August 31; PROVIDED that the cost of. preparation of said financial
statements shall be paid solely by Telco.

                                       30


<PAGE>   35

     Any Partner, or his duly-authorized representatives, upon paying the costs
of preparation, duplication and mailing, shall be entitled for any proper
purpose to a copy of the list of names and addresses and Interests of the
Partners. The Partnership may maintain such other books and records and may
provide such financial or other statements as the General Partners in their
discretion deem advisable.

Section 9.3 Reports and Accountant
            ----------------------

     Within one hundred twenty (120) days after the end of each Fiscal Year of
the Partnership, the Partnership shall cause to be delivered to each Limited
Partner an annual report, prepared by the Accountant, containing (i) an audited
statement of financial condition as of the end of the Fiscal Year then ended,
(ii) an audited operating statement for the Fiscal Year then ended, (iii) an
opinion of the Accountant as to the fairness of presentation of such statement
of financial condition and operating statement. and (iv) an audited statement of
sources and application of funds for the Fiscal Year then ended.

     Within ninety (90) days after the end of each Fiscal Year of the
Partnership, the Partnership shall cause to be delivered to each Limited Partner
(i) a report describing the Distributions to Partners for the Fiscal Year then
ended, and (ii) all information necessary for the preparationof such Limited
Partner's federal, state and local income tax returns.

Section 9.4 Federal Tax Elections
            ---------------------

   The Partnership shall make elections for federal income tax purposes as
follows:

     A.   In case of a Transfer of all or part of the Partnership Interest of a
          Partner, the Partnership may, in the sole discretion of the General
          Partners, timely elect pursuant to Sections 743 and 754 of the Code
          (or corresponding provisions of future law) and pursuant to similar
          provisions of applicable state or local income tax laws, to adjust the
          basis of the Assets of the Partnership. In such event, any basis
          adjustment attributable to such Transfer shall be allocated solely to
          the Transferee.

     B.   The Partnership shall elect the straight-line method (over the
          shortest period of years allowed) of depreciation for so-called
          "18-year real property" owned by the Partnership pursuant to the
          accelerated cost recovery system set forth in the Code.

     C.   All other elections required or permitted to be made by the
          Partnership under the Code and not otherwise expressly provided for in
          this Agreement shall be made by the General Partners with the Consent
          of a Majority in Interest of the Limited Partners.

                                       31


<PAGE>   36


                                   ARTICLE TEN
                                   -----------

                 MEETINGS AND VOTING RIGHTS OF LIMITED PARTNERS
                 ----------------------------------------------

Section 10.1 Meetings
             --------

     A.   Meetings of the Limited Partners for any purpose may be called by the
          General Partners and shall be called by the General Partners upon
          receipt of a request in writing signed by a Majority in Interest of
          the Limited Partners. Notice of such meeting shall be sent within ten
          (10) days after receipt of such request. Such request shall state the
          purpose of the proposed meeting and the matters proposed to be acted
          upon thereat. Such meeting shall be held at the principal office of
          the Partnership. or at such other place in Massachusetts as may be
          designated by the General Partners or, if called upon the request of
          Limited Partners, at such place in Massachusetts as designated by such
          Limited Partners. In addition, upon receipt of a request in writing
          signed by a Majority in Interest of the Limited Partners, the General
          Partners shall submit any matter (upon which the Limited Partners are
          entitled to act) to the Limited Partners for a-vote by written Consent
          without a meeting.

     B.   A notice of any such meeting shall be given to each Limited Partner
          not less than fifteen (15) days nor more than sixty (60) days before
          the date of the meeting. Such notice shall state the place, date and
          hour of the meeting, and shall indicate that it is being issued at or
          by the direction of the Partners calling the meeting. The notice shall
          state the purpose or purposes of the meeting. If a meeting is
          adjourned to another time and/or place, and if announcement of such
          adjournment is made at the meeting, it shall not be necessary to give
          notice with respect to the adjourned meeting.

          The presence in person or by proxy of a Majority in Interest of the
          Limited Partners shall constitute a quorum at all meetings of the
          Limited Partners; PROVIDED, however, that if there be no such quorum,
          holders of a majority of the Limited Partner Interests so present or
          so represented may adjourn the meeting from time to time without
          further notice, until a quorum shall have been obtained.

          No notice of the time, place, or purpose of any meeting of Limited
          Partners need be given to any Limited Partner who attends in person or
          is represented by proxy (except when the Limited Partner attends a
          meeting for the express purpose of objecting at the beginning of the
          meeting to the transaction of any business on the ground that the
          meeting is not lawfully called or convened), or to any Limited Partner
          entitled to such notice who, in writing, executed and filed with the
          records of the meeting, either before or after the time thereof,
          waives such notice.

     C.   For the purpose of determining the Limited Partners entitled to vote
          on, or to vote at, any meeting of the Limited Partners or any
          adjournment thereof, the General Partners or the Limited Partners
          requesting such meeting may fix, in advance, a date as the record date
          for any such determination. Such date shall not be more than fifty
          (50) days nor less than ten (10) days before any such meeting.

                                       32


<PAGE>   37


     D.   Each Limited Partner may authorize any person or persons to act for
          him by proxy in all matters in which a Limited Partner is entitled to
          participate, whether by waiving notice of any meeting, or voting or
          participating at a meeting. Every proxy must be signed by the Limited
          Partner or his attorney-in-fact . No proxy shall be valid after the
          expiration of six (6) months from the date thereof unless otherwise
          provided in the proxy. Every proxy shall be revocable at the pleasure
          of the Limited Partner executing it.

     E.   At each meeting of Limited Partners, the Limited Partners present or
          represented by proxy shall elect such officers and adopt such rules
          for the conduct of such meeting as they shall deem appropriate.

Section 10.2 Voting Rights of Limited Partners
             ---------------------------------

     Subject to Section 10.3, a Substantial Majority in Interest of the Limited
Partners, without the concurrence of the General Partners, may by affirmative
vote or written Consent:

     A.   Amend this Agreement, subject to the provisions of Section 11.1 and to
          the conditions that such amendment (a) may not alter in any way the
          purpose of the Partnership; (b) may not in any manner allow the
          Limited Partners to take part in the control of the Partnership's
          business; and (c) may not, without the Consent of the General
          Partners: (1) alter the rights, powers and duties of the General
          Partners as set forth in Article Five or the interests of the Partners
          in Distributions, Profits and/or Losses; (2) increase the liability of
          the General Partners hereunder; or (3) amend this Section 10.2.

     B.   Dissolve the Partnership; PROVIDED that no such vote or Consent shall
          be effective prior to the tenth (10th) anniversary of the date of this
          Agreement.

Section 10.3 Conditions to Action by Limited Partners
             ----------------------------------------

     The right of the Limited Partners under this Agreement to amend this
Agreement, to dissolve the Partnership, or to designate a Substitute General
Partner shall not come into existence or be effective in any manner unless and
until (i) the Partnership has received an opinion of qualified, independent;
counsel, which counsel is also satisfactory to a Majority in Interest of the
Limited Partners, as to the legality of such action; (ii) either (a) the
Partnership has received an opinion of qualified, independent counsel, which
counsel is also satisfactory to a Majority in Interest of the Limited Partners,
that such action may be effected without subjecting the Limited Partners to
liability as general partners under the Act or under the laws of such other
jurisdictions in which the Partnership is formed or qualified, or (b) a court
having original jurisdiction in the matter has entered a judgment; to the
foregoing effect; and (iii) either (a) the Partnership has received an opinion
of qualified, independent counsel, which counsel is also satisfactory, to a
Majority in Interest of the Limited Partners, that such action may be effected
without changing the Partnership's status for federal income tax purposes or (b)
either a court having original jurisdiction has entered a, judgment, or the
Internal Revenue Service has issued a ruling, to the

                                       33


<PAGE>   38


foregoing effect. For purposes of this Section 10.3, counsel will be deemed
satisfactory to a Majority in Interest of the Limited Partners if proposed by,
and affirmatively approved in writing within fifteen (15) days thereafter by, ,a
Majority in Interest of the Limited Partners.

                                 ARTICLE ELEVEN
                                 --------------

                                   AMENDMENTS
                                   ----------

Section 11.1 Adoption of Amendments
             ----------------------

     A.   In addition to the amendments otherwise authorized herein. amendments
          may be made to this Agreement from time to time by the General
          Partners with the Consent of a Majority in Interest of the Limited
          Partners; PROVIDED however, that without the Consent of the Partners
          to be adversely affected by the amendment, this Agreement may not be
          amended so as to CO convert a Limited Partner's Interest into a
          General Partner's Interest; (ii) modify the limited liability of a
          Limited Partner; or (iii) alter the Interest of a Partner in
          Distributions, Profits and/or Losses.

     B.   The General Partners shall, within a reasonable time after the
          adoption of any amendment to this Agreement, make any filings or
          publications required or desirable to reflect such amendment,
          including any required filing or recordation of an amended Certificate
          or similar instrument or document.

Section 11.2 Amendments on Admission or Substitution of Partners
             ---------------------------------------------------

     A.   Each Limited Partner, Substitute Limited Partner, General Partner, and
          Substitute General Partner shall become a signatory hereof by signing
          such number of counterpart signature pages to this Agreement and such
          other instrument or instruments, and in such manner and at such time,
          as the General Partners shall determine. By so signing, each Limited
          Partner, Substitute Limited Partner, General Partner or Substitute
          General Partner, as the case may be, shall be deemed to have adopted,
          and to have agreed to be bound by all the provisions of, this
          Agreement, as amended from time to time in accordance with the
          provisions of this Agreement.

     B.   If this Agreement shall be amended to reflect the admission or
          substitution of a Limited Partner. the amendment to this Agreement
          shall be signed by the General Partners, the Person to be substitute
          or added, and the assigning Limited Partner or his attorney-in-fact.

     C.   If this Agreement shall be amended to reflect the replacement of the
          Former General Partner by the Substitute General Partner, such
          amendment shall be signed by the Substitute General Partner.

