EXHIBIT 10.18

                                   Mass Mutual



                                  Office Lease

                                 By And Between

                                 Mass Mutual and

                           Saville Systems U.S., Inc.



                             For: Suite #500 & #501
                                  Landmark One
                              1 Van de Graaff Drive
                                 Burlington, MA


                            A "Mass Mutual" Property



<PAGE>


MM Equity No. 9615

                                  OFFICE LEASE

THIS LEASE,  made as of this 15 day of May , 1997 by and  between  MASSACHUSETTS
MUTUAL LIFE INSURANCE COMPANY, a Massachusetts  corporation ("Landlord") through
its agent  CORNERSTONE  REAL  ESTATE  ADVISERS,  INC.,  having an address at One
Financial Plaza, Suite 1700, Hartford, Connecticut 061032604 and SAVILLE SYSTEMS
U.S., INC., a Massachusetts company ("Tenant") having its principal office at 25
Mall Road, Sixth Floor, Burlington, Massachusetts 01803.

                                      INDEX
<TABLE>

Article Title                                                         Page
<S>     <C>                                                           <C> 

1       Basic Provisions                                               2
2       Premises, Term and Commencement Date                           4
3       Rent                                                           4
4       Taxes and Operating Expenses                                   4
5       Landlord's Work, Tenant's Work, Alterations and Additions      6
6       Use                                                            7
7       Services                                                       7
8       Insurance                                                      9
9       Indemnification                                                9
10      Casualty Damage                                               10
11      Condemnation                                                  10
12      Repair and Maintenance                                        11
13      Inspection of Premises                                        11
14      Surrender of Premises                                         12
15      Holding Over                                                  12
16      Subletting and Assignment                                     12
17      Subordination, Attornment and Mortgagee Protection            13
18      Estoppel Certificate                                          13
19      Defaults                                                      14
20      Remedies of Landlord                                          14
21      Quiet Enjoyment                                               15
22      Accord and Satisfaction                                       15
23      Security Deposit                                              15
24      Brokerage Commission                                          16
25      Force Majeure                                                 16
26      Parking                                                       17
27      Hazardous Materials                                           17
28      Additional Rights Reserved by Landlord                        18
29      Defined Terms                                                 19
30      Miscellaneous Provisions                                      22
31      Special Provisions                                            25

</TABLE>


EXHIBITS

Exhibit A  Plan Showing Property and Premises                         28
Exhibit B  Landlord's Work Letter                                     29
Exhibit C  Tenant's Work                                              33
Exhibit D  Building's Rules and Regulations;Janitorial Specifications 34
Exhibit E  Commencement Date Confirmation                             37



<PAGE>


                                   ARTICLE 1.

                                BASIC PROVISIONS


A.     Tenant's Trade Name:               Saville Systems U.S., Inc.

B.     Tenant's Address:                  Suite 500 & 501
                                          One Van de Graaff Drive
                                          Burlington, Massachusetts 01803

C.     Office Building Name:              Landmark One

       Address:                           One Van de Graaff Drive
                                          Burlington, Massachusetts 01803

D.     Premises: Suite/Unit No.:          500 & 501
       Square feet (Rentable):            12,417 rsf

E.     Landlord:                          Massachusetts Mutual Life Insurance 
                                          Company

F.     Landlord's Address:            c/o Cornerstone Real Estate Advisers,Inc.
                                          311 S. Wacker Drive
                                          Suite 980
                                          Chicago, Illinois 60606

G.     Building Manager/Address:          Peter Elliot LLC
                                          980 Washington Street
                                          Dedham, Massachusetts 02026

H.     Commencement Date:                 July 15, 1997

I.     Expiration Date:                   July 31, 2002

J.     Security Deposit:                  $49,668.00

K.     Monthly Rent:                      Year l:$24,834.00, Year 2:$25,351.38, 
                                          Year 3:$25,868.75, Year 4:$26,386.13,
                                          Year 5:$26,903.50

L.     Operating Expenses Base:           Actual 1996 Calendar Year

M.     Tax Base:                          Actual 1997 Fiscal Year

N.     Tenant's  Pro Rata  Share:  7.70 %.  Tenant's  Pro Rata Share  shall be
determined  by and  adjusted  by  Landlord  from time to time (but  shall not be
readjusted  sooner than the  commencement of the second Lease year), by dividing
the Tenant's  Rentable  Square Feet of the Premises by the rentable  area of the
Building and multiplying the resulting quotient, to the second decimal place, by
one hundred.

O.     Normal Business Hours of Building:
        Monday through Friday: 8:00 a.m. to 6:00 p.m.
        Saturday: 8:00 a.m. to 1:00 p.m.
        Sunday: N/A am. to  N/A p.m.

P.    Brokers:                   Peter Elliot LLC / Spaulding & Slye
Q.    Parking Fee:               41 unreserved spaces at no charge
R.    Tenant's Original
      Electrical Factor:         $.90 per rentable square foot per year
                                 $931.28 per month
                                 $11,175.30 per year

The foregoing provisions shall be interpreted and applied in accordance with the
other provisions of this Lease set forth below.  The capitalized  terms, and the
terms defined in Article 29, shall have the meanings set forth herein or therein
(unless otherwise modified in the Lease) when used as capitalized terms in other
provisions of the Lease.


                                   ARTICLE 2.

                      PREMISES, TERM AND COMMENCEMENT DATE

Landlord  hereby  leases and demises to the Tenant and Tenant  hereby  takes and
leases from Landlord  that certain space  identified in Article 1 and shown on a
plan attached hereto as Exhibit A ("Premises") for a term ("Term") commencing on
the Commencement  Date and ending on the Expiration Date set forth in Article 1,
unless sooner  terminated as provided herein,  subject to the provisions  herein
contained.  The  Commencement  Date set forth in Article 1 shall be  advanced to
such earlier date as Tenant commences  occupancy of the Premises for the conduct
of its business.  Such date shall be confirmed by execution of the  Commencement
Date  Confirmation  in the form as set forth in  Exhibit E. If  Landlord  delays
delivering  possession  of  the  Premises  or  substantial   completion  of  any
Landlord's  Work  under  Exhibit B, this  Lease  shall not be void or  voidable,
except as provided in Article 5, and Landlord  shall have no liability  for loss
or damage resulting therefrom.


                                   ARTICLE 3.

                                      RENT

A. Monthly Rent. Tenant shall pay Monthly Rent in advance on or before the first
day of each month of the Term. If the Term shall commence and end on a day other
than the first day of a month,  the Monthly  Rent for the first and last partial
month shall be prorated on a per diem basis.  Upon the  execution of this Lease,
Tenant shall pay one installment of Monthly Rent for the first full month of the
Term and a prorated Monthly Rent for any partial month which may precede it.

B. Additional Rent. All costs and expenses which Tenant assumes or agrees to pay
and any other sum payable by Tenant pursuant to this Lease,  including,  without
limitation,  its  share  of  Taxes  and  Operating  Expenses,  shall  be  deemed
Additional Rent.

C. Rent.  Monthly Rent,  Additional Rent,  Taxes and Operating  Expenses and any
other  amounts which Tenant is or becomes  obligated to pay Landlord  under this
Lease are herein referred to collectively as "Rent", and all remedies applicable
to the  nonpayment  of Rent  shall be  applicable  thereto.  Landlord  may apply
payments received from Tenant to any obligations of Tenant then accrued, without
regard to such obligations as may be designated by Tenant.

D. Place of Payment,  Late  Charge,  Default  Interest.  Rent and other  charges
required to be paid under this Lease, no matter how described,  shall be paid by
Tenant to Landlord at the Building  Manager's address listed in Article 1, or to
such other person and/or  address as Landlord may designate in writing,  without
any prior  notice  or demand  therefor  and  without  deduction  or  set-off  or
counterclaim and without relief from any valuation or appraisement  laws. In the
event  Tenant fails to pay Rent due under this Lease within ten (1O) days of due
date of said Rent,  Tenant  shall pay to  Landlord a late  charge of ten percent
(10%) on the amount overdue. Any Rent not paid when due shall also bear interest
at the Default Rate.

                                   ARTICLE 4.

                          TAXES AND OPERATING EXPENSES
                                                        
A. Payment of Taxes and Operating Expenses.  It is agreed that during each Lease
Year  beginning  with the first  month of the  second  Lease Year and each month
thereafter  during the original  Lease Term,  or any extension  thereof,  Tenant
shall pay to Landlord as  Additional  Rent, at the same time as the Monthly Rent
is paid,  an amount  equal to  one-twelfth  (1/12) of  Landlord's  estimate  (as
determined by Landlord in its reasonable discretion)of  Tenant's Pro Rata Share
of any projected  increase in the Taxes or Operating Expenses for the particular
Lease Year in excess of the Tax Base or Operating Expenses Base, as the case may
be (the "Estimated  Escalation  Increase").  A final adjustment (the "Escalation
Reconciliation") to be made between the parties as soon as practicable following
the end of each Lease  Year,  but in no event  later than ninety (90) days after
the end of each Lease Year. In computing the Estimated  Escalation  Increase for
any particular Lease Year,  Landlord shall take into account any prior increases
in Tenant's Pro Rata Share of Taxes and Operating Expenses.  If during any Lease
Year the Estimated  Escalation  Increase is less than the  Estimated  Escalation
Increase  for the  previous  Lease  Year on which  Tenant's  share of Taxes  and
Operating  Expenses were based for said year,  such  Additional  Rent  payments,
attributable to Estimated Escalation Increase,  to be paid by Tenant for the new
Lease Year shall be decreased accordingly;  provided,  however, in no event will
the Rent paid by Tenant  hereunder  ever be less than the Monthly  Rent plus all
other amounts of Additional Rent.

As soon as practicable following the end of each Lease Year,but no later than 90
days  following  the end of each Lease Year, Landlord  shall  submit to Tenant a
statement setting forth the Estimated  Escalation  Increase,  if any.  Beginning
with said  statement  for the  second  Lease  Year,  it shall also set forth the
Escalation  Reconciliation for the Lease Year just completed. To the extent that
the  Operating  Expense  Escalation is different  from the Estimated  Escalation
Increase  upon which  Tenant  paid Rent  during  the Lease Year just  completed,
Tenant  shall pay  Landlord  the  difference  in cash  within  thirty  (30) days
following receipt by Tenant of such statement from Landlord, or receive a credit
on  future  Rent  owing  hereunder  (or cash if there is no  future  Rent  owing
hereunder) as the case may be. Until Tenant  receives such  statement,  Tenant's
Rent for the new Lease Year shall continue to be paid at the rate being paid for
the particular  Lease Year just completed,  but Tenant shall commence payment to
Landlord  of the monthly  installment  of  Additional  Rent on the basis of said
statement  beginning on the first day of the month  following the month in which
Tenant  receives  such  statement.  In  addition  to the above,  if,  during any
particular  Lease Year,  there is a change in the  information on which Landlord
based the  estimate  upon which Tenant is then making its  estimated  payment of
Taxes  and  Operating  Expenses  so  that  such  Estimated  Escalation  Increase
furnished to Tenant is no longer accurate, Landlord shall be permitted to revise
such Estimated  Escalation Increase by notifying Tenant, and there shall be such
adjustments  made in the Additional Rent on the first day of the month following
the  serving  of such  statement  on  Tenant  as shall be  necessary  by  either
increasing or decreasing, as the case may be, the amount of Additional Rent then
being  paid by Tenant for the  balance of the Lease Year (but in no event  shall
any such decrease  result in a reduction of the rent below the Monthly Rent plus
all other amounts of Additional Rent). Landlord's and Tenant's  responsibilities
with respect to the Tax and Operating Expense adjustments described herein shall
survive the expiration or early termination of this Lease.
     If the Building is not fully  occupied  during any  particular  Lease Year,
Landlord  may adjust  those  Operating  Expenses  which are affected by Building
occupancy for the particular Lease Year, or portion thereof, as the case may be,
to reflect an occupancy of not less than  ninety-five  percent (95%) of all such
rentable area of the Building.

B. Disputes Over Taxes or Operating  Expenses.  If Tenant disputes the amount of
an  adjustment  or the  proposed  estimated  increase  or  decrease  in Taxes or
Operating  Expenses,  Tenant shall give Landlord  written notice of such dispute
within thirty (30) days after Landlord gives notice to Tenant of such adjustment
or proposed  increase or  decrease.  Tenant's  failure to give such notice shall
waive its right to dispute the amounts so determined.  If Tenant timely objects,
Tenant  shall  have  the  right  to  engage  its  own   accountants   ("Tenant's
Accountants")  for the purpose of  verifying  the  accuracy of the  statement in
dispute,  or the  reasonableness  of the  adjustment  or  estimated  increase or
decrease.  If  Tenant's  Accountants  determine  that an error  has  been  made,
Landlord  and  Tenant's  Accountants  shall  endeavor  to agree upon the matter,
failing  which  Landlord  and  Tenant's  Accountants  shall  jointly  select  an
independent  certified  public  accounting firm (the  "Independent  Accountant")
which firm shall  conclusively  determine  whether the  adjustment  or estimated
increase or decrease is reasonable, and if not, what amount is reasonable.  Both
parties shall be bound by such  determination.  If Tenant's  Accountants  do not
participate  in choosing  the  Independent  Accountant  within 20 days notice by
Landlord, then Landlord's  determination of the adjustment or estimated increase
or decrease shall be  conclusively  determined to be reasonable and Tenant shall
be bound thereby. All costs incurred by Tenant in obtaining Tenant's Accountants
and the  cost of the  Independent  Accountant  shall  be paid by  Tenant  unless
Tenant's  Accountants  disclose an error,  acknowledged by Landlord (or found to
have conclusively  occurred by the Independent  Accountant),  of more than seven
percent  (7%) in the  computation  of the  total  amount  of Taxes or  Operating
Expenses as set forth in the statement submitted by Landlord with respect to the
matter in  dispute;  in which  event  Landlord  shall pay the  reasonable  costs
incurred by Tenant in obtaining such audits. Tenant shall continue to timely pay
Landlord the amount of the prior year's adjustment and adjusted  Additional Rent
determined to be incorrect as aforesaid  until the parties have  concurred as to
the appropriate  adjustment or have deemed to be bound by the  determination  of
the Independent  Accountant in accordance with the preceding  terms.  Landlord's
delay in submitting,  any statement contemplated herein for any Lease Year shall
not  affect  the  provisions  of this  paragraph,  nor  constitute  a waiver  of
Landlord's  rights as set forth  herein for said  Lease  Year or any  subsequent
Lease Years during the Lease Term or any extensions thereof.

                                   ARTICLE 5.

                         LANDLORD'S WORK, TENANT'S WORK,
                            ALTERATIONS AND ADDITIONS

A.  Landlord's  Work.  Landlord shall  construct the Premises in accordance with
Landlord's  obligations  as set  forth in the work  letter  attached  hereto  as
Exhibit B, and  hereinafter  referred to as  "Landlord's  Work."  Landlord  will
deliver the Premises to Tenant with all of Landlord's Work completed (except for
minor and non-material punch list items which in Landlord's  reasonable judgment
will not delay completion of Tenant's Work, as defined in subparagraph B of this
Article)  on or  before  the date  specified  in  Exhibit  B and  Tenant  agrees
thereupon to commence and complete  Tenant's Work on or before the  Commencement
Date. If Landlord is delayed in completing Landlord's Work by strike,  shortages
of labor or materials,  delivery  delays or other matters  beyond the reasonable
control of Landlord,  then Landlord  shall give notice thereof to Tenant and the
date on which  Landlord is to turn the Premises over to Tenant for Tenant's Work
and the Commencement  Date shall be postponed for an equal number of days as the
delay as set forth in the notice. Providing,  however, if such delays exceed one
hundred and twenty (120) days, then either Landlord or Tenant upon notice to the
other shall have the right to terminate  this Lease without  liability to either
party. If the  Commencement  Date is postponed as aforesaid,  Tenant agrees upon
request of Landlord to execute a writing  confirming  the  Commencement  Date on
such form as set forth in Exhibit E attached hereto.

B. Tenant's Work. On and after the date specified in the  immediately  preceding
subparagraph A for delivery of the Premises to Tenant for Tenant's Work, Tenant,
at its sole cost and expense,  shall perform and complete all other improvements
to the Premises (herein called "Tenant's Work")  including,  but not limited to,
all improvements,  work and requirements  required of Tenant under the foregoing
work letter.  Tenant shall complete all of Tenant's Work in good and workmanlike
manner,  fully paid for and free from liens,  in  accordance  with the plans and
specifications  approved by Landlord  and Tenant as provided in Exhibit C, on or
prior to the  scheduled  Commencement  Date.  Tenant  shall  also have the right
during this period to come onto the Premises to install its fixtures and prepare
the Premises for the operation of Tenant's  business.  Notwithstanding  the fact
that  foregoing   activities  by  Tenant  will  occur  prior  to  the  scheduled
Commencement Date, Tenant agrees that all of Tenant's  obligations  provided for
in this  Lease  shall  apply  during  such  period  with  the  exception  of any
obligation to pay Rent.

