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                                                            EXHIBIT NUMBER 10.13

                              FOURTH AMENDMENT TO
                     AMENDED AND RESTATED CREDIT AGREEMENT
                                (MULTICURRENCY)


          THIS FOURTH AMENDMENT TO AMENDED AND RESTATED CREDIT AGREEMENT
(MULTICURRENCY) (the "Amendment"), dated as of December 18, 1998, is entered
into by and between STANFORD TELECOMMUNICATIONS, INC. (the "Borrower") and BANK
OF AMERICA NATIONAL TRUST AND SAVINGS ASSOCIATION (the "Bank").

                                    RECITALS

          A.   The Borrower and the Bank are parties to an Amended and Restated
Credit Agreement (Multicurrency) dated as of December 20, 1995, as amended by a
First Amendment thereto dated as of December 5, 1996, a Second Amendment thereto
dated as of December 12, 1997, and a Third Amendment thereto dated as of August
24, 1998 (as so amended, the "Credit Agreement") pursuant to which the Bank has
extended certain credit facilities to the Borrower.

          B.   The Borrower has requested that the Bank agree to certain
amendments of the Credit Agreement.

          C.   The Bank is willing to amend the Credit Agreement, subject to the
terms and conditions of this Amendment.

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

          1.   Defined Terms.  Unless otherwise defined herein, capitalized
terms used herein shall have the meanings, if any, assigned to them in the
Credit Agreement.

          2.   Amendments to Credit Agreement.

               (a) Section 1.01 of the Credit Agreement shall be amended at the
defined term "Availability Period" by amending and restating such defined term
as follows:

               "'Availability Period':  the period commencing on the date of
          this Agreement and ending on the date that is the earlier to occur of
          (a) December 17, 1999, and (b) the date on which the Bank's commitment
          to extend credit hereunder terminates."

               (b) Section 1.01 of the Credit Agreement shall be amended at the
defined term "Final Maturity Date" by amending and restating such defined term
as follows:

               "'Final Maturity Date':  (a) in respect of any Advances, December
          17, 1999; (b) in respect of any commercial letters of credit, June 17,
          2000; (c) in respect of any standby letters of credit, December 17,
          2000; (d) in respect of any Bank Guaranties, December 17, 2000; and
          (e) in respect of any acceptances, June 17, 2000."


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          (c) Article II of the Credit Agreement shall be amended by inserting
the following new Section 2.12 immediately following Section 2.11:

               (a)  Definitions.

               In this Section and in each other provision of this Agreement to
               which reference is made in this Section expressly or implicitly,
               the following terms have the following meanings:

               "commencement of the third stage of EMU" means the date of
              commencement of the third stage of EMU (at the date of this
              Agreement expected to be January 1, 1999) or the date on which
              circumstances arise which (in the opinion of the Bank) have
              substantially the same effect and result in substantially the same
              consequences as commencement of the third stage of EMU as
              contemplated by the Treaty on European Union.

               "EMU" means economic and monetary union as contemplated in the
              Treaty on European Union.

               "EMU legislation" means legislative measures of the European
              Council for the introduction of, changeover to, or operation of a
              single or unified European currency (whether known as the euro or
              otherwise), being in part the implementation of the third stage of
              EMU.

               "euro" means the single currency of participating member states
              of the European Union.

               "euro unit" means the currency unit of the euro.

               "national currency unit" means the unit of currency (other than
              a euro unit) of a participating member state.

               "participating member state" means each state so described in any
              EMU legislation.

               "Treaty on European Union" means the Treaty of Rome of March 25,
              1957, as amended by the Single European Act 1986 and the
              Maastricht Treaty (which was signed at Maastricht on February 7,
              1992, and came into force on November 1, 1993), as amended from
              time to time.

               (b)  Effectiveness of Provisions.

               The provisions of subsections (c) through (i) of this Section
              shall be effective at and from the commencement of the third stage
              of EMU; provided, that if and to the extent that any such
              provision relates to any state (or the currency of such state)
              that is not a participating member state on the commencement of
              the third stage of EMU, such provision shall become effective in
              relation to such state (and the currency of such state) at and
              from the date on which such state becomes a participating member
              state.

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               (c) Redenomination and Alternative Currencies.

               Each obligation under this Agreement of the Bank and the
              Borrower which has been denominated in the national currency unit
              of a participating member state shall be redenominated into the
              euro unit in accordance with EMU legislation; provided, that if
              and to the extent that any EMU legislation provides that following
              the commencement of the third stage of EMU an amount denominated
              either in the euro unit or in the national currency unit of a
              participating member state and payable within that participating
              member state by crediting an account of the creditor can be paid
              by the debtor either in the euro unit or in that national currency
              unit, the Bank and the Borrower shall be entitled to pay or repay
              any such amount either in the euro unit or in such national
              currency unit.