     D.   No person shall become a Partner unless such Person shall have:

          (1)  become a party to, and adopted all of the terms and conditions;
               of, this Agreement;

                                       34


<PAGE>   39


          (2)  if such Person is a corporation, association or trust, provided
               the General Partners with evidence satisfactory to counsel to the
               Partnership of such Person's authority to become a Partner under
               the terms and provisions of this Agreement;

          (3)  except as to an initial Partner under this Agreement, paid all
               reasonable legal fees of the Partnership and the General Partners
               and filing and publication costs in connection with such Person's
               becoming a Partner; and

          (4)  except as to an initial Partner under this Agreement, furnished
               to the Partnership such legal opinions with respect to compliance
               with the provisions of Section 7.2.A as counsel to the
               Partnership may reasonably request, and such opinions shall be
               reasonably satisfactory in form and substance (and also as to the
               Person rendering the same) to counsel to the Partnership.


                                 ARTICLE TWELVE
                                 --------------

                        VALUATION AND APPRAISAL PROCEDURE
                        ---------------------------------

Section 12.1 General
             -------

     The determination of the fair market value of the Premises pursuant to
Section 3.5, the determination of the net fair market value of the Interest of
a. retiring General Partner pursuant to Section 6.1, and. the determination of
the net fair market value of the Defaulting Partner's Partnership Interest
pursuant to Section 3.3.B(2) shall be accomplished in accordance with the
provisions of Subsection A, Subsection B or Subsection C, as the case may be. of
Section 12.2. All Partners acknowledge and confirm that the guiding principle
underlying the appraisal procedure set forth in Section 12.2 shall be that each
determination of such fair market value or of such net fair market value, as the
case may be, shall be accomplished expeditiously, in good faith and at
reasonable expense to the Partnership and to the particular Partner or Partners
in question.

     Any appraiser designated or appointed to serve in accordance with the
provisions of Section 12.2 shall be disinterested and shall be qualified to
appraise real estate of the same type as the Premises and situated in the
vicinity of the Premises, shall be a member of the American Institute of Real
Estate Appraisers (or any successor association or body of comparable standing
if such Institute is not then in existence), and shall have been actively
engaged in the appraisal of real estate situated in the vicinity of the Premises
for a period of not less than ten (10) years immediately preceding his
designation or appointment.

Section 12.2 Appraisal Procedure
             -------------------

     A.   The determination of the fair market value of the Premises pursuant to
          Section 3.5 shall be accomplished in accordance with the procedure set
          forth in this Subsection A of Section 12.2.

                                       35


<PAGE>   40


          If the General Partners (on behalf of the Partnership) and Telco are
          unable to agree on the fair market value of the Premises within ten
          (10) business days of the occurrence of an Excess Cash Proceeds Event
          giving rise to the determination, then either party (that is, either
          the General Partners on behalf of the Partnership or Telco) may
          request, on behalf of both, within an additional further period of ten
          (10) business days, the appointment of a qualified appraiser (the
          "Appraiser") by the President of The Greater Boston Real Estate Board
          (or any successor association or body of comparable standing if such
          Board is not then in existence) or the person to whom the President
          may delegate that function; and if no person then serves in that
          capacity, then by the person serving in comparable position. The party
          so requesting shall give notice to the other party of the appointment
          of the Appraiser within three (3) business days of such appointment.
          Within fifteen (15) business days following such notice of the
          appointment of the Appraiser, each party shall set forth and deliver
          in writing, in duplicate, to the Appraiser its position as to such
          fair market value supported by the reasons therefor. If either party
          fails timely to submit its position, the position submitted by the
          other party shall constitute the decision of the Appraiser and shall
          be final and binding upon the parties. Neither party may amend its
          position once such position has been delivered to the Appraiser'. At
          the expiration of such fifteen (15) business day period, the Appraiser
          shall transmit the position of each party to the other party.

          The Appraiser shall independently investigate all 'matters bearing on
          the determination of such fair market value, shall select within
          fifteen (15) business days following the expiration of the foregoing
          fifteen (15) business day period, which of the two submitted positions
          more closely approximates his determination of such fair market value
          and shall immediately give notice of such selection to each party. The
          Appraiser shall, have no right to propose a middle ground or any
          modification of either of the two submitted positions. The Appraiser
          shall have the right to consult experts and competent authorities with
          factual information or knowledge concerning the determination of such
          fair market value. The position the Appraiser selects as more closely
          approximating his determination shall constitute the decision of the
          Appraiser and shall be final and binding upon the parties.
          Notwithstanding anything to the contrary contained in this Subsection
          A, the determination by the Appraiser of such fair market value shall
          be based upon the following conditions and assumptions:

          (1)  that the valuation date is the effective date of the Excess Cash
               Proceeds Event giving rise to the determination;

          (2)  that the then current use of the Premises is the highest and best
               use thereof; and

          (3)  that, even if the Premises are encumbered by the TIAA Lease on
               the valuation date, the determination shall nevertheless be made
               as if the Premises are not then encumbered by the TIAA Lease.

                                       36

             
<PAGE>   41


          In the event of the failure, refusal or inability of the Appraiser to
          act, a new Appraiser shall be appointed in his stead, which
          appointment shall be made in the same manner as hereinbefore provided
          for the appointment of such Appraiser so failing, refusing or being
          unable to act.

          All fees and expenses incurred with respect to the determination of
          such fair market value in accordance with this Subsection A --
          including, without limitation, the fees of the Appraiser and the costs
          of both parties (including their reasonable attorneys' fees) with
          respect to the preparation and submission of their respective
          positions -- shall be paid by the party whose position is not selected
          by the Appraiser.

     B.   The determination of the net fair market value of the Interest of a
          retiring General Partner pursuant to Section 6.1 shall be accomplished
          in accordance with the procedure set forth in this Subsection B of
          Section 12.2.

          If the Partnership. and the retiring General Partner are unable to
          agree on the net fair market value of the Interest within ten (10)
          business days of the effective date of the retirement of a General
          Partner, then either party (that is, either the Partnership or the on
          behalf of both, within an retiring General Partner) may request,
          additional further period of ten business (10) days. the appointment
          of a qualified appraiser (the "Appraiser") by the President of The
          Greater Boston Real Estate Board (or any successor association or body
          of comparable standing if such Board is not then in existence) or the
          person to whom the President may delegate that function; and if no
          person then serves in that capacity, then by the person serving in
          comparable position. The party so requesting shall give notice to the
          other party of the appointment of the Appraiser within three (3)
          business days of such appointment. Within fifteen (15) business days
          following such notice of the appointment of the Appraiser, each party
          shall set forth and deliver in writing, in. duplicate, to the
          Appraiser its position as to such net fair market value supported by
          the reasons therefor. If either party fails timely to submit its
          position, the position submitted by the other party shall constitute
          the decision of the Appraiser and shall be final and binding upon the
          parties. Neither party may amend its position once such position has
          been delivered to the Appraiser. At the expiration of such fifteen
          (15) business day period, the Appraiser shall transmit the position of
          each party to the other party.

          The Appraiser shall independently investigate all matters bearing on
          the determination of such net fair market value, shall select, within
          fifteen (15) business days following the expiration of the foregoing
          fifteen (15) business day period, which of the two submitted positions
          more closely approximates his determination of such net fair market
          value and shall immediately give notice of such selection to each
          party. The Appraiser shall have no right to propose it middle ground
          or any modification of either of the two submitted positions. The
          Appraiser shall have the right to consult experts and competent
          authorities with factual information or knowledge concerning the

                                       37


<PAGE>   42


          determination of such net fair market value. The position the
          Appraiser selects as more closely approximating his determination
          shall constitute the decision of the Appraiser and shall be final and
          binding upon the parties. Notwithstanding anything to the contrary
          contained in this Subsection B, the determination by the Appraiser of
          such net fair market value shall be based upon the following
          conditions and assumptions:

          (1)  that the valuation date is the effective date of retirement of
               the General Partner;

          (2)  that the then current use of the Premises is the highest and best
               use thereof; and

          (3)  that, even if the Premises are encumbered by the TIAA Lease on
               the valuation date, the determination shall nevertheless be made
               as if the Premises are not then encumbered by the TIAA Lease.

          In the event of the failure, refusal or inability of the Appraiser to
          act, a new Appraiser shall be appointed in his stead, which
          appointment shall be made in the same manner as hereinbefore Provided
          for the appointment of such Appraiser so failing, refusing or being
          unable to act.

          All fees and expenses incurred with respect to the determination of
          such net fair market value in accordance with this Subsection B
          including, without limitation, the fees of the Appraiser and the costs
          of both parties (including their reasonable attorneys' fees) with
          respect to the preparation and submission of their respective
          positions -- shall be paid by the party whose position is not selected
          by the Appraiser.

     C.   The determination of the net fair market value of the Defaulting
          Partner's Partnership Interest pursuant to Section 3.3.B(2) shall be
          accomplished in accordance with the procedure set forth in Subsection
          B of this Section 12.2; PROVIDED that the Acquiring Partner shall be
          substituted for the Partnership and the Defaulting Partner shall be
          substituted for the retiring General Partner; and PROVIDED FURTHER
          that notwithstanding anything to the contrary contained in said
          Subsection B, the determination by the Appraiser of such net fair
          market value shall be based upon the following conditions and
          assumptions:

          (1)  that the valuation date is the date of default of the Defaulting
               Partner pursuant to Section 3.3.B;

          (2)  that the then current use of the Premises is the highest and best
               use thereof; and

          (3)  that, if the Premises. are encumbered by the TiAA Lease on the
               valuation date, the determination shall be made taking into
               account such encurmbrance.