C. Alterations.  Except as provided in the immediately  preceding  subparagraph,
Tenant  shall make no  structural  alterations  or  additions to the Premises in
excess of $10,000.00  without the prior written  consent of the Landlord,  which
consent Landlord shall not unreasonably withhold or delay.

D. Liens. Tenant shall give Landlord at least ten (10) days prior written notice
(or such  additional  time as may be  necessary  under  applicable  laws) of the
commencement of any Tenant's Work, to afford Landlord the opportunity of posting
and recording notices of non-responsibility. Tenant will not cause or permit any
mechanic's,  materialman's or similar liens or encumbrances to be filed or exist
against  the  Premises or the  Building  or  Tenant's  interest in this Lease in
connection  with work done under this  Article or in  connection  with any other
work.  Tenant  shall  remove any such lien or  encumbrance  by bond or otherwise
within twenty (20) days from the date Tenant receives notice of their existence.
If Tenant falls to do so,  Landlord may pay the amount or take such other action
as Landlord  deems  necessary  to remove any such lien or  encumbrance,  without
being responsible to investigate the validity  thereof.  The amounts so paid and
costs incurred by Landlord shall be deemed  Additional Rent under this Lease and
payable in full upon demand.
         
E. Compliance with ADA.  Notwithstanding  anything to the contrary  contained in
this Lease,  Landlord and Tenant agree that  responsibility  for compliance with
the Americans  With  Disabilities  Act of 1990 (the "ADA") shall be allocated as
follows: (i) Landlord shall be responsible for compliance with the provisions of
Title III of the ADA for all Common Areas, including exterior and interior areas
of the  Building  not  included  within the  Premises  or the  premises of other
tenants;  (ii) Landlord shall be responsible  for compliance with the provisions
of  Title  III of the ADA for any  construction,  renovations,  alterations  and
repairs made within the Premises if such construction,  renovations, alterations
or repairs are made by Landlord (iii) Tenant shall be responsible for compliance
with the provisions of Title III of the ADA for any  construction,  renovations,
alterations  and  repairs  made  within  the  Premises  if  such   construction,
renovations,  alterations and repairs are made by Tenant, its employees,  agents
or contractors, at Tenant's expense or at the direction of Tenant.

                                   ARTICLE 6.

                                       USE

                                                    
A. Use.  Tenant shall use the Premises for general  office  purposes and related
uses, and for no other purpose whatsoever, subject to and in compliance with all
other  provisions of this Lease,  including,  without  limitation the Building's
Rules and  Regulations  attached  as Exhibit D hereto.  Tenant and its  invitees
shall  also have the  non-exclusive  right,  along  with  other  tenants  of the
Building and others  authorized by Landlord,  to use the Common Areas subject to
such  reasonable  rules and regulations as Landlord in its discretion may impose
from time to time.

B. Restrictions. Tenant shall not at any time use or occupy, or suffer or permit
anyone to use or occupy, the Premises or do or permit anything to be done in the
Premises  which:  (a)  causes or is liable to cause  injury to  persons,  to the
Building or its equipment, facilities or systems; (b) impairs or tends to impair
the character,  reputation or appearance of the Building as a first class office
building;  (c) impairs or tends to impair the proper and  economic  maintenance,
operation and repair of the Building or its equipment, facilities or systems; or
(d) annoys or inconveniences or tends to annoy or inconvenience other tenants or
occupants of the Building

C.  Compliance with Laws.  Tenant shall keep and maintain the Premises,  its use
thereof and its business in compliance with all governmental  laws,  ordinances,
rules  and  regulations.  Tenant  shall  comply  with all Laws  relating  to the
Premises  and  Tenant's  use  thereof,  including  without  limitation,  Laws in
connection with the health, safety and building codes, and any permit or license
requirements.  Landlord makes no  representation  that the Premises are suitable
for Tenant's purposes.
                                   ARTICLE 7.

                                    SERVICES

   
A. Climate  Control.  Landlord  shall  furnish heat or air  conditioning  to the
Premises  during Normal  Business Hours of Building as set forth in Article 1 as
required  in  Landlord's   reasonable  judgment  for  the  comfortable  use  and
occupation  of the Premises  consistent  with  standards  for other  first-class
office  buildings.If Tenant requires heat or air conditioning at any other time,
Landlord  shall use reasonable  efforts to furnish such service upon  reasonable
notice from Tenant,  and Tenant shall pay all of Landlord's  reasonable  charges
therefor within 15 days of invoice.

The performance by Landlord of its obligations  under this Article is subject to
Tenant's  compliance  with  the  terms of this  Lease  including  any  connected
electrical  load  established by Landlord.  Tenant shall not use the Premises or
any  part  thereof  in  a  manner   exceeding   the  heating,   ventilating   or
air-conditioning   ("HVAC")  design  conditions   (including  any  occupancy  or
connected   electrical  load   conditions),   including  the   rearrangement  of
partitioning  which  may  interfere  with  the  normal  operation  of  the  HVAC
equipment,  or the use of computer or data processing machines or other machines
or equipment in excess of that  normally  required for a standard  office use of
the Premises.  If any such use requires  changes in the HVAC or plumbing systems
or controls  servicing  the  Premises  or  portions  thereof in order to provide
comfortable occupancy,  such changes may be made by Landlord at Tenant's expense
and Tenant  agrees to promptly  pay any such  amount to  Landlord as  Additional
Rent.

B.  Elevator  Service.  If the Building is equipped  with  elevators,  Landlord,
during Normal  Business  Hours of Building,  shall furnish  elevator  service to
Tenant to be used in common with others.  At least one elevator  shall remain in
service during all other hours.  Landlord may designate a specific  elevator for
use as a service elevator.

C. Janitorial Services.  Landlord shall provide janitorial and cleaning services
to the Premises, substantially as described in Exhibit D attached hereto. Tenant
shall pay to Landlord on demand the  reasonable  costs  incurred by Landlord for
(i) any  cleaning of the Premises in excess of the  specifications  in Exhibit D
for any reason including,  without limitation,  cleaning required because of (A)
misuse  or  neglect  on the part of  Tenant  or  Tenant's  agents,  contractors,
invitees,  employees and customers,  (B) the use of portions of the Premises for
special purposes  requiring greater or more difficult  cleaning work than office
areas,  (C) interior  glass  partitions or unusual  quantities of interior glass
surfaces,  and (D)  non-building  standard  materials  or finishes  installed by
Tenant or at its  request;  and (ii) removal from the Premises of any refuse and
rubbish of Tenant in excess of that  ordinarily  accumulated  in general  office
occupancy or at times other than Landlord's standard cleaning times.

D. Water and  Electricity.  Landlord  shall  make  available  domestic  water in
reasonable  quantities  to the common areas of the Building (and to the Premises
if so  designated  in  Exhibit  B) and cause  electric  service  sufficient  for
lighting  the  Premises  and for the  operation  of Ordinary  Office  Equipment.
"Ordinary  Office  Equipment"  shall mean  office  equipment  wired for 120 volt
electric  service  and  rated and  using  less  than 6  amperes  or 750 watts of
electric current or other office equipment approved by Landlord in writing, such
approval not to be  unreasonably  withheld or delayed.  Landlord  shall have the
exclusive  right to make any  replacement of lamps,  fluorescent  tubes and lamp
ballasts in the  Premises.  Landlord may adopt a system of revamping and ballast
replacement  periodically  on a group basis in accordance  with good  management
practice.  Tenant's use of electric energy in the Premises shall not at any time
exceed the  capacity of any of the risers,  piping,  electrical  conductors  and
other  equipment  in or  serving  the  Premises.  In order to  insure  that such
capacity  is not  exceeded  and to avert any  possible  adverse  effect upon the
Building's  electric system,  Tenant shall not, without Landlord's prior written
consent in each instance*,  connect  appliances or heavy duty  equipment,  other
than ordinary office  equipment,  to the Building's  electric system or make any
alteration or addition to the Building's electric system.  Should Landlord grant
its consent in writing, all additional risers,  piping and electrical conductors
or other  equipment  therefor shall be provided by Landlord and the cost thereof
shall be paid by  Tenant  within 15 days of  Landlord's  demand  therefor.  As a
condition to granting such consent,  Landlord may require  Tenant to agree to an
increase  in  Monthly  Rent to offset  the  expected  cost to  Landlord  of such
additional  service,  that is, the cost of the additional  electric energy to be
made  available to Tenant based upon the estimated  additional  capacity of such
additional  risers,  piping and  electrical  conductors or other  equipment.  If
Landlord and Tenant  cannot agree  thereon,  such cost shall be determined by an
independent  electrical engineer, to be selected by Landlord and paid equally by
both parties.

E.  Separate  Meters.  If the Premises are  separately  metered for any utility,
Tenant  shall pay a utility  charge to  Landlord  (or  directly  to the  utility
company,  if possible) based upon the Tenant's actual consumption as measured by
the meter.  Landlord also reserves the right to install  separate meters for the
Premises to register  the usage of all or any one of the  utilities  and in such
event Tenant shall pay for the cost of utility  usage as metered to the Premises
and which is in  excess of the usage  reasonably  anticipated  by  Landlord  for
normal office usage of the  Premises.  Tenant shall  reimburse  Landlord for the
cost of  installation of meters if Tenant's actual usage exceeds the anticipated
usage level by more than 10 percent.  In any event,  Landlord may require Tenant
to reduce its consumption to the anticipated usage level. The term "utility" for
purposes  hereof may refer to but is not  limited to  electricity,  gas,  water,
sewer, steam, fire protection system,  telephone or other communication or alarm
service, as well as HVAC, and all taxes or other charges thereon.

F. Interruptions. Landlord does not warrant that any of the services referred to
above,  or any other  services  which  Landlord  may  supply,  will be free from
interruption and Tenant  acknowledges  that any one or more of such services may
be  suspended  by reason  of  accident,  repairs,  inspections,  alterations  or
improvements  necessary to be made,  or by strikes or lockouts,  or by reason of
operation  of law, or causes  beyond the  reasonable  control of  Landlord.  Any
interruption  or  discontinuance  of service  shall not be deemed an eviction or
disturbance of Tenant's use and possession of the Premises, or any part thereof,
nor render  Landlord  liable to Tenant for damages by  abatement  of the Rent or
otherwise,  nor relieve Tenant from  performance of Tenant's  obligations  under
this Lease. Landlord shall however, exercise reasonable diligence to restore any
service  so   interrupted and   will  use   reasonable   efforts  to  minimize
interference  with  conduct of Tenant's  business in the  Premises,  and provide
notice when practicable.

G. Utilities  Provided by Tenant.  Tenant shall make application in Tenant's own
name for all utilities  not provided by Landlord and shall:  (i) comply with all
utility company regulations for such utilities,  including  requirements for the
installation  of meters,  and (ii) obtain such utilities  directly from, and pay
for the same when due  directly to, the  applicable  utility  company.  The term
"utilities" for purposes hereof shall include but not be limited to electricity,
gas, water, sewer, steam, fire protection, telephone and other communication and
alarm services, as well as HVAC, and all taxes or other charges thereon.  Tenant
shall  install  and  connect  all  equipment  and lines  required to supply such
utilities to the extent not already available at or serving the Premises,  or at
Landlord's option shall repair, alter or replace any such existing items. Tenant
shall  maintain,  repair and replace all such items,  operate the same, and keep
the same in good  working  order and  condition.  Tenant  shall not  install any
equipment  or  fixtures,  or use the same,  so as to exceed  the safe and lawful
capacity of any utility  equipment or lines serving the same.  The  installation
alteration,  replacement or connection of any utility  equipment and lines shall
be subject to the  requirements  for  alterations  of the  Premises set forth in
Article 5. Tenant shall ensure that all Tenant's  HVAC  equipment,  is installed
and  operated at all times in a manner to prevent roof leaks,  damage,  or noise
due to vibrations or improper installation, maintenance or operation.

                                   ARTICLE 8.

                                   INSURANCE

A.  Required  Insurance.   Tenant  shall  maintain  insurance   policies,   with
responsible companies licensed to do business in the state where the Building is
located and reasonably  satisfactory to Landlord,  naming  Landlord,  Landlord's
Building  Manager,  Cornerstone  Real  Estate  Advisers,  Inc.,  Tenant  and any
Mortgagee  of  Landlord  of which  Tenant is given  notice ,as their  respective
interests  may  appear,  at its own cost and  expense  including  (i) "all risk"
property insurance which shall be primary on the lease  improvements  referenced
in  Article  5  and  Tenant's  property,  including  its  goods,  equipment  and
inventory,  in an amount adequate to cover their replacement cost; (ii) business
interruption  insurance,  (iii) comprehensive  general liability insurance on an
occurrence  basis with limits of liability in an amount not less than $1,000,000
(One  Million  Dollars)   combined  single  limit  for  each   occurrence.   The
comprehensive general liability policy shall include contractual liability which
includes the provisions of Article 9 herein.

On or before  the  Commencement  Date of the  Lease,  Tenant  shall  furnish  to
Landlord and its Building,  Manager,  certificates  of insurance  evidencing the
aforesaid  insurance  coverage,  including  naming,  Landlord,  Cornerstone Real
Estate Advisers,  Inc. and Landlord's  Building Manager as additional  insureds.
Renewal  certificates  must be  furnished  to Landlord at least thirty (30) days
prior to the  expiration  date of such  insurance  policies  showing  the  above
coverage to be in full force and effect.

All such insurance  shall provide that it cannot be canceled  except upon thirty
(30) days prior written  notice to Landlord.  Tenant shall comply with all rules
and directives of any insurance board,  company or agency  determining  rates of
hazard coverage for the Premises,  including but not limited to the installation
of any equipment  and/or the correction of any,  condition  necessary to prevent
any increase in such rates,  unless the same  constitutes  Landlord s obligation
under the Lease, including without limitation, Article 12.

B. Waiver of Subrogation.  Landlord and Tenant each agree that neither  Landlord
nor Tenant will have any claim against the other for any loss,  damage or injury
which is covered by  insurance  carried by either  party and for which  recovery
from such insurer is made,  notwithstanding  the  negligence  of either party in
causing the loss.  This release shall be valid only if the  insurance  policy in
question  permits waiver of subrogation or if the insurer agrees in writing that
such waiver of  subrogation  will not affect  coverage  under said policy.  Each
party  agrees to use its best  efforts  to  obtain  such an  agreement  from its
insurer if the policy does not expressly permit a waiver of subrogation.

C.  Waiver  of  Claims.  Except  for  claims  arising  from  Landlord's  willful
misconduct that are not covered by Tenant's insurance required hereunder, Tenant
waives all claims  against  Landlord  for injury or death to persons,  damage to
property  or to any other  interest of Tenant  sustained  by Tenant or any party
claiming,  through  Tenant  resulting  from:  (i) any  occurrence in or upon the
Premises,  (ii) leaking of roofs,  bursting,  stoppage or leaking of water, gas,
sewer or steam pipes or equipment, including sprinklers, (iii) wind, rain, snow,
ice, flooding, freezing, fire, explosion, earthquake, excessive heat or cold, or
other  casualty,  (iv) the Building,  Premises,  or the operating and mechanical
systems or equipment  of the  Building,  being  defective,  or failing,  and (v)
vandalism,  malicious  mischief,  theft or other acts or  omissions of any other
parties including without limitation, other tenants, contractors and invitees at
the Building.  Tenant agrees that Tenant's property loss risks shall be borne by
its  insurance,  and Tenant agrees to look solely to and seek recovery only from
its insurance  carriers in the event of such losses.  For purposes  hereof,  any
deductible  amount  shall be  treated as though it were  recoverable  under such
policies. see ARTICLE 8.D, page 9a

                                   ARTICLE 9.

                                 INDEMNlFICATION
                                                           
Tenant shall indemnify and hold harmless Landlord and its agents, successors and
assigns,  including  its Building  Manager,  from and against all injury,  loss,
costs, expenses, claims or damage (including reasonable attorney's fees and




<PAGE>



ARTICLE 8. INSURANCE new paragraph D.


