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                                                                    Exhibit 10.9
                               ASECO CORPORATION
                          500 Donald Lynch Boulevard
                             Marlborough, MA 01752


                                                               November 27, 1998


Fleet National Bank
One Federal Street
Boston, MA  02110

Gentlemen:

     This letter agreement will set forth certain understandings between Aseco
Corporation, a Delaware corporation (the "Borrower") and Fleet National Bank
(the "Bank") with respect to Revolving Loans (hereinafter defined) to be made by
the Bank to the Borrower, with respect to letters of credit which may hereafter
be issued by the Bank for the account of the Borrower and with respect to other
facilities to be provided by the Bank for the Borrower.  This letter agreement
amends and restates in its entirety that certain letter agreement dated November
27, 1992, as amended and modified (as so amended and modified, the "Prior
Agreement") between the Borrower and Fleet Bank of Massachusetts, N.A., the Bank
having succeeded by merger to the rights of Fleet Bank of Massachusetts, N.A.
thereunder.  In consideration of the mutual promises contained herein and in the
other documents referred to below, and for other good and valuable
consideration, receipt and sufficiency of which are hereby acknowledged, the
Borrower and the Bank agree as follows:

     I.  AMOUNTS AND TERMS
         -----------------

     1.1. Reference to Documents.  Reference is made to (i) that certain
          ----------------------
$5,000,000 principal amount promissory note (the "Revolving Note") of even date
herewith made by the Borrower and payable to the order of the Bank, (ii) that
certain Inventory, Accounts Receivable and Intangibles Security Agreement and
that certain Supplementary Security Agreement -Security Interest in Goods and
Chattels, each of even date herewith, from the Borrower to the Bank
(collectively, the "Security Agreement"), (iii) a Security Agreement (Patents)
of even date herewith (the "Intellectual Property Security Agreement") from the
Borrower to the Bank relating to the Borrower's registered patents, and (iv) a
pledge agreement (the "Pledge") from the Borrower to the Bank with respect to
the capital stock of Aseco Investment Corporation ("Securities Corp.") and a
related letter of representations from Securities Corp.

     1.2. The Borrowing; Revolving Note.  Subject to the terms and conditions
          -----------------------------
hereinafter set forth, the Bank will make loans ("Revolving Loans") to the
Borrower, in such amounts as the Borrower may request, on any Business Day prior
to the first to occur of (i) the Expiration Date, or (ii) the earlier
termination of the within-described revolving financing arrangements

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pursuant to (S)5.2 or (S)6.7; provided, however, that (1) the aggregate
principal amount of Revolving Loans outstanding shall at no time exceed the
Maximum Revolving Amount (hereinafter defined) and (2) the Aggregate Bank
Liabilities (hereinafter defined) shall at no time exceed the Borrowing Base
(hereinafter defined). Within such limits, and subject to the terms and
conditions hereof, the Borrower may obtain Revolving Loans, repay Revolving
Loans and obtain Revolving Loans again on one or more occasions. The Revolving
Loans shall be evidenced by the Revolving Note and interest thereon shall be
payable at the times and at the rate provided for in the Revolving Note. Overdue
principal of the Revolving Loans and, to the extent permitted by law, overdue
interest shall bear interest at a fluctuating rate per annum which at all times
shall be equal to the sum of (i) four (4%) percent per annum plus (ii) the per
annum rate otherwise payable under the Revolving Note (but in no event in excess
of the maximum rate from time to time permitted by then applicable law),
compounded monthly and payable on demand. The Borrower hereby irrevocably
authorizes the Bank to make or cause to be made, on a schedule attached to the
Revolving Note or on the books of the Bank, at or following the time of making
each Revolving Loan and of receiving any payment of principal, an appropriate
notation reflecting such transaction and the then aggregate unpaid principal
balance of the Revolving Loans. The amount so noted shall constitute presumptive
evidence as to the amount owed by the Borrower with respect to principal of the
Revolving Loans. Failure of the Bank to make any such notation shall not,
however, affect any obligation of the Borrower or any right of the Bank
hereunder or under the Revolving Note. All payments of interest, principal and
any other sum payable hereunder and/or under the Revolving Note and/or with
respect to any of the other Obligations shall be made to the Bank, in lawful
money of the United States in immediately available funds, at its office at One
Federal Street, Boston, MA 02110 or to such other address as the Bank may from
time to time direct. All payments received by the Bank after 2:00 p.m. on any
day shall be deemed received as of the next succeeding Business Day. All monies
received by the Bank shall be applied first to fees, charges, costs and expenses
payable to the Bank under this letter agreement, the Revolving Note and/or any
of the other Loan Documents and/or with respect to any of the other Obligations,
next to interest then accrued on account of any Revolving Loans or letter of
credit reimbursement obligations or on any of the other Obligations and only
thereafter to principal of the Revolving Loans, the letter of credit
reimbursement obligations and the other Obligations. All interest and fees
payable hereunder and/or under the Revolving Note and/or with respect to any of
the other Obligations shall be calculated on the basis of a 360-day year for the
actual number of days elapsed.

