EXHIBIT 10.7


Scotiabank
The Bank of Nova Scotia

10050 Jasper Avenue   Edmonton   Alberta   T5J 1V7


                                                              August 27, 1997

Saville Systems PLC
Saville Systems Canada, Ltd.
Saville Systems, Inc., on a Joint & Several Basis

Dear Sirs:

We are pleased to confirm  that subject to  acceptance  by you, the Bank of Nova
Scotia (the "Bank") will make available to Saville Systems PLC,  Saville Systems
Canada,  Ltd.  and  Saville  Systems,  Inc.  on a joint  &  several  basis  (the
"Borrower"),  credit  facilities  on the  terms  and  conditions  set out in the
attached Terms and Conditions Sheet and Schedule "A".

If the  arrangements  set out in  this  letter  and in the  attached  Terms  and
Conditions  Sheet and Schedule "A"  (collectively  the "Commitment  Letter") are
acceptable  to you,  please sign the  enclosed  copy of this letter in the space
indicated  below  and  return  the  letter  to us by the  close of  business  on
September 5, 1997 after which date this offer will lapse.

This Commitment Letter replaces all previous  commitments  issued by the Bank to
the Borrower.

                                           Yours very truly,
/s/J.M. Kozell                             /s/ G.R. Flumerfelt
J.M. Kozell                          FOR:  K.B. Kalansky
Account Manager                            Vice-President & Centre Manager

The  arrangements  set out above and in the attached Terms and Conditions  Sheet
and Schedule  "A"(collectively  the "Commitment Letter") are hereby acknowledged
and accepted by:

Saville Systems PLC                         Saville Systems, Inc.
Name                                        Name

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

Date:  9/4/97                               Date:  9/4/97

Saville Systems Canada, Ltd.
Name

By:  /s/Christopher A. Hanson
Date:  9/4/97



<PAGE>


                              TERMS AND CONDITIONS

CREDIT NUMBER:  01                               AUTHORIZED AMOUNT:  $15,000,000


TYPE
         Operating

PURPOSE
         General operating requirements

CURRENCY
         US dollar and/or Canadian dollar  equivalent  thereof and/or Irish punt
         equivalent thereof.

AVAILMENT
         The Borrower may avail the Credit by way of direct  advances  evidenced
         by Demand  Promissory  Notes and/or  Bankers'  Acceptances  in Canadian
         dollars (in multiples of $100,000 and having terms of maturity of 30 to
         180 days without grace) and/or Standby Letters of Credit and/or Letters
         of Guarantee.

         The maximum  availment  under Standby  Letters of Credit and Letters of
         Guarantee is US $1,000,000 and/or the CDN dollar equivalent thereof.

INTEREST RATE/FEES/COMMISSION
         (US dollars):  The Bank's U.S. Dollar Base Rate in Canada, from time to
         time, plus 0.25% per annum with interest payable monthly.

         (US dollars):  The Bank's London Interbank Offer Rate (LIBOR),  plus 1%
         per  annum  for  periods  of  1,  2,  3 or 6  months,  the  rate  to be
         established  two (2) business  days prior to each  drawdown or rollover
         (Interest Adjustment Date) with interest payable monthly in arrears.

         (CDN  dollars):  The Bank's Prime Lending Rate from time to time,  plus
         0.25% per annum, with interest payable monthly.

         (CDN dollars):  The Bank's Corporate Bankers'  Acceptance Fee, (subject
         to  revision at any time),  plus 0.25% per annum,  subject to a minimum
         fee of $100 per transaction, payable at the time of each acceptance.

         (IEP):  The Bank's Dublin  Interbank  Offer Rate  (DIBOR),  plus 1% per
         annum for  periods of 1, 2, 3 or 6 months,  the rate to be  established
         two (2)  business  days prior to each  drawdown or  rollover  (Interest
         Adjustment Date) with interest payable monthly in arrears.