Landlord shall procure and maintain throughout the term of the Lease a policy or
policies  of  commercial  property  insurance,  issued  on an "all  risk"  basis
insuring the full replacement cost of the Building and improvements  thereto and
the value of the  improvements  to the  Premises  together  with the  furniture,
equipment,  supplies and other property owned,  leased, held or used by Landlord
in connection with the operation and maintenance of the Building,  and workman's
compensation  insurance  as  required by  applicable  law.  Landlord  shall also
procure and  maintain  throughout  the term of the Lease a policy or policies of
commercial  general  liability  insurance  written  on an  occurrence  basis and
insuring Landlord against any and all liability for injury or death of person or
persons  and  for  damage  to  property  occasioned  by or  arising  out  of any
construction being done on the Building, (except in the Premises) or arising out
of the condition,  use or occupancy of the Building, or in any way occasioned by
or  arising  out  of  the  activities  of  Landlord,  its  agents,  contractors,
employees,  guests or  licensees in the  Building,  the limits of such policy or
policies to be in combined single limits for both damaged  property and personal
liability  in amounts not less than Five  Million  dollars for each  occurrence.
Landlord shall also carry such other types of insurance in form and amount which
shall be  comparable  to those  carried  by other  landlords  comparable  office
buildings in the Burlington office market.  All insurance  policies procured and
maintained by Landlord shall be carried with  companies  licensed to do business
in the State of  Massachusetts  and shall be  non-cancelable  and not subject to
material change as to required amounts of coverage.


<PAGE>


disbursements)  to any  person  or  property  arising  from,  related  to, or in
connection  with any use or  occupancy of the Premises by or any act or omission
(including, without limitation,  construction and repair of the Premises arising
out of Tenant's Work or  subsequent  work) of Tenant,  its agents,  contractors,
employees,  customers,  and  invitees,  which  indemnity  extends to any and all
claims  arising from any breach or default in the  performance of any obligation
on  Tenant's  part  to  be  performed  under  the  terms  of  this  Lease.  This
indemnification shall survive the expiration or termination of the Lease Term.

Landlord  shall not be liable  to  Tenant  for any  damage by or from any act or
negligence of any co-tenant or other  occupant of the Building,  or by any owner
or occupants of adjoining or contiguous  property.  Landlord shall not be liable
for any injury or damage to persons or  property  resulting  in whole or in part
from the criminal  activities or willful misconduct of others. To the extent not
covered by all risk property  insurance,  Tenant agrees to pay for all damage to
the  Building,  as well as all damage to persons or property of other tenants or
occupants  thereof,  caused by the  negligence,  fraud or willful  misconduct of
Tenant or any of its agents,  contractors,  employees,  customers  and invitees.
Nothing  contained  herein shall be construed to relieve Landlord from liability
for any personal injury  resulting from its gross  negligence,  fraud or willful
misconduct.

                                   ARTICLE 10.

                                 CASUALTY DAMAGE

Tenant shall  promptly  notify  Landlord or the Building  Manager of any fire or
other  casualty  to the  Premises  or to the extent it knows of  damage,  to the
Building.  In the event the Premises or any substantial  part of the Building is
wholly or  partially  damaged or destroyed  by fire or other  casualty  which is
covered by Landlord's  insurance,  the Landlord will proceed to restore the same
to substantially the same condition  existing,  immediately prior to such damage
or  destruction  unless such damage or  destruction  is  incapable  of repair or
restoration  within,  one hundred  eighty (180) days, in which event Landlord or
tenant  may, at their  option and by written  notice  given to the other  within
sixty (60) days of such damage or destruction,  declare this Lease terminated as
of the  happening of such damage or  destruction.  If in  Landlord's  reasonable
opinion  the net  insurance  proceeds  recovered  by  reason  of the  damage  or
destruction  will not be adequate to complete the  restoration  of the Building,
Landlord  shall  have the  fight  to  terminate  this  Lease  and all  unaccrued
obligations  of the parties  hereto by sending a notice of such  termination  to
Tenant. To the extent after fire or other casualty that Tenant shall be deprived
of the use and  occupancy of the Premises or any portion  thereof as a result of
any such damage,  destruction or the repair  thereof,  providing  Tenant did not
cause the fire or other  casualty,  Tenant shall be relieved of the same ratable
portion of the Monthly Rent  hereunder as the amount of damaged or useless space
in the Premises bears to the rentable  square footage of the Premises until such
time as the Premises may be restored.*  Landlord shall reasonably  determine the
amount of  damaged  or useless  space and the  square  footage  of the  Premises
referenced in the prior  sentence.  Provided if as a result of partial damage or
restriction,  in access to Building or  elimination  of parking,  Tenant  cannot
reasonably  use the  Premises,  Tenant  shall be relieved  of the  Monthly  Rent
hereunder until repairs to the Premises are completed.

                                   ARTICLE 11.

                                  CONDEMNATION

In the event of a condemnation  or taking of the entire  Premises by a public or
quasi-public authority, this Lease shall terminate as of the date title vests in
the public or quasi-public  authority. In the event of a taking, or condemnation
of fifteen  percent  (15%) or more (but less than the whole) of the Building and
without regard to whether the Premises are part of such taking, or condemnation,
Landlord may elect to  terminate  this Lease by giving  notice to Tenant  within
sixty  (60)  days  of  Landlord  receiving  notice  of  such  condemnation.  All
compensation  awarded for any  condemnation  shall be the  property of Landlord,
whether such damages shall be awarded as a  compensation  for  diminution in the
value of the leasehold or to the fee of the Premises,  and Tenant hereby assigns
to Landlord all of Tenant's right, title and interest in and to any and all such
compensation.  Providing,  however  that in the event this Lease is  terminated,
Tenant  shall be  entitled  to make a separate  claim for the taking of Tenant's
personal  property  (including,  fixtures paid for by Tenant),  and for costs of
moving.  Notwithstanding anything herein to the contrary, any condemnation award
to Tenant shall be available only to the extent such award is payable separately
to Tenant and does not diminish the award available to Landlord or any Lender of
Landlord.



<PAGE>



                                   ARTICLE 12.

                             REPAIR AND MAINTENANCE

A. Tenant's  Obligations.  Tenant shall keep the Premises in good working order,
repair (and in compliance with all Laws now or hereafter  adopted) and condition
(which  condition  shall be neat,  clean  and  sanitary,  and free of pests  and
rodents) and shall make all  necessary  non-structural  repairs  thereto and any
repairs to  non-Building  standard  mechanical,  HVAC,  electrical  and plumbing
systems or components in or serving the Premises. Tenant's obligations hereunder
shall  include  but not be limited to Tenant's  trade  fixtures  and  equipment,
security systems, signs, interior decorations, floor-coverings,  wall-coverings,
entry and interior  doors,  interior glass,  light fixtures and bulbs,  keys and
locks, and alterations to the Premises whether installed by Tenant or Landlord.

B. Landlord's Obligations.  Landlord shall make all necessary structural repairs
to the  Building,  and any  necessary  repairs or  maintenance  to the  Building
standard mechanical,  HVAC, electrical, and plumbing systems in or servicing the
Common Areas or the Premises  (the cost of which shall be included in Operating,
Expenses  under  Article  4),  excluding  repairs  required to be made by Tenant
pursuant to this  Article.  Landlord  shall have no  responsibility  to make any
repairs unless and until Landlord  receives  written notice of the need for such
repair.  Landlord  shall not be liable  for any  failure  to make  repairs or to
perform any  maintenance  unless such failure shall persist for an  unreasonable
time  after  written  notice  of the need for such  repairs  or  maintenance  is
received by landlord from Tenant. Landlord shall make every reasonable effort to
perform all such repairs or  maintenance  in a reasonable  period of time and in
such a manner (in its judgment) so as to cause minimum  interference with Tenant
and the Premises but Landlord shall not be liable to Tenant for any interruption
or loss of business pertaining to such activities. Landlord shall have the right
to require that any damage caused by the willful  misconduct of Tenant or any of
Tenant's agents, contractors,  employees, invitees or customers, be paid for and
performed by the Tenant (without limiting, Landlord's other remedies herein).

C. Signs and  Obstructions.  Tenant shall not obstruct or permit the obstruction
of light, halls, Common Areas,  roofs,  parapets,  stairways or entrances to the
Building or the Premises and will not affix,  paint, erect or inscribe any sign,
projection,  awning,  signal  or  advertisement  of any  kind to any part of the
Building  or the  Premises,  including  the inside or outside of the  windows or
doors, without the written consent of Landlord. Landlord shall have the right to
withdraw  such  consent  at any time and to  require  Tenant to remove any sign,
projection, awning, signal or advertisement to be affixed to the Building or the
Premises. If such work is done by Tenant through any person, firm or corporation
not designated by Landlord,  or without the express written consent of Landlord,
Landlord  shall  have the  right to remove  such  signs,  projections,  awnings,
signals or  advertisements  without being liable to the Tenant by reason thereof
and to charge the cost of such  removal to Tenant as  Additional  Rent,  payable
within ten (10) days of Landlord's demand therefor.

D. Outside Services.  Tenant shall not permit, except by Landlord or a person or
company reasonably satisfactory to and approved by Landlord which approved shall
not be unreasonably  withheld or delayed. (i) the extermination of vermin in, on
or about the  Premises;  (ii) the  servicing,  of heating,  ventilating  and air
conditioning equipment;  (iii) the collection of rubbish and trash other than in
compliance with local government health  requirements and in accordance with the
rules and regulations  established by Landlord,  which shall  minimally  provide
that Tenant's rubbish and trash shall be kept in containers located so as not to
be visible to members  of the public and in a sanitary  and neat  condition;  or
(iv) window cleaning, janitorial services or similar work in the Premises.

                                   ARTICLE 13.

                             INSPECTION OF PREMISES
                                                    
Tenant  shall  permit the  Landlord,  the  Building  Manager and its  authorized
representatives  to enter  the  Premises  to show the  Premises  to  prospective
tenants  during  the  last 6  months  of the  Term  and  to  prospective  buyers
throughout  the Term during Normal  Business  Hours of Building  after notice to
Tenant and at other  reasonable  times to inspect the  Premises and to make such
repairs,  improvements,  alterations  or  additions  in the  Premises  or in the
Building, of which they are a part as Landlord may deem necessary or appropriate
after notice to Tenant except in an emergency.


                                   ARTICLE 14.

                              SURRENDER OF PREMISES

Upon the  expiration of the Term,  or sooner  termination  of the Lease,  Tenant
shall quit and  surrender to Landlord the Premises,  broom clean,  in good order
and  condition,  normal  wear and tear and  damage  by fire and  other  casualty
excepted. All leasehold improvements and other fixtures,  such as light fixtures
and HVAC  equipment,  wall  coverings,  carpeting and drapes,  in or serving the
Premises,  whether installed by Tenant or Landlord, shall be Landlord's property
and shall remain, all without  compensation,  allowance or credit to Tenant. Any
property not removed shall be deemed to have been abandoned by Tenant and may be
retained or disposed  of by  Landlord  at Tenant's  expense  free of any and all
claims of Tenant,  as Landlord  shall desire.  All property not removed from the
Premises by Tenant may be handled or stored by Landlord at Tenant's  expense and
Landlord shall not be liable for the value, preservation or safekeeping thereof.
At Landlord's option all or part of such property may be conclusively  deemed to
have been  conveyed by Tenant to Landlord as if by bill of sale without  payment
by  Landlord.  The Tenant  hereby  waives to the maximum  extent  allowable  the
benefit  of all  laws now or  hereafter  in  force  in this  state or  elsewhere
exempting property from liability for rent or for debt.

                                   ARTICLE 15.

                                  HOLDING OVER
                                                        
Tenant shall pay Landlord 150% of the amount of Rent then applicable prorated on
a per diem basis for each day Tenant shall retain  possession of the Premises or
any part thereof after expiration or earlier termination of this Lease, together
with all actual damages sustained by Landlord on account thereof.  The foregoing
provisions  shall not serve as permission for Tenant to hold-over,  nor serve to
extend  the  Term  (although  Tenant  shall  remain  bound  to  comply  with all
provisions of this Lease until Tenant  vacates the Premises) and Landlord  shall
have the right at any time  thereafter  to enter and  possess the  Premises  and
remove all property and persons therefrom.

                                   ARTICLE 16.

                            SUBLETTING AND ASSIGNMENT


Tenant shall not,  without the prior written  consent of Landlord  which consent
shall not be  unreasonably  withheld or delayed,  list the  Premises or any part
thereof as  available  for  assignment  or sublease  with any broker or agent or
otherwise  advertise,  post,  communicate  or solicit  prospective  assignees or
subtenants  through any direct or indirect  means,  nor assign this Lease or any
interest  thereunder,  or sublet Premises or any part thereof, or permit the use
of Premises by any party other than Tenant. In the event that during the term of
this Lease,  Tenant desires to sublease or assign and  introduces  Landlord to a
proposed  replacement  tenant for  Tenant for all or a portion of the  Premises,
which  replacement  tenant has a good  reputation,  is of financial  strength at
least  equal to that of Tenant (as  determined  by  Landlord  in its  reasonable
discretion)  and has a use for  Premises  and a number of  employees  reasonably
consistent  with that of Tenant's  operation,  the Landlord  may  consider  such
replacement tenant and notify Tenant with reasonable promptness as to Landlord's
choice, at Landlord's sole discretion, of the following:

(1) That Landlord  consents to a subleasing of the Premises or assignment of the
lease to such replacement  tenant provided that Tenant shall remain fully liable
for all of its obligations and liabilities under this Lease and provided further
that  Landlord  shall be entitled  to 50% of any profit  obtained by Tenant from
such subletting or assignment after Tenant's  reasonable  pre-approved  expenses
incurred in such subletting or;

(2) In the case of an assignment that upon such  replacement  tenant's  entering
into a mutually  satisfactory  new Lease for the Premises  with  Landlord,  then
Tenant shall be released from all further obligations and liabilities under this
Lease (excepting, only any unpaid rentals or any unperformed covenants then past
due  under  this  Lease or any  guarantee  by  Tenant  of  replacement  tenant's
obligations); or

(3) That  Landlord  declines to consent to such  sublease or  assignment  due to
insufficient or unsatisfactory  documentation furnished to Landlord to establish
Tenant's reputation,  financial strength and proposed use of and operations upon
Premises; or


(4)  That Landlord elects to cancel the Lease and recapture the Premises (in the
     case of an  assignment)  or that Landlord  elects to cancel the Lease as to
     the  portion  thereof  that Tenant had wished to  sublease.  In either such
     event Tenant shall  surrender  possession of the  Premises,  or the portion
     thereof which is the subject of Tenant's request on the date set forth in a
     notice  from  Landlord  in  accordance  with the  provisions  of this lease
     relating to the surrender of the Premises.  If this Lease shall be canceled
     as to a portion of the Premises only, the Rent payable by Tenant  hereunder
     shall be abated proportionately according to the ratio that the area of the
     portion of the Premises  surrendered (as computed by Landlord) bears to the
     area of the Premises immediately prior to such surrender. If Landlord shall
     cancel this  Lease,  Landlord  may relet the  Premises,  or the  applicable
     portion of the Premises, to any other party (including, without limitation,
     the proposed  assignee or subtenant  of Tenant),  without any  liability to
     Tenant.

Notwithstanding anything to the contrary contained herein, Tenant shall have the
right at any time  during the term of this Lease to assign  this Lease or sublet
all or any  portion of the  Premises  to any entity (i) owned or  controlled  by
Tenant or which shall hold a majority of Tenant's stock or which is under common
ownership  or control  with  Tenant;  (ii)  which is the  result of any  merger,
consolidation  or  reorganization  of  Tenant;  or (iii)  which  shall  purchase
substantially all of the assets of Tenant (collectively,  "Business Assignment")
provided that any such entity assumes the  obligations of Tenant under the Lease
in writing and a copy thereof is promptly delivered to Landlord.

Except in the case of a Business  Assignment,  in no event may Tenant assign any
options to sublessee(s) or assignee(s) hereunder,  all such options being deemed
personal to SAVILLE SYSTEMS U.S., INC. only. Consent by Landlord hereunder shall
in no way operate as a waiver by Landlord of, or to release or discharge  Tenant
from,  any  liability  under this Lease or be construed  to relieve  Tenant from
obtaining Landlord's consent to any subsequent assignment, subletting, transfer,
use or occupancy.

                                   ARTICLE 17.