                                       38


<PAGE>   43


                                ARTICLE THIRTEEN
                                ----------------
 
                           MISCELLANEOUS PROVISIONS
                           ------------------------

Section 13.1 Appointment of Each General Partner as Attorney-in-Fact
             -------------------------------------------------------

     A.   Each Limited Partner irrevocably constitutes and appoints each General
          Partner, with full power of substitution, as his true and lawful
          attorney-in-fact, with full power and authority in his name, place,
          and stead to execute, acknowledge, make, swear to, consent to, verify,
          deliver, record, file, and/or publish at the appropriate public
          offices such documents, instruments and conveyances as may be
          reasonably necessary or appropriate to carry out the provisions or
          purposes of this Agreement, including without limitation, the
          following:

          (1)  the Certificate;

          (2)  all other certificates and instruments and amendments thereto
               which the General Partners deem appropriate to qualify or
               continue the Partnership as a limited partnership (or a
               partnership in which the Limited Partners will have limited
               liability comparable to that provided by the Act) in the
               jurisdictions in which the Partnership may conduct business;

          (3)  all instruments which the General Partners deem appropriate to
               reflect (a) any change or modification of the Partnership in
               accordance with the provisions of this Agreement or (b) any
               action of the Partners provided for in this Agreement's

          (4)  all conveyances and other instruments which the General Partners
               deem appropriate to reflect the dissolution and termination of
               the Partnership;

          (5)  all fictitious or assumed name certificates required or permitted
               to be filed on behalf of the Partnership;

          (6)  any and all amendments of the Partnership necessary to admit
               Limited Partners to the Partnership or to reflect any change in
               or Transfer of a Partner's Partnership Interest;

          (7)  any and all instruments and documents referred to in Subsection B
               of this Section 13.1; and

          (8)  all other instruments which may be required or permitted by law
               to be filed on behalf of the Partnership and which are not
               inconsistent with this Agreement.

     B.   Each Limited Partner hereby affirms that he is aware that the terms of
          this Agreement permit certain amendments hereof to be effected and
          certain other actions to be taken or omitted by or with respect to the
          Partnership with the approval or Consent of fewer than all of the
          Limited Partners. If, as and when

                                       39


<PAGE>   44


          (1)  an amendment of this Agreement is proposed or an action is
               proposed to be taken or omitted by or with respect to the
               Partnership which requires, under the terms hereof, the approval
               or Consent of fewer than all of the Limited Partners,

          (2)  sufficient Limited Partners as required under this Agreement for
               such amendment or action have approved or Consented to such
               amendment or action in the manner contemplated by this Agreement,
               and

          (3)  one or more Limited Partners have failed or refused to approve or
               Consent to such amendment or action,

     then each Limited Partner hereby agrees that if from time to time he is a
     Limited Partner referred to in Subsection B(3) of this Section 13.1, then
     the attorney-in-fact specified in Subsection A of this Section 13.1, with
     full power of substitution, is hereby authorized and empowered to execute,
     acknowledge, makes swear to, consent to, verify, deliver, record, file,
     and/or publish, for and on his behalf, and in his name, place, and stead,
     any and all instruments and documents which may be necessary or appropriate
     to permit such amendment to be lawfully made or such action to be lawfully
     taken or omitted.

     Each Limited Partner is fully aware that he and each other Limited Partner
     have executed this special power of attorney, and that each Limited Partner
     will rely on the effectiveness of such powers with a view to the orderly
     administration of the Partnership's affairs.

     C. The grant of authority in Subsections A and B of this Section 13.1:

          (1)  is a special power of attorney coupled with an interest, is
               irrevocable, and shall survive any Incapacity of the Limited
               Partner to the extent he may legally contract for such survival;

          (2)  may be exercised by a signature for each Limited Partner or by
               listing the names of all the Limited Partners executing this
               Agreement with a single signature of any such Person acting as
               attorney-in-fact for all of them;

          (3)  shall survive the Transfer by a Limited Partner of the whole or
               any portion of his Interest; PROVIDED that where the Transferee
               thereof has been approved by the General Partners for admission
               to the Partnership as a Substitute Limited Partner, this special
               power of attorney shall survive such Transfer for the sole
               purpose of enabling the General Partners to execute, acknowledge
               and file any instrument necessary to effect such substitution and
               shall thereafter terminate.

     D.   Any Person dealing with the Partnership may conclusively presume and
          rely upon the fact that any certificate, instruments document or
          conveyance referred to in this Section 13.1, executed by such Person
          acting as attorney-in-fact, is authorized, regular and binding,
          without further inquiry.

                                       40


<PAGE>   45


Section 13.2 Notices, Approvals, and Consents
             --------------------------------

     All notices, approvals, Consents or other communications hereunder shall be
in writing and signed by the party giving the same and shall be deemed to have
been given when the same are (i) deposited in the United States mail and sent by
certified or registered mail, postage prepaid, or (ii) delivered -- in each case
to the parties at the addresses referred to below or at such other addresses as
such parties may designate by notice to the Partnership:

     (1)  if to the Partnership or to the General Partners, at the Principal
          office of the Partnership, with a copy of such notice by first class
          mail to the General Partners at their addresses listed in, Section
          2.5, or to such other address or addresses as may be designated by
          notice from the Partnership or the General Partners;

     (2)  if to the Limited Partners, at their addresses as set forth on Exhibit
          A attached hereto, with a copy of such notice by first class mail to
          the Partnership at its principal office, or to such other address or
          addresses as may be designated by notice from the Limited Partners or
          the Partnership or any of them.

     Except as otherwise expressly stated in this Agreement, all approvals and
Consents hereunder shall not be unreasonably withheld or delayed.

Section 13.3 Binding Provisions
             ------------------

     The covenants and agreements contained herein shall be binding upon and
shall inure to the benefit of the legal representatives, heirs, executors,
administrators, successors and, subject to the provisions hereof, the assigns of
the respective parties hereto.

Section 13.4 Applicable Law
             --------------

     This Agreement shall be construed and enforced in accordance with and
governed by the laws of the-State.

Section 13.5 Entire Agreement
             ----------------

     Except as otherwise expressly set forth in this Agreement, this Agreement
constitutes the entire agreement among the parties with respect to the
Partnership. This Agreement supersedes any prior agreement or understanding
among the parties and may not be modified or amended in any manner other than
as; set forth herein.

Section 13.6 Further Assurances
             ------------------

     The Partners will execute, acknowledge and deliver such further instruments
and do such further acts and things as may be required to carry out the intent
and purpose of this Agreement.

Section 13.7 Captions
             --------

     Captions contained in this Agreement are inserted only as a matter of
convenience and in no way define, limit the extent, or describe the scope Of
this Agreement or the intent of any of the provisions thereof.

                                       41


<PAGE>   46


Section 13.8 Effect on Creditors
             -------------------

     Except to the extent required under the Act, none of the provisions of this
Agreement shall be for the benefit of or be enforceable by any creditor of the
Partnership, other than a Partner or an Affiliate of a Partner as a creditor.

Section 13.9 Separability
             ------------

     If one or more of the provisions of this Agreement or any application
thereof shall be invalid, illegal or unenforceable in any respect, the validity,
legality and enforceability of the remaining provisions contained herein and any
other application thereof shall not in any way be affected or impaired thereby.

Section 13.10 Counterparts
              ------------

     This Agreement may be signed by each party hereto in several counterparts,
in which event all such counterparts shall constitute one agreement, binding on
all the parties hereto, except that no counterpart shall be binding; unless
signed by the General Partners.

Section 13.11 Jurisdiction
              ------------

     At the request of the General Partners, any Limited Partner who is not a
Massachusetts resident shall execute any documents necessary to designate the
Secretary of the State or any other Person chosen by the General Partners, in
their sole discretion, for service of process on him in any, action or
proceeding brought by any party to this Agreement against him or 'Arising out of
this Agreement or in breach thereof.

Section 13.12 Attorneys' Fees
              ---------------

     A Partner shall pay all reasonable attorneys' fees and expenses of the
Partnership incurred in the successful enforcement by the Partnership of any of
the obligations of such Partner under this Agreement. If the obligations of'
more than one Partner are the subject of such successful enforcement, by the
Partnership, then the responsibility for payment of such fees and expenses shall
be allocated between or among such Partners in proportion to their respective
Partnership Interests.

     The Partnership shall pay all reasonable attorneys' fees and expenses of a
Partner or Partners incurred in the successful enforcement by such Partner or
Partners of any of the obligations of the Partnership under this Agreement.

     IN WITNESS WHEREOF, the parties hereto have executed under seal and sworn
to this Agreement on the dates set opposite their respective signatures below,
but effective as of the date first above written.

                                       42


<PAGE>   47
                                                                               
                                                                               
Date: 8/29/85                              /s/ James F. Carlin                 
-------------                              ------------------------------------
                                           James F. Carlin, General Partner    
                                            and Limited Partner                
                                                                               
Date: 8/29/85                              /s/ William A. Yetman               
-------------                              ------------------------------------
                                           William A. Yetman, General Partner  
                                            and Limited Partner                
                                                                               
Date:                                                                          
-------------                              ------------------------------------
                                           Craig L. Burr, Limited Partner      
                                                                               
Date:                                                                          
-------------                              ------------------------------------
                                           Jean Deleage, Limited Partner       
                                                                               
Date:                                                                          
-------------                              ------------------------------------
                                           John J. Egan, Limited Partner       
                                                                               
Date:                                                                          
-------------                              ------------------------------------
                                           William P. Egan, Limited Partner    
                                                                               
Date:                                                                          
-------------                              ------------------------------------
                                           James W. Intinarelli, Limited       
                                            Partner                            
                                                                               
                                                                               
                                                                               
                                           Telco Systems, Inc., Limited Partner
                                                                               
Date: 8/29/85                              By: /s/ Kent L. Robertson, CFO      
-------------                              ------------------------------------
                                           President, hereunto duly            
                                            authorized

                                       43




<PAGE>   48


     Richard R. Vazza, Francis M. Vazza and Nahatan Street Development
Corporation hereby confirm and recognize that their respective interests in the
Partnership are fully redeemed by the Partnership effective herewith so that the
same are no longer partners in the Partnership.

     IN WITNESS WHEREOF, the undersigned have executed under seal and. sworn to
this Agreement on the dates set opposite their respective signatures below, but
effective as of the date first above written.