     1.3. Repayment; Renewal.  The Borrower shall repay in full all Revolving
          ------------------
Loans and all interest thereon upon the first to occur of: (i) the Expiration
Date or (ii) an acceleration under (S)5.2(a) following an Event of Default.  The
Borrower may repay, at any time, without penalty or premium, the whole or any
portion of any Revolving Loan.  In addition, if at any time the Borrowing Base
is in an amount which is less than the then outstanding Aggregate Bank
Liabilities, the Borrower will forthwith pay so much of the Revolving Loans as
may be required (or arrange for the termination of such letters of credit as may
be required) so that the Aggregate Bank Liabilities will not exceed the
Borrowing Base.  The Bank may, at its sole discretion, renew the financing
arrangements described in this letter agreement by extending the

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Expiration Date in a writing signed by the Bank and accepted by the Borrower.
Neither the inclusion in this letter agreement or elsewhere of covenants
relating to periods of time after the Expiration Date, nor any other provision
hereof, nor any action (except a written extension pursuant to the immediately
preceding sentence), non-action or course of dealing on the part of the Bank
will be deemed an extension of, or agreement on the part of the Bank to extend,
the Expiration Date.

     1.4. Advances and Payments.  The proceeds of all Revolving Loans shall be
          ---------------------
credited by the Bank to a general deposit account maintained by the Borrower
with the Bank.  The proceeds of each Revolving Loan will be used by the Borrower
solely for working capital purposes and other general corporate purposes
(including loans to Subsidiaries, but only within the limits set forth in (S)4.5
below).

     The Bank may charge any general deposit account of the Borrower at the Bank
with the amount of all payments of interest, principal and other sums due, from
time to time, under this letter agreement and/or the Revolving Note and/or with
respect to any letter of credit and/or with respect to any of the other
Obligations; and will thereafter notify the Borrower of the amount so charged.
The failure of the Bank so to charge any account or to give any such notice
shall not affect the obligation of the Borrower to pay interest, principal or
other sums as provided herein or in the Revolving Note or with respect to any
letter of credit or with respect to any of the other Obligations.

     Whenever any payment to be made to the Bank hereunder or under the
Revolving Note or with respect to any letter of credit or with respect to any of
the other Obligations shall be stated to be due on a day which is not a Business
Day, such payment may be made on the next succeeding Business Day, and interest
payable on each such date shall include the amount thereof which shall accrue
during the period of such extension of time.  All payments by the Borrower
hereunder and/or in respect of the Revolving Note and/or with respect to any
letter of credit or any of the other Obligations shall be made net of any
impositions or taxes and without deduction, set-off or counterclaim,
notwithstanding any claim which the Borrower may now or at any time hereafter
have against the Bank.

     1.5. Letters of Credit.  The Bank has issued for the account of the
          -----------------
Borrower a stand-by letter of credit (the "Existing L/C") in the stated amount
of $200,000.  The Existing L/C has been issued for a per annum fee of 1.5% of
the maximum stated amount thereof (payable in advance), and is subject to the
Bank's standard documentation and such other terms and conditions as were agreed
to by the Bank and the Borrower at the time of issuance.  In addition, the
Borrower shall be liable to pay to the Bank the Bank's then customary
negotiation, transfer, drawing and other fees in connection with the Existing
L/C.

     In addition to the foregoing, at the Borrower's request, the Bank may from
time to time, in its sole discretion, issue one or more letters of credit for
the account of the Borrower; provided that at the time of such issuance and
after giving effect thereto (A) the aggregate stated amounts of all letters of
credit issued under this paragraph will not exceed $500,000 and

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(B) the Aggregate Bank Liabilities will not exceed the lesser of (i) $5,000,000
or (ii) the then effective Borrowing Base. Any such letter of credit will be
issued for such fee and upon such terms and conditions as may be agreed to by
the Bank and the Borrower at the time of issuance. The Borrower hereby
authorizes the Bank, without further request from the Borrower, to cause the
Borrower's liability to the Bank for reimbursement of funds drawn under any such
letter of credit to be repaid from the proceeds of a Revolving Loan to be made
hereunder. The Borrower hereby irrevocably requests that such Revolving Loans be
made.

     1.6. ACH Transactions.  The Bank may from time to time prior the Expiration
          ----------------
Date, at the request of the Borrower, initiate automated clearinghouse ("ACH")
transactions for the Borrower; provided that the Bank's total ACH Exposure shall
not (unless otherwise agreed by the Bank in its sole discretion) exceed
$1,500,000 at any one time.  ACH transactions will bear such fees and charges
and as may be agreed upon by the Bank and the Borrower and will be governed by
the Bank's then current documentation and practices with respect to such
transactions.  As used herein, "ACH Exposure" as determined at any date means
the sum of (i) all amounts then owed by the Borrower to the Bank in connection
with any ACH transaction pursuant to which the Bank has advanced funds on behalf
of the Borrower plus (ii) the maximum amount which could be owed by the Borrower
(assuming settlement within two (2) Business Days of each date when funds are
advanced) to the Bank in connection with all ACH transactions then authorized by
the Borrower but as to which the Bank has not yet advanced funds.

