<PAGE>   1

                                                                  EXHIBIT 10.18


                         AMENDMENT TO CREDIT AGREEMENTS

        THIS AMENDMENT ("Amendment") made as of October 13, 1995, between ECC 
INTERNATIONAL CORP. ("ECC"), ECC SIMULATION LIMITED ("Simulation") and FIRST 
FIDELITY BANK, NATIONAL ASSOCIATION ("Bank").


                                   Background

        Bank and ECC entered into a certain Term Loan and Revolving Credit 
Agreement dated as of September 20, 1994 (as amended to date, the "ECC Credit 
Agreement") relative to, inter alia, a Revolver (the "ECC Revolver"), as more 
fully set forth therein, the terms of which are incorporated herein by 
reference. Bank and Simulation entered into a certain Revolving Credit 
Agreement dated as of September 20, 1994 (as amended to date, the "Simulation 
Credit Agreement") relative to a Revolver (the "Simulation Revolver"), as more 
fully set forth therein, the terms of which are incorporated herein by 
reference. The parties desire to amend the ECC Credit Agreement and the 
Simulation Credit Agreement in the manner hereinafter provided.

        NOW, THEREFORE, the parties, INTENDING TO BE LEGALLY BOUND, agree as
follows:

        1.  Maximum Principal Amount of ECC Revolver.  Effective October 13, 
1995 and notwithstanding Section A.2.b. of the ECC Credit Agreement to the 
contrary, the maximum aggregate principal amount of advances, including the 
face amount of Letters of Credit (as defined in the ECC Credit Agreement), to 
be outstanding at any time under the ECC Revolver (the "Maximum Principal 
Amount") shall be an amount which, when taken together with the principal 
amount of cash advances and the face amount of letters of credit outstanding 
under the Simulation Revolver, is not greater than $15,000,000.

        2.  Maximum Principal Amount of Simulation Revolver.  Effective October 
13, 1995 and notwithstanding Section A.1.b. of the Simulation Credit Agreement 
to the contrary, the Maximum Principal Amount (as defined in the Simulation 
Credit Agreement) of advances, including the face amount of letters of credit, 
to be outstanding at any time under the Simulation Revolver shall be an amount 
which is equal to the lesser of (i) $4,000,000 or (ii) an amount which, when 
taken together with the principal amount of cash advances and the face amount 
of letters of credit outstanding under the ECC Revolver, is not greater than
$15,000,000.

        3.  Currency Fluctuations.  Notwithstanding Section A.1.i. of the 
Simulation Credit Agreement to the contrary, if due solely to fluctuations in 
the exchange rate for Dollars and Pounds


        
<PAGE>   2

Sterling, the Equivalent Dollar Amount (as defined in the Simulation Credit 
Agreement) of outstanding cash advances and the face amount of outstanding 
letters of credit made in Pounds Sterling, when taken together with outstanding 
cash advances and the face amount of outstanding letters of credit made in 
Dollars under the Simulation Credit Agreement, exceeds $4,000,000 but does not 
exceed $4,400,000, Simulation need not repay such excess until the Expiration 
Date, provided, that if the same exceeds $4,400,000 or if the Equivalent Dollar 
Amount of outstanding cash advances and the face amount of outstanding letters 
of credit made in Pounds Sterling, when taken together with the sum of
outstanding cash advances and the face amount of outstanding letters of credit
made in Dollars and the principal amount of cash advances and the face amount of
credit outstanding under the ECC Revolver, exceeds $15,000,000, Simulation will
repay the principal of the Simulation Revolver in the amount of such excess
within one (1) Business Day after notice thereof from Bank.

        4.  Simulation Letters of Credit.   Bank agrees that advances under the 
Simulation Revolver may, if requested by Simulation, be in the form of one or 
more letters of credit (each a "Letter of Credit" and, collectively, the 
"Letters of Credit"), subject to the following terms:

                a.  Upon the request of Simulation made to Bank not later than 
ten (10) Business Days prior to the date on which Simulation requests that a 
Letter of Credit be issued hereunder, Bank shall under and subject to the terms 
and conditions hereof issue standby letters of credit under the Revolver for 
the account of Simulation from time to time through but not including the 
Expiration Date, up to an aggregate face amount (the "LC Sublimit") at any time 
outstanding equal to $500,000. letters of Credit issued hereunder shall be 
under such terms, including provisions for draw and expiration date, as shall 
be acceptable to Bank in its discretion, and shall be available only for the 
purpose of securing rental obligations of Simulation for leased locations. 
Letters of Credit shall be denominated in Dollars or Pounds Sterling.

                b.  Bank shall have the right, in its absolute discretion and 
whether or not an Event of Default has occurred or is continuing under the 
Simulation Credit Agreement, to provide the beneficiary of any of the Letters 
of Credit with notice of non-renewal in accordance with the provisions, if any, 
of the Letters of Credit relating thereto.

                c.  Simulation agrees to provide Bank with Cash Collateral 
(meaning for all purposes hereof cash in Dollars) in the following amounts upon 
the following events:


                                       2


<PAGE>   3
                        (1)  On the Expiration Date, Simulation will provide
                             Bank with Cash Collateral in an amount equal to
                             the face amount of all Letters of Credit then
                             outstanding;

                        (2)  If at any time the face amount of Letters of
                             Credit then outstanding exceeds the LC Sublimit,
                             Simulation will at such time provide Bank with
                             Cash Collateral in an amount equal to the
                             aggregate of such excess;

                        (3)  Upon the occurrence of an event of Default,
                             Simulation will provide Bank with Cash Collateral
                             in an amount equal to the aggregate face amount of
                             all outstanding Letters of Credit.

                d.  Cash Collateral provided to Bank pursuant to subparagraph 
c. above shall be held by Bank as security for the prompt satisfaction of all 
of the Liabilities (as defined in the Simulation Credit Agreement), and shall 
be deemed to be "Collateral" for all purposes of the Simulation Credit
Agreement.

                e.  Reimbursement of Letters of Credit Disbursements. 
Simulation agrees to reimburse Bank for the amount of each payment by Bank 
under any Letter of Credit (a "Letter of Credit Disbursement") made by Bank on 
the date (the "Letter of Credit Disbursement Date") on which the Letter of 
Credit Disbursement was made. Such obligation of Simulation to reimburse Bank 
for any such Letter of Credit Disbursement is herein referred to as a 
"Reimbursement Obligation." If any Reimbursement Obligation is not paid in full 
by Simulation to Bank on the corresponding Letter of Credit Disbursement Date 
(for this purpose payments received by Bank after 1:30 p.m., Philadelphia, 
Pennsylvania time on any Business Day shall be deemed to have been made on the 
next succeeding Business Day), the unpaid amount of such Reimbursement 
Obligation shall bear interest for each day from the corresponding Letter of 
Credit Disbursement Date until payment in full thereof (after, as well as 
before, judgment), payable on demand, at the Default Rate (as defined in the 
Revolving Credit Note to be executed pursuant to Section 6.b. hereof).

                f.  Letter of Credit Charges and Fees.  Simulation agrees to 
pay on demand to Bank, with respect to the amendment or transfer of any Letter 
of Credit and each drawing made under any Letter of Credit, documentary and 
processing fees and charges in accordance with Bank's fees and charges in 
effect at the time of such amendment, transfer or drawing, as the case may be. 
Also, a letter of credit fee will be payable by Simulation in the amount of 1% 
of the face amount of each Letter of Credit, payable upon issuance thereof and 
on each anniversary thereof.

                                       3



<PAGE>   4
                g.  Obligations Absolute.  All Reimbursement Obligations of 
Simulation arising from Letter of Credit Disbursements shall be unconditional 
and absolute and shall be paid strictly in accordance with the terms of this 
Agreement under all circumstances whatsoever including, without limitation, the 
following circumstances: (i) any lack of validity or enforceability of any 
Letter of Credit; (ii) the existence of any claim, set-off, defense or other 
right which Simulation may have at any time against any beneficiary or any 
transferee of any Letter of Credit (or any person for whom any such beneficiary 
or transferee may be acting), or any other person, whether in connection with 
the Simulation Credit Agreement, the transactions contemplated therein or any 
unrelated transaction (including any underlying transaction between Simulation 
or any of its subsidiaries or affiliates and the beneficiary for which any 
Letter of Credit was procured); (iii) any draft, demand, certificate or any 
other document presented under any Letter of Credit proving to be forged, 
fraudulent, invalid or insufficient in any respect or any statement therein 
being untrue or inaccurate in any respect, except to the extent Simulation 
proves that such payment constituted negligence or willful misconduct on the 
part of Bank; or (iv) payment by Bank under any Letter of Credit against 
presentation of a demand, draft, certificate or other document which does not 
comply with the terms of the Letter of Credit, except to the extent that 
Simulation proves that such payment constituted negligence or willful 
misconduct on the part of Bank; (v) the failure or delay on the part of Bank in 
giving any notice hereunder; (vi) any draw thereunder being a consequence of 
Bank's non-renewal of any Letter of Credit; or (vii) any other circumstance or 
happening whatsoever, whether similar or dissimilar to any of the foregoing.

                h.  Indemnification; Nature of Duties.

                        (1)  In addition to amounts payable as elsewhere
                             provided in the Simulation Credit Agreement and/or
                             in this Amendment, Simulation hereby indemnifies
                             and holds harmless Bank from and against any and
                             all claims, damages, losses, liabilities, costs or
                             expenses whatsoever which Bank may incur (or which
                             may be claimed against Bank by any person) by
                             reason of or in connection with the issuance or
                             transfer of, or payment or failure to pay under,
                             any Letter of Credit, or the involvement by Bank in
                             any suit, proceeding or action as a consequence,
                             direct or indirect, of Bank's issuance of any
                             Letter of Credit, except for any such claims,
                             damages, losses, liabilities, costs or expenses to
                             the extent, but only to the extent, which 
                             Simulation proves were caused by the gross 
                             negligence or 

                
                                    4
<PAGE>   5

                             willful misconduct of Bank in determining whether
                             a certificate, draft, statement or document 
                             presented under any Letter of Credit complied with 
                             the terms of the Letter of Credit.