Date: AUG 29, 1985                         /s/ Richard R. Vazza,
------------------                         -------------------------------------
                                           Richard R. Vazza, withdrawing        
                                            general partner                     
                                                                                
                                                                                
Date: AUG 29, 1985                         /s/ Francis M. Vazza,                
------------------                         -------------------------------------
                                           Francis M. Vazza, withdrawing        
                                            general partner                     
                                                                                
                                                                                
                                           NAHATAN STREET DEVELOPMENT           
                                           CORPORATION, withdrawing general     
                                           partner                              
                                                                                
                                                                                
Date: AUG 29, 1985                         /s/ Richard R. Vazza, President      
------------------                         -------------------------------------
                                                       , hereunto duly          
                                            authorized                          
                                                                                
                                                                                
                                       44                                       
                                                                                
                                                                                
                                                                                
<PAGE>   49


                          COMMONWEALTH OF MASSACHUSETTS

  Suffolk ,ss.                                               August 29, 1985

     Then personally appeared before me, James F. Carlin, who, being duly sworn,
acknowKedged that he executed the foregoing instrument. as his free act: and
deed as general Partner and Limited Partner of Nahatan Street Associates Limited
Partnership, and that the statements set forth therein are true to the best of
his Knowledge and belief,

[Seal]                                       /s/ Saul Weber
                                             ----------------------------------
                                             Notary Public                     
                                                                               
My commission expires: 2/11/88                                                 
                                                                               
                                                                               
                                                                               
                                                                               
                          COMMONWEALTH OF MASSACHUSETTS                        
                                                                               
  Suffolk ,ss.                                               August 29, 1985   
                                                                               
     Then personally appeared before me, William A. Yetman, who, being duly    
sworn, acknowledged that he executed the foregoing instrument as his free act  
and deed as General Partner and Limited Partner of Nahatan Street Associates   
LIMITED Partnership, and that the statements set forth therein are true to the 
best of his knowledge and belief,                                              
                                                                               
[Seal]                                       /s/ Cynthia A. Bacon              
                                             ----------------------------------
                                             Notary Public                     
                                                                               
                                               CYNTHIA A. BACON, Notary Public 
My commission expires:                       My Commission Expires April 7 1989
                                                                               
                                                                               
                                                                               
                                                                               
                          COMMONWEALTH OF MASSACHUSETTS                        
                                                                               
          ,ss.                                                        , 1985   
                                                                               
     Then personally appeared before me, Craig L. Burr, who, being duly sworn, 
acknowledged that he executed the foregoing instrument as his free act and deed
as Limited Partner of Nahatan Street Associates Limited Partnership, and that  
the statements set forth therein are true to the best of his knowledge and     
belief,                                                                        
                                                                               
                                             ----------------------------------
                                             Notary Public                     
                                                                               
My commission expires:                                                         


                                       45


<PAGE>   50


                               STATE OF CALIFORNIA

          ,ss.                                                        , 1985

     Then personally appeared before me, Jean Deleage, who, being duly sworn,
acknowledged that he executed the foregoing instrument as his free act: and deed
as Limited Partner of Nahatan Street Associates Limited Partnership, and that
the statements set forth therein are true to the best of his knowledge and
belief,
                                                                             
                                             ----------------------------------
                                             Notary Public                     
                                                                               
My commission expires:                                                         
                                                                               
                                                                               
                                                                               
                                                                               
                          COMMONWEALTH OF MASSACHUSETTS                        
                                                                               
          ,ss.                                                        , 1985   
                                                                               
     Then personally appeared before me, John J. Egan, who, being duly sworn,  
acknowledged that he executed the foregoing instrument as his free act and deed
as Limited Partner of Nahatan Street Associates Limited Partnership, and that  
the statements set forth therein are true to the best of his knowledge and     
belief,                                                                        
                                                                               
                                             ----------------------------------
                                             Notary Public                     
                                                                               
My commission expires:                                                         
                                                                               
                                                                               
                                                                               
                                                                               
                          COMMONWEALTH OF MASSACHUSETTS                        
                                                                               
          ,ss.                                                        , 1985   
                                                                               
  Then personally appeared before me, William P. Egan, who, being duly sworn,  
acknowledged that he executed the foregoing instrument as his free act and deed
as Limited Partner of Nahatan Street Associates Limited Partnership, and that  
the statements set forth therein are true to the best of his knowledge and     
belief,                                                                        
                                                                               
                                             ----------------------------------
                                             Notary Public                     

My commission expires: 

                                       46


<PAGE>   51


                          COMMONWEALTH OF MASSACHUSETTS

          ,ss.                                                        , 1985

  Then personally appeared before me, James W. Intinarelli, who, being duly
sworn, acknowledged that he executed the foregoing instrument as his free act
and deed as Limited Partner of Nahatan Street Associates Limited Partnership,
and that the statements set forth therein are true to the best of his knowledge
and belief,

                                             ----------------------------------
                                             Notary Public

My commission expires: 




                          COMMONWEALTH OF MASSACHUSETTS

  Suffolk ,ss.                                               August 29, 1985

     Then personally appeared before me, Kent L. Robertson, the President of
Telco Systems, Inc., who, being duly sworn, acknowledged that he executed the
foregoing instrument as the free act and deed of Telco Systems, Inc. as Limited
Partner of Nahatan Street Associates Limited Partnership, and that the
statements set forth therein are true to the best of his knowledge and belief,

[Seal]                                       /s/ Cynthia A. Bacon
                                             ----------------------------------
                                             Notary Public

                                               CYNTHIA A. BACON, Notary Public
My commission expires:                       My Commission Expires April 7 1989



                                       47



<PAGE>   52



                          COMMONWEALTH OF MASSACHUSETTS

  Suffolk ,ss.                                               August 29, 1985

     Then personally appeared before me, Richard R. Vazza, who, being duly
sworn, acknowledged that he executed the foregoing instrument as his free act
and deed as general partner of Nahatan Street Associates Limited Partnership,
and that the statements set forth therein are true to the best of his knowledge
and belief,
                                             /s/ William R. Rody
                                             ----------------------------------
                                             Notary Public

My commission expires: 11/2/90





                          COMMONWEALTH OF MASSACHUSETTS

  Suffolk ,ss.                                               August 29, 1985

     Then personally appeared before me, Francis M. Vazza, who, being duly
sworn, acknowledged that he executed the foregoing instrument as his free act
and deed as general partner of Nahatan Street Associates Limited Partnership,
and that the statements set forth therein are true to the best of his knowledge
and belief,

                                             /s/ William R. Rody
                                             ----------------------------------
                                             Notary Public

My commission expires: 11/2/90




                          COMMONWEALTH OF MASSACHUSETTS

  Suffolk ,ss.                                               August 29, 1985

     Then personally appeared before me, the President of Nahatan Street
Development corporation, being duly sworn, acknowledged that he executed the
foregoing instrument as the free act and deed of Nahatan Street Development
Corporation, as general partner of Nahatan Street Associates Limited
Partnership, and that the statements set forth therein are true to the best of
his knowledge and belief,

                                             /s/ William R. Rody
                                             ----------------------------------
                                             Notary Public

My commission expires: 11/2/90

                                                  48


<PAGE>   53


Date: 8/29/85                              /s/ James F. Carlin                 
-------------                              ------------------------------------
                                           James F. Carlin, General Partner    
                                            and Limited Partner                
                                                                               
Date: 8/29/85                              /s/ William A. Yetman               
-------------                              ------------------------------------
                                           William A. Yetman, General Partner  
                                            and Limited Partner                
                                                                               
Date:                                                                          
-------------                              ------------------------------------
                                           Craig L. Burr, Limited Partner      
                                                                               
Date: 8/26/85                              /s/ Jean Deleage                    
-------------                              ------------------------------------
                                           Jean Deleage, Limited Partner       
                                                                               
Date:                                                                          
-------------                              ------------------------------------
                                           John J. Egan, Limited Partner       
                                                                               
Date:                                                                          
-------------                              ------------------------------------
                                           William P. Egan, Limited Partner    
                                                                               
Date:                                                                          
-------------                              ------------------------------------
                                           James W. Intinarelli, Limited       
                                            Partner                            
                                                                               
Date:                                                                          
-------------                              ------------------------------------
                                           James A. Radley, Limited Partner    
                                                                               
                                                                               
                                           Telco Systems, Inc., Limited Partner
                                                                               
Date:                                      By:                                 
-------------                                 ---------------------------------
                                                      , hereunto duly          
                                            authorized                         
                                                                               
                                       43




<PAGE>   54
                                                                               
Date: 8/29/85                              /s/ James F. Carlin                 
-------------                              ------------------------------------
                                           James F. Carlin, General Partner    
                                            and Limited Partner                
                                                                               
Date: 8/29/85                              /s/ William A. Yetman               
-------------                              ------------------------------------
                                           William A. Yetman, General Partner  
                                            and Limited Partner                
                                                                               
Date:                                                                          
-------------                              ------------------------------------
                                           Craig L. Burr, Limited Partner      
                                                                               
Date:                                                                          
-------------                              ------------------------------------
                                           Jean Deleage, Limited Partner       
                                                                               
Date:                                                                          
-------------                              ------------------------------------
                                           John J. Egan, Limited Partner       
                                                                               
Date:                                                                          
-------------                              ------------------------------------
                                           William P. Egan, Limited Partner    
                                                                               
Date: 8/22/95                              /s/ James W. Intinarelli            
-------------                              ------------------------------------
                                           James W. Intinarelli, Limited       
                                            Partner                            
                                                                               
Date:                                                                          
-------------                              ------------------------------------
                                           James A. Radley, Limited Partner    
                                                                               
                                                                               
                                           Telco Systems, Inc., Limited Partner
                                                                               
Date: 8/29/85                              By:                                 
-------------                                 ---------------------------------
                                                    , hereunto duly            
                                            authorized


                                       43
<PAGE>   55

Date: 8/29/85                              /s/ James F. Carlin
-------------                              ------------------------------------
                                           James F. Carlin, General Partner    
                                            and Limited Partner                
                                                                               
Date: 8/29/85                              /s/ William A. Yetman               
-------------                              ------------------------------------
                                           William A. Yetman, General Partner  
                                            and Limited Partner                
                                                                               
Date:                                                                          
-------------                              ------------------------------------
                                           Craig L. Burr, Limited Partner      
                                                                               
Date:                                                                          
-------------                              ------------------------------------
                                           Jean Deleage, Limited Partner       
                                                                               