     1.7. Foreign Exchange Contracts.  During the term of this letter agreement
          --------------------------
and subject to the terms and conditions hereof, the Bank may from time to time
prior to the Expiration Date, at the Borrower's request, provide to the Borrower
one or more forward contracts ("Foreign Exchange Contracts") for the purchase by
the Borrower of foreign currency from the Bank; provided that (i) each such
Foreign Exchange Contract will be at such pricing as the Bank and the Borrower
may agree at the time of execution of such Foreign Exchange Contract, (ii) the
documentation for each such Foreign Exchange Contract will be in such form as is
then customarily used by the Bank for transactions of this type, (iii) the
Foreign Exchange Contracts will be used by the Borrower to minimize its exposure
to the fluctuation of the value of those foreign currencies in which payments
are expected to be made to the Borrower by customers or in which the Borrower is
required to make payments to suppliers, (iv) the United States Dollar equivalent
of all amounts subject to the Foreign Exchange Contracts will not exceed
$10,000,000 in the aggregate and (v) the F/X Exposure will at no time exceed
$1,500,000.  As used herein, "F/X Exposure" as determined at any date means the
sum of (i) all amounts then owed by the Borrower to the Bank in connection with
settlement of any Foreign Exchange Contract, plus (ii) the maximum two-day
settlement amount for all then outstanding Foreign Exchange Contracts.

     1.8. Conditions to Advance.  Prior to the making of the initial Revolving
          ---------------------
Loan or the issuance of any letter of credit hereunder or the initiation of any
ACH transaction or the issuance of any Foreign Exchange Contract hereunder, the
Borrower shall deliver to the Bank duly executed copies of this letter
agreement, the Security Agreement, the Intellectual Property

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Security Agreement, the Revolving Note and the documents and other items listed
on the Closing Agenda delivered herewith by the Bank to the Borrower, all of
which shall be satisfactory in form and substance to the Bank and its counsel.

     Without limiting the foregoing, any Revolving Loan or letter of credit
issuance or ACH transaction or the issuance of a Foreign Exchange Contract
(including the initial Revolving Loan, letter of credit issuance, ACH
transaction or the issuance of a Foreign Exchange Contract) is subject to the
further conditions precedent that on the date on which such Revolving Loan is
made or such letter of credit is issued or such ACH transaction is initiated or
such Foreign Exchange Contract is issued (and after giving effect thereto):

     (a) All statements, representations and warranties of the Borrower made in
this letter agreement and/or in the Security Agreement shall continue to be
correct in all material respects as of the date of such Revolving Loan or the
date of issuance of such letter of credit or the date of such ACH transaction or
the date of issuance of such Foreign Exchange Contract, as the case may be,
except any such statements, representations and warranties which are
specifically stated herein as being made as of a particular date.

     (b) All covenants and agreements of the Borrower contained herein and/or in
any of the other Loan Documents shall have been complied with in all material
respects on and as of the date of such Revolving Loan or the date of issuance of
such letter of credit or the date of such ACH transaction or the date of
issuance of such Foreign Exchange Contract, as the case may be.

     (c) No event which constitutes, or which with notice or lapse of time or
both could constitute, an Event of Default shall have occurred and be
continuing.

     (d) No material adverse change shall have occurred in the financial
condition of the Borrower from that disclosed in the financial statements then
most recently furnished to the Bank (being, at the date hereof, the Borrower's
management-generated financial statements as at September 27, 1998).

     Each request by the Borrower for any Revolving Loan or for the issuance of
any letter of credit or for any ACH transaction or for the issuance of any
Foreign Exchange Contract, and each acceptance by the Borrower of the proceeds
of any Revolving Loan or delivery of a letter of credit or delivery of a Foreign
Exchange Contract, will be deemed a representation and warranty by the Borrower
that at the date of any such event, and after giving effect thereto, all of the
conditions set forth in the foregoing clauses (a)-(d) of this (S)1.8 will be
satisfied.  Each request for a Revolving Loan or letter of credit issuance will
be accompanied by a Borrowing Base certificate on a form satisfactory to the
Bank, executed by the chief financial officer of the Borrower, unless such a
certificate shall have been previously furnished as required by clause (iv) of
(S)3.6 setting forth the Borrowing Base as at the most recent month-end prior to
the date of the requested borrowing or the requested letter of credit issuance,
as the case may be.