                        (2)  As between Simulation and Bank, Simulation assumes
                             all risks of the act or omissions of the
                             beneficiary or any transferee of any Letter of
                             Credit with respect to such beneficiary's or
                             transferee's use of the Letter of Credit. Bank
                             shall not be liable or responsible for: (A) the use
                             which may be made of any Letter of Credit or the
                             proceeds of any drawing thereunder or for any
                             acts or omissions of the beneficiary or any
                             transferee in connection therewith; (B) the
                             validity, sufficiency or genuineness of
                             certificates, drafts or documents presented under
                             any Letter of Credit that appear on their face to
                             be in order, or of any endorsement thereon, even if
                             any of the same should in fact prove to be in any
                             or all respects invalid, insufficient, fraudulent
                             or forged; (C) payment by Bank under any Letter of
                             Credit against presentation of drafts, certificates
                             or documents which do not comply with the terms of
                             the Letter of Credit, including failure of any such
                             drafts, certificates or documents to bear any
                             reference or adequate reference to the Letter of
                             Credit, or for any failure of the beneficiary of
                             any Letter of Credit otherwise to comply fully with
                             the conditions required in order to draw under the
                             Letter of Credit; (D) the validity or sufficiency
                             of any instrument transferring or assigning or
                             purporting to transfer or assign any Letter of
                             Credit or the rights or benefits thereunder or the
                             proceeds thereof, in whole or in part, which may
                             prove to be invalid or ineffective for any reason;
                             or (E) any other circumstances whatsoever in making
                             or failing to make payment under any Letter of
                             Credit, except only that Bank shall be liable to
                             Simulation to the extent, but only to the extent, 
                             of any direct, as opposed to consequential, damages
                             suffered by Simulation which Simulation proves were
                             caused by Bank's gross negligence or willful 
                             misconduct in connection with the matters referred 
                             to in clauses (B) through (E) above. In


                                       5

<PAGE>   6
                             furtherance and not in limitation of the foregoing,
                             Bank may accept drafts, certificates or documents
                             presented to it under any Letter of Credit that
                             appear on their face to be in order, without 
                             responsibility for further investigation,
                             regardless of any notice or information to the
                             contrary, and any action taken or omitted by Bank
                             under or in connection with any Letter of Credit,
                             if taken or omitted in good faith and without 
                             willful misconduct or gross negligence, shall not
                             put Bank to any resulting liability to Simulation.

                i.  Payments to Bank.  All payments to be made by Simulation to 
Bank in respect of Reimbursement Obligations due from Simulation shall be 
payable in Dollars on the day when due without presentment, demand, protest or 
notice of any kind, all of which are hereby expressly waived, and an action 
therefor shall immediately accrue.

                j.  Application.  Simulation shall, as a condition to the 
issuance by Bank of any Letter of Credit, execute and deliver to Bank Bank's 
then standard Letter of Credit Application as Bank may require in connection 
with the issuance of a Letter of Credit, provided, that in the event of any 
express inconsistency between the terms of any such Application and the terms 
hereof, the latter shall control.

        5.  Commitment Fee.  Effective October 1, 1995, and in lieu of the
Commitment Fee payable by ECC under Section F.2. of the ECC Credit Agreement,
ECC shall pay to Bank an unused commitment fee in the amount of 1/4 of 1% of
the average unused portion of Bank's aggregate commitment under the ECC 
Revolver and the Simulation Revolver, determined quarterly and payable in 
arrears at the end of each such quarterly period.

        6.  Conditions.  The obligation of Bank to increase the Maximum 
Principal Amount of the Revolvers as set forth in Sections 1 and 2 hereof is 
subject to the following conditions precedent:

                a.  ECC shall, concurrently herewith, execute and deliver to 
Bank an amended and restated Revolving Credit Note in the face amount of 
$15,000,000, which amended and restated Revolving Credit Note, together with 
any attachments thereto and amendments, modifications or restatements thereof 
or thereto, shall constitute the "Revolving Credit Note" for all purposes of 
the ECC Credit Agreement and other Loan Documents referred to therein;


                                    6
<PAGE>   7
                b. Simulation shall, concurrently herewith, execute and deliver 
to Bank an amended and restated Revolving Credit Note in the face amount of 
$4,000,000, which amended and restated Revolving Credit Note, together with any 
attachments thereto and amendments, modifications or restatements thereof or 
thereto, shall constitute the "Revolving Credit Note" for all purposes of the 
Simulation Credit Agreement and other Loan Documents referred to therein;

                c. Each of ECC and Simulation shall, concurrently herewith, 
deliver to Bank certified resolutions of its Board of Directors authorizing ECC 
and Simulation, as applicable, to execute, deliver and perform this Amendment 
and any documents required to be executed by it in connection herewith.