               SUBORDINATION, ATTORNMENT AND MORTGAGEE PROTECTION

This Lease is subject and  subordinate to all Mortgages now or hereafter  placed
upon the  Building,  and all other  encumbrances  and  matters of public  record
applicable to the Building including without limitation, any reciprocal easement
or operating,  agreements,  covenants,  conditions and  restrictions  and Tenant
shall not act or permit the Premises to be operated in violation thereof. If any
foreclosure or power of sale  proceedings  are initiated by any Lender or a deed
in lieu is granted (or if any ground lease is terminated),  Tenant agrees,  upon
written request of any such Lender or any purchaser at such foreclosure sale, to
attorn and pay Rent to such party and to execute  and  deliver  any  instruments
necessary or appropriate to evidence or effectuate such attornment. In the event
of  attornment,  no Lender  shall be:  (i)  liable  for any act or  omission  of
Landlord,  or subject to any offsets or defenses which Tenant might have against
Landlord (prior to such Lender becoming  Landlord under such  attornment),  (ii)
liable for any security deposit not actually received by such Lender or bound by
any prepaid  Rent not actually  received by such  Lender,  or (iii) bound by any
future modification of this Lease amending any material business term hereof,not
consented  to by such  Lender.  Any Lender may elect to make this Lease prior to
the lien of its  Mortgage,  and if the  Lender  under any prior  Mortgage  shall
require, this Lease shall be prior to any subordinate  Mortgage;  such elections
shall be effective  upon  written  notice to Tenant.  Tenant  agrees to give any
Lender by certified  mail,  return  receipt  requested,  a copy of any notice of
default  served by Tenant  upon  Landlord,  provided  that prior to such  notice
Tenant has been  notified in writing,  (by way of service on Tenant of a copy of
an assignment  of leases,  or otherwise) of the name and address of such Lender.
Tenant  further  agrees that if Landlord  shall have failed to cure such default
within the time  permitted  Landlord for cure under this Lease,  any such Lender
whose address has been so provided to Tenant shall have an additional  period of
thirty  (30) days in which to cure (or such  additional  time as may be required
due to causes beyond such Lender's control,  including time to obtain possession
of the  Building,  by  power  of  sale  or  judicial  action  or deed in lieu of
foreclosure so long as Lender  diligently  pursues such cure). The provisions of
this  Article  shall be  self-operative;  however,  Tenant  shall  execute  such
documentation  as Landlord or any Lender may request  from time to time in order
to confirm the  matters set forth in this  Article in  recordable  form.  To the
extent not expressly  prohibited by Law, Tenant waives the provisions of any Law
now or hereafter  adopted  which may give or purport to give Tenant any right or
election  to  terminate  or  otherwise  adversely  affect this Lease or Tenant's
obligations  hereunder  if such  foreclosure  or power of sale  proceedings  are
initiated, prosecuted or completed.


                                   ARTICLE 18.

                              ESTOPPEL CERTIFICATE


Tenant or Landlord shall from time to time, upon written request by the other or
Lender,  deliver to the other or  Lender,  within  fifteen  (15) days after from
receipt of such request, a statement in writing certifying:  (i) that this Lease
is unmodified and in full force and effect (or if there have been modifications,
identifying such modifications and certifying that the Lease, as modified, is in
full force and  effect);  (ii) the dates to which the Rent has been paid;  (iii)
that  Landlord  is not in  default  under  any  provision  of this  Lease (or if
Landlord is in default, specifying each such default); and,

Notwithstanding  the above,  Landlord  agrees  that as an express  condition  of
Tenant's  subordination,  Landlord  shall obtain from the applicable  Lender,  a
written  subordination and non-disturbance  agreement for the benefit of Tenant.
Said  subordination  and  non-disturbance  agreement  shall  be in the  Lender's
standard form and shall provide,  among other  provisions,  that so long as this
Lease  shall be in full  force and  effect  that in the  event it should  become
necessary to foreclose the  Mortgage,  the Lender  thereunder  will not join the
Tenant in summary or  foreclosure  proceedings or otherwise  interrupt  Tenant's
quiet use,  enjoyment,  or possession of the Premises  pursuant to the Lease, so
long as the  Tenant is not in  default  under  any of the  terms,  covenants  or
conditions of the Lease.












<PAGE>



(iv) the address to which notices to Tenant shall be sent;  it being  understood
that any such  statement so delivered may be relied upon in connection  with any
lease, mortgage or transfer.

Tenant's  failure to deliver such statement within such time shall be conclusive
upon Tenant  that:  (i) this Lease is in full force and effect and not  modified
except as Landlord may  represent;  (ii) not more than one month's Rent has been
paid in advance;  (iii) there are no defaults by Landlord;  and, (iv) notices to
Tenant  shall be sent to  Tenant's  Address  as set  forth in  Article 1 of this
Lease.  Notwithstanding,  the presumptions of this Article,  Tenant shall not be
relieved of its obligation to deliver said statement.

                                   ARTICLE 19.

                                    DEFAULTS

If Tenant: (i) fails to pay when due any instalment or other payment of Rent for
more than 10 days after notice but in no event more than 2 times in any 12 month
period or to keep in effect any  insurance  required to be  maintained;  or (ii)
vacates or abandons the Premises  without  providing  Landlord  with at least 30
days' prior  written  notice.  Such notice shall  indicate  Tenant's  reason for
vacating or  abandoning  the  Premises , or (iii)  becomes  insolvent,  makes an
assignment  for the benefit of  creditors,  files a voluntary  bankruptcy  or an
involuntary petition in bankruptcy is filed against Tenant which petition is not
dismissed  within  sixty  (60) days of its  filing,  or (iv) fails to perform or
observe any of the other covenants, conditions or agreements contained herein on
Tenant's part to be kept or performed and such failure shall continue for thirty
(30) days after notice  thereof given by or on behalf of Landlord or such longer
period as may  reasonably be required  provided that Tenant  diligently  pursues
such cure,  or (v) if the  interest of Tenant  shall be offered for sale or sold
under execution or other legal process if Tenant makes any transfer, assignment,
conveyance,  sale,  pledge,  disposition  of all  or a  substantial  portion  of
Tenant's  property  without  providing  Landlord at least 30 days prior  written
notice then any such event or conduct shall constitute a"default" hereunder.

If  Tenant  shall  file a  voluntary  petition  pursuant  to the  United  States
Bankruptcy  Reform Act of 1978,  as the same may be from time to time be amended
(the  "Bankruptcy  Code"),  or take  the  benefit  of any  insolvency  act or be
dissolved, or if an involuntary petition be filed against Tenant pursuant to the
Bankruptcy  Code and said petition is not dismissed  within sixty (60)days after
such filing,  or if a receiver shall be appointed for its business or its assets
and the appointment of such receiver is not vacated within sixty (60) days after
such  appointment,  or if it shall  make an  assignment  for the  benefit of its
creditors,  then Landlord shall have all of the rights provided for in the event
of nonpayment of the Rent.

If any alleged  default on the part of the  Landlord  hereunder  occurs,  Tenant
shall give written  notice to Landlord in the manner  herein set forth and shall
afford Landlord a reasonable  opportunity to cure any such default. In addition,
Tenant  shall send  notice of such  default by  certified  or  registered  mail,
postage  prepaid,  to the holder of any Mortgage  whose address  Tenant has been
notified  of in writing,  and shall  afford such  Mortgage  holder a  reasonable
opportunity to cure any alleged  default on Landlord's  behalf  consistent  with
Article 17. In no event will Landlord be responsible for any damages incurred by
Tenant,  including but not limited to, lost profits or  interruption of business
as a result of any alleged default by Landlord hereunder.

                                   ARTICLE 20.

                              REMEDIES OF LANDLORD

The remedies provided Landlord under this Lease are cumulative.

(a) Upon the occurrence of any default, Landlord may serve notice on Tenant that
the Term and the estate  hereby vested in Tenant and any and all other rights of
Tenant  hereunder  shall cease on the date  specified  in such notice and on the
specified date this Lease shall cease and expire as fully and with the effect as
if the Term had expired for passage of time.

(b) Without terminating,  this Lease in case of a default or if this Lease shall
be  terminated  for  default as  provided  herein,  Landlord  may  re-enter  the
Premises, remove Tenant, or cause Tenant to be removed from the Premises in such
manner as Landlord may deem advisable, with or without legal process, and using,
such  reasonable  force as may be  necessary.  In the event of re-entry  without
terminating  this Lease,  Tenant  shall  continue to be liable for all Rents and
other charges accruing, or coming due under this Lease.

(c) If Landlord,  without terminating this Lease, shall re-enter the Premises or
if this Lease shall be terminated as provided in paragraph (a) above:

         (i) All Rent due from Tenant to Landlord shall thereupon become due and
         shall be paid up to the time of re-entry,  dispossession or expiration,
         together  with  reasonable  costs  and  expenses  (including,   without
         limitation, attorney's fees) of Landlord;

         (ii) Landlord,  without any obligation to do so, may relet the Premises
         or any part thereof for a term or terms which may at Landlord's  option
         be  less  than  or  exceed  the  period  which  would   otherwise  have
         constituted  the balance of the Term and may grant such  concessions in
         reletting  as  Landlord,  in the  exercise of its  reasonable  business
         judgment,  deems desirable.  In connection with such reletting,  Tenant
         shall be  liable  for all  costs of the  reletting  including,  without
         limitation,  rent  concessions,  leasing,  commissions,  legal fees and
         alteration and remodeling costs; and

         (iii) If Landlord shall have terminated  this Lease,  Tenant shall also
         be liable to  Landlord  for all damages  provided  for in law and under
         this  Lease   resulting  from  Tenant's   breach   including,   without
         limitation, the difference between the aggregate rentals reserved under
         the terms of this Lease for the balance of the Term  together  with all
         other sums payable  hereunder as Rent for the balance of the Term, less
         the fair rental value of the Premises for that period  determined as of
         the date of such  termination.  For purposes of this paragraph,  Tenant
         shall be deemed to include any guarantor or surety of the Lease.

(d)  Tenant  hereby  waives  all  right to trial  by jury in any  claim,  action
proceeding or  counterclaim  by either  Landlord or Tenant against each other or
any  matter  arising  out  of or in any  way  connected  with  this  Lease,  the
relationship  of Landlord  and Tenant,  and/or  Tenant's use or occupancy of the
Premises.

(e) In  addition  to the above,  Landlord  shall  have any and all other  rights
provided  a  Landlord  under law or equity for breach of a lease or tenancy by a
Tenant.

(f) Notwithstanding  anything, in this Article to the contrary,  Landlord agrees
to use commercially reasonable efforts to mitigate its damages under this Lease.

                                   ARTICLE 21.

                                 QUIET ENJOYMENT

Landlord  covenants  and agrees with Tenant that so long as Tenant pays the Rent
and observes and performs all the terms, covenants, and conditions of this Lease
on Tenant's part to be observed and performed,  Tenant may peaceably and quietly
enjoy the Premises  subject,  nevertheless,  to the terms and conditions of this
Lease,  and Tenant's  possession will not be disturbed by anyone  claiming,  by,
through, or under Landlord.

                                   ARTICLE 22.

                             ACCORD AND SATISFACT1ON

No payment by Tenant or receipt by Landlord of an amount less than full  payment
of Rent then due and payable  shall be deemed to be other than on account of the
Rent then due and payable,  nor shall any  endorsement or statement on any check
or any letter  accompanying any check or payment as Rent be deemed an accord and
satisfaction, and Landlord may accept such check or payment without prejudice to
Landlord's  right to recover the balance of such Rent or pursue any other remedy
provided for in this Lease or available at law or in equity.

                                   ARTICLE 23.

                                SECURITY DEPOSIT

To secure the faithful performance by Tenant of all of the covenants, conditions
and agreements set forth in this Lease to be performed by it, including, without
limitation,  foregoing such  covenants,  conditions and agreements in this Lease
which become  applicable upon its  termination by re-entry or otherwise,  Tenant
has deposited  with Landlord the sum shown in Article 1 as a "Security  Deposit"
on the understanding:


<PAGE>


(a) that the  Security  Deposit  or any  portion  thereof  may be applied to the
curing of any default that may exist,  without  prejudice to any other remedy or
remedies  which  the  Landlord  may  have on  account  thereof,  and  upon  such
application  Tenant  shall pay  Landlord  on demand the amount so applied  which
shall be added to the  Security  Deposit  so the same  will be  restored  to its
original amount;

                                                                            
(b) that should the  Premises be conveyed by Landlord,  the Security  Deposit or
any balance  thereof shall be turned over to the Landlord's  grantee, and if the
same be turned over as aforesaid,  Tenant hereby releases  Landlord from any and
all  liability  with  respect to the  Security  Deposit and its  application  or
return, and Tenant agrees to look solely to such grantee for such application or
return; and,

(c) that Landlord may commingle the Security Deposit with other funds and not be
obligated to pay Tenant any interest;

(d) that the Security Deposit shall not be considered as advance payment of Rent
or a measure of  damages  for any  default  by Tenant,  nor shall it be a bar or
defense to any actions by Landlord against Tenant;

(e) that if Tenant shall faithfully  perform all of the covenants and agreements
contained in this Lease on the part of the Tenant to be performed,  the Security
Deposit or any then  remaining,  balance  thereof,  shall be returned to Tenant,
without  interest,  within  thirty (30) days after the  expiration  of the Term.
Tenant further covenants that it will not assign or encumber the money deposited
herein as a Security  Deposit and that neither  Landlord nor its  successors  or
assigns shall be bound by any such assignment, encumbrance, attempted assignment
or attempted encumbrance.

                                   ARTICLE 24.

                              BROKERAGE COMMISSION


Landlord and Tenant  represent  and warrant to each other that neither has dealt
with any broker,  finder or agent except for the Broker(s) identified in Article
1.  Landlord  and Tenant  represent  and warrant to the other that  (except with
respect to the Broker identified in Article I and with whom Landlord has entered
into a separate  brokerage  agreement  pursuant to which  Landlord  will pay the
commission of such Broker) no broker, agent,  commission  salesperson,  or other
person  has  represented   Landlord  or  Tenant  in  the  negotiations  for  and
procurement of this Lease and the Premises and, except as set forth herein, that
no  commissions,  fees,  or  compensation  of any  kind are due and  payable  in
connection  herewith  to any  broker,  agent  commission  salesperson,  or other
person. Landlord and Tenant agree to indemnify and hold harmless the other party
from any and all claims,  suits, or judgments  (including,  without  limitation,
reasonable  attorneys' fees and court costs incurred in connection with any such
claims,  suits,  or judgments,  or in connection  with the  enforcement  of this
indemnity) for any fees,  commissions,  or  compensation of any kind which arise
out of or are in any way connected with any claimed agency relationship with the
indemnifying  party  which is not  referenced  in Article 1 or any breach of the
representation or warranty contained in this Article.



<PAGE>



                                   ARTICLE 25.

                                  FORCE MAJEURE

Landlord shall be excused for the period of any delay in the  performance of any
obligation  hereunder  when  prevented from so doing by a cause or causes beyond
its control,  including  all labor  disputes,  civil  commotion,  war,  war-like
operations,  invasion,  rebellion,   hostilities,  military  or  usurped  power,
sabotage,   governmental  regulations  or  controls,  fire  or  other  casualty,
inability to obtain any material, services or financing, or through acts of God.
Tenant shall similarly be excused for delay in the performance of any obligation
hereunder; provided:

(a) nothing contained in this Section or elsewhere in this Lease shall be deemed
to excuse or permit any delay in the  payment  of the Rent,  or any delay in the
cure of any default which may be cured by the payment of money;

(b) no reliance by Tenant upon this  Section  shall limit or restrict in any way
Landlord's right of self-help as provided in this Lease; and

(c) Tenant shall not be entitled to rely upon this Section unless it shall first
have given Landlord notice of the





<PAGE>


existence of any force majeure  preventing  the  performance of an obligation of
Tenant within *five days after the Commencement of the force majeure. *ten

                                   ARTICLE 26.

                                     PARKING

(a) Landlord hereby grants to Tenant the right, in common with others authorized
by  Landlord,  to use the  parking  facilities  owned by  Landlord  and shown on
Exhibit A, if any. Landlord,  at its sole election,  may designate the types and
locations of parking spaces within the parking  facilities which Tenant shall be
allowed to use.  Landlord shall have the right, at Landlord's sole election,  to
change  said types and  locations  from time to time;  provided,  however,  such
designation  shall be uniformly  applied and shall not unfairly favor any tenant
in the Building.

(b) Commencing on the Commencement  Date,  Tenant shall pay Landlord the Parking
Fee, if any, shown in Article 1, as Additional Rent,  payable monthly in advance
with the  Monthly  Rent.  If there is a Parking,  Fee shown in  Schedule 1, then
thereafter,  and  throughout the Term, the parking rate for each type of parking
space  provided to Tenant  hereunder  shall be the  prevailing  parking rate, as
Landlord may designate from time to time, at Landlord's sole election,  for each
such type of parking  space.  In addition  to the right  reserved  hereunder  by
Landlord to designate  the parking rate from time to time,  Landlord  shall have
the right to change the parking rate at any time to include  therein any amounts
levied,  assessed,  imposed or required to be paid to any governmental authority
on account of the parking, of motor vehicles,  including all sums required to be
paid pursuant to transportation controls imposed by the Environmental Protection
Agency under the Clean Air Act of 1970, as amended, or other-wise required to be
paid  by any  governmental  authority  with  respect  to the  parking,  use,  or
transportation  of motor vehicles,  or the reduction or control of motor vehicle
traffic, or motor vehicle pollution.