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     II.  REPRESENTATIONS AND WARRANTIES
          ------------------------------

     2.1. Representations and Warranties.  In order to induce the Bank to enter
          ------------------------------
into this letter agreement and to make Revolving Loans hereunder and/or issue
letters of credit hereunder and/or engage in ACH transactions for the Borrower
and/or issue Foreign Exchange Contracts, the Borrower warrants and represents to
the Bank as follows:

     (a) The Borrower is a corporation duly organized, validly existing and in
good standing under the laws of Delaware.  The Borrower has full corporate power
to own its property and conduct its business as now conducted, to grant the
security interests contemplated by the Security Agreement and the Intellectual
Property Security Agreement and to enter into and perform this letter agreement
and the other Loan Documents.  The Borrower is duly qualified to do business and
is in good standing in Massachusetts and is also duly qualified to do business
in and is in good standing in each other jurisdiction in which the Borrower
maintains any facility, sales office, warehouse or other location, and in each
other jurisdiction where the failure so to qualify could (singly or in the
aggregate with all other such failures) have a material adverse effect on the
financial condition, business or prospects of the Borrower, all such
jurisdictions being listed on item 2.1(a) of the attached Disclosure Schedule.
At the date hereof, the Borrower has no Subsidiaries, except as shown on said
item 2.1(a) of the attached Disclosure Schedule.  The Borrower is not a member
of any partnership or joint venture.

     (b) The execution, delivery and performance by the Borrower of this letter
agreement and each of the other Loan Documents have been duly authorized by all
necessary corporate and other action and do not and will not:

          (i)  violate any provision of, or require (as a prerequisite to
     effectiveness) any filings (other than filings under the Uniform Commercial
     Code), registration, consent or approval under, any law, rule, regulation,
     order, writ, judgment, injunction, decree, determination or award presently
     in effect having applicability to the Borrower;

          (ii)  violate any provision of the charter or by-laws of the Borrower,
     or result in a breach of or constitute a default or require any waiver or
     consent under any indenture or loan or credit agreement or any other
     material agreement, lease or instrument to which the Borrower is a party or
     by which the Borrower or any of its properties may be bound or affected or
     require any other consent of any Person; or

          (iii)  result in, or require, the creation or imposition of any lien,
     security interest or other encumbrance (other than in favor of the Bank)
     upon or with respect to any of the properties now owned or hereafter
     acquired by the Borrower.

     (c) This letter agreement and each of the other Loan Documents has been
duly executed and delivered by the Borrower and each is a legal, valid and
binding obligation of the Borrower, enforceable against the Borrower in
accordance with its respective terms.

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     (d) Except as described on item 2.1(d) of the attached Disclosure Schedule,
there are no actions, suits, proceedings or investigations pending or, to the
knowledge of the Borrower, threatened by or against the Borrower or any
Subsidiary before any court or governmental department, commission, board,
bureau, agency or instrumentality, domestic or foreign, which could hinder or
prevent the consummation of the transactions contemplated hereby or call into
question the validity of this letter agreement or any of the other Loan
Documents or any action taken or to be taken in connection with the transactions
contemplated hereby or thereby or which in any single case or in the aggregate
might result in any adverse change in the business, prospects, condition,
affairs or operations of the Borrower or any Subsidiary, which change would be
material to the Borrower and its Subsidiaries, taken as a whole.

     (e) The Borrower is not in violation of any term of its charter or by-laws
as now in effect.  Neither the Borrower nor any Subsidiary of the Borrower is in
material violation of any term of any mortgage, indenture or judgment, decree or
order, or any other instrument, contract or agreement to which it is a party or
by which any of its property is bound which in any single case or in the
aggregate might result in any adverse change in the business, prospects,
condition, affairs or operations of the Borrower or any Subsidiary which change
would be material to the Borrower and its Subsidiaries, taken as a whole.

     (f) The Borrower has filed (and has caused each of its Subsidiaries to
file) all federal, state and local tax returns, reports and estimates required
to be filed by the Borrower and/or by any such Subsidiary.  All such filed
returns, reports and estimates are proper and accurate and the Borrower or the
relevant Subsidiary has paid all taxes, assessments, impositions, fees and other
governmental charges required to be paid in respect of the periods covered by
such returns, reports or estimates.  No deficiencies for any tax, assessment or
governmental charge have been asserted or assessed, and the Borrower knows of no
material tax liability or basis therefor.

     (g) The Borrower is in compliance (and each Subsidiary of the Borrower is
in compliance) with all requirements of law, federal, state and local, and all
requirements of all governmental bodies or agencies having jurisdiction over it,
the conduct of its business, the use of its properties and assets, and all
premises occupied by it, failure to comply with any of which could (singly or in
the aggregate with all other such failures) have a material adverse effect upon
the assets, business, financial condition or prospects of the Borrower and its
Subsidiaries, taken as a whole.  Without limiting the foregoing, the Borrower
has all the material franchises, licenses, leases, permits, certificates and
authorizations needed for the conduct of its business and the use of its
properties and all premises occupied by it, as now conducted, owned and used.