        7. Reaffirmation. Except as specifically modified by this Amendment, 
the ECC Credit Agreement and the Simulation Credit Agreement and all other Loan 
Documents referred to in either thereof shall remain unchanged and in full 
force and effect, and this Amendment shall be construed as supplemental 
thereto, and each of ECC and Simulation hereby reaffirms all of its Liabilities 
thereunder and agrees that the same are owing to Bank in accordance with the 
terms thereof without off-set, counterclaim or defense of any nature. Each of 
ECC and Simulation further reaffirms all guaranties, liens and security 
interests heretofore granted by it to Bank pursuant to the Loan Documents, 
including without limitation the liens, security interests and guaranties 
granted pursuant to the Security Agreement dated September 20, 1994 among Bank, 
ECC, ECC International, Inc. and Educational Computer Corporation International 
("Security Agreement"), that certain Guarantee and Debenture dated September 
20, 1994 executed and delivered by Simulation to Bank ("Guaranty and 
Debenture") and that certain Guaranty and Surety Agreement dated September 20, 
1994 from ECC, ECC International, Inc. and Educational Computer Corporation to 
Bank ("Guaranty"); and agrees that the ECC Revolver and the Simulation 
Revolver, as the Maximum Principal Amount of each thereof is amended pursuant 
to Sections 1 and 2 hereof, and all Reimbursement Obligations of Simulation, 
constitute a "Liability" for all purposes of said Security Agreement, a 
"Secured Liability" for all purposes of said Guaranty and Debenture and a 
"Liability" for all purposes of said Guaranty.

                                       7

<PAGE>   8


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

                                        ECC INTERNATIONAL CORP.


                                        By:  /s/  G. W. Murphy, CEO
                                            -----------------------------------
                                            Name:  George W. Murphy
                                            Title: President/CEO

                                    Attest:  /s/  Richard F. Thompson
                                            -----------------------------------
                                            Name:  Richard F. Thompson
                                            Title:  Secretary/Treasurer



                                        ECC SIMULATION LIMITED


                                        By:  /s/  G. W. Murphy, Director
                                            -----------------------------------
                                            Name:  George W. Murphy
                                            Title:  Director

                                    Attest:  /s/  Richard F. Thompson
                                            -----------------------------------
                                            Name:  Richard F. Thompson
                                            Title:  Secretary/Treasurer



                                        FIRST FIDELITY BANK,
                                        NATIONAL ASSOCIATION


                                        By:  /s/  Jack P. Albaugh
                                            ----------------------------------
                                            Name:  Jack P. Albaugh
                                            Title:  Vice President



                                     8
<PAGE>   9
                                JOINDER


        Each of the undersigned consents to the foregoing Amendment, the terms 
of which are incorporated herein by reference, and agrees with Bank that the 
Revolver for ECC International Corp. and the Revolver for ECC Simulation 
Limited, as the Maximum Principal Amount of each thereof is amended pursuant to
Sections 1 and 2 of the within Amendment, and all Reimbursement Obligations of 
Simulation for letters of credit, constitute a "Liability" for all purposes of 
(A) that certain Guaranty and Surety Agreement dated September 20, 1994 
executed and delivered by Educational Computer Corporation International and 
ECC International, Inc. to Bank, (B) that certain Guaranty and Surety Agreement 
dated September 20, 1994 executed and delivered by Educational Computer 
Corporation International, ECC International, Inc. and ECC International Corp. 
to Bank, and (C) that certain General Security Agreement dated September 20, 
1994 among Bank, ECC International Corp., Educational Computer Corporation 
International and ECC International, Inc.

        IN WITNESS WHEREOF, the undersigned have executed this Joinder this
13th day of October, 1995.


                                        ECC INTERNATIONAL, INC.


                                        By:  /s/  G. W. Murphy, CEO
                                            -----------------------------------
                                            Name:  George W. Murphy
                                            Title: President/CEO


                                        EDUCATIONAL COMPUTER CORPORATION
                                        INTERNATIONAL

                                        By:  /s/  G. W. Murphy, Director
                                            -----------------------------------
                                            Name:  George W. Murphy
                                            Title:  Director


                                     9

<PAGE>   10
                                                      REVOLVING CREDIT NOTE
                                                   Obligation No.______________

                                                               October 13, 1995
                                                     Philadelphia, Pennsylvania

$15,000,000

FOR VALUE RECEIVED, and intending to be legally bound hereby, the undersigned 
Borrower, ECC International Corp., unconditionally promises to pay to the order 
of FIRST FIDELITY BANK, NATIONAL ASSOCIATION (the "Bank"), the principal amount 
of all advances that are now or may hereafter be made hereunder and that are 
then outstanding, together with accrued, unpaid interest thereon and any unpaid 
costs and expenses payable hereunder, on September 19, 1997.

A.  Terms of Note.

    1. Interest Payments. Interest on the principal balance hereof shall, 
       except as provided in subpart A.B. below, accrue at such rates and be
       payable in accordance with Section A.2. of that certain Term Loan and
       Revolving Credit Agreement dated September 20, 1994 between the Bank and
       the Borrower, as amended to date, including by Amendment of even date
       herewith (together with any exhibits thereto and amendments and
       modifications thereto in effect from time to time, the "Loan Agreement").