Date: 8/23/85                               /s/ John J. Egan                   
-------------                              ------------------------------------
                                           John J. Egan, Limited Partner       
                                                                               
Date: 8/26/85                              /s/ William P. Egan                 
-------------                              ------------------------------------
                                           William P. Egan, Limited Partner    
                                                                               
Date:                                                                          
-------------                              ------------------------------------
                                           James W. Intinarelli, Limited       
                                            Partner                            
                                                                               
Date:                                                                          
-------------                              ------------------------------------
                                           James A. Radley, Limited Partner    
                                                                               
                                                                               
                                           Telco Systems, Inc., Limited Partner
                                                                               
Date: 8/29/85                              By:                                 
-------------                                 ---------------------------------
                                                    , hereunto duly            
                                            authorized


                                       43
<PAGE>   56
Date: 8/29/85                              /s/ James F. Carlin
------------------                         ------------------------------------
                                           James F. Carlin, General Partner    
                                            and Limited Partner                
                                                                               
Date: 8/29/85                              /s/ William A. Yetman               
------------------                         ------------------------------------
                                           William A. Yetman, General Partner  
                                            and Limited Partner                
                                                                               
Date: Aug 26, 1985                         /s/ Craig L. Burr                   
------------------                         ------------------------------------
                                           Craig L. Burr, Limited Partner      
                                                                               
Date:                                                                          
------------------                         ------------------------------------
                                           Jean Deleage, Limited Partner       
                                                                               
Date:                                                                          
------------------                         ------------------------------------
                                           John J. Egan, Limited Partner       
                                                                               
Date:                                                                          
------------------                         ------------------------------------
                                           William P. Egan, Limited Partner    
                                                                               
Date:                                                                          
------------------                         ------------------------------------
                                           James W. Intinarelli, Limited       
                                            Partner                            
                                                                               
Date:                                                                          
------------------                         ------------------------------------
                                           James A. Radley, Limited Partner    
                                                                               
                                                                               
                                           Telco Systems, Inc., Limited Partner
                                                                               
                                                                               
Date:                                      By:                                 
------------------                            ---------------------------------
                                                    , hereunto duly            
                                            authorized


                                       43

<PAGE>   57


                          COMMONWEALTH OF MASSACHUSETTS

  Suffolk ,ss.                                               August 29, 1985

     Then personally appeared before me, James F. Carlin, who, being duly sworn,
acknowKedged that he executed the foregoing instrument. as his free act: and
deed as general Partner and Limited Partner of Nahatan Street Associates Limited
Partnership, and that the statements set forth therein are true to the best of
his Knowledge and belief,

[Seal]                                       /s/ Saul Weber
                                             ----------------------------------
                                             Notary Public

My commission expires: 2/11/88




                          COMMONWEALTH OF MASSACHUSETTS

          ,ss.                                                        , 1985

     Then personally appeared before me, William A. Yetman, who, being duly
sworn, acknowledged that he executed the foregoing instrument as his free act
and deed as General Partner and Limited Partner of Nahatan Street Associates
LIMITED Partnership, and that the statements set forth therein are true to the
best of his knowledge and belief,

                                                                  
                                             ----------------------------------
                                             Notary Public

                                                                              
My commission expires:                                                         




                          COMMONWEALTH OF MASSACHUSETTS

  Suffolk ,ss.                                               August 26, 1985

     Then personally appeared before me, Craig L. Burr, who, being duly sworn,
acknowledged that he executed the foregoing instrument as his free act and deed
as Limited Partner of Nahatan Street Associates Limited Partnership, and that
the statements set forth therein are true to the best of his knowledge and
belief,
                                             /s/ Rochelle A. Bennett
                                             ----------------------------------
                                             Notary Public

My commission expires: 
       ROCHELLE A. BENNETT
           Notary Public
MY COMMISSION EXPIRES FEBRUARY 23, 1990

                                       45

<PAGE>   58

                  STATE OF CALIFORNIA, COUNTY OF SAN FRANCISCO

          ,ss.                                         AUGUST 26, 1985

     Then personally appeared before me, Jean Deleage, who, being duly sworn,
acknowledged that he executed the foregoing instrument as his free act: and deed
as Limited Partner of Nahatan Street Associates Limited Partnership, and that
the statements set forth therein are true to the best of his knowledge and
belief,

        OFFICIAL SEAL
       DIANE R. IMAI                        /s/ Diane R. Imai 
    NOTARY PUBLIC - CALIFORNIA              -----------------------------------
     San Francisco County                   Notary Public                      
  My Commission Expires Jan 18 1988     

My commission expires:




                          COMMONWEALTH OF MASSACHUSETTS

          ,ss.                                                        , 1985

     Then personally appeared before me, John J. Egan, who, being duly sworn,
acknowledged that he executed the foregoing instrument as his free act and deed
as Limited Partner of Nahatan Street Associates Limited Partnership, and that
the statements set forth therein are true to the best of his knowledge and
belief,

                                             ----------------------------------
                                             Notary Public

My commission expires: 




                          COMMONWEALTH OF MASSACHUSETTS

          ,ss.                                                        , 1985

  Then personally appeared before me, William P. Egan, who, being duly sworn,
acknowledged that he executed the foregoing instrument as his free act and deed
as Limited Partner of Nahatan Street Associates Limited Partnership, and that
the statements set forth therein are true to the best of his knowledge and
belief,

                                             ----------------------------------
                                             Notary Public

My commission expires: 

                                       46


<PAGE>   59


                               STATE OF CALIFORNIA

          ,ss.                                                        , 1985

     Then personally appeared before me, Jean Deleage, who, being duly sworn,
acknowledged that he executed the foregoing instrument as his free act: and deed
as Limited Partner of Nahatan Street Associates Limited Partnership, and that
the statements set forth therein are true to the best of his knowledge and
belief,

                                             ----------------------------------
                                             Notary Public

My commission expires: 




                          COMMONWEALTH OF MASSACHUSETTS

Suffolk County,ss.                                             August 23, 1985

     Then personally appeared before me, John J. Egan, who, being duly sworn,
acknowledged that he executed the foregoing instrument as his free act and deed
as Limited Partner of Nahatan Street Associates Limited Partnership, and that
the statements set forth therein are true to the best of his knowledge and
belief,
                                             /s/ Francis F. Kingsley Jr. 
                                             ----------------------------------
                                             Notary Public
                                             FRANCIS F. KINGSLEY JR.
My commission expires:                       My Commission Expires July 16, 1987




                          COMMONWEALTH OF MASSACHUSETTS

Suffolk County,ss.                                             August 26, 1985

  Then personally appeared before me, William P. Egan, who, being duly sworn,
acknowledged that he executed the foregoing instrument as his free act and deed
as Limited Partner of Nahatan Street Associates Limited Partnership, and that
the statements set forth therein are true to the best of his knowledge and
belief,

                                             /s/ Francis F. Kingsley Jr. 
                                             ----------------------------------
                                             Notary Public
                                             FRANCIS F. KINGSLEY JR.
My commission expires:                       My Commission Expires July 16, 1987


                                       46


<PAGE>   60


                          COMMONWEALTH OF MASSACHUSETTS

Suffolk, ss.                                                August 22, 1985

     Then personally appeared before me, James W. Intinarelli, who, being duly
sworn, acknowledged that he executed the foregoing instrument as his free act
and deed as Limited Partner of Nahatan Street Associates Limited Partnership,
and that the statements set forth therein are true to the best of his knowledge
and belief
                                             Sanford M. McDonald 
                                             ----------------------------------
                                             Notary Public

My commission expires: 



                          COMMONWEALTH OF MASSACHUSETTS

           , ss.                                                        1985

     Then personally appeared before me. James A. Radley, who, being duly sworn,
acknowledged that he executed the foregoing instrument as his free act and deed
as Limited Partner of Nahatan Street Associates Limited Partnership, and that
the statements set forth therein are true to the best of his knowledge and
belief,

                                             ----------------------------------
                                             Notary Public

My commission expires: 



                               STATE OF CALIFORNIA

           , ss.                                                        1985

     Then personally appeared before me, the President of Telco Systems, Inc.',
who, being duly sworn, acknowledged that he executed the foregoing instrument as
the free act and deed of Telco Systems, Inc. as Limited Partner of Nahatan
Street Associates Limited Partnership, and that the statements set forth therein
are true to the best of his knowledge and belief,

                                             ----------------------------------
                                             Notary Public

My commission expires: 

                                       47


<PAGE>   61


                                   SCHEDULE A
                                   ----------
<TABLE>

     The initial Capital Contributions and the initial Capital Accounts of the
Partners are as follows:

<CAPTION>
                                   Initial Capital       Initial Capital
Partner                             Contribution             Account
-------                             ------------             -------

<S>                                    <C>                    <C>   
James F. Carlin                        $10.25                 $10.25
   (as General Partner)                                      
                                                             
William A. Yetman                      $10.25                 $10.25
   (as General Partner)                                      
                                                             
Craig L. Burr                            8.25                 $ 8.25
                                                             
Jean Deleage                           $ 8.25                 $ 8.25
                                                             
John J. Egan                           $ 1.00                 $ 1.00
                                                             
William P. Egan                        $ 8.25                 $ 8.25
                                                             
James W. Intinarelli                   $ 2.50                 $ 2.50
                                                             
James F. Carlin                        $ 0.50                 $ 0.50
   (as Limited Partner)                                      
                                                             
William A. Yetman                      $ 0.75                 $ 0.75
   (as Limited Partner)                                      
                                                             
Telco Systems, Inc.                    $50.00                 $50.00*
                                               

<FN>

* Subject to adjustment to reflect the Capital Account of TSFOC, its
  predecessor in interest.
</TABLE>

                                       49




<PAGE>   62




                                    EXHIBIT A
                                    ---------
<TABLE>

     The names and addresses of the Limited Partners of the Partnership and
their respective Partnership Interests are as follows:

<CAPTION>
NAME and ADDRESS                            PARTNERSHIP INTEREST
----------------                            --------------------

<S>                                                 <C>  
Craig L. Burr                                       8.25%
237 West Street
Carlisle, MA 01741

Jean Deleage                                        8.25%
98 Sotello Avenue
San Francisco, CA 94116

John J. Egan                                        1.00%
Ocean Drive
Newport, RI 02840

William P. Egan                                     8.25%
Nine Phillips Pond
South Natick, MA 01760

James W. Intinarelli                                2.50%
27 Chamberlain Street
Hopkinton. MA 01748

James F. Carlin                                     0.50%
99 Woodland Street
Natick, MA 01760

William A. Yetman                                   0.75%
5 Bryant Lane
Dover, MA 02030

Telco Systems, Inc.                                50.00%
1040 Marsh Road
Suite 100
Menlo Park, CA 94025
</TABLE>

                                       50


<PAGE>   63

                             SUPPLEMENTARY AGREEMENT
                                       TO
                AMENDED AND RESTATED AGREEMENT AND CERTIFICATE OF
                  NAHATAN STREET ASSOCIATES LIMITED PARTNERSHIP
                             LIMITED PARTNERSHIP OF

     This supplementary Agreement to the Amended and Restated Agreement and
Certificate of Limited Partnership of Nahatan Street Associates Limited
Partnership is made as of this day of August, 1985, by and among James F.
Carlin, William A. Yetman, Craig L. Burr, Jean Deleage, John J. Egan, William P.
Egan, James W. Intinarelli, James A. Radley (the above referred to herein
collectively as the "Crosspoint Group") and Telco Systems, Inc. ("Telco"), all
of whose addresses are set forth on the signature pages hereof.