     (h) The audited financial statements of the Borrower as at March 29, 1998
and the management-generated statements of the Borrower as at September 27,
1998, each heretofore delivered to the Bank, are complete and accurate and
fairly present the financial condition of the Borrower as at the respective
dates thereof and for the periods covered thereby, except that

                                      -7-
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the management-generated statements do not have footnotes and thus do not
present the information which would normally be contained in footnotes to
financial statements. Neither the Borrower nor any of the Borrower's
Subsidiaries has any liability, contingent or otherwise, not disclosed in the
aforesaid financial statements or in any notes thereto that could materially
affect the financial condition of the Borrower. Since September 27, 1998, there
has been no material adverse development in the business, condition or prospects
of the Borrower, and the Borrower has not entered into any transaction other
than in the ordinary course.

     (i) The principal place of business and chief executive office of the
Borrower are located at 500 Donald Lynch Boulevard, Marlborough, MA  01752.  All
of the books and records of the Borrower are located at said address.  Except as
described on item 2.1(i) of the attached Disclosure Schedule, no assets of the
Borrower are located at any other address.  Said item 2.1(i) of the attached
Disclosure Schedule sets forth the names and addresses of all record owners of
any premises where any material amount of Collateral is located.

     (j) The Borrower owns or has a valid right to use all of the patents,
licenses, copyrights, trademarks, trade names and franchises ("Intellectual
Property") now being used to conduct its business, all of which are described on
item 2.1(j) of the attached Disclosure Schedule.  None of the Intellectual
Property owned by the Borrower is represented by a registered copyright,
trademark, patent or other federal or state registration, except as shown on
said item 2.1(j).  The conduct of the Borrower's business as now operated does
not conflict with valid patents, licenses, copyrights, trademarks, trade names
or franchises of others in any manner that could materially adversely affect the
business, prospects, assets or condition, financial or otherwise, of the
Borrower.

     (k) None of the executive officers or key employees of the Borrower is
subject to any agreement in favor of anyone other than the Borrower which limits
or restricts that person's right to engage in the type of business activity
conducted or proposed to be conducted by the Borrower or which grants to anyone
other than the Borrower any rights in any inventions or other ideas susceptible
to legal protection developed or conceived by any such officer or key employee.

     (l) The Borrower is not a party to any contract or agreement which now has
or, as far as can be foreseen by the Borrower at the date hereof, may have a
material adverse effect on the financial condition, business, prospects or
properties of the Borrower.

     (m) The Borrower has reviewed the software which it uses in its business
for "Year 2000" compliance and has determined that such software will continue
to function in the manner intended without material interruption of service or
other difficulty resulting from the "Year 2000 problem".  The Borrower will, at
the request of the Bank, provide such reports and other information as the Bank
may reasonably request in order to evidence such Year 2000 compliance.

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     III.  AFFIRMATIVE COVENANTS AND REPORTING REQUIREMENTS
           ------------------------------------------------

     Without limitation of any other covenants and agreements contained herein
or elsewhere, the Borrower agrees that so long as the financing arrangements
contemplated hereby are in effect or any Revolving Loan or any of the other
Obligations shall be outstanding or any letter of credit issued hereunder shall
be outstanding or any Foreign Exchange Contract shall be outstanding or any
amount shall be owed by the Borrower in respect of any ACH transaction or any
Foreign Exchange Contract:

     3.1.  Legal Existence; Qualification; Compliance.  The Borrower will
           ------------------------------------------
maintain (and will cause each Subsidiary of the Borrower to maintain) its
corporate existence and good standing in the jurisdiction of its incorporation;
provided that the Borrower may cause WED to be dissolved after WED conveys its
assets to the Borrower.  The Borrower will remain qualified to do business and
in good standing in Massachusetts.  The Borrower will qualify to do business and
will remain qualified and in good standing (and the Borrower will cause each
domestic Subsidiary of the Borrower (other than WED) to qualify and remain
qualified and in good standing) in each jurisdiction where the Borrower or such
Subsidiary, as the case may be, maintains any plant, sales office, warehouse or
other facility and in each other jurisdiction in which the failure so to qualify
could (singly or in the aggregate with all other such failures) have a material
adverse effect on the financial condition, business or prospects of the Borrower
and its Subsidiaries, taken as a whole.  The Borrower will comply (and will
cause each Subsidiary of the Borrower to comply) with its charter documents and
by-laws, to the extent applicable.  The Borrower will comply with (and will
cause each Subsidiary of the Borrower to comply with) all applicable laws, rules
and regulations (including, without limitation, ERISA and those relating to
environmental protection) other than (i) laws, rules or regulations the validity
or applicability of which the Borrower or such Subsidiary shall be contesting in
good faith by proceedings which serve as a matter of law to stay the enforcement
thereof and (ii) those laws, rules and regulations the failure to comply with
any of which could not (singly or in the aggregate) have a material adverse
effect on the financial condition, business or prospects of the Borrower and its
Subsidiaries, taken as a whole.