    2. Computation of Interest. Interest hereunder shall be computed daily on 
       the basis of a year of 360 days for the actual number of days elapsed.
       All payments hereunder shall be made in lawful currency of the United
       States of America and in immediately available funds at the Bank's
       address set forth in the Loan Agreement or at such other address as the
       Bank shall notify the Borrower of in writing.

    3. Incorporation by Reference. This Note is the Revolving Credit Note 
       referred to in the Loan Agreement and is subject to the terms and
       conditions thereof, which terms and conditions are incorporated herein,
       including, without limitation, terms pertaining to definitions,
       representations, warranties, covenants, events of default and remedies.
       Any capitalized term used herein without definition shall have the
       definition contained in the Loan Agreement.

    4. Borrowing Requests; Crediting of Account. Any request for borrowing 
       pursuant to this Note shall be made by the Borrower in writing in the
       form of a "Notice of Borrowing Under Revolving Credit" attached hereto as
       Exhibit A and in accordance with the terms of the Loan Agreement. Unless
       otherwise requested by the Borrower in writing at least one (1) Business
       Day prior to the date of a requested advance, each advance hereunder
       shall be made by crediting the Account as defined in the Loan Agreement
       with the amount of the advance. All advances made by crediting the
       Account or any other account of the Borrower at the Bank shall be
       conclusively presumed to have been properly authorized by the Borrower.

    5. Bank Records of Advance. The Bank may enter in its business records the 
       date and the amount of each advance, each conversion from one interest
       rate basis to another and each payment made pursuant to this Note and the
       Loan Agreement. The Bank's records of such advance, conversion or payment
       shall, in the absence of manifest error, be conclusively binding upon the
       Borrower. In the event the Bank gives notice or renders a statement by
       mailing such notice or statement to the Borrower, concerning any such
       advance, conversion or payment, or the amount of principal and interest
       due on this Note, the Borrower agrees that, unless the Bank receives a
       written notification of exceptions to this statement within forty-five
       (45) calendar days after such statement or notice is mailed, the
       statement or notice shall be an account stated, correct and acceptable
       and binding upon the Borrower.

    6. Advance Requests Exceeding Maximum Principal Amount. The Borrower shall 
       not request the Bank to make any advances under this Note or the Loan
       Agreement which exceeds the Maximum Principal Amount set forth in Section
       A.2.b. of the Loan Agreement. In the event that the principal balance
       outstanding under this Note exceeds at any time the Maximum Principal
       Amount, the Borrower shall immediately, and without demand from the Bank,
       pay to the Bank the amount in excess thereof, and the Borrower agrees
       that until such excess is paid to the Bank, this Note shall evidence and
       be enforceable with respect to any and all amounts outstanding hereunder
       including such excess.

<PAGE>   11
    7. Application of Payments. All payments received on this Note shall be 
       applied first to the Bank's fees, costs and expenses which the Borrower
       is obligated to pay pursuant to the terms hereof and under any other 
       Loan Document, then to accrued and unpaid interest and then to principal 
       or such payments may be applied in such other order as the Bank in its 
       sole discretion shall determine.

    8. Default Rate. At the Bank's option, interest will be assessed on any
       principal which remains unpaid at the maturity of this Note, whether by
       acceleration or otherwise, or upon and following any Event of Default, at
       a rate which is four percent (4%) higher than the rate otherwise charged
       hereunder (the "Default Rate") provided that at no time shall the Default
       Rate exceed the highest rate of interest allowed by law. Such Default 
       Rate of interest shall also be charged on the amounts owed by the 
       Borrower to the Bank pursuant to any judgments entered in favor of Bank
       in respect of this Note or any other Loan Document.

    9. Prepayment. Prepayment of principal may be made subject to payment of 
       all amounts required to be paid in connection with such prepayment as
       provided in the Loan Agreement.

B.  Remedies.

    1. Generally. Upon and following an Event of Default, the Bank, at its 
       option, may exercise any and all rights and remedies it has under this
       Note, the Loan Agreement and/or the other Loan Documents and under
       applicable law, including, without limitation, the right to charge and 
       collect interest on the principal portion of the amounts outstanding 
       hereunder at the Default Rate. Upon and following an Event of Default,
       the Bank may proceed to protect and enforce the Bank's rights under any
       Loan Document and/or under applicable law by action at law, in equity, 
       or other appropriate proceeding, including, without limitation, an 
       action for specific performance to enforce or aid in the enforcement of 
       any provision contained herein or in any other Loan Document.

    2. Remedies Cumulative; No Waiver. The remedies hereunder and under the
       other Loan Documents are cumulative and concurrent, and are not 
       exclusive of any other remedies available to the Bank. No failure or
       delay on the part of the Bank in the exercise of any right, power,
       remedy or privilege shall operate as a waiver thereof, nor shall any
       single or partial exercise of any right, power, remedy or privilege
       preclude any other or further exercise thereof, or the exercise of any
       other right, power, remedy or privilege.

C.  Miscellaneous.

    1. Governing Law. This Note shall be construed in accordance with and 
       governed by the substantive laws of the Commonwealth of Pennsylvania 
       without reference to conflict of laws principles.