                                    RECITALS:
                                    ---------

     A. 'Reference is made to the Amended and Restated Agreement and Certificate
of Limited Partnership of Nahatan Street Associates Limited Partnership of even
date herewith (the "Agreement"). Terms used herein which are defined in the
Agreement and not otherwise defined herein shall have the same meanings herein
as therein.

     B. The parties view the payment of the Excess Rent to TSFOC as a rebate of
the Excess Rent so that, to the extent such payment does occur, such Excess Rent
shall not be included in the gross income of the Partnership.

     C. The undersigned, being all the Partners in the Partnership, wish to
clarify the intent of the Agreement (in the event that the intended treatment of
the Excess Rent described immediately above is not determinative) regarding the
allocations of Profits and Losses set forth in the Agreement as such allocations
pertain to the Partnership's receipt from and/or payment to TSFOC of the Excess
Rent. Furthermore, the Partners wish to provide for the making of a certain
preferential payment to the Crosspoint Group by the Partnership in the event
that such allocations are not effective, for whatever reason, in achieving in
whole the intent of the Agreement.

     NOW, THEREFORE, for good and valuable consideration, the receipt and legal
sufficiency of which are hereby acknowledged, the undersigned hereby amend the
Agreement as follows:

     1. Section 4.1.B is amended by inserting after the word and numerals
"Section 4.1" in the first line thereof (and before the comma) thefollowing
words and numerals:'

          "and to Section 4.4".


<PAGE>   64


     2. Section 4.2.B is amended by inserting after the word and numerals
"Section 4.2.D in the first line thereof the following word and numerals:

          ", Section 4.5".

     3. Section 4.2.C is amended by inserting after the word and numerals
"Section 4.2.1)" in the first line thereof the following word and numerals;

          ", Section 4.5".

     4. New section 4.4 and new Section 4.5 are added to the Agreement as
follows:

"Section 4.4 Treatment of Excess Rent
             ------------------------

     The Partners confirm and agree that the Crosspoint Group shall be allocated
Profits and Losses in accordance with this Agreement so that such allocations
shall be unaffected by the Partnership's receipt from and/or payment to TSFOC of
the Excess Rent (including, for purposes of this Section 4.4, any portion
thereof) -- that is, the allocations to the Crosspoint Group shall be determined
and made as if the Excess Rent were neither received nor paid out by the
Partnership. Accordingly, the Partners agree that, in the event that the
Partnership's treatment of the receipt from and the payment to TSFOC of the
Excess Rent is not effective, for whatever reason, in excluding such Excess Rent
from Partnership gross income for federal income tax purposes, and
notwithstanding any other provision of this Agreement, all items, if any, of
income, gain and ,deduction of the Partnership for federal income tax purposes
relating to the Partnership's receipt from and/or payment to TSFOC of the Excess
Rent shall be allocated to Telco (such allocation hereinafter referred to as the
"Allocation"). All other items of income, gain, loss, deduction, credit or the
like shall be allocated in accordance with Section 4.1.

"Section 4.5 Required Payment Amount
             -----------------------

     In the event that the Allocation set forth in Section 4.4 is not effective,
for whatever reason, in achieving in whole the purpose set forth in Section 4.4,
the Partners agree that;

          (i)  the General Partners shall promptly give notice of such fact to
               all Partners;

          (ii) each member of the Crosspoint Group shall deliver to the General
               Partners accurate copies of the portions of his federal, state
               and local income tax returns showing taxable income and
               applicable rate of tax for the relevant period; and

                                        2


<PAGE>   65


         (iii) the Partnership shall determine, in conjunction with the
               Accountant and with reference to the portions of the income tax
               returns delivered in accordance with clause (ii) immediately
               above, and shall pay to each Person comprising the Crosspoint
               Group the amount of cash (the "Required Payment Amount")
               necessary to compensate such Person for federal, state and local
               income tax liability with respect to (1) the excess, if any, of
               (a) the increase in such Person's share of Partnership income and
               gain attributable to the Partnership's receipt from TSFOC of the
               Excess Rent over (b) such Person's share of the Partnership
               deduction, if any, attributable to the Partnership's payment to
               TSFOC of the Excess Rent and (2) the payment to such Person in a
               prior year or years of the Required Payment Amount (such excess
               and such payment hereinafter referred to collectively as the
               "Income").

     If the Partnership's treatment for income tax purposes ofthe Excess Rent is
challenged by the Internal Revenue Service or by. any state or local taxing
authority or enforcement agency, either at the Partnership level or at the level
of any Partner, then Telco shall have the right to select and retain qualified,
independent counsel, at its own expense, for the purpose of defending, in
concert with Partnership counsel or counsel for such Partner, as the case may
be, such treatment against such challenge. If the Partnership's treatment for
income tax purposes as to a prior Fiscal Year(s) of the Excess Rent is
disallowed or adjusted either at the Partnership level or at the level of any
Partner, then the Income and the Required Payment Amount as to such prior Fiscal
Year(s) and as to each Person comprising the Crosspoint Group shall be
determined or redetermined, as the case may. be, in accordance with such
disallowance or adjustment (and taking into account interest and penalties
assessed or imposed with respect thereto) and any increases) in the Required
Payment Amount of any such Person (that is, any increase in the Required Payment
Amount as determined or redetermined for such prior Fiscal Year(s) over the
Required Payment Amount, if any, previously calculated as to such prior Fiscal
Year(s)) shall be paid to such Person within thirty (30) days after such
disallowance or adjustment. Otherwise, the determination and payment of the
Required Payment Amount with respect to each Person comprising the Crosspoint
Group shall occur on a yearly basis not later than thirty (30) days after such
Person delivers to the General Partners copies of appropriate portions of his
federal, state and local income tax returns in accordance with clause (ii)
above.

     Notwithstanding any other provision of this Section 4.5, if, in the case of
any Person comprising the Crosspoint Group,

                                        3


<PAGE>   66


the Income or any portion thereof is sheltered from federal, state and/or local
income taxation by net operating losses of the Partnership and/or otherwise
(that is, such Person does not have taxable income in such taxable year or such
taxable income is less than the Income), then the determination and payment of
the Required Payment Amount with respect to such sheltered Income shall occur
with respect to the taxable year or years of such Person as to which such
sheltered Income or portion thereof is no longer so sheltered (that is, the
first taxable year(s) in which such Person has taxable income equal at least to
such sheltered Income).

     The Required Payment Amount shall be paid to the Crosspoint Group
preferentially out of Distributable Cash and/or Excess Cash Proceeds before any
Distributions are made pursuant to Section 4.2 or Section 4.3. If Distributable
Cash and Excess Cash Proceeds are not sufficient in any Fiscal Year to pay the
Required Payment Amount to the Crosspoint Group, then the amount by which (a)
the Required Payment Amount exceeds (b) the amount, if any, actually paid to the
Crosspoint Group in such Fiscal Year by the Partnership pursuant to this Section
4.5 shall be paid by Telco in accordance with this Section 4.5.

     The costs of Partnership counsel in defending the Partnership's treatment
for income tax purposes of the Excess Rent and all costs with respect to
determining the Required Payment Amount shall be expenses of the Partnership but
shall not be taken into account as such for the purposes of Section 5.3.B.(7).".

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

     The provisions of this Supplementary Agreement shall bind and inure to the
benefit of the undersigned and their respective heirs, executors,
administrators, legal representatives, successors and assigns and shall not be
affected by any amendment or other modification of the Agreement except by
express written reference hereto in such amendment or modification.

     This Supplementary Agreement may be signed by each party hereto in several
counterparts, in which event all such counterparts shall constitute one
agreement, binding on all the parties hereto, except that no counterpart shall
be binding unless signed by the General Partners.

     In all other respects and to the extent not inconsistent herewith the terms
of the Agreement remain in full force and effect and are incorporated herein by
reference.

     IN WITNESS WHEREOF, the undersigned have sworn to and have executed this
Supplementary Agreement as a sealed instrument on the dates set opposite their
respective signatures below, but effective as of the date first above written.