     3.2.  Maintenance of Property; Insurance.  The Borrower will maintain and
           ----------------------------------
preserve (and will cause each Subsidiary of the Borrower to maintain and
preserve) all of its material fixed assets in good working order and condition,
making all necessary repairs thereto and replacements thereof.  The Borrower
will maintain all such insurance as may be required under the Security Agreement
and will also maintain, with financially sound and reputable insurers, insurance
with respect to its property and business against such liabilities, casualties
and contingencies and of such types and in such amounts as shall be reasonably
satisfactory to the Bank from time to time and in any event all such insurance
as may from time to time be customary for companies conducting a business
similar to that of the Borrower in similar locales, with the Bank named as loss
payee with respect to all Collateral.

     3.3.  Payment of Taxes and Charges.  The Borrower will pay and discharge
           ----------------------------
(and will cause each Subsidiary of the Borrower to pay and discharge) all taxes,
assessments and governmental charges or levies imposed upon it or upon its
income or property, including, without limitation, taxes, assessments, charges
or levies relating to real and personal property,

                                      -9-
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franchises, income, unemployment, old age benefits, withholding, or sales or
use, prior to the date on which penalties would attach thereto, and all lawful
claims (whether for any of the foregoing or otherwise) which, if unpaid, might
give rise to a lien upon any property of the Borrower or any such Subsidiary,
except any of the foregoing which is being contested in good faith and by
appropriate proceedings which serve as a matter of law to stay the enforcement
thereof and for which the Borrower (or such Subsidiary, as the case may be) has
established and is maintaining adequate reserves. The Borrower will pay, and
will cause each of its Subsidiaries to pay, in a timely manner, all lease
obligations, all trade debt, purchase money obligations, equipment lease
obligations and all of its other material Indebtedness. The Borrower will
perform and fulfill all material covenants and agreements under any leases of
real estate, agreements relating to purchase money debt, equipment leases and
other material contracts. The Borrower will maintain in full force and effect,
and comply with the terms and conditions of, all permits, permissions and
licenses necessary or desirable for its business.

     3.4.  Accounts.  The Borrower will maintain its principal depository and
           --------
operating accounts with the Bank.

     3.5.  Conduct of Business.  The Borrower will conduct, in the ordinary
           -------------------
course, the business in which it is presently engaged.  The Borrower will not,
without the prior written consent of the Bank, directly or indirectly (itself or
through any Subsidiary) enter into any other lines of business, businesses or
ventures.

     3.6.  Reporting Requirements.  The Borrower will furnish to the Bank:
           ----------------------

          (i) Within 2 days after the Borrower files with the Securities and
     Exchange Commission ("SEC") its Annual Report on Form 10-K for any fiscal
     year of the Borrower (but in any event within 120 days after the end of
     each such fiscal year), a copy of the annual audit report for such fiscal
     year for the Borrower, including therein consolidated and consolidating
     balance sheets of the Borrower and Subsidiaries as at the end of such
     fiscal year and related consolidated and consolidating statements of
     income, stockholders' equity and cash flow for the fiscal year then ended.
     The annual consolidated financial statements shall be certified by
     independent public accountants selected by the Borrower and reasonably
     acceptable to the Bank, such certification to be in such form as is
     generally recognized as "unqualified".

          (ii) Within 30 days after the end of each month, consolidated balance
     sheets of the Borrower and its Subsidiaries and related consolidated
     statements of income and stockholders' equity and cash flow, unaudited but
     complete and accurate and prepared in accordance with generally accepted
     accounting principles consistently applied fairly presenting the financial
     condition of the Borrower as at the dates thereof and for the periods
     covered thereby (except that such monthly statements need not contain
     footnotes) and certified as accurate (subject to normal year-end audit
     adjustments, which shall not be material) by the chief financial officer of
     the Borrower, such balance sheets to be as at the end of such month and
     such statements of income

                                      -10-
<PAGE>

     and stockholders' equity and cash flow to be for such month and for the
     fiscal year to date, in each case together with a comparison to budget.

          (iii) At the time of delivery of each annual or monthly statement of
     the Borrower, a certificate executed by the chief financial officer of the
     Borrower stating that he or she has reviewed this letter agreement and the
     other Loan Documents and has no knowledge of any default by the Borrower in
     the performance or observance of any of the provisions of this letter
     agreement or of any of the other Loan Documents or, if he or she has such
     knowledge, specifying each such default and the nature thereof. Each
     financial statement given as at the end of any fiscal quarter of the
     Borrower will also set forth the calculations necessary to evidence
     compliance with (S)(S)3.7-3.10.