    2. Integration. This Note and the other Loan Documents constitute the sole
       agreement of the parties with respect to the subject matter hereof and
       thereof and supersede all oral negotiations and prior writings with
       respect to the subject matter hereof and thereof.

    3. Amendment; Waiver. No amendment of this Note, and no waiver of any one 
       or more of the provisions hereof shall be effective unless set forth in 
       writing and signed by the parties hereto.

    4. Successors and Assigns. This Note (i) shall be binding upon the Borrower 
       and the Bank and their respective successors and permitted assigns, and 
       (ii) shall inure to the benefit of the Borrower and the Bank and their 
       respective successors and permitted assigns; provided, however, that the 
       Borrower may not assign its rights or obligations hereunder or any 
       interest herein without the prior written consent of the Bank, and any 
       such assignment or attempted assignment by the Borrower shall be void and
       of no effect with respect to the Bank.

    5. Severability. The illegality or unenforceability of any provision of 
       this Note or any instrument or agreement required hereunder shall not in 
       any way affect or impair the legality or enforceability of the remaining 
       provisions of this Note or any instrument or agreement required 
       hereunder. In lieu of any illegal or unenforceable provision in this 
       Note, there shall be added automatically as part of this Note a legal 
       and enforceable provision as similar in terms to such illegal or 
       unenforceable provision as may be possible.

    6. Inconsistencies. The Loan Documents are intended to be consistent. 
       However, in the event of any inconsistencies among any of the Loan 
       Documents, such inconsistency shall not affect the validity or 
       enforceability of each Loan Document. The Borrower agrees that in the 
       event of any inconsistency or 


                                      -2-

<PAGE>   12
       ambiguity in any of the Loan Documents, the Loan Documents shall not be 
       construed against any one party but shall be interpreted consistent with 
       the Bank's policies and procedures.

    7. Headings. The headings of sections and paragraphs have been included 
       herein for convenience only and shall not be considered in interpreting 
       this Note.

    8. Schedules. If a Schedule and/or an Exhibit is attached hereto, the 
       provisions thereof are incorporated herein.

    9. Judicial Proceeding; Waivers.

       a. THE BORROWER AGREES THAT ANY SUIT, ACTION OR PROCEEDING, WHETHER 
          CLAIM OR COUNTERCLAIM, BROUGHT OR INSTITUTED BY THE BANK OR THE 
          BORROWER OR ANY SUCCESSOR OR ASSIGN OF THE BANK OR THE BORROWER, ON
          OR WITH RESPECT TO THIS NOTE OR ANY OTHER LOAN DOCUMENT OR THE
          DEALINGS OF THE PARTIES WITH RESPECT HERETO, OR THERETO, SHALL BE 
          TRIED ONLY BY A COURT AND NOT BY A JURY.

       b. THE BANK AND THE BORROWER EACH HEREBY KNOWINGLY, VOLUNTARILY AND
          INTENTIONALLY WAIVE ANY RIGHT TO A TRIAL BY JURY IN ANY SUCH SUIT,
          ACTION OR PROCEEDING. FURTHER, THE BORROWER WAIVES ANY RIGHT IT MAY 
          HAVE TO CLAIM OR RECOVER, IN ANY SUCH SUIT, ACTION OR PROCEEDING, ANY
          SPECIAL, EXEMPLARY, PUNITIVE OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 
          OTHER THAN, OR IN ADDITION TO, ACTUAL DAMAGES.

       c. THE BORROWER ACKNOWLEDGES AND AGREES THAT THIS SECTION IS A SPECIFIC 
          AND MATERIAL ASPECT OF THIS NOTE AND THAT THE BANK WOULD NOT EXTEND 
          CREDIT TO THE BORROWER IF THE WAIVERS SET FORTH IN THIS SECTION WERE 
          NOT A PART OF THIS NOTE.

IN WITNESS WHEREOF, the Borrower has duly executed and delivered to the Bank 
this Note as of the date first above written.

ATTEST:                                 ECC INTERNATIONAL CORP.


By:  /s/  Richard F. Thompson               /s/  G. W. Murphy
     ----------------------------           -----------------------------------
     Name:  Richard F. Thompson             Name:  George W. Murphy
     Title: Secretary/Treasurer             Title: President/CEO

                                                  Address:  175 Stafford Avenue
                                                            Wayne, PA 19087
                                                  Telecopier No. (610) 254-9268


                                      -3-
<PAGE>   13
                                                      REVOLVING CREDIT NOTE
                                                   Obligation No.______________

                                                               October 13, 1995
                                                     Philadelphia, Pennsylvania

$4,000,000

FOR VALUE RECEIVED, and intending to be legally bound hereby, the undersigned 
Borrower, ECC SIMULATION LIMITED, unconditionally promises to pay to the order 
of FIRST FIDELITY BANK, NATIONAL ASSOCIATION (the "Bank"), the principal amount 
of all advances that are now or may hereafter be made hereunder and that are 
then outstanding, together with accrued, unpaid interest thereon and any unpaid 
costs and expenses payable hereunder, on September 19, 1997.