(c) If requested by Landlord,  Tenant shall notify Landlord of the license plate
number,  year,  make and model of the  automobiles  entitled  to use the parking
facilities and if requested by Landlord, such automobiles shall be identified by
automobile  window  stickers  provided  by  Landlord,  and only such  designated
automobiles  shall be  permitted  to use the  parking,  facilities.  If Landlord
institutes such an  identification  procedure,  Landlord may provide  additional
parking,  spaces for use by customers and invitees of Tenant on a daily basis at
prevailing parking rates, if any. At Landlord's sole election, Landlord may make
validation  stickers available to Tenant for any such additional parking spaces,
provided,  however, if Landlord makes validation stickers available to any other
tenant in the Building,  Landlord shall make such validation  stickers available
to Tenant.

(d) The  parking  facilities  provided  for herein are  provided  solely for the
accommodation of Tenant and Landlord assumes no  responsibility  or liability of
any kind whatsoever  from whatever cause with respect to the automobile  parking
areas,  including  adjoining  streets,   sidewalks,   driveways,   property  and
passageways,  or the use  thereof by Tenant or  tenant's  employees,  customers,
agents, contractors or invitees.

                                   ARTICLE 27.

                               HAZARDOUS MATERIALS

A.  Definition  of  Hazardous  Materials.  The term  "Hazardous  Materials"  for
purposes  hereof  shall  mean any  chemical,  substance,  materials  or waste or
component  thereof which is now or hereafter  listed,  defined or regulated as a
hazardous or toxic chemical, substance,  materials or waste or component thereof
by any federal, state or local governing or regulatory body having jurisdiction,
or which would  trigger any employee or community  "right-to-know"  requirements
adopted  by any  such  body,  or  for  which  any  such  body  has  adopted  any
requirements  for the  preparation or  distribution  of a materials  safety data
sheet ("MSDS").

B. No Hazardous  Materials.  Tenant shall not transport,  use, store,  maintain,
generate,  manufacture,  handle,  dispose,  release or discharge  any  Hazardous
Materials.   However,   the   foregoing   provisions   shall  not  prohibit  the
transportation to and from, and use, storage,  maintenance and handling,  within
the Premises of Hazardous Materials customarily used in the business or activity
expressly  permitted to be undertaken in the Premises under Article 6, provided:
(a)  such  Hazardous  Materials  shall  be  used  and  maintained  only  in such
quantities as are  reasonably  necessary for such  permitted use of the Premises
and the ordinary  course of Tenant's  business  therein,  strictly in accordance
with applicable  Law,  highest  prevailing,  standards,  and the  manufacturers'
instructions  therefor,  (b) such Hazardous  Materials shall not be disposed of,
released or discharged in the Building, and shall be transported to and from the
Premises  in  compliance  with  all  applicable  Laws,  and  as  Landlord  shall
reasonably  require,  (c) if any  applicable  Law or  Landlord's  trash  removal
contractor  requires that any such Hazardous Materials be disposed of separately
from ordinary trash, Tenant shall make arrangements at Tenant's expense for such
disposal  directly  with a qualified and licensed  disposal  company at a lawful
disposal  site (subject to  scheduling  and approval by  Landlord),  and (d) any
remaining such Hazardous  Materials  shall be completely,  properly and lawfully
removed from the Building, upon expiration or earlier termination of this Lease.

C.  Notices To  Landlord.  Tenant  shall  promptly  notify  Landlord of: (i) any
enforcement  cleanup  or other  regulatory  action  taken or  threatened  by any
governmental  or  regulatory  authority  with  respect  to the  presence  of any
Hazardous  Materials on the Premises or the  migration  thereof from or to other
property, (ii) any demands or claims made or threatened by any party relating to
any loss or injury resulting from any Hazardous Materials on the Premises, (iii)
any  release,  discharge  or  non-routine,  improper  or  unlawful  disposal  or
transportation  of  any  Hazardous  Materials  on or  from  the  Premises  or in
violation of this Article,  and (iv) any matters where Tenant is required by Law
to give a notice to any  governmental  or regulatory  authority  respecting  any
Hazardous Materials on the Premises.  Landlord shall have the right (but not the
obligation) to join and  participate,  as a party,  in any legal  proceedings or
actions affecting the Premises  initiated in connection with any  environmental,
health or safety law. At such times as Landlord may reasonably  request,  Tenant
shall provide  Landlord with a written list,  certified to be true and complete,
identifying any Hazardous  Materials then used,  stored,  or maintained upon the
Premises, the use and approximate quantity of each such materials, a copy of any
MSDS issued by the manufacturer therefor, and such other information as Landlord
may reasonably require or as may be required by Law.

D.  Indemnification  of  Landlord.  If any  Hazardous  Materials  are  released,
discharged or disposed of by Tenant or any other  occupant of the  Premises,  or
their employees,  agents,  invitees or contractors,  on or about the Building in
violation of the foregoing provisions, Tenant shall immediately, properly and in
compliance  with  applicable  Laws clean up,  remediate and remove the Hazardous
Materials  from the  Building,  and any  other  affected  property  and clean or
replace any affected personal  property  (whether or not owned by Landlord),  at
Tenant's expense (without limiting Landlord's other remedies  therefor).  Tenant
shall further be required to indemnify and hold Landlord,  Landlord's directors,
officers,  employees  and agents  harmless  from and against any and all claims,
demands,  liabilities,  losses,  damages,  penalties and  judgments  directly or
indirectly  arising out of or  attributable  to a violation of the provisions of
this Article by Tenant,  Tenant's occupants,  employees,  contractors or agents.
Any clean up,  remediation and removal work shall be subject to Landlord's prior
written approval (except in emergencies), and shall include, without limitation,
any  testing,  investigation,  and the  preparation  and  implementation  of any
remedial action plan required by any  governmental  body having  jurisdiction or
reasonably required by Landlord.  If Landlord or any Lender or governmental body
arranges for any tests or studies  showing that this Article has been  violated,
Tenant  shall pay for the costs of such test.  The  provisions  of this  Article
shall survive the expiration or earlier termination of this Lease.

Landlord  shall  indemnify and hold Tenant,  its officers,  employees and agents
harmless  from and  against any and all claims,  demands,  liabilities,  losses,
damages,  penalties  and  judgments  directly  or  indirectly  arising out of or
attributable to (i) the presence as of the date hereof any Hazardous Material on
the Property in violation  of any existing  law, or (ii) a release,  disposal or
discharge  of  Hazardous  Material  in  violation  of  law by  Landlord,  or its
employees,  contractors  or agents.  The provisions of this  subparagraph  shall
survive the expiration or earlier termination of this Lease.


                                   ARTICLE 28.

                     ADDITIONAL RIGHTS RESERVED BY LANDLORD

In addition to any other  rights  provided  for herein,  Landlord  reserves  the
following rights,  exercisable  without liability to Tenant for damage or injury
to property, person or business and without effecting an eviction,  constructive
or actual,  or  disturbance  of Tenant's use or possession or giving rise to any
claim:

(a) To name the  Building,  and to  change  the name or  street  address  of the
Building;
(b) To install  and  maintain  all signs on the  exterior  and  interior  of the
Building;
(c) To designate  all sources  furnishing  sign painting or lettering for use in
the Building,:
(d) During the last  ninety  (90) days of the Term,  if Tenant has  vacated  the
Premises, to decorate,  remodel,  repair alter or otherwise prepare the Premises
for occupancy, without affecting Tenant's obligation to pay



<PAGE>


         Rent for the Premises;

(e) To have pass keys to the Premises and all doors therein,  excluding Tenant's
vaults and safes;

(f) On  reasonable  prior  notice to Tenant,  to  exhibit  the  Premises  to any
prospective  purchaser,  Lender,  mortgagee,  or assignee of any mortgage on the
Building or Land and to others having an interest therein at any time during the
Term, and to prospective tenants during the last six months of the Term;

(g) After reasonable notice except in an emergency to take any and all measures,
including entering the Premises for the purpose of making inspections,  repairs,
alterations,  additions  and  improvements  to the  Premises or to the  Building
(including  for the purpose of checking,  calibrating,  adjusting  and balancing
controls  and other  parts of the  Building  Systems),  as may be  necessary  or
desirable for the operation,  improvement safety,  protection or preservation of
the Premises or the  Building,  or in order to comply with all Laws,  orders and
requirements  of  governmental  or  other  authority,  or as  may  otherwise  be
permitted or required by this Lease;  provided,  however,  that  Landlord  shall
endeavor to minimize  interference  with Tenant's use of the Premises during the
progress of any work on the Premises or at the  Building,  Landlord will attempt
not to  inconvenience  Tenant,  but  shall  not  be  liable  for  inconvenience,
annoyance, disturbance, loss of business, or other damage to Tenant by reason of
performing  any work or by bringing  or storing  materials,  supplies,  tools or
equipment in the Building or Premises  during the  performance  of any work, and
the  obligations of Tenant under this Lease shall not thereby be affected in any
manner whatsoever;

(h) To relocate various  facilities within the Building and on the land of which
the Building is a part if Landlord shall  determine such relocation to be in the
best interest of the  development  of the Building and  Property,  provided that
such relocation shall not materially restrict access to the Premise or otherwise
have a material adverse impact on the Premises;and

(i) To install vending  machines of all kinds in the Building and to receive all
of the revenue derived Premises therefrom,  provided,  however,  that no vending
machines  shall be  installed  by  Landlord  in the  Premises  unless  Tenant so
requests.

                                   ARTICLE 29.

                                  DEFINED TERMS

A.  "Building,"  shall  refer to the  Building  named in  Article 1 of which the
leased  Premises  are  a  part  (including  all  modifications,   additions  and
alterations  made to the  Building  during  the  term of this  Lease),  the real
property on which the same is located,  all plazas,  common  areas and any other
areas  located on said real  property and  designated by Landlord for use by all
tenants in the  Building.  A plan  showing,  the Building is attached  hereto as
Exhibit A and made a part  hereof and the  Premises  is defined in Article 2 and
shown on said Exhibit A by cross-hatched lines.

B.  "Common  Areas"  shall mean and  include all areas,  facilities,  equipment,
directories  and signs of the  Building  (exclusive  of the  Premises  and areas
leased to other  Tenants)  made  available  and  designated  by Landlord for the
common and joint use and  benefit of  Landlord,  Tenant  and other  tenants  and
occupants  of the  Building  including,  but not  limited  to,  lobbies,  public
washrooms,  hallways,  sidewalks,  parking areas,  landscaped  areas and service
entrances. Common Areas may further include such areas in adjoining,  properties
under  reciprocal  easement  agreements,  operating  agreements  or  other  such
agreements  now or  hereafter  in effect and which are  available  to  Landlord,
Tenant and Tenant's  employees and invitees.  Landlord reserves the right in its
sole discretion and from time to time, to construct,  maintain, operate, repair,
close, limit, take out of service,  alter, change, and modify all or any part of
the Common Areas.

C. "Default Rate" shall mean fifteen percent(15%) per annum, or the highest rate
permitted by applicable law,  whichever shall be less. If the application of the
Default Rate causes any provision of this Lease to be usurious or unenforceable,
the Default Rate shall automatically be reduced so as to prevent such result.

D.  "Hazardous Materials" shall have the meaning, set forth in Article 27.

E.  "Landlord"  and "Tenant"  shall be  applicable to one or more parties as the
case may be, and the  singular  shall  include the plural,  and the neuter shall
include  the  masculine  and  feminine;  and if  there  be more  than  one,  the
obligations  thereof shall be joint and several.  For purposes of any provisions
indemnifying or limiting the liability of Landlord,  the term  "Landlord"  shall
include  Landlord's  present  and  future  partners,  beneficiaries,   trustees,
officers, directors,  employees,  shareholders,  principals, agents, affiliates,
successors and assigns.

F. "Law" or "Laws" shall mean all federal,  state, county and local governmental
and municipal laws, statutes,  ordinances,  rules, regulations,  codes, decrees,
orders and other such requirements,  applicable equitable remedies and decisions
by courts in cases where such  decisions are binding  precedents in the state in
which the Building is located, and decisions of federal courts applying the Laws
of such state.

G. "Lease" shall mean this lease executed between Tenant and Landlord, including
any extensions, amendments or modifications and any Exhibits attached hereto.

H. "Lease  Year" shall mean each  calendar  year or portion  thereof  during the
Term.

I.  "Lender"  shall mean the holder of a Mortgage at the time in  question,  and
where such  Mortgage  is a ground  lease,  such term  shall  refer to the ground
lessee.

J. "Mortgage" shall mean all mortgages,  deeds of trust, ground leases and other
such encumbrances now or hereafter placed upon the Building, or any part thereof
with  the  written  consent  of  Landlord,  and  all  renewals,   modifications,
consolidations,  replacements or extensions thereof, and all indebtedness now or
hereafter secured thereby and all interest thereon.

K. "Operating  Expenses" shall mean all operating expenses of any kind or nature
which are  necessary,  ordinary or customarily  incurred in connection  with the
operation, maintenance or repair of the Building, as determined by Landlord.

Operating Expenses shall include, but not be limited to:

         1.1 costs of  supplies,  including,  but not  limited  to,  the cost of
revamping all Building, standard lighting, as the same may be required from time
to time;

         1.2 costs incurred in connection  with  obtaining and providing  energy
for the  Building,  including,  but not  limited to,  costs of propane,  butane,
natural gas, steam,  electricity,  solar energy and fuel oils, coal or any other
energy sources;

         1.3 costs of water and sanitary and storm drainage services;

         1.4 costs of janitorial and security services;

         1.5 costs of general  maintenance  and repairs,  including  costs under
HVAC and other mechanical  maintenance  contracts and  maintenance,  repairs and
replacement  of  equipment  and tools  used in  connection  with  operating  the
Building;

         1.6 costs of maintenance and replacement of landscaping,;

         1.7 insurance premiums,  including fire and all-risk coverage, together
with loss of rent endorsements,  the part of any claim required to be paid under
the  deductible  portion  of any  insurance  policies  carried  by  Landlord  in
connection  with the  Building  (where  Landlord  is unable to obtain  insurance
without such  deductible from a major  insurance  carrier at reasonable  rates),
public  liability  insurance and any other insurance  carried by Landlord on the
Building,  or any component  parts thereof (all such insurance  shall be in such
amounts  as may be  required  by any  holder of a Mortgage  or as  Landlord  may
reasonably determine);

     1.8 labor costs for personnel  on-site and directly  engaged in maintenance
or  management  of the  Building  including  wages and other  payments,costs  to
Landlord of worker's  compensation  and  disability  insurance,  payroll  taxes,
welfare fringe benefits, and all legal fees and other costs or expenses incurred
in resolving any labor dispute;

     1.9  reasonable   professional   building   management  fees  required  for
management of the Building;

         1.10  legal,  accounting,   inspection,  and  other  consultation  fees
(including, without limitation, fees charged by consultants retained by Landlord
for services  that are designed to produce a reduction in Operating  Expenses or
to  reasonably  improve  the  operation,  maintenance  or state of repair of the
Building)  incurred  in the  ordinary  course of  operating  the  Building or in
connection with making the  computations  required  hereunder or in any audit of
operations of the Building;

     1.11  the  costs  of  capital   improvements   or  structural   repairs  or
replacements  made  in or to the  Building  in  order  to  conform  to  changes,
subsequent to the date of this Lease, in any applicable laws, ordinances, rules,
regulations or orders of any governmental or quasi-governmental authority having
jurisdiction over the Building (herein  "Required Capital  Improvements") or the
costs incurred by Landlord to install a new or replacement  capital item for the
purpose of reducing Operating Expenses (herein "Cost Savings improvements"), and
a reasonable  reserve for all other capital  improvements and structural repairs
and  replacements  reasonably  necessary  to permit  Landlord  to  maintain  the
Building  in  its  current  class.   The   expenditures   for  Required  Capital
Improvements  and Cost Savings  Improvements  shall be amortized over the useful
life of such  capital  improvement  or  structural  repair  or  replacement  (as
reasonably  determined  by  Landlord  in  accordance  with  GAAP ). All costs so
amortized  shall bear  interest on the  amortized  balance at the rate of twelve
Prime  Rate  plus 2% per  annum or such  higher  rate as may have  been  paid by
Landlord  on funds  borrowed  for the  purpose  of  constructing  these  capital
improvements.

In making any computations contemplated hereby, Landlord shall also be permitted
to make such  adjustments and  modifications to the provisions of this paragraph
and Article 4 as shall be reasonable and necessary to achieve the
intention of the parties hereto.