          (iv) Monthly, within 15 days after the end of each month, (A) an aging
     report in form satisfactory to the Bank covering all Receivables of the
     Borrower outstanding as at the end of such month, (B) a certificate of the
     chief financial officer of the Borrower setting forth the Borrowing Base as
     at the end of such month (except that the Borrowing Base certificate
     otherwise required with respect to Borrowing Base as at November 30, 1998
     may be given with respect to Borrowing Base as at December 1, 1998) and
     (C) an accounts payable aging, all in form reasonably satisfactory to the
     Bank.

          (v) Promptly after receipt, a copy of all audits or reports submitted
     to the Borrower by independent public accountants in connection with any
     annual, special or interim audits of the books of the Borrower and any
     "management letter" prepared by such accountants. The management letter for
     each fiscal year will be delivered within 120 days after the close of such
     fiscal year. The Borrower will provide to the Bank, prior to the first
     Revolving Loan or other extension of credit under this letter agreement, a
     copy of the management letter for the fiscal year ended March 29, 1998.

          (vi) As soon as possible and in any event within five days of the
     occurrence of any Event of Default or any event which, with the giving of
     notice or passage of time or both, would constitute an Event of Default,
     the statement of the Borrower setting forth details of each such Event of
     Default or event and the action which the Borrower proposes to take with
     respect thereto.

          (vii) Promptly after the commencement thereof, notice of all actions,
     suits and proceedings before any court or governmental department,
     commission, board, bureau, agency or instrumentality, domestic or foreign,
     to which the Borrower or any Subsidiary of the Borrower is a party;
     provided that nothing in this clause (vii) will be deemed to require the
     Borrower to give notice of any such action, suit or proceeding in which
     only monetary damages are sought and the damages so sought are less than
     $50,000.

                                      -11-
<PAGE>

          (viii) Promptly upon filing any registration statement or listing
     application (or any supplement or amendment to any registration statement
     or listing application) with the SEC or any successor agency or with any
     stock exchange or with the National Association of Securities Dealers
     quotations system, a copy of same.

          (ix) A copy of each periodic or current report filed with the SEC or
     any successor agency and each annual report, proxy statement and other
     communication sent to shareholders or other securityholders generally, such
     copy to be provided to the Bank promptly upon such filing with the SEC or
     such communication with shareholders or securityholders, as the case may
     be.

          (x) Promptly upon applying for, or being granted, a federal or state
     registration for any copyright, trademark or patent or purchasing any
     registered copyright, trademark or patent, written notice to the Bank
     describing same, together with all such documents as may be required to
     give the Bank a fully perfected first priority security interest in each
     such copyright, trademark or patent.

          (xi) Promptly after the Borrower has knowledge thereof, written notice
     of any development or circumstance which may reasonably be expected to have
     a material adverse effect on the business, properties, assets, or
     condition, financial or otherwise, of the Borrower and its Subsidiaries
     taken as a whole.

          (xii) Promptly upon request, such other information respecting the
     financial condition, operations, Receivables, inventory, machinery or
     equipment of the Borrower or any Subsidiary as the Bank may from time to
     time reasonably request.

     3.7.  Debt to Worth.  The Borrower will maintain as at the last day of each
           -------------
fiscal quarter of the Borrower (each, a "Determination Date") (commencing with
its results as at September 27, 1998) on a consolidated basis a Leverage Ratio
which is less than 1.0 to 1.  As used herein, "Leverage Ratio" means, as at any
Determination Date, the ratio of (x) the total consolidated Senior Liabilities
of the Borrower and/or its Subsidiaries then outstanding to (y) the Borrower's
then consolidated Capital Base.

     3.8.  Capital Base.  The Borrower will maintain as at each Determination
           ------------
Date (commencing December 27, 1998) a consolidated Capital Base of not less than
the following: as at December 27, 1998 - not less than $15,400,000; and as at
March 28, 1999 and as at each Determination Date thereafter - not less than
$14,300,000.

     3.9.  Profitability.  The Borrower will not incur a quarterly consolidated
           -------------
Net Loss in excess of $1,600,000 for its fiscal quarter ending December 27,
1998, nor a quarterly consolidated Net Loss in excess of $1,400,000 for its
fiscal quarter ending March 28, 1999, nor a quarterly consolidated Net Loss in
excess of $1,100,000 for its fiscal quarter ending June 27, 1999 or any
subsequent fiscal quarter.  Without limitation of the foregoing, the Borrower
will not incur an annual consolidated Net Loss in excess of $7,900,000 for its
fiscal year ending March 28, 1999.

                                      -12-
<PAGE>

     3.10.  Current Ratio.  The Borrower will maintain as at the end of each
            -------------
fiscal quarter of Borrower (commencing with its results as at September 27,
1998) a Current Ratio which is greater than 2.0 to 1. As used herein, "Current
Ratio" means, as at any date when same is to be determined, the ratio of (x) Net
Current Assets to (y) consolidated Current Liabilities.