               (d)  Local Currency Advances.

               Any Local Currency Advance or other obligation denominated in
              Local Currency which is denominated in the currency of a
              participating member state shall be made in the euro unit.

               (e)  Banking Days.

               With respect to any amount denominated or to be denominated in
              the euro unit or a national currency unit, any reference to a
              "Banking Day" shall be construed as a reference to a day (other
              than a Saturday or Sunday) on which banks are generally open for
              business in (i) London and New York City, and (ii) Frankfurt am
              Main, Germany (or such principal financial center or centers in
              such participating member state or states as the Bank may from
              time to time nominate for this purpose).

               (f)  Payments to the Bank.

               Each provision of this Agreement calling for payments in a
              specified currency shall be construed so that, in relation to the
              payment of any amount of euro units or national currency units,
              such amount shall be made available to the Bank in immediately
              available, freely transferable, cleared funds to such account of
              the Bank's in Frankfurt am Main, Germany (or such other principal
              financial center in such participating member state as the Bank
              may from time to time nominate for this purpose) as the Bank shall
              from time to time nominate for this purpose.

               (g)  Payments by the Bank Generally.

               With respect to the payment of any amount denominated in the
              euro unit or in a national currency unit, the Bank shall not be
              liable to the Borrower in any way whatsoever for any delay, or the
              consequences of any delay, in the crediting to any account of any
              amount required by this Agreement to be paid by the Bank if the
              Bank shall have taken all relevant steps to achieve, on the date
              required by this Agreement, the payment of such amount in
              immediately available, freely transferable, cleared funds (in the
              euro unit or, as the case may be, in a national currency unit) to
              the account with the bank in the principal financial center in the


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              participating member state which the Borrower or, as the case may
              be, the Bank shall have specified for such purpose.  In this
              subsection, "all relevant steps" means all such steps as may be
              prescribed from time to time by the regulations or operating
              procedures of such clearing or settlement system as the Bank may
              from time to time determine for the purpose of clearing or
              settling payments of the euro.

               (h)  Basis of Accrual.

               If the basis of accrual of interest or fees expressed in this
              Agreement with respect to the currency of any state that becomes a
              participating member state shall be inconsistent with any
              convention or practice in the London interbank market or, as the
              case may be, another applicable interbank market for the basis of
              accrual of interest or fees in respect of the euro, such
              convention or practice shall replace such expressed basis
              effective as of and from the date on which such state becomes a
              participating member state; provided, that if any Local Currency
              Advance in the currency of such state is outstanding immediately
              prior to such date, such replacement shall take effect, with
              respect to such Advance, at the end of the then current interest
              period or other applicable period.

               (i) Rounding and Other Consequential Changes.

               Without prejudice and in addition to any method of conversion or
              rounding prescribed by any EMU legislation and without prejudice
              to the respective liabilities of the Borrower to the Bank or the
              Bank to the Borrower under or pursuant to this Agreement:  (i)
              each reference in this Agreement to a minimum amount (or an
              integral multiple thereof) in a national currency unit to be paid
              to or by the Bank shall be replaced by a reference to such
              reasonably comparable and convenient amount (or an integral
              multiple thereof) in the euro unit as the Bank may from time to
              time specify; and (ii) except as expressly provided in this
              Section, each provision of this Agreement shall be subject to such
              reasonable changes of construction as the Bank may from time to
              time specify to be necessary or appropriate to reflect the
              introduction of or changeover to the euro in participating member
              states.

               (j)  Increased Costs.

               The Borrower shall, from time to time at the request of the
              Bank, pay to the Bank the amount of any cost or increased cost
              incurred by, or of any reduction in any amount payable to or in
              the effective return on its capital to, or of interest or other
              return foregone by, the Bank or any holding company of the Bank as
              a result of the introduction of, changeover to or operation of the
              euro in any participating member state, other than any such cost
              or reduction or amount foregone reflected in any interest rate
              hereunder.

          (c) Article V of the Credit Agreement shall be amended by inserting
the following new Section 5.15 immediately following Section 5.14:

          5.15  Year 2000.  On the basis of a comprehensive review and
     assessment of the Borrower's and its Subsidiaries' systems and equipment
     and inquiry made of the Borrower's and its Subsidiaries' material suppliers
     and vendors, the Borrower reasonably believes that the "Year

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     2000 problem" (that is, the inability of computers, as well as embedded
     microchips in non-computing devices, to perform properly date-sensitive
     functions with respect to certain dates prior to and after December 31,
     1999), including costs of remediation, will not result in a Material
     Adverse Effect.