L.       "Rent" shall have the meaning specified therefor in Article 3.

M.       "Tax" or "Taxes" shall mean:

         1.1 all real property taxes and assessments levied against the Building
by any governmental or quasi-governmental authority. The foregoing shall include
all federal, state, county, or local governmental, special district, improvement
district,   municipal  or  other  political  subdivision  taxes,  fees,  levies,
assessments,  charges or other  impositions  of every kind and  nature,  whether
general, special, ordinary or extraordinary,  respecting the Building, including
without limitation, real estate taxes, general and special assessments, interest
on any special assessments paid in installments,  transit taxes, water and sewer
rents,  taxes based upon the receipt of rent,  personal  property  taxes imposed
upon the fixtures, machinery, equipment, apparatus, appurtenances, furniture and
other  personal  property used in connection  with the Building  which  Landlord
shall pay during any calendar  year, any portion of which occurs during the Term
(without  regard  to any  different  fiscal  year  used  by such  government  or
municipal  authority except as provided  below).  Provided,  however,  any taxes
which shall be levied on the rentals of the Building  shall be  determined as if
the Building were  Landlord's  only  property,  and provided  further that in no
event  shall the term "taxes or  assessment,"  as used  herein,  include any net
federal or state income taxes levied or assessed on Landlord,  unless such taxes
are a specific  substitute for real property  taxes.  Such term shall,  however,
include  gross  taxes  on  rentals.   Expenses  incurred  by  Landlord  for  tax
consultants  and in  contesting  the  amount or  validity  of any such  taxes or
assessments shall be included in such computations.

         1.2 all "assessments", including so-called special assessments, license
tax,  business license fee, business license tax, levy,  charge,  penalty or tax
imposed by any  authority  having the direct power to tax,  including  any city,
county,  state or federal  Government,  or any school,  agricultural,  lighting,
water,  drainage, or other improvement or special district thereof,  against the
Premises of the Building or any legal or equitable interest of Landlord therein.
For the purposes of this lease, any special  assessments shall be deemed payable
in such number of installments  as is permitted by law,  whether or not actually
so paid. If as of the Commencement Date the Building has not been fully assessed
as a completed project,  for the purpose of computing the Operating Expenses for
any adjustment  required herein or under Article 4, the Tax shall be adjusted by
Landlord,  as of the date on which the adjustment is to be made, to reflect full
completion  of the Building  including  all standard  Tenant  finish work if the
method of taxation of real estate  prevailing  to the time of  execution  hereof
shall be, or has been altered, so as to cause the whole or any part of the taxes
now, hereafter or theretofore  levied,  assessed or imposed on real estate to be
levied, assessed or imposed on Landlord,  wholly or partially, as a capital levy
or otherwise,  or on or measured by the rents received therefrom,  then such new
or altered taxes  attributable to the Building shall be included within the term
real estate  taxes,  except that the same shall not include any  enhancement  of
said tax attributable to other income of Landlord.  All of the preceding clauses
K (1.1 and 1.2) are collectively referred to as the "Tax" or "Taxes".

All other capitalized terms shall have the definition set forth in the Lease.

                                   ARTICLE 30.

                            MISCELLANEOUS PROVISIONS

A. RULES AND REGULATIONS.

Tenant  shall  comply  with all of the  rules  and  regulations  promulgated  by
Landlord  from time to time for the  Building.  A copy of the  current  rule and
regulations is attached hereto as Exhibit D.

B. EXECUTION OF LEASE.

If more than one  person or entity  executes  this  Lease as  Tenant,  each such
person or entity  shall be  jointly  and  severally  liable  for  observing  and
performing  each  of the  terms,  covenants,  conditions  and  provisions  to be
observed or performed by Tenant.

C. NOTICES.

All notices under this Lease shall be in writing and will be deemed sufficiently
given for all  purposes  if, to Tenant,  by delivery  to Tenant at the  Premises
during the hours the Building, is open for business or by certified mail, return
receipt  requested  or by  overnight  delivery  service  (with one  acknowledged
receipt),  to Tenant at the  address set forth  below,  and if to  Landlord,  by
certified mail, return receipt requested or by overnight  delivery service (with
one acknowledged receipt), at the addresses set forth below.

Landlord:         at address shown in Article 1, item F.

with copy to:     Legal Department
                  Cornerstone Real Estate Advisers, Inc.
                  One Financial Plaza, Suite 1700
                  Hartford, Connecticut 06103-2604

with an additional copy to: Building Manager at address shown in Article 1, 
item G.

Tenant: at address shown in Article 1, item B.

with copy to:     Melvin R. Shuman, Esq.
                  Hale and Dorr
                  60 State Street, Boston, MA 02109

D. TRANSFERS.

The term "Landlord"  appearing herein shall mean only the owner of the Building,
from time to time and,  upon a sale or transfer of its interest in the Building,
the then Landlord and  transferring  party shall have no further  obligations or
liabilities for matters accruing after the date of transfer of that interest and
Tenant, upon such sale or transfer, shall look solely to the successor owner and
transferee of the Building for performance of Landlord's obligations hereunder.


E. RELOCATION.

(Deleted)

F. TENANT FINANCIAL STATEMENTS.

Upon the written request of Landlord,  Tenant shall submit financial  statements
for its most  recent  financial  reporting  period and for the prior Lease Year.
Landlord  shall make such request no more than twice during any Lease Year.  All
such  financial  statements  shall  be  certified  as true  and  correct  by the
responsible  officer  or  partner  of Tenant  and if  Tenant is then in  default
hereunder,  the  financial  statements  shall  be  certified  by an  independent
certified public accountant.

G. RELATIONSHIP OF THE PARTIES.

Nothing  contained in this Lease shall be construed by the parties hereto, or by
any third party, as constituting the parties as principal and agent, partners or
joint  venturers,  nor shall  anything  herein render either party (other than a
guarantor)  liable for the debts and  obligations  of any other party,  it being
understood and agreed that the only relationship  between Landlord and Tenant is
that of Landlord and Tenant.

H. ENTIRE AGREEMENT: MERGER

This Lease embodies the entire agreement and understanding,  between the parties
respecting  the Lease and the Premises and  supersedes  all prior  negotiations,
agreements  and  understandings  between  the  parties,  all of which are merged
herein. No provision of this Lease may be modified,  waived or discharged except
by an instrument in writing,  signed by the party against which  enforcement  of
such modification, waiver or discharge is sought.

I. NO REPRESENTATION BY LANDLORD.

Neither  Landlord  nor any  agent of  Landlord  has  made  any  representations,
warranties,  or promises with respect to the Premises or the Building  except as
expressly set forth herein.

J.  LIMITATION OF LIABILITY.

Notwithstanding,  any  provision  in  this  Lease  to  the  contrary,  under  no
circumstances  shall  Landlord's  liability or that of its directors,  officers,
employees and agents for failure to perform any obligations arising out of or in
connection  with the Lease or for any breach of the terms or  conditions of this
Lease (whether  written or implied)  exceed  Landlord's  equity  interest in the
Building.  Any judgments rendered against Landlord shall be satisfied solely out
of proceeds of sale of  Landlord's  interest  in the  Building.  Except for such
proceeds, no personal judgment shall lie against Landlord upon extinguishment of
its rights in the Building, and any judgments so rendered shall not give rise to
any right of execution or levy against  Landlord's assets. The provisions hereof
shall inure to  Landlord's  successors  and assigns  including  any Lender.  The
foregoing  provisions are not intended to relieve  Landlord from the performance
of any of  Landlord's  obligations  under  this  Lease,  but only to  limit  the
personal  liability  of  Landlord  in case of  recovery  of a  judgment  against
Landlord; nor shall the foregoing,  be deemed to limit Tenant's rights to obtain
injunctive relief or specific  performance or other remedy which may be accorded
Tenant by law or under this Lease. If Tenant claims or asserts that Landlord has
violated or failed to perform a covenant  under the Lease,  Tenant's sole remedy
shall be an action for specific performance,  declaratory judgment or injunction
and in no event shall  Tenant be entitled to any money  damages in any action or
by way of set off, defense or counterclaim and Tenant hereby specifically waives
the right to any money  damages  or other  remedies  for any such  violation  or
failure.

K. MEMORANDUM OF LEASE.

Neither party,  without the written consent of the other, will execute or record
any  this  Lease or any  summary  or  memorandum  of this  Lease  in any  public
recorders office.

L. NO WAIVERS: AMENDMENTS.

Failure of Landlord to insist upon strict  compliance by Tenant of any condition
or  provision  of this Lease  shall not be deemed a waiver by  Landlord  of that
condition.  No waiver shall be effective  against Landlord unless in writing and
signed by Landlord.  Similarly, this Lease cannot be amended except by a writing
signed by Landlord and Tenant.

M. SUCCESSORS AND ASSIGNS.

The conditions,  covenants and agreements contained herein shall be binding upon
and inure to the  benefit  of the  parties  hereto and their  respective  heirs,
executors, administrators, successors and assigns.

N. GOVERNING LAW.

This Lease  shall be  governed  by the law of the State  where the  Building  is
located.

O. EXHIBITS.

All  exhibits  attached  to this Lease are a part  hereof  and are  incorporated
herein  by  reference  and all  provisions  of such  exhibits  shall  constitute
agreements, promises and covenants of this Lease.

P. CAPTIONS.

The captions and headings used in this Lease are for convenience  only and in no
way define or limit the scope, interpretation or content of this Lease.

Q. COUNTERPARTS.

This Lease may be executed in one (1) or more counterparts,  each of which shall
be deemed an original,  but all of which together  shall  constitute one and the
same instrument.


                                   ARTICLE 31.

                               SPECIAL PROVISIONS

A. OPTION TO EXTEND.

(a) Tenant shall have one (1) option to extend this Lease in accordance with the
provisions of this paragraph for an additional  term of five (5) years on all of
the same terms and  conditions  of this lease  with the  exception  of base rent
payable under Article 1 K. hereof which shall be Landlord's then prevailing base
rent being charged by Landlord for space in the Building  reasonably  comparable
to the Premises. Provided, however, Tenant may not exercise the foregoing option
to extend if it shall be in default under the Lease and any  attempted  exercise
while in default  shall be null and void and of no effect.  If Tenant  elects to
exercise the foregoing  option to extend,  it shall give Landlord written notice
of its  election  to do so on or before  eight (8)  months  prior to the  normal
expiration  date of the Lease,  but not prior to twelve (12) months prior to the
normal  expiration  date of the Lease,  time being of the essence,  which notice
shall  also  request  that  Landlord  furnish  Tenant  with the base rent of the
extended term which shall be derived using  Landlord's  then prevailing rate for
space in the Building comparable to the Premises.  Landlord shall furnish Tenant
with the base rent figure for the term extension within ten (10) days of receipt
of Tenant's  notice of exercise.  Provided,  however,  in the event Landlord and
Tenant have not signed an amendment to this Lease for any reason  confirming the
extended  term of the Lease and  setting  forth the base rent for the term by no
less than six (6) months prior to the normal  expiration date of the Lease, time
being of the essence,  then Tenant's extension of the Lease shall be deemed null
and void and this Lease shall  expire on its initial  expiration  date as if the
above  extension  option had not been  exercised.  Tenant agrees to execute such
additional documents,  if any, as Landlord may reasonably require regarding such
extension.  Tenant has no other options to extend this Lease except as set forth
in this paragraph.


B. RIGHT OF FIRST OFFER

During  the term of this  lease but  subject  to the  prior  rights of any other
party,  if any,  tenant  is hereby  granted a Right of First  Offer on the fifth
(5th) floor space which may from time to time become vacant (the "ROFO  Space").
Before  Landlord  markets  any portion of the ROFO Space to any party other than
the then current occupant,  if any, or those having a prior right, Landlord will
notify  Tenant of the  availability  and  description  of the ROFO Space and the
basic terms  under  which  Landlord is going to market the ROFO Space and Tenant
will have the first  opportunity  to lease such ROFO Space  prior to other third
parties. Within seven (7) days of such notice, time being of the essence, Tenant
shall give  Landlord a notice that it either does or does not wish to enter into
a Lease with  Landlord  for the ROFO Space.  In the event that  Tenant's  notice
provides  that it does not wish to enter  into a Lease for the ROFO  Space or if
Tenant  fails to give  Landlord  the notice of its desires  respecting  the ROFO
Space within the foregoing required seven (7) day period, then Landlord shall be
entitled to proceed to market  and/or lease the ROFO Space to a third party free
and  clear of  Tenant's  right of first  offer  and such  right  shall be deemed
terminated with respect to the ROFO Space described in the notice from Landlord.

In the event that Tenant  gives  Landlord a notice as required in the  preceding
paragraph  that it wishes to lease the ROFO Space  from  Landlord,  then  Tenant
shall have thirty (30) days from the date of the notice  within  which to sign a
new lease  covering  the ROFO  Space or to amend  this  Lease by adding the ROFO
Space. In the event Tenant fails to sign such a lease or amendment to this Lease
within said thirty (30) day period,  time being of the  essence,  then  Landlord
shall be  entitled to proceed to market  and/or  lease the ROFO Space to a third
party  free and clear of such right and such  right  shall be deemed  terminated
with respect to the ROFO Space described in the notice from Landlord.












<PAGE>


IN WITNESS WHEREOF,  and intending to be legally bound hereby,  the parties have
duly executed this Lease with the Exhibits attached hereto, as of this 15 day of
May ,1997 .




Attest or Witness:                            LANDLORD:

                                              MASSACHUSETTS MUTUAL LIFE
INSURANCE COMPANY

                                              By:      CORNERSTONE REAL ESTATE
                                                       ADVISERS, INC., its agent


By:      /s/Heather  D. Stastny               By:      /s/Robert Whitney
                                              Name:    Robert Whitney
                                              Title:   Vice President



Attest or Witness:                            TENANT:

                                              SAVILLE SYSTEMS U.S., INC.


By:      /s/Lisa Miller                       By:      /s/Christopher A. Hanson
                                              Name:    Christopher A. Hanson
                                              Title:   CFO
                                              Date:    May 15, 1997










<PAGE>


                              Certificate of Tenant
                        (If A Corporation or Partnership)


I, John J. Boyle,  III,  Secretary or General  Partner of SAVILLE  SYSTEMS U.S.,
INC., Tenant,  hereby certify that the officers executing the foregoing Lease on
behalf of Tenant is/are duly authorized to act on behalf of and bind the Tenant.

(Corporate Seal)                                  John J. Boyle, III
                                                  Secretary or General Partner



Date:








                                    EXHIBIT A

                       Plan Showing Property and Premises



<PAGE>



                                    EXHIBIT B

                             Landlord's Work Letter

                                    Allowance


                                  May 15, 1997


Re:      SAVILLE SYSTEMS U.S., INC.
         Suite #500 & #501
         1 Van de Graaff Drive
         Burlington, Massachusetts 01803

Simultaneously with the execution of this Work Letter Agreement,  you ("Tenant")
and Massachusetts Mutual Life Insurance Company ("Landlord") are entering into a
lease (the "Lease") pertaining to the space referred to above (the "Premises").

In consideration of the covenants contained in this Work Letter Agreement and in
the Lease, Landlord and Tenant agree as follows:

TENANT'S PLANS

1. Tenant desires  Landlord to perform certain  leasehold  improvement work (the
"Work") in the Premises pursuant to a plan (the "Plan") for the Work prepared by
MPA  Architects,  dated  May 8,  1997,  a copy of which is  attached  hereto  as
Schedule 1. Not later than two (2) weeks from the  signing of the lease,  Tenant
shall furnish to Landlord all construction drawings, including a final telephone
layout and special electrical connection requirements,  if any. The Work and all
plans, drawings and specifications to be furnished by Tenant shall be subject to
Landlord's and Landlord's architect/engineer's approval, such approval not to be
unreasonably withheld or delayed.  Approval by Landlord of the Work and the Plan
shall not  constitute  any warranty by Landlord to Tenant of the adequacy of the
design for Tenant's  intended use of the Premises nor shall Landlord's  approval
of the Plan create any liability or  responsibility  on the part of Landlord for
compliance with applicable statutes,  ordinances,  regulations,  laws, codes and
industry  standards  relating to  handicap  discrimination  (including,  without
limitation,  the  Americans  with  Disabilities  Act).  All  Tenant  Improvement
drawings  to be  prepared  by the  Tenant's  architect  from  the  CAD  drawings
submitted by Cubellis & Associates will remain the property of the Landlord.