A.  Terms of Note.

    1.  Interest Payments. Interest on the principal balance hereof shall, 
        except as provided in subpart A.B. below, accrue at such rates and be
        payable in accordance with Section A.1. of that certain Revolving Credit
        Agreement dated September 20, 1994 between the Bank and the Borrower, as
        amended to date, including by Amendment (the "Amendment") of even date
        herewith (together with any exhibits thereto and amendments and
        modifications thereto in effect from time to time, the "Loan
        Agreement").

    2.  Computation of Interest. Interest hereunder shall be computed daily in 
        accordance with the Loan Agreement. All payments hereunder shall be made
        in lawful currency of the United States of America or in pounds
        sterling, as set forth in the Loan Agreement, and in immediately
        available funds at the Bank's address set forth in the Loan Agreement or
        at such other address as the Bank shall notify the Borrower of in
        writing.

    3.  Incorporation by Reference. This Note is the Revolving Credit Note 
        referred to in the Loan Agreement and is subject to the terms and
        conditions thereof, which terms and conditions are incorporated herein,
        including, without limitation, terms pertaining to definitions,
        representations, warranties, covenants, events of default and remedies.
        Any capitalized term used herein without definition shall have the
        definition contained in the Loan Agreement.

    4.  Borrowing Requests; Crediting of Account. Any request for borrowing 
        pursuant to this Note shall be made by the Borrower in writing in the
        form of a "Notice of Borrowing Under Revolving Credit" attached hereto
        as Exhibit A and in accordance with the terms of the Loan Agreement.
        Unless otherwise requested by the Borrower in writing at least five (5)
        Business Days prior to the date of a requested advance, each advance
        hereunder shall be made by crediting the Account as defined in the Loan
        Agreement with the amount of the advance. All advances made by crediting
        the Account or any other account of the Borrower at the Bank shall be
        conclusively presumed to have been properly authorized by the Borrower.

    5.  Bank Records of Advance. The Bank may enter in its business records the 
        date and the amount of each advance, each conversion from one interest
        rate basis to another and each payment made pursuant to this Note and
        the Loan Agreement. The Bank's records of such advance, conversion or
        payment shall, in the absence of manifest error, be conclusively binding
        upon the Borrower. In the event the Bank gives notice or renders a
        statement by mailing such notice or statement to the Borrower,
        concerning any such advance, conversion or payment, or the amount of
        principal and interest due on this Note, the Borrower agrees that,
        unless the Bank receives a written notification of exceptions to this
        statement within forty-five (45) calendar days after such statement or
        notice is mailed, the statement or notice shall be an account stated,
        correct and acceptable and binding upon the Borrower.

    6.  Advance Requests Exceeding Maximum Principal Amount. The Borrower shall 
        not request the Bank to make any advances under this Note or the Loan
        Agreement which exceeds the Maximum Principal Amount set forth in
        Section A.1.b. of the Loan Agreement. In the event that the principal
        balance outstanding under this Note exceeds at any time the Maximum
        Principal Amount, the Borrower shall, subject to the terms of the
        Amendment, immediately, and without demand from the Bank, pay to the
        Bank the amount in excess thereof, and the Borrower agrees that until
        such excess is paid to the Bank, this Note shall evidence and be
        enforceable with respect to any and all amounts outstanding hereunder
        including such excess.
 
    7.  Application of Payments. All payments received on this Note shall be 
        applied first to the Bank's fees, costs and expenses which the Borrower
        is obligated to pay pursuant to the terms hereof and under any other
        Loan Document, then to accrued and unpaid interest and then to principal
        or such payments may be applied in such other order as the Bank in its
        sole discretion shall determine.

    8.  Default Rate. At the Bank's option, interest will be assessed on any 
        principal which remains unpaid at the maturity of this Note, whether by
        acceleration or otherwise, or upon and following any Event of Default,
        at a rate which is four percent (4%) higher than the rate otherwise
        charged hereunder (the "Default Rate") provided that at no time shall
        the Default Rate


<PAGE>   14
                exceed the highest rate of interest allowed by law. Such
                Default Rate of interest shall also be charged on the amounts
                owed by the Borrower to the Bank pursuant to any judgments
                entered in favor of Bank in respect of this Note or any other
                Loan Document.

        9.      Prepayment. Prepayment of principal may be made subject to 
                payment of all amounts required to be paid in connection with 
                such prepayment as provided in the Loan Agreement.

B.      Remedies.

        1.      Generally. Upon and following an Event of Default, the Bank, at
                its option, may exercise any and all rights and remedies it has
                under this Note, the Loan Agreement and/or the other Loan
                Documents and under applicable law, including, without
                limitation, the right to charge and collect interest on the
                principal portion of the amounts outstanding hereunder at the
                Default Rate. Upon and following an Event of Default, the Bank
                may proceed to protect and enforce the Bank's rights under any
                Loan Document and/or under applicable law by action at law, in
                equity, or other appropriate proceeding, including, without
                limitation, an action for specific performance to enforce or
                aid in the enforcement of any provision contained herein or in
                any other Loan Document.