          3.    Representations and Warranties.  The Borrower hereby represents
and warrants to the Bank as follows:

                (a) No Default or Event of Default has occurred and is
continuing.

                (b) The execution, delivery and performance by the Borrower of
this Amendment have been duly authorized by all necessary corporate and other
action and do not and will not require any registration with, consent or
approval of, notice to or action by, any person (including any governmental
authority) in order to be effective and enforceable. The Credit Agreement as
amended by this Amendment constitutes the legal, valid and binding obligations
of the Borrower, enforceable against it in accordance with its respective terms,
without defense, counterclaim or offset.

                (c) All representations and warranties of the Borrower contained
in the Credit Agreement are true and correct.

                (d) The Borrower is entering into this Amendment on the basis of
its own investigation and for its own reasons, without reliance upon the Bank or
any other person.

          4.    Effective Date.  This Fourth Amendment will become effective as
of the date first above written (the "Effective Date"), provided that each of
the following conditions is satisfied:

                (a)  The Bank has received from the Borrower a duly executed
original (or, if elected by the Bank, an executed facsimile copy) of this
Amendment; and

                (b)  The Bank has received from the Borrower a copy of a
resolution passed by the board of directors of such corporation, certified by
the Secretary or an Assistant Secretary of such corporation as being in full
force and effect on the date hereof, authorizing the execution, delivery and
performance of this Amendment.

          5.    Reservation of Rights. The Borrower acknowledges and agrees that
the execution and delivery by the Bank of this Amendment shall not be deemed to
create a course of dealing or otherwise obligate the Bank to enter into
amendments under the same, similar or any other circumstances in the future.

          6.    Miscellaneous.

                (a) Except as herein expressly amended, all terms, covenants and
provisions of the Credit Agreement are and shall remain in full force and effect
and all references therein and in any other Credit Documents to such Credit
Agreement shall henceforth refer to the Credit Agreement as amended by this
Amendment.  This Amendment shall be deemed incorporated into, and a part of, the
Credit Agreement.  This Amendment is a Credit Document.


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               (b)   This Amendment shall be binding upon and inure to the
benefit of the parties hereto and thereto and their respective successors and
assigns. No third party beneficiaries are intended in connection with this
Amendment.

               (c)   This Amendment shall be governed by and construed in
accordance with the law of the State of California.

               (d)   This Amendment may be executed in any number of
counterparts, each of which shall be deemed an original, but all such
counterparts together shall constitute but one and the same instrument. Each of
the parties hereto understands and agrees that this document (and any other
document required herein) may be delivered by any party thereto either in the
form of an executed original or an executed original sent by facsimile
transmission to be followed promptly by mailing of a hard copy original, and
that receipt by the Bank of a facsimile transmitted document purportedly bearing
the signature of the Borrower shall bind the Borrower with the same force and
effect as the delivery of a hard copy original. Any failure by the Bank to
receive the hard copy executed original of such document shall not diminish the
binding effect of receipt of the facsimile transmitted executed original of such
document which hard copy page was not received by the Bank, and the Bank is
hereby authorized to make sufficient photocopies thereof to assemble complete
counterparty documents.

               (e)   This Amendment, together with the Credit Agreement,
contains the entire and exclusive agreement of the parties hereto with reference
to the matters discussed herein and therein. This Amendment supersedes all prior
drafts and communications with respect thereto. This Amendment may not be
amended or modified except in writing executed by both of the parties hereto.

               (f)   If any term or provision of this Amendment shall be deemed
prohibited by or invalid under any applicable law, such provision shall be
invalidated without affecting the remaining provisions of this Amendment or the
Credit Agreement, respectively.

               (g)   The Borrower covenants to pay to or reimburse the Bank,
upon demand, for all costs and expenses (including allocated costs of in-house
counsel) incurred in connection with the development, preparation, negotiation,
execution and delivery of this Amendment.


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               IN WITNESS WHEREOF, the parties hereto have executed and
delivered this Amendment as of the date first above written.



                              STANFORD TELECOMMUNICATIONS, INC.


                              By:
                                 ------------------------------
                              Name:
                                   ----------------------------
                              Title:
                                    ---------------------------

                              By:
                                 ------------------------------
                              Name:
                                   ----------------------------
                              Title:
                                    ---------------------------


                              BANK OF AMERICA NATIONAL TRUST
                              AND SAVINGS ASSOCIATION


                              By:
                                 ------------------------------
                              Name: Michael J. McCutchin
                              Title:  Managing Director