WORKING DRAWINGS

(Deleted)

PERFORMANCE OF THE WORK

3 . Except as hereinafter  provided to the contrary,  Landlord shall perform the
Work shown on the Plan and  Working  Drawings in a good and  workmanlike  manner
using  (except  as may be stated or shown in the Plan or the  Working  Drawings)
building  standard  materials and quantities  ("Building  Standards").  Landlord
shall  pay for a  portion  of the cost of the Work in an  amount  not to  exceed
$15.00 per rentable  square foot of the Premises  (the  "Allowance")  and Tenant
shall  pay  for  any and  all  costs  and  expenses  associated  with  the  Work
(including,  without limitation,  such additional expenses which result from any
special  work,  materials,   finishes  or  installations   required  by  Tenant,
unforeseen  field  conditions,  or from any  delays  in the Work  occasioned  by
Tenant) in excess of the  Allowance.  Tenant shall not be entitled to any credit
or payment  from  Landlord  for any  portion of the  Allowance  not  utilized by
Tenant.

PAYMENT

4.  Prior to  commencing  the  Work,  Landlord  will  submit to Tenant a written
statement  of the cost of that  portion  of the  Work to be paid for by  Tenant,
which cost shall include a 15% add-on charge for Landlord's  field  supervision,
administration  and  overhead.  Tenant  agrees,  within  three  (3)  days  after
submission to it of such  statement of cost, to execute and deliver to Landlord,
in the form then in use by  Landlord,  an  authorization  to  proceed  with that
portion of the Work to be paid for by Tenant,  and Tenant shall also then pay to
Landlord the amount set forth in Landlord's statement within thirty (30) days of
submission of such  statement.  Delays in the  performance of the Work resulting
from the  failure  of Tenant  to comply  with the  provisions  of the  preceding
sentence  shall be deemed  to be  delays  caused  by  Tenant.  No Work  shall be
commenced  until Tenant has fully  complied with the preceding  portions of this
Paragraph 4.

<PAGE>



SUBSTANTIAL COMPLETION

5. Landlord  shall cause the Work to be  "substantially  completed" on or before
the date described in Article 1.H. of Basic Provisions in the Lease,  subject to
delays  described in Article 5. of the Lease and delays described in Paragraph 6
of this Work  Letter  Agreement.  The Work  shall be  considered  "substantially
completed"  for all purposes  under this Work Letter  Agreement and the Lease if
and when  Landlord's  architect  issues a written  certificate  to Landlord  and
Tenant, certifying that the Work has been completed (except for minor finish-out
and  "punchlist"  items  which  Landlord  shall  endeavor to complete as soon as
practicable)  in substantial  compliance  with the Plan and, if applicable,  the
Working Drawings, and a Certificate of Occupancy has been issued, or when Tenant
first takes occupancy of the Premises,  whichever  first occurs.  If the Work is
not  substantially  completed on or before the date described in Article 1.H. of
Basic Provisions in the Lease, the Commencement  Date shall be extended (subject
to Paragraph 6 below) to the date on which the Work is  substantially  completed
and the  expiration  date  described in Article 1.I. of Basic  Provisions in the
Lease shall be extended by an equal number of days.
TENANT DELAYS

6. There shall be no  extension  of the date  described in Article 1.H. of Basic
Provisions in the Lease (as permissibly extended under Paragraph 5 above) to the
extent that the Work has not been substantially completed on said date by reason
of any delay attributable to Tenant, including without limitation:

(i) the failure of Tenant to furnish all plans, drawings, specifications, finish
details or the other  information  required under Paragraph 1 above on or before
the date stated in Paragraph 1;

(ii) the failure of Tenant to comply with the requirements of Paragraph 4 above;

(iii)  Tenant's  requirements  for  special  work  or  materials,  finishes,  or
installations other than the Building Standards;

(iv) the  performance  of any other work in the Premises by any person,  firm or
corporation  employed  by or on behalf of Tenant,  or any failure to complete or
delay in completion of such work; or

(v) any other act or omission of Tenant.

ADDITIONAL WORK

7. Upon  Tenant's  request and  submission  by Tenant (at Tenant's sole cost and
expense) of the necessary  information  and/or plans and specifications for work
other than the Work specified in the Plan and Working  Drawings (the "Additional
Work"), Landlord may, at its election,  perform the Additional Work, at Tenant's
sole cost and expense.  Prior to commencing  any  Additional  Work  requested by
Tenant,  Landlord shall submit to Tenant a written statement of the cost of such
Additional  Work  which cost shall  include a 15% add-on  charge for  Landlord's
field supervision, administration and overhead and a proposed Tenant Extra Order
(the "TEO") for Additional Work in the standard form then in use by Landlord. If
Tenant  shall fail to enter  into said TEO  within  one (1) week after  Tenant's
receipt  thereof,  Landlord  shall proceed to do only the Work  specified in the
Plan and Working Drawings.  Tenant agrees to pay to Landlord,  concurrently with
its execution of the TEO, the entire cost of the Additional Work as shown in the
statement delivered by Landlord.

TENANT ACCESS

8. Landlord,  in Landlord's reasonable discretion and upon reasonable request by
Tenant, and subject to Landlord's approval,  not to be unreasonably  withheld or
delayed, may grant to Tenant and Tenant's agents a license to enter the Premises
prior to the date  designated in the Lease for the  commencement  of the Term in
order  that  Tenant may do other work  required  by Tenant to make the  Premises
ready for  Tenant's use and  occupancy.  It shall be a condition to the grant by
Landlord and continued effectiveness of such license that:

(a) Tenant  shall  give to  Landlord  not less than five (5) days prior  written
notice of its request to have such access to the  Premises,  which  notice shall
contain  and/or shall be  accompanied  by: (i) a description of and schedule for
the work to be performed  by those  persons and entities for whom and which such
access is being  requested;  (ii) the names and  addresses  of all  contractors,
subcontractors  and material  suppliers  for whom and which such early access is
being  requested and the approximate  number of individuals,  itemized by trade,
who will be present in the Premises; (iii) copies of all contracts pertaining to
the performance of the work for which such early access is being requested; (iv)
copies of all plans and  specifications  pertaining  to the work for which  such
access is being  requested;  (v) copies of all licenses and permits  required in
connection  with the  performance  of the work for  which  such  access is being
requested;  (vi)  certificates of insurance (in amounts and with insured parties
satisfactory to Landlord) and instruments of indemnification against all claims,
costs, expenses, damages and liabilities which may arise in connection with such
work; and (vii)  assurances of the  availability of funds  sufficient to pay for
all such work.  All of the foregoing  shall be subject to  Landlord's  approval,
which shall not be unreasonably withheld or delayed.

(b) Such, early access shall be subject to reasonable scheduling by Landlord.

(c) Tenant's agents,  contractors,  workmen,  mechanics,  suppliers and invitees
shall work in harmony and not interfere with Landlord and  Landlord's  agents in
performing  the Work any  Additional  Work in the Premises,  Landlord's  work in
other premises and in common areas of the Building,  or the general operation of
the  Building.  If at any time such entry  shall cause or threaten to cause such
disharmony, Landlord may withdraw such license upon twenty-four (24) hours'prior
written  notice to Tenant Any such entry into and  occupation of the Premises by
Tenant shall be deemed to be under all of the terms,  covenants,  conditions and
provisions  of  the  Lease,   excluding  only  the  covenant  to  pay  Rent  and
specifically including the provisions of Section 10 thereof.  Landlord shall not
be liable for any injury, loss or damage which may occur to any of Tenant's work
or installations made in the Premises or to property placed therein prior to the
commencement  of the Term,  the same being at Tenant's sole risk and  liability.
Tenant  shall be liable to  Landlord  for any damage to the  Premises  or to any
portion  of the Work  caused  by Tenant or any of  Tenant's  employees,  agents,
contractors,  workmen or suppliers.  In the event the performance of the work by
Tenant, its agents, employees or contractors causes extra out-of-pocket costs to
Landlord or requires the use of  elevators  during hours other than 8:00 a.m. to
4:30 p.m. on Monday  through Friday (except  holidays),  Tenant shall  reimburse
Landlord  for the entire  extra cost and the cost  incurred by Landlord  for the
engineers or operators under applicable union regulations or contracts.

9. The terms and provisions of the Lease, insofar as they are applicable to this
Work Letter Agreement, are hereby incorporated herein by reference.

10. All amounts  payable by Tenant to Landlord  hereunder  shall be deemed to be
Rent under the Lease and upon any default in the payment of same, Landlord shall
have all of the rights and remedies provided for in the Lease.




<PAGE>


TENANT:                                LANDLORD:

SAVILLE SYSTEMS U.S., INC.             MASSACHUSETTS MUTUAL LIFE
                                       INSURANCE COMPANY

                                       By:      CORNERSTONE REAL ESTATE
                                       ADVISERS, INC., its agent



By:      /s/Christopher A. Hanson      By:      /s/Robert Whitney
         ------------------------               -----------------
Name:    Christopher A. Hanson         Name:    Robert Whitney
Title:   CFO                           Title:   Vice President
Date:    May 15, 1997                  Date:    May 19, 1997




<PAGE>


                                    EXHIBIT C

                                  Tenant's Work
                           (Intentionally Left Blank)










<PAGE>


                                    EXHIBIT D

                        Building's Rules and Regulations
                          and Janitorial Specifications

1. The sidewalks, entrances, passages, courts, elevators, vestibules, stairways,
corridors or halls of the Building shall not be obstructed or encumbered or used
for any purpose  other than ingress and egress to and from the premises  demised
to any tenant or occupant.

2. No awnings or other  projection  shall be attached  to the  outside  walls or
windows of the  Building  without the prior  consent of  Landlord.  No curtains,
blinds,  shades,  or  screens  shall  be  attached  to or  hung  in,  or used in
connection  with,  any window or door of the  premises  demised to any tenant or
occupant,  without the prior  consent of Landlord.  Such  awnings,  projections,
curtains,  blinds, shades, screens or other fixtures must be of a quality, type,
design and color, and attached in a manner, approved by Landlord.

3. No sign, advertisement, object, notice or other lettering shall be exhibited,
inscribed,  painted  or  affixed  on any part of the  outside  or  inside of the
premises  demised to any tenant or  occupant of the  Building  without the prior
consent of Landlord. Interior signs on doors and directory tables, if any, shall
be of a size, color and style approved by Landlord.

4. The sashes, sash doors,  skylights,  windows, and doors that reflect or admit
light and air into the halls, passageways or other public places in the Building
shall not be covered or  obstructed,  nor shall any bottles,  parcels,  or other
articles be placed on any window sills.

5. No show  cases or other  articles  shall be put in front of or affixed to any
part of the  exterior  of the  Building,  nor  placed in the  halls,  corridors,
vestibules or other public parts of the Building.

6. The water and wash closets and other plumbing  fixtures shall not be used for
any purposes other than those for which they were constructed, and no sweepings,
rubbish,  rags, or other  substances  shall be thrown  therein.  No tenant shall
bring or keep, or permit to be brought or kept,  any  inflammable,  combustible,
explosive or hazardous fluid,  materials,  chemical or substance in or about the
premises demised to such tenant.

7. No tenant or occupant shall mark, paint, drill into, or in any way deface any
part of the  Building or the  premises  demised to such tenant or  occupant.  No
boring, cutting or stringing of wires shall be permitted,  except with the prior
consent of  Landlord,  and as Landlord may direct.  No tenant or occupant  shall
install any resilient tile or similar floor covering in the premises  demised to
such tenant or occupant except in a manner approved by Landlord.

8. No bicycles, vehicles or animals of any kind shall be brought into or kept in
or about  the  premises  demised  to any  tenant.  No  cooking  shall be done or
permitted in the Building by any tenant without the approval of the Landlord. No
tenant shall cause or permit any unusual or objectionable  odors to emanate from
the premises demised to such tenant.

9. No space in the Building shall be used for manufacturing,  for the storage of
merchandise,  or for the sale of merchandise,  goods, or property of any kind at
auction, without the prior consent of Landlord.

10. No tenant  shall make,  or permit to be made,  any  unseemly  or  disturbing
noises or disturb or interfere  with other  tenants or occupants of the Building
or  neighboring  buildings  or  premises  whether  by the  use  of  any  musical
instrument,  radio,  television  set or other  audio  device,  unmusical  noise,
whistling, singing or in any other way. Nothing shall be thrown out of any doors
or window.

11. No  additional  locks or bolts of any kind  shall be placed  upon any of the
doors or  windows,  nor  shall  any  changes  be made in locks or the  mechanism
thereof.  Each tenant must,  upon the  termination  of its  tenancy,  restore to
Landlord all keys of stores,  offices and toilet rooms,  either furnished to, or
otherwise procured by, such tenant.

12. All removals from the Building, or the carrying in or out of the Building or
the premises demised to any tenant,  of any safes,  freight,  furniture or bulky
matter of any  description  must take  place at such time and in such  manner as
Landlord or its agents may determine,  from time to time.  Landlord reserves the
right to inspect all freight to be brought into the Building and to exclude from
the Building all freight which violates any of the Rules and  Regulations or the
provisions of such tenant's lease.

13. No tenant shall use or occupy, or permit any portion of the premises demised
to such tenant to be used or occupied, as an office for a public stenographer or
typist,  or to a barber or manicure shop, or as an employment  bureau. No tenant
or occupant  shall  engage or pay any  employees in the  Building,  except those
actually working for such tenant or occupant in the Building,  nor advertise for
laborers giving an address at the Building.

14. No tenant or occupant shall  purchase  spring water,  ice,  food,  beverage,
lighting maintenance, cleaning towels or other like service, from any company or
person not approved by Landlord. No vending machines of any description shall be
installed,  maintained  or  operated  upon the  premises  demised  to any tenant
without the prior consent of Landlord.

15.  Landlord shall have the right to prohibit any  advertising by any tenant or
occupant  which,  in Landlord's  opinion,  tends to impair the reputation of the
Building or its  desirability  as a building for  offices,  and upon notice from
Landlord,  such  tenant or  occupant  shall  refrain  from or  discontinue  such
advertising.

16. Landlord reserves the right to exclude from the Building,  between the hours
of 6:00  P.M.  and 8:00 A.M.  on  business  days and at all hours on  Saturdays,
Sundays and  holidays,  all  persons  who do not present a pass to the  Building
signed by Landlord.  Landlord will furnish passes to persons for whom any tenant
requests such passes.  Each tenant shall be responsible for all persons for whom
it requests  such  passes and shall be liable to  Landlord  for all acts of such
persons.

17. Each tenant,  before closing and leaving the premises demised to such tenant
at any  time,  shall see that all  entrance  doors are  locked  and all  windows
closed. Corridor doors, when not in use, shall be kept closed.

18. Each tenant shall, at its expense,  provide artificial light in the premises
demised to such tenant for Landlord's  agents,  contractors  and employees while
performing   janitorial  or  other  cleaning  services  and  making  repairs  or
alterations in said premises.

19. No premises  shall be used,  or permitted to be used for lodging or sleeping
or for any immoral or illegal purposes.

20. The requirements of tenants will be attended to only upon application at the
office of Landlord.  Building,  employees shall not be required to perform,  and
shall not be  requested by any tenant or occupant to perform and work outside of
their regular  duties,  unless under  specific  instructions  from the office of
Landlord.

21. Canvassing,  soliciting and peddling in the Building are prohibited and each
tenant and occupant shall cooperate in seeking their prevention.

22. There shall not be used in the Building, either by any tenant or occupant or
by their  agents or  contractors,  in the  delivery  or receipt of  merchandise,
freight,  or other matter,  any hand trucks or other means of conveyance  except
those equipped with rubber tires,  rubber side guards and such other  safeguards
as Landlord may require.

23. If the Premises  demised to any tenant  become  infested  with vermin,  such
tenant,  at  its  sole  cost  and  expense,  shall  cause  its  premises  to  be
exterminated,  from time to time,  to the  satisfaction  of Landlord,  and shall
employ such exterminators therefor as shall be approved by Landlord.

24. No premises shall be used, or permitted to be used, at any time, without the
prior approval of Landlord,  as a store for the sale or display of goods,  wares
or merchandise of any kind, or as a restaurant,  shop, booth, bootblack or other
stand,  or for the conduct of any  business or  occupation  which  predominantly
involves direct  patronage of the general public in the premises demised to such
tenant, or for manufacturing or for other similar purposes.

25. No tenant shall clean any window in the Building from the outside.

26. No tenant shall move, or permit to be moved,  into or out of the Building or
the premises  demised to such  tenant,  any heavy or bulky  matter,  without the
specific  approval of Landlord.  If any such matter requires  special  handling;
only a qualified person shall be employed to perform such special  handling.  No
tenant shall place,  or permit to be placed,  on any part of the floor or floors
of the premises  demised to such  tenant,  a load  exceeding  the floor load per
square foot which such floor was  designed to carry and which is allowed by law.
Landlord  reserves the right to  prescribe  the weight and position of safes and
other heavy matter, which must be placed so as to distribute the weight.

27. Landlord shall provide and maintain an  alphabetical  directory board in the
first  floor  (main  lobby)  of the  Building  and no other  directory  shall be
permitted  without the prior  consent of Landlord.  Each tenant shall be allowed
one line on such board unless otherwise agreed to in writing.