        2.      Remedies Cumulative; No Waiver. The remedies hereunder and under
                the other Loan Documents are cumulative and concurrent, and are
                not exclusive of any other remedies available to the Bank. No
                failure or delay on the part of the Bank in the exercise of any
                right, power, remedy or privilege shall operate as a waiver
                thereof, nor shall any single or partial exercise of any right,
                power, remedy or privilege preclude any other or further
                exercise thereof, or the exercise of any other right, power,
                remedy or privilege.

C.      Miscellaneous.

        1.      Governing Law. This Note shall be construed in accordance with
                and governed by the substantive laws of the Commonwealth of
                Pennsylvania without reference to conflict of laws principles.

        2.      Integration. This Note and the other Loan Documents constitute
                the sole agreement of the parties with respect to the subject
                matter hereof and thereof and supersede all oral negotiations
                and prior writings with respect to the subject matter hereof and
                thereof.

        3.      Amendment; Waiver. No amendment of this Note, and no waiver of
                any one or more of the provisions hereof shall be effective
                unless set forth in writing and signed by the parties hereto.

        4.      Successors and Assigns. This Note (i) shall be binding upon the
                Borrower and the Bank and their respective successors and
                permitted assigns, and (ii) shall inure to the benefit of the
                Borrower and the Bank and their respective successors and
                permitted assigns; provided, however, that the Borrower may not
                assign its rights or obligations hereunder or any interest
                herein without the prior written consent of the Bank, and any
                such assignment or attempted assignment by the Borrower shall be
                void and of no effect with respect to the Bank.

        5.      Severability. The illegality or unenforceability of any
                provision of this Note or any instrument or agreement required
                hereunder shall not in any way affect or impair the legality or
                enforceability of the remaining provisions of this Note or any
                instrument or agreement required hereunder. In lieu of any
                illegal or unenforceable provision in this Note, there shall be
                added automatically as part of this Note a legal and enforceable
                provision as similar in terms to such illegal or unenforceable
                provision as may be possible.

        6.      Inconsistencies. The Loan Documents are intended to be
                consistent. However, in the event of any inconsistencies among
                any of the Loan Documents, such inconsistency shall not affect
                the validity or enforceability of each Loan Document. The
                Borrower agrees that in the event of any inconsistency or
                ambiguity in any of the Loan Documents, the Loan Documents shall
                not be construed against any one party but shall be interpreted
                consistent with the Bank's policies and procedures.

        7.      Headings. The headings of sections and paragraphs have been
                included herein for convenience only and shall not be considered
                in interpreting this Note.

        8.      Schedules. If a Schedule and/or an Exhibit is attached hereto,
                the provisions thereof are incorporated herein.

        9.      Judicial Proceeding; Waivers.

                a.      THE BORROWER AGREES THAT ANY SUIT, ACTION OR PROCEEDING,
                        WHETHER CLAIM OR COUNTERCLAIM, BROUGHT OR INSTITUTED BY
                        THE BANK OR THE BORROWER OR ANY SUCCESSOR OR ASSIGN OF
                        THE BANK OR THE BORROWER, ON OR WITH RESPECT TO THIS
                        NOTE OR ANY OTHER LOAN DOCUMENT OR THE DEALINGS OF THE
                        PARTIES WITH RESPECT HERETO, OR THERETO, SHALL BE TRIED
                        ONLY BY A COURT AND NOT BY A JURY.

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<PAGE>   15
    b.  THE BANK AND THE BORROWER EACH HEREBY KNOWINGLY, VOLUNTARILY AND 
        INTENTIONALLY WAIVE ANY RIGHT TO A TRIAL BY JURY IN ANY SUCH SUIT, 
        ACTION OR PROCEEDING. FURTHER, THE BORROWER WAIVES ANY RIGHT IT MAY 
        HAVE TO CLAIM OR RECOVER, IN ANY SUCH SUIT, ACTION OR PROCEEDING, ANY 
        SPECIAL, EXEMPLARY, PUNITIVE OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 
        OTHER THAN, OR IN ADDITION TO, ACTUAL DAMAGES.

    c.  THE BORROWER ACKNOWLEDGES AND AGREES THAT THIS SECTION IS A SPECIFIC 
        AND MATERIAL ASPECT OF THIS NOTE AND THAT THE BANK WOULD NOT EXTEND 
        CREDIT TO THE BORROWER IF THE WAIVERS SET FORTH IN THIS SECTION WERE 
        NOT A PART OF THIS NOTE.

IN WITNESS WHEREOF, the Borrower has duly executed and delivered to the Bank 
this Note as of the date first above written.


ATTEST:                                 ECC SIMULATION LIMITED  


/s/  Richard F. Thompson                By:  /s/  G.W. Murphy, Director
----------------------------                 -----------------------------------
Name:  Richard F. Thompson                   Name:  George W. Murphy
Title: Secretary/Treasurer                   Title: Director     

                                                  Address:  175 Strafford Avenue
                                                            Wayne, PA 19087

                                                  Telecopier No. (215) 254-9268


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