     3.11.  Books and Records.  The Borrower will maintain (and will cause each
            -----------------
of its Subsidiaries to maintain) complete and accurate books, records and
accounts which will at all times accurately and fairly reflect all of its
transactions in accordance with generally accepted accounting principles
consistently applied. The Borrower will, at any reasonable time and from time to
time upon reasonable written notice and during normal business hours (and at any
time and without any necessity for notice following the occurrence of an Event
of Default), permit the Bank, and any agents or representatives thereof, to
examine and make copies of and take abstracts from the records and books of
account of, and visit the properties of the Borrower and any of its
Subsidiaries, and to discuss its affairs, finances and accounts with its
officers, directors and/or independent accountants, all of whom are hereby
authorized and directed to cooperate with the Bank in carrying out the intent of
this (S)3.11. Each financial statement of the Borrower hereafter delivered
pursuant to this letter agreement will be complete and accurate and will fairly
present the financial condition of the Borrower as at the date thereof and for
the periods covered thereby. Without limitation of the foregoing, the Bank may
conduct field audits of the Borrower and may arrange for equipment appraisals at
such reasonable intervals as the Bank may determine and the Borrower will pay
the reasonable costs thereof.

     IV.  NEGATIVE COVENANTS
          ------------------

     Without limitation of any other covenants and agreements contained herein
or elsewhere, the Borrower agrees that so long as the financing arrangements
contemplated hereby are in effect or any Revolving Loan or any of the other
Obligations shall be outstanding or any letter of credit issued hereunder shall
be outstanding or any Foreign Exchange Contract shall be outstanding or any
amount shall be owed by the Borrower in respect of any ACH transaction or any
Foreign Exchange Contract:

     4.1.  Indebtedness.  The Borrower will not create, incur, assume or suffer
           ------------
to exist any Indebtedness (nor allow any of its Subsidiaries to create, incur,
assume or suffer to exist any Indebtedness), except for:

           (i) Indebtedness owed to the Bank, including, without limitation, the
     Indebtedness represented by the Revolving Note and any Indebtedness in
     respect of letters of credit issued by the Bank or in respect of any ACH
     transactions or in respect of any Foreign Exchange Contracts;

           (ii) Indebtedness of the Borrower or any Subsidiary for taxes,
     assessments and governmental charges or levies not yet due and payable;

                                      -13-
<PAGE>

           (iii) unsecured current liabilities of the Borrower or any Subsidiary
     (other than for money borrowed or for purchase money Indebtedness with
     respect to fixed assets) incurred upon customary terms in the ordinary
     course of business;

           (iv) purchase money Indebtedness (including, without limitation,
     Indebtedness in respect of capitalized equipment leases) owed to equipment
     vendors and/or lessors for equipment purchased or leased by the Borrower
     for use in the Borrower's business, provided that the total of Indebtedness
     permitted under this clause (iv) plus presently-existing equipment
     financing permitted under clause (v) of this (S)4.1 will not exceed
     $1,000,000 in the aggregate outstanding at any one time;

           (v) other Indebtedness existing at the date hereof (including,
     without limitation, existing Subordinated Debt), but only to the extent set
     forth on item 4.1 of the attached Disclosure Schedule;

           (vi) any guaranties or other contingent liabilities expressly
     permitted pursuant to (S)4.3;

           (vii) net intercompany amounts (not to exceed $5,800,000 in the
     aggregate) due from WED;

           (viii) loans made by the Borrower to Securities Corp. or by
     Securities Corp. to the Borrower; and

           (ix) net intercompany amounts due from Subsidiaries other than WED
     and Securities Corp.; provided that same do not exceed $800,000 in the
     aggregate outstanding at any one time exclusive of amounts permitted by
     clauses (vii) and (viii) above.

     4.2.  Liens.  The Borrower will not create, incur, assume or suffer to
           -----
exist (nor allow any of its Subsidiaries to create, incur, assume or suffer to
exist) any mortgage, deed of trust, pledge, lien, security interest, or other
charge or encumbrance (including the lien or retained security title of a
conditional vendor) of any nature (collectively, "Liens"), upon or with respect
to any of its property or assets, now owned or hereafter acquired, except that
the foregoing restrictions shall not apply to:

           (i) Liens for taxes, assessments or governmental charges or levies on
     property of the Borrower or any of its Subsidiaries if the same shall not
     at the time be delinquent or thereafter can be paid without interest or
     penalty;

           (ii) Liens imposed by law, such as carriers', warehousemen's and
     mechanics' liens and other similar Liens arising in the ordinary course of
     business for sums not yet due or which are being contested in good faith
     and by appropriate proceedings which serve as a matter of law to stay the
     enforcement thereof and as to which adequate reserves have been made;

                                      -14-
<PAGE>

           (iii) pledges or deposits under workmen's compensation laws,
     unemployment insurance, social security, retirement benefits or similar
     legislation;

           (iv)  Liens in favor of the Bank;

           (v) Liens in favor of equipment vendors and/or lessors securing
     purchase money Indebtedness to the extent permitted by clause