                                        4


<PAGE>   67


ADDRESS:

99 Woodland Street                       /s/ James F. Carlin
                                         ------------------------------------
Natick , MA  01760                       James F. Carlin
Date:                                    Partner and Limited Partner


Five Bryant Lane                         /s/ William A. Yetman   
                                         ------------------------------------
Dover, MA 02030                          William A. Yetman , General
Date:                                    Partner and Limited Partner

237 West Street
                                         ------------------------------------
Carlisle, MA 01741                       Craig L. Burr, Limited Partner
Date:

98 Sotello Avenue
                                         ------------------------------------
San Francisco, CA 94116                  Jean Deleage, Limited Partner
Date:

Ocean Drive
                                         ------------------------------------
Newport, RI 02840                        John J. Egan, Limited Partner
Date:

Nine Phillips Pond
                                         ------------------------------------
South Natick, MA 01760                   William P. Egan, Limited
Date:                                    Partner


27 Chamberlain Street
                                         ------------------------------------
Hopkinton, MA 01748                      James W. Intinarelli, Limited
Date:                                    Partner

One Phillips Pond
                                         ------------------------------------
South Natick, MA 01760                   James A. Radley, Limited
Date:                                    Partner


1040 Marsh Road                          Telco Systems, Inc., Limited
Suite 100                                Partner
Menlo Park, Ca 94025
Date:          
                                         By:
                                            ---------------------------------
                                                           , hereunto
                                           duly authorized


                                        5


<PAGE>   68


                          COMMONWEALTH OF MASSACHUSETTS

Suffolk, ss.                                          August 29, 1985

     Then personally appeared before me, James F. Carlin, who, being duly sworn,
acknowledged that he executed the foregoing instrument as his free act and deed
as General Partner and Limited Partner of Nahatan Street Associates Limited
Partnership, and that the statements set forth therein are true to the best of
his knowledge and belief,

                                                 /s/ Saul Weber 
                                                 -------------------------------
                                                 Notary Public

My commission expires: 2/11/88

                          COMMONWEALTH OF MASSACHUSETTS

Suffolk, ss.                                          August 29, 1985

     Then personally appeared before me, William A. Yetman, who, being duly
sworn, acknowledged that he executed the foregoing instrument as his free act
and deed as General Partner and Limited Partner of Nahatan Street Associates
Limited Partnership, and that the statements set forth. therein are true
to the best of his knowledge and belief,
                                                 /s/ Cynthia A. Bacon
                                                 -------------------------------
                                                 Notary Public
                                                CYNTHIA A. BACON, Notary Public
My commission expires:                         My Commission Expires Apr 7 1989
                                               


                         COMMONWEALTH OF MASSACHUSETTS

       , ss.                                                   , 1985

     Then personally appeared before me, Craig L. Burr, who, being duly sworn,
acknowledged that he executed the foregoing instrument as his free act and deed
as Limited Partner of Nahatan Street Associates Limited Partnership, and that
the statements set forth therein are true to the best of his knowledge and
belief,

                                                                 
                                                 -------------------------------
                                                 Notary Public

My commission expires:

                                        6


<PAGE>   69


                               STATE OF CALIFORNIA

          ,ss.                                                        , 1985

     Then personally appeared before me, Jean Deleage, who, being duly sworn,
acknowledged that he executed the foregoing instrument as his free act: and deed
as Limited Partner of Nahatan Street Associates Limited Partnership, and that
the statements set forth therein are true to the best of his knowledge and
belief,

                                             ----------------------------------
                                             Notary Public

My commission expires: 




                          COMMONWEALTH OF MASSACHUSETTS

          ,ss.                                                        , 1985

     Then personally appeared before me, John J. Egan, who, being duly sworn,
acknowledged that he executed the foregoing instrument as his free act and deed
as Limited Partner of Nahatan Street Associates Limited Partnership, and that
the statements set forth therein are true to the best of his knowledge and
belief,

                                             ----------------------------------
                                             Notary Public

My commission expires: 




                          COMMONWEALTH OF MASSACHUSETTS

          ,ss.                                                        , 1985

  Then personally appeared before me, William P. Egan, who, being duly sworn,
acknowledged that he executed the foregoing instrument as his free act and deed
as Limited Partner of Nahatan Street Associates Limited Partnership, and that
the statements set forth therein are true to the best of his knowledge and
belief,

                                             ----------------------------------
                                             Notary Public

My commission expires: 

                                        7


<PAGE>   70


                          COMMONWEALTH OF MASSACHUSETTS

       , ss.                                                         , 1985

     Then personally appeared before me, James W. Intinarelli, who, being duly
sworn, acknowledged that he executed the foregoing instrument as his free act
and deed as Limited Partner of Nahatan Street Associates Limited Partnership,
and that the statements set forth therein are true to the best of his knowledge
and belief
                                                                 
                                             ----------------------------------
                                             Notary Public

My commission expires: 



                          COMMONWEALTH OF MASSACHUSETTS

           , ss.                                                        1985

     Then personally appeared before me. James A. Radley, who, being duly sworn,
acknowledged that he executed the foregoing instrument as his free act and deed
as Limited Partner of Nahatan Street Associates Limited Partnership, and that
the statements set forth therein are true to the best of his knowledge and
belief,

                                             ----------------------------------
                                             Notary Public

My commission expires: 



                               STATE OF CALIFORNIA

           , ss.                                                        1985

     Then personally appeared before me, the President of Telco Systems, Inc.',
who, being duly sworn, acknowledged that he executed the foregoing instrument as
the free act and deed of Telco Systems, Inc. as Limited Partner of Nahatan
Street Associates Limited Partnership, and that the statements set forth therein
are true to the best of his knowledge and belief,

                                             ----------------------------------
                                             Notary Public

My commission expires: 


                                       8
<PAGE>   71

ADDRESS:

99 Woodland Street                       /s/ James F. Carlin
                                         ------------------------------------
Natick , MA  01760                       James F. Carlin
Date: 8/29/85                            Partner and Limited Partner
     -------------

Five Bryant Lane                         /s/ William A. Yetman   
                                         ------------------------------------
Dover, MA 02030                          William A. Yetman , General
Date: 8/29/85                            Partner and Limited Partner
     -------------

237 West Street                          /s/ Craig L. Burr
                                         ------------------------------------
Carlisle, MA 01741                       Craig L. Burr, Limited Partner
Date:
     -------------

98 Sotello Avenue
                                         ------------------------------------
San Francisco, CA 94116                  Jean Deleage, Limited Partner
Date:
     -------------

Ocean Drive
                                         ------------------------------------
Newport, RI 02840                        John J. Egan, Limited Partner
Date:
     -------------

Nine Phillips Pond
                                         ------------------------------------
South Natick, MA 01760                   William P. Egan, Limited
Date:                                    Partner
     -------------


27 Chamberlain Street
                                         ------------------------------------
Hopkinton, MA 01748                      James W. Intinarelli, Limited
Date:                                    Partner
     -------------

One Phillips Pond
                                         ------------------------------------
South Natick, MA 01760                   James A. Radley, Limited
Date:                                    Partner
     -------------


1040 Marsh Road                          Telco Systems, Inc., Limited
Suite 100                                Partner
Menlo Park, Ca 94025
Date:          
     -------------
                                         By:
                                            ---------------------------------
                                                           , hereunto
                                           duly authorized


                                        5


<PAGE>   72


ADDRESS:

99 Woodland Street                       /s/ James F. Carlin
                                         ------------------------------------
Natick , MA  01760                       James F. Carlin
Date:                                    Partner and Limited Partner
     -------------


Five Bryant Lane                         /s/ William A. Yetman   
                                         ------------------------------------
Dover, MA 02030                          William A. Yetman , General
Date:                                    Partner and Limited Partner
     -------------

237 West Street
                                         ------------------------------------
Carlisle, MA 01741                       Craig L. Burr, Limited Partner
Date:
     -------------

98 Sotello Avenue                        /s/ Jean Deleage
                                         ------------------------------------
San Francisco, CA 94116                  Jean Deleage, Limited Partner
Date: 8/26/85
     -------------

Ocean Drive
                                         ------------------------------------
Newport, RI 02840                        John J. Egan, Limited Partner
Date:
     -------------

Nine Phillips Pond
                                         ------------------------------------
South Natick, MA 01760                   William P. Egan, Limited
Date:                                    Partner
     -------------


27 Chamberlain Street
                                         ------------------------------------
Hopkinton, MA 01748                      James W. Intinarelli, Limited
Date:                                    Partner
     -------------

One Phillips Pond
                                         ------------------------------------
South Natick, MA 01760                   James A. Radley, Limited
Date:                                    Partner
     -------------


1040 Marsh Road                          Telco Systems, Inc., Limited
Suite 100                                Partner
Menlo Park, Ca 94025
Date:          
     -------------
                                         By:
                                            ---------------------------------
                                                           , hereunto
                                           duly authorized


                                        5



<PAGE>   73

ADDRESS:

99 Woodland Street                       /s/ James F. Carlin
                                         ------------------------------------
Natick , MA  01760                       James F. Carlin
Date:  8/29/85                           Partner and Limited Partner
     -------------


Five Bryant Lane                         /s/ William A. Yetman   
                                         ------------------------------------
Dover, MA 02030                          William A. Yetman , General
Date:  8/29/85                           Partner and Limited Partner
     -------------

237 West Street
                                         ------------------------------------
Carlisle, MA 01741                       Craig L. Burr, Limited Partner
Date:
     -------------

98 Sotello Avenue                        
                                         ------------------------------------
San Francisco, CA 94116                  Jean Deleage, Limited Partner
Date:
     -------------

Ocean Drive                              /s/ John J. Egan
                                         ------------------------------------
Newport, RI 02840                        John J. Egan, Limited Partner
Date: 8/26/85
     -------------

Nine Phillips Pond                       /s/ William P. Egan
                                         ------------------------------------
South Natick, MA 01760                   William P. Egan, Limited
Date: 8/26/85                            Partner
     -------------


27 Chamberlain Street
                                         ------------------------------------
Hopkinton, MA 01748                      James W. Intinarelli, Limited
Date:                                    Partner
     -------------

One Phillips Pond
                                         ------------------------------------
South Natick, MA 01760                   James A. Radley, Limited
Date:                                    Partner
     -------------


1040 Marsh Road                          Telco Systems, Inc., Limited
Suite 100                                Partner
Menlo Park, Ca 94025
Date: 8/29/85  
     -------------
                                         By: /s/ Kent L. Robertson CFO
                                            ---------------------------------
                                                           , hereunto
                                           duly authorized


                                        5


<PAGE>   74

ADDRESS:

99 Woodland Street                       /s/ James F. Carlin
                                         ------------------------------------
Natick , MA  01760                       James F. Carlin
Date: 8/29/85                            Partner and Limited Partner
     -------------