         (L/G's & Standby L/C's): 1% per annum,  calculated on the issue amount,
         based on  increments  of 30 days or  multiples  thereof,  from  date of
         issuance to expiry  date.  Periods of less than 30 days will be counted
         as a thirty day increment.  The amount is subject to the Bank's minimum
         Standby  fee as  well as  revision  at any  time  and is  payable  upon
         issuance.

STANDBY FEE
         A Standby  Fee of 0.25% per annum on the daily  unused  portion  of the
         Credit payable in USD is payable monthly  commencing the earlier of all
         security being in place or 30 days from acceptance of this commitment.


<PAGE>



DRAWDOWN
         Advances are to be made in minimum  multiples of US $50,000  and/or CDN
         dollar equivalent thereof and/or Irish punt equivalent thereof.

REPAYMENT
         The  credit is for a period  of 2 years  until  August  31,  1999.  The
         Borrower  has the  option,  provided  60 days prior to August 31,  1998
         written  notice has been  presented  to the Bank to request the Bank to
         extend the  Operating  Facility  for a further  period of 2 years.  Any
         extension is subject to the Bank's approval.

GENERAL SECURITY

         The following security,  evidenced by documents in form satisfactory to
         the Bank is to be provided  prior to any  advances or  availment  being
         made under the Credit(s):

          General  Security  Agreement from each of Saville Systems PLC, Saville
          Systems Canada,  Ltd. and Saville  Systems,  Inc. over all present and
          future personal property with appropriate insurance coverage,  loss if
          any, payable to the Bank.

          The General Security agreements will be held in unregistered form. The
          Bank  reserves the right to register the General  Security  Agreements
          should either:

          The consolidated * working capital ratio decrease below 2.0:1.
          or
          The consolidated  ratio of  Debt:Tangible  Net Worth (TNW) ** increase
          above 1.2:1.

          *Consolidated  includes  Saville Systems PLC,  Saville Systems Canada,
          Ltd. and Saville Systems, Inc.

          **TNW is defined as the sum of share capital,  earned and  contributed
          surplus   less  (i)   amounts  due  from   officers/affiliates,   (ii)
          investments  in affiliates and (iii)  intangible  assets as defined by
          the Bank.

          Negative  Pledge  affirming  assets  will not be  further  encumbered,
          without the Bank's prior written consent.

          Bankers' Acceptance Agreement

          Reimbursement Agreement for Standby Letter of Credit.

CONDITIONS PRECEDENT
          The  following  conditions  have to be  met,  in  form  and  substance
          satisfactory  to the Bank,  prior to any advances or availments  being
          made under the credit:

          Due  Diligence  process  by the Bank  including  a review of  existing
          contracts  and licence  agreements.  Receipt of written  legal and tax
          opinions on the structure of the credit facility and security. Receipt
          of a Business Plan including projections for fiscal 1997 and a capital
          expenditure  budget.  Receipt of an organization chart and family tree
          for the Saville Group.

<PAGE>



GENERAL CONDITIONS
         Until all debts and liabilities  under the Credits have been discharged
         in full, the following conditions will apply in respect of the Credits:
          
          Operating loans, Bankers'  Acceptances,  Standby Letters of Credit and
          Letters  of  Guarantee  are not to exceed  at any time the  "Borrowing
          Base"  which  is  defined  as the  aggregate  of 80% of  good  quality
          accounts  receivable  (excluding accounts over 90 days accounts due by
          employees,  offsets and  inter-company  accounts)  plus  combined cash
          holdings  or cash  equivalents  held on deposit  with The Bank of Nova
          Scotia,  or its affiliates,  less security interest or charges held by
          other  parties and specific  payables  which have or may have priority
          over the Bank's security.

          The consolidated ratio of current assets to current  liabilities is to
          be maintained at all times at 1.5:1 or better.

          The consolidated ratio of Debt (including  deferred taxes) to Tangible
          Net Worth (TNW) is not to exceed 1.5:1.

          Guarantees or other contingent  liabilities are not to be entered into
          in excess of the aggregate of $1,000,000  per annum without the Bank's
          prior written consent.

          The  Borrower  will not  grant or  permit a  Purchase  Money  Security
          Interest to any supplier or creditor.