28. With respect to work being  performed  by a tenant in its premises  with the
approval  of  Landlord,  the tenant  shall refer all  contractors,  contractors'
representatives  and  installation  technicians to Landlord for its supervision,
approval and control  prior to the  performance  of any work or  services.  This
provision  shall  apply  to  all  work  performed  in  the  Building   including
installation  of  telephones,   telegraph  equipment,   electrical  devices  and
attachments,   and  installations  of  every  nature  affecting  floors,  walls,
woodwork,  trim,  ceilings,  equipment  and any other  physical  portion  of the
Building.

29.  Landlord shall not be  responsible  for lost or stolen  personal  property,
equipment,  money,  or jewelry  from the  premises  of  tenants or public  rooms
whether or not such loss occurs when the  Building,  or the  premises are locked
against entry.

30. Landlord shall not permit entrance to the premises of tenants by use of pass
keys  controlled  by  Landlord,  to any  person  at  any  time  without  written
permission from such tenant, except employees, contractors, or service personnel
directly  supervised  by Landlord  and  employees  of the United  States  Postal
Service.

31. Each tenant and all of tenant's  employees  and invitees  shall  observe and
comply with the driving  and parking  signs and markers on the Land  surrounding
the  Building,  and  Landlord  shall not be  responsible  for any  damage to any
vehicle towed because of noncompliance with parking regulations.

32.  Without  Landlord's  prior  approval,  no tenant shall install any radio or
television  antenna,  loudspeaker,  music  system or other device on the roof or
exterior walls of the Building or on common walls with adjacent tenants.

33. Each tenant shall store all trash and garbage within its premises or in such
other areas specifically designated by Landlord. No materials shall be placed in
the trash boxes or  receptacles  in the Building  unless such  materials  may be
disposed of in the ordinary and  customary  manner of removing and  disposing of
trash and  garbage and will not result in a  violation  of any law or  ordinance
governing such disposal.  All garbage and refuse  disposal shall be only through
entryways and elevators provided for such purposes and at such times as Landlord
shall designate.

34. No tenant  shall  employ any persons  other than the janitor or Landlord for
the purpose of cleaning its premises  without the prior consent of Landlord.  No
tenant  shall  cause any  unnecessary  labor by reason  of its  carelessness  or
indifference in the preservation of good order and cleanliness.  Janitor service
shall include ordinary dusting and cleaning by the janitor assigned to such work
and shall not include beating of carpets or rugs or moving of furniture or other
special  services.  Janitor service shall be furnished  Mondays through Fridays,
legal holidays  excepted;  janitor  service will not be furnished to areas which
are occupied after 9:30 P.M. Window cleaning shall be done only by Landlord, and
only between 6:00 A.M and 5:00 P.M.





<PAGE>


                                    EXHIBIT E

                         Commencement Date Confirmation


          DECLARATION BY LANDLORD AND TENANT AS TO DATE OF DELIVERY AND
                      ACCEPTANCE OF POSSESSION OF PREMISES

Attached to and made a part of the Lease dated the 15th day of May 1997  entered
into and by MASSACHUSETTS MUTUAL LIFE INSURANCE COMPANY as LANDLORD, and SAVILLE
SYSTEMS US, INC. as TENANT.

LANDLORD  AND TENANT do hereby  declare  that  possession  of the  Premises  was
accepted  by  TENANT  on 15th day of May,  1997.  The  Premises  required  to be
constructed  and finished by LANDLORD in accordance  with the  provisions of the
Lease have been satisfactorily completed by LANDLORD and accepted by TENANT, the
Lease is now in full force and effect,  and as of the date hereof,  LANDLORD has
fulfilled all of its obligations under the Lease. The Lease Commencement Date is
hereby  established as July 15, 1997. The Term of this Lease shall  terminate on
July 31, 2002.


LANDLORD:

MASSACHUSETTS MUTUAL LIFE
INSURANCE COMPANY
By:      CORNERSTONE REAL ESTATE
         ADVISERS, INC., its agent


By:      /s/Robert Whitney
         Name Typed:  Robert Whitney
         Title:  Vice President
         Date:  May 19, 1997


TENANT:

SAVILLE SYSTEMS US, INC.



By:      /s/Christopher A. Hanson
         Name Typed:  Christopher A. Hanson
         Title:  CFO
         Date:  May 15, 1997












<PAGE>


                                GUARANTY OF LEASE


In consideration of and as an inducement to Massachusetts  Mutual Life Insurance
Company  (hereinafter  "Landlord")  to enter into that certain  Lease  Agreement
(herein the "Lease") of even date  herewith  with  Saville  Systems  U.S.,  Inc.
(hereinafter  "Tenant")  respecting  space  in the  property  commonly  known as
Landmark One and located at One Van de Graaff Drive, Burlington,  Massachusetts,
01803, the undersigned(s) hereby  unconditionally  guarantee to Landlord and the
successors  and  assigns of  Landlord's  interest  under the Lease  and/or  this
Guaranty (i) the full and prompt  payment of all rent and other  charges from as
and when the same become due and payable under the Lease,  and (ii) the full and
punctual  performance  and  observance of all of the  covenants,  conditions and
agreements  provided in said Lease to be performed or observed by Tenant. If, at
any  time,  default  shall be made by  Tenant  in the  payment,  performance  or
observance  of any of the  obligations,  terms,  covenants or  conditions in the
Lease on Tenant's part to be paid,  kept,  performed or observed,  which default
continues  after the giving of any  required  notice and the  expiration  of any
applicable  grace  period,  the  undersigned(s)  upon  demand by  Landlord  will
forthwith  pay,  keep  perform  and  observe  the same in the place and stead of
Tenant.

In connection with the giving of the foregoing  guarantees,  the  undersigned(s)
hereby agree as follows:

1. Any act of Landlord, or the successors or assigns of Landlord,  consisting of
a waiver of any of the terms or  conditions  of the Lease,  or the giving of any
consent to any manner or thing  relating  to the Lease,  or the  granting of any
indulgences  or extensions of time to Tenant,  may be done without notice to the
undersigned(s)  and without  releasing  the  obligations  of the  undersigned(s)
hereunder;

2. The  obligations  of the  undersigned(s)  shall not be released by Landlord's
receipt,  application or release of security given for the payment,  performance
or  observance of any covenants or conditions in the Lease on the part of Tenant
to be paid, performed or observed;

3. The  undersigned(s)  hereby waive  notice of any and all  defaults  under the
Lease by  Tenant  including,  without  limitation,  notice  of  non-payment  and
non-performance  and non-observance of any term, covenant or condition by Tenant
under the Lease.  The  undersigned(s)  specifically  agree  that the  continuing
validity and enforceability of this Guaranty and the obligations and liabilities
of the undersigned(s) hereunder shall not be terminated, affected or impaired by
reason of the assertion or enforcement by Landlord  against Tenant of any of the
rights or remedies  reserved to Landlord pursuant to the provisions of the Lease
or under law;

4. The undersigned(s) covenant and agree (a) that this Guaranty shall remain and
continue in full force and effect as to any and all modifications,  renewals and
extensions of the Lease, and during any period when Tenant occupies the Premises
whether as a holdover tenant or otherwise to the same extent as if such renewal,
modification,  occupancy or extension were in effect at the time of execution of
this  guaranty,  and (b) the  liability  of the  undersigned(s)  shall be deemed
modified in accordance with terms of such  modification,  renewal,  extension or
occupancy,  all of the foregoing whether or not the undersigned has received any
notice  thereof  either  before,  at the time of or  after  the same is made and
whether or not the  undersigned(s)  consent or agree or have consented or agreed
thereto (all such notices and any requirements for undersigned(s) consent and/or
agreement being hereby specifically waived);

5 The liability of the  undersigned(s)  under this  Guaranty  shall in no way be
affected  or  impaired  by (a) the  release  or  discharge  of the Tenant in any
creditors'  receivership,  bankruptcy or other proceedings,  (b) the impairment,
limitation or  modification  of the liability of the Tenant or the estate of the
Tenant in  bankruptcy,  or of any remedy  for the  enforcement  of the  Tenant's
obligations and liabilities under the Lease, resulting from the operation of any
present or future  provision of the Bankruptcy Code or other statute or from the
decision of any court,  (c) the rejection or  disaffirmance  of the Lease in any
such proceedings,  (d) the assignment or transfer of the Lease by Tenant, or (e)
the cessation from any cause whatsoever of the liability of the Tenant;

6. Until all the covenants  and  conditions in the Lease on the Tenant's part to
be performed and observed are fully performed and observed,  the undersigned(s):
(a) shall have no right of subrogation  against Tenant by reason of any payments
or acts of performance by the undersigned(s), in compliance with the obligations
of the undersigned(s) hereunder: (b) waive any right to enforce any remedy which
the  undersigned(s) now or hereafter has or may have against Tenant by reason of
any one or  more  payments  or  acts  of  performance  in  compliance  with  the
obligations of the undersigned(s) hereunder; and, (c) subordinates any liability
or  indebtedness  of Tenant now or hereafter held by the  undersigned(s)  to the
obligations  of  Tenant  now or  hereafter  held  by the  undersigned(s)  to the
obligations of Tenant to Landlord under the Lease;

7. The undersigned(s)  agree that if more than one person executes this guaranty
or one or more counterparts  hereof,  their liability shall be joint and several
and each of the  undersigned(s)'  liability hereunder shall remain in full force
and effect  whether or not anyone else  executes  this guaranty or a counterpart
hereof.  References  in this  Guaranty  to the  "undersigned(s)"  shall mean and
include the undersigned(s)  collectively and each of the undersigned(s) in their
individual capacities. The undersigned(s) represent and warrant to Landlord that
this Guaranty has been duly  authorized  and  constitutes  the valid and binding
obligation  of the  undersigned(s).  In any  action  or  proceeding  brought  by
Landlord to enforce this  Guaranty,  the  undersigned(s)  to the maximum  extent
permitted by law shall and do hereby waive trial by jury;

8. This Guaranty may not be changed,  modified,  discharged or terminated orally
or  in  any  manner  other  than  by an  agreement  in  writing  signed  by  the
undersigned(s)  and  Landlord.  In  all  cases,  notices  may  be  given  to the
undersigned(s)   at  the  addresses  set  forth  below  under  their  respective
signatures  and such notice will be deemed to have been  sufficiently  given for
all purposes if hand  delivered or, if sent by prepaid  certified  mail,  return
receipt  requested,  as of the date of mailing.  By a notice  similarly given to
Landlord c/o Cornerstone Real Estate Advisers,  311 S. Wacker Drive,  Suite 980,
Chicago, Illinois 60606, attention: Asset Manager, the undersigned(s) may change
their address for notice purposes.

9. The  Guarantor  irrevocably  and  unconditionally  (a) agrees  that any suit,
action or legal  proceeding  arising out of this  Guaranty may be brought in the
courts of record of the State of  Massachusetts in Middlesex County or in any of
the courts of the United States;  (b) consents to the jurisdiction of each court
in any such suit,  action, or proceeding;  and (c) waives any objection which it
may have to the laying of venue of any such suit,  action,  or proceeding in any
of such  courts.  For such  time as any of the  obligations  hereunder  shall be
unpaid in whole,  or in part, the Guarantor  appoints the Tenant as its agent to
accept and acknowledge on the Guarantor's  behalf service of any and all process
in any such suit, action, or proceeding brought in any such court. The Guarantor
agrees  and  consents  that any such  service of  process  upon such  agents and
written  notice of such  service  to the  Guarantor  in the  manner set forth in
Section 8 hereof shall be taken and held to be valid  personal  service upon the
Guarantor whether or not the Guarantor shall then be doing, or at any time shall
have done,  business  within the State of  Massachusetts.  Such agents shall not
have  the  power  or  authority  to enter  into  any  appearance  or to file any
pleadings  in  connection  with any suit,  action,  or other  legal  proceedings
against the  Guarantor  or to conduct the  defense of any suit,  action,  or any
other legal proceeding, except as expressly authorized by the Guarantor.

Executed this 15th day of May 1997.


Guarantor:
Saville Systems PLC
By: /s/Christopher A. Hanson
Name Typed: Christopher A. Hanson
Title: CFO
Address: 25 Burlington Mall Rd.
Burlington, MA 01803




<PAGE>


                                 NOTICE OF LEASE


Notice is hereby given, pursuant to the provisions of Chapter 183A, Section 4 of
the Massachusetts General Laws, of the following Lease:

LANDLORD:                  Massachusetts Mutual Life Insurance Company
                           c/o Cornerstone Real Estate Advisors, Inc.
                           311 S. Wacker Drive, Suite 980
                           Chicago, Illinois 60606

TENANT:                    Saville Systems U.S., Inc.
                           Suite 500 and 501
                           1Van de Graaff Drive
                           Burlington, Massachusetts 01803

DATE OF EXECUTION:         May 15,  1997

PREMISES:                  Suite/Unit  No.:  500 &  501,  consisting  of  12,417
                           rentable  square  feet and  shown on a plan  attached
                           hereto as Exhibit A in the Building known as Landmark
                           One (the  "Building')  located  at One Van de  Graaff
                           Drive,  Burlington,   Massachusetts.  For  Landlord's
                           title, see Middlesex South Registry of Deeds, Book___
                           , Page _.

TERM:                      July 15, 1997 through July 31, 2002,  provided that 
                           the Commencement  Date shall be advanced to such  
                           earlier  date as Tenant  commences  occupancy  of the
                           Premises for the conduct of its  business,  and  
                           provided  further that the Term Commencement  Date 
                           and Expiration Date shall be postponed for an equal 
                           number of days as the delay of Landlord in completing
                           improvements  to the  premises for Tenant's initial  
                           occupancy  caused by strike,  shortages of labor or 
                           materials, delivery  delays or other matters beyond 
                           the  reasonable  control of Landlord as set forth in 
                           a notice from Landlord to Tenant of such delay.

OPTION TO EXTEND:          Tenant shall have one option to extend the Lease for 
                           an additional term of five (5) years on the terms and
                           conditions set forth in the Lease.

RIGHT OF FIRST
OFFER:                     Under the term of the Lease but  subject to the prior
                           rights of any other party, if any, Tenant has a right
                           of first  offer on all space on the fifth (5th) floor
                           of the Building on the terms and conditions set forth
                           in the Lease.



<PAGE>


WITNESS the execution hereof under seal this 15 day of May, 1997.

LANDLORD:

Massachusetts Mutual Life Insurance
Company

By: Cornerstone Real Estate Advisers, Inc.,
its agent


By: /s/Robert Whitney
Name: Robert Whitney
Title: Vice President

TENANT:

Saville Systems U.S., Inc.

By: /s/Christopher A. Hanson
Name: Christopher A. Hanson
Title: CFO










<PAGE>


                          COMMONWEALTH OF MASSACHUSETTS

                                , ss: May 19 1997          

         Then  personally  appeared the  above-named  Robert  Whitney,  the Vice
President of Cornerstone  Real Estate  Advisers,  Inc.,  agent of  Massachusetts
Mutual Life Insurance Company, and acknowledged the foregoing to be the free act
and deed of Cornerstone  Real Estate  Advisers,  Inc. on behalf of Massachusetts
Mutual Life Insurance company, before me,

/s/Heather D. Stastny
Notary Public
My Commission Expires: 05/02/00

"OFFICIAL SEAL"
HEATHER D. STASTNY
NOTARY PUBLIC STATE OF ILLINOIS
MY COMMISION EXPIRES 05102100


                          COMMONWEALTH OF MASSACHUSETTS

                                , ss: May 15 1997  

         Then  personally  appeared the  above-named  Chris  Hanson,  the CFO of
Saville Systems U.S., Inc. and acknowledged the foregoing to be the free act and
deed of said corporation, before, me,


/s/Elizabeth Anika Bales
Notary Public
My Commission Expires: Oct. 9 2003






<PAGE>


ACKNOWLEDGMENT


CORPORATE ACKNOWLEDGMENT

STATE OF:                  Massachusetts

COUNTY OF:                 Middlesex

On this 15 day of May,  1997,  before me, a Notary Public in and for said State,
personally appeared Chris Hanson,  known to me to be the person described in and
who executed such instrument as Chief  Financial  Officer of Saville Systems US,
Inc.  , a Delaware  corporation,  and who  acknowledged  the  execution  of such
instrument  as such officer for and on behalf of and as the free act and deed of
such corporation, and the seal affixed thereto is the true and genuine corporate
seal of such corporation.

         IN WITNESS WHEREOF, I have hereunto set my hand and affixed my official
seal the day and year set forth above.

/s/Elizabeth Anika Bales
Notary Public
My Commission Expires: Oct. 9 2003