Five Bryant Lane                         /s/ William A. Yetman   
                                         ------------------------------------
Dover, MA 02030                          William A. Yetman , General
Date: 8/29/85                            Partner and Limited Partner
     -------------

237 West Street
                                         ------------------------------------
Carlisle, MA 01741                       Craig L. Burr, Limited Partner
Date:
     -------------

98 Sotello Avenue
                                         ------------------------------------
San Francisco, CA 94116                  Jean Deleage, Limited Partner
Date:
     -------------

Ocean Drive
                                         ------------------------------------
Newport, RI 02840                        John J. Egan, Limited Partner
Date:
     -------------

Nine Phillips Pond
                                         ------------------------------------
South Natick, MA 01760                   William P. Egan, Limited
Date:                                    Partner
     -------------


27 Chamberlain Street                    /s/ James W. Intinarelli
                                         ------------------------------------
Hopkinton, MA 01748                      James W. Intinarelli, Limited
Date: 8/22/85                            Partner
     -------------

One Phillips Pond
                                         ------------------------------------
South Natick, MA 01760                   James A. Radley, Limited
Date:                                    Partner
     -------------


1040 Marsh Road                          Telco Systems, Inc., Limited
Suite 100                                Partner
Menlo Park, Ca 94025
Date: 8/29/85  
     -------------
                                         By: /s/ Kent L. Robertson, CFO
                                            ---------------------------------
                                                           , hereunto
                                           duly authorized


                                        5

<PAGE>   75



                          COMMONWEALTH OF MASSACHUSETTS

  Suffolk ,ss.                                               August 29, 1985

     Then personally appeared before me, James F. Carlin, who, being duly sworn,
acknowKedged that he executed the foregoing instrument. as his free act: and
deed as general Partner and Limited Partner of Nahatan Street Associates Limited
Partnership, and that the statements set forth therein are true to the best of
his Knowledge and belief,

[Seal]                                       /s/ Saul Weber
                                             ----------------------------------
                                             Notary Public

My commission expires: 2/11/88




                          COMMONWEALTH OF MASSACHUSETTS

          ,ss.                                                        , 1985

     Then personally appeared before me, William A. Yetman, who, being duly
sworn, acknowledged that he executed the foregoing instrument as his free act
and deed as General Partner and Limited Partner of Nahatan Street Associates
LIMITED Partnership, and that the statements set forth therein are true to the
best of his knowledge and belief,

                                                                  
                                             ----------------------------------
                                             Notary Public

                                                                              
My commission expires:                                                         




                          COMMONWEALTH OF MASSACHUSETTS

  Suffolk ,ss.                                               August 26, 1985

     Then personally appeared before me, Craig L. Burr, who, being duly sworn,
acknowledged that he executed the foregoing instrument as his free act and deed
as Limited Partner of Nahatan Street Associates Limited Partnership, and that
the statements set forth therein are true to the best of his knowledge and
belief,
                                             /s/ Rochelle A. Bennett
                                             ----------------------------------
                                             Notary Public

My commission expires: 
       ROCHELLE A. BENNETT
           Notary Public
MY COMMISSION EXPIRES FEBRUARY 23, 1990


                                        6


<PAGE>   76
                  STATE OF CALIFORNIA, COUNTY OF SAN FRANCISCO

          ,ss.                                         AUGUST 26, 1985

     Then personally appeared before me, Jean Deleage, who, being duly sworn,
acknowledged that he executed the foregoing instrument as his free act: and deed
as Limited Partner of Nahatan Street Associates Limited Partnership, and that
the statements set forth therein are true to the best of his knowledge and
belief,

        OFFICIAL SEAL
       DIANE R. IMAI                        /s/ Diane R. Imai 
    NOTARY PUBLIC - CALIFORNIA              -----------------------------------
     San Francisco County                   Notary Public                      
  My Commission Expires Jan 18 1988     

My commission expires:




                          COMMONWEALTH OF MASSACHUSETTS

          ,ss.                                                        , 1985

     Then personally appeared before me, John J. Egan, who, being duly sworn,
acknowledged that he executed the foregoing instrument as his free act and deed
as Limited Partner of Nahatan Street Associates Limited Partnership, and that
the statements set forth therein are true to the best of his knowledge and
belief,

                                             -----------------------------------
                                             Notary Public

My commission expires: 




                          COMMONWEALTH OF MASSACHUSETTS

          ,ss.                                                        , 1985

  Then personally appeared before me, William P. Egan, who, being duly sworn,
acknowledged that he executed the foregoing instrument as his free act and deed
as Limited Partner of Nahatan Street Associates Limited Partnership, and that
the statements set forth therein are true to the best of his knowledge and
belief,

                                             -----------------------------------
                                             Notary Public

My commission expires: 

                                                7


<PAGE>   77


                               STATE OF CALIFORNIA

          ,ss.                                                        , 1985

     Then personally appeared before me, Jean Deleage, who, being duly sworn,
acknowledged that he executed the foregoing instrument as his free act: and deed
as Limited Partner of Nahatan Street Associates Limited Partnership, and that
the statements set forth therein are true to the best of his knowledge and
belief,

                                             -----------------------------------
                                             Notary Public                      
                                                                                
My commission expires:                                                          
                                                                                
                                                                                
                                                                                
                                                                                
                          COMMONWEALTH OF MASSACHUSETTS                         
                                                                                
Suffolk County,ss.                                             August 23, 1985  
                                                                                
     Then personally appeared before me, John J. Egan, who, being duly sworn,   
acknowledged that he executed the foregoing instrument as his free act and deed 
as Limited Partner of Nahatan Street Associates Limited Partnership, and that   
the statements set forth therein are true to the best of his knowledge and      
belief,                                                                         
                                             /s/ Francis F. Kingsley Jr.        
                                             -----------------------------------
                                             Notary Public                      
                                             FRANCIS F. KINGSLEY JR.            
My commission expires:                       My Commission Expires July 16, 1987
                                                                                
                                                                                
                                                                                
                                                                                
                          COMMONWEALTH OF MASSACHUSETTS                         
                                                                                
Suffolk County,ss.                                             August 26, 1985  
                                                                                
  Then personally appeared before me, William P. Egan, who, being duly sworn,   
acknowledged that he executed the foregoing instrument as his free act and deed 
as Limited Partner of Nahatan Street Associates Limited Partnership, and that   
the statements set forth therein are true to the best of his knowledge and      
belief,                                                                         
                                                                                
                                             /s/ Francis F. Kingsley Jr.        
                                             -----------------------------------
                                             Notary Public                      
                                             FRANCIS F. KINGSLEY JR.            
My commission expires:                       My Commission Expires July 16, 1987
                                                                                

                                        7


<PAGE>   78




                          COMMONWEALTH OF MASSACHUSETTS

Suffolk, ss.                                                August 22, 1985

     Then personally appeared before me, James W. Intinarelli, who, being duly
sworn, acknowledged that he executed the foregoing instrument as his free act
and deed as Limited Partner of Nahatan Street Associates Limited Partnership,
and that the statements set forth therein are true to the best of his knowledge
and belief
                                             Sanford M. McDonald 
                                             ----------------------------------
                                             Notary Public

My commission expires: 



                          COMMONWEALTH OF MASSACHUSETTS

           , ss.                                                        1985

     Then personally appeared before me. James A. Radley, who, being duly sworn,
acknowledged that he executed the foregoing instrument as his free act and deed
as Limited Partner of Nahatan Street Associates Limited Partnership, and that
the statements set forth therein are true to the best of his knowledge and
belief,

                                             ----------------------------------
                                             Notary Public

My commission expires: 



                               STATE OF CALIFORNIA

           , ss.                                                        1985

     Then personally appeared before me, the President of Telco Systems, Inc.',
who, being duly sworn, acknowledged that he executed the foregoing instrument as
the free act and deed of Telco Systems, Inc. as Limited Partner of Nahatan
Street Associates Limited Partnership, and that the statements set forth therein
are true to the best of his knowledge and belief,

                                             ----------------------------------
                                             Notary Public

My commission expires: 


                                       8
<PAGE>   79


                                                 August 29, 1985

Mr. Kent Robertson
Chief Financial Officer
Telco Systems, Inc.
1040 Marsh Road - Suite 100
Menlo Park, California 94025

Dear Mr. Robertson:

     As consideration for your execution of that certain Amended and Restated
Agreement of Limited Partnership of Nahatan Street Associates Limited
Partnership (the "Agreement"), we hereby agree to vote to amend the Agreement as
set forth below.

     1.   The definition of "Affiliate" shall be amended and restated in its
          entirety as follows:

          "AFFILIATE: with respect to any specified Person, any other Person
          directly controlling or controlled by or under direct common control
          with such specified Person. For the purposes of this definition, the
          term control when used with respect to any specified Person means the
          power to direct the management and policies of such Person, whether
          through the ownership of voting securities, by contract or otherwise;
          and the terms CONTROLLING and CONTROLLED BY have the meaning
          correlative to the foregoing.

     2.   The definition of "Substantial Majority In Interest" shall be amended
          by deleting the term "seventy-five percent MU" and substituting the
          term "seventy-two percent (72%)".

     3.   Section 5.3.B.(2) shall be amended by inserting the phrase "or any
          other material asset of the Partnership" after the word "Premises" in
          the first line thereof.

     4.   Section 7.5A shall be amended by deleting clause (iii) and
          substituting the following language therefor:

          "(iii) otherwise, only with the Consent of the General Partners and a
          Majority in Interest of the Limited Partners which may not be withheld
          unreasonably"


<PAGE>   80


     5.   A new Section 13.13 shall be added which states as follows:

          "Section 13.13 No Partition. No Partner shall cause or permit the
          Premises to be partitioned or otherwise divided except as expressly
          permitted hereunder."

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

     With your approval, the Agreement will be amended as set forth above on or
before September 15, 1985.

                                                Very truly yours,
                                               
                                                /s/ William A. Yetman
                                                ---------------------
                                                William A. Yetman
                                               
                                                /s/ James F. Carlin
                                                ---------------------
                                                James F. Carlin