          Additional terms and conditions in Schedule A are to apply.

GENERAL BORROWER REPORTING CONDITIONS
          Until  all  debts  and  liabilities  under  the  Credit(s)  have  been
          discharged  in full,  the  Borrower  will  provide  the Bank  with the
          following:

          Annual Audited Consolidated  Financial Statements,  within 120 days of
          the Borrower's fiscal year end, duly signed.

          Annual  Unconsolidated  Financial  Statements,  for  each  of  Saville
          Systems PLC, Saville Systems Canada,  Ltd. and Saville  Systems,  Inc.
          prepared  under Review  Engagement,  within 120 days of the Borrower's
          fiscal year end.

          Quarterly  Consolidated Interim Financial Statements within 45 days of
          period end.

          A  Statement  of  Security   quarterly,   to  include  information  on
          inventory, accounts receivable and accounts payable, within 45 days of
          period end.

                                   SCHEDULE A

            ADDITIONAL TERMS AND CONDITIONS APPLICABLE TO ALL CREDITS

Calculation and Payment of Interest

1.   Interest on loans/advances made in Canadian dollars will be calculated on a
     daily  basis and  payable  monthly  on the 22nd day of each  month  (unless
     otherwise stipulated by the Bank). Interest shall be payable not in advance
     on the basis of a calendar  year for the actual number of days elapsed both
     before and after demand of payment of default and/or judgment.

Interest on Overdue Interest

2.   Interest  on  overdue  interest  shall be  calculated  at the same  rate as
     interest on the loans/advances in respect of which interest is overdue, but
     shall be compounded monthly and be payable on demand, both before and after
     demand and judgment.

Indemnity Provision

3.   If the  introduction of or any change in, or in the  interpretation  of, or
     any change in its application to the Borrower of, any law or regulation, or
     compliance  with any guideline from any central bank or other  governmental
     authority  (whether  or not  having  the  force of law) has the  effect  of
     increasing the cost to the Bank of performing its obligations  hereunder or
     otherwise  reducing  its  effective  return  hereunder  or on  its  capital
     allocated in support of the  credit(s),  then upon demand from time to time
     the Borrower shall compensate the Bank for such cost or reduction  pursuant
     to a certificate reasonably prepared by the Bank.

     (a)  Prepayment without fee

         In the  event of the  Borrower  becoming  liable  for such  costs,  the
         Borrower  shall  have  the  right  to  cancel  without  fee  all or any
         unutilized  portion of the affected  credit  (other than any portion in
         respect of which the Borrower has requested  utilization  of the credit
         in which case cancellation may be effected upon  indemnification of the
         Bank for any  costs  incurred  by the  Bank  thereby),  and to  prepay,
         without fee the outstanding principal balance thereunder other than the
         face  amount of any  document or  instrument  issued or accepted by the
         Bank for the  account of the  Borrower,  such as a Letter of Credit,  a
         Guarantee or a Bankers' Acceptance.

Calculation and Payment of Bankers' Acceptance Fee

1.   The fee for the acceptance of each Bankers'  Acceptance  will be payable on
     the face amount of each  Bankers'  Acceptance  at the time of acceptance of
     each draft calculated on the basis of a calendar year for the actual number
     of days elapsed from and  including  the date of acceptance to the due date
     of the draft.

Calculation and Payment of Standby Fee

2.    Standby fees shall be calculated daily and payable monthly on the basis of
      a 360 year day for U.S. dollar credits.

Environment

3.    The Borrower agrees:

     (a) to  obey  all  applicable   laws  and   requirements  of  any  federal,
         provincial,  or  any  other  governmental  authority  relating  to  the
         environment  and  the  operation  of  the  business  activities  of the
         Borrower;
     (b) to allow  the  Bank  access  at all  reasonable  times to the  business
         premises  of the  Borrower to monitor  and  inspect  all  property  and
         business activities of the Borrower;
     (c) to notify the Bank from time to time of any business activity conducted
         by the  Borrower  which  involves  the  use or  handling  of  hazardous
         materials or wastes or which increases the  environmental  liability of
         the Borrower in any material manner;
     (d) to notify the Bank of any proposed  change in the use or  occupation of
         the property of the Borrower prior to any change occurring;
     (e) to provide the Bank with immediate  written notice of any environmental
         problem and any hazardous materials or substances which have an adverse
         effect  on  the  property,  equipment  or  business  activities  of the
         Borrower and with any other environmental  information requested by the
         Bank from time to time;
     (f) to conduct all environmental  remedial  activities which a commercially
         reasonable  person would perform in similar  circumstances  to meet its
         environmental  responsibilities and if the Borrower fails to do so, the
         Bank may perform such activities; and
     (g) to pay for any  environmental  investigations,  assessments or remedial
         activities  with respect to any  property of the  Borrower  that may be
         performed for or by the Bank from time to time.

If the  Borrower  notifies  the Bank of any  specified  activity  or  change  or
provides the Bank with any information pursuant to subsections (c), (d), or (e),
or if the Bank receives any  environmental  information from other sources,  the
Bank,  in its  sole  discretion,  may  decide  that  an  adverse  change  in the
environmental  condition of the Borrower or any of the property,  equipment,  or
business activities of the Borrower has occurred which decision will constitute,
in the absence of manifest  error,  conclusive  evidence of the adverse  change.
Following  this  decision  being  made by the Bank,  the Bank  shall  notify the
Borrower of the Bank's decision concerning the adverse change.

If the Bank decides or is required to incur  expenses in compliance or to verify
the Borrower's  compliance with applicable  environmental or other  regulations,
the Borrower shall  indemnify the Bank in respect of such  expenses,  which will
constitute further advances by the Bank to the Borrower under this Agreement.

Evidence of Indebtedness

1.   The  Bank's  accounts,  books and  records  constitute,  in the  absence of
     manifest error, conclusive evidence of the advances made under this Credit,
     repayments on account  thereof and the  indebtedness of the Borrower to the
     Bank.

Acceleration

2.   All  indebtedness  and liability of the Borrower to the Bank not payable on
     demand,  shall,  at the  option of the  Bank,  become  immediately  due and
     payable,   the  security  held  by  the  Bank  shall   immediately   become
     enforceable,  and the  obligation  of the Bank to make further  advances or
     other accommodation available under the Credits shall terminate, if any one
     of the following Events or Default occurs:

         (i)      the Borrower fails to make when due, whether on demand or at a
                  fixed payment date, by acceleration or otherwise,  any payment
                  of interest,  principal,  fees,  commissions  or other amounts
                  payable to the Bank;
         (ii)     there  is a  breach  by the  Borrower  of any  other  term  or
                  condition  contained in this Commitment Letter or in any other
                  agreement to which the Borrower and the Bank are parties;
         (iii)    any  default   occurs  under  any  security   listed  in  this
                  Commitment  Letter under the headings  "Specific  Security" or
                  "General Security" or under any other credit, loan or security
                  agreement to which the Borrower is a party;
         (iv)     any  bankruptcy,  re-organization,   compromise,  arrangement,
                  insolvency or liquidation proceedings or other proceedings for
                  the  relief  of  debtors  are  instituted  by or  against  the
                  Borrower,  and if instituted against the Borrower, are allowed
                  against or consented  to by the Borrower or are not  dismissed
                  or stayed within 60 days after such institution;
         (v)      a receiver is  appointed  over any property of the Borrower or
                  any  judgment  or order or any  process  of any court  becomes
                  enforceable  against  the  Borrower  or  any  property  of the
                  Borrower or any creditor  takes  possession of any property of
                  the Borrower;
         (vi)     any material  adverse change occurs in the financial condition
                  of the  Borrower;   
         (vii)    any  material  adverse  change  occurs  in  the environmental 
                  condition of:
          (A) the Borrower; or
          (B) any property, equipment, or business activities of the Borrower.



                                           /s/ Bruce A. Saville
                                           Bruce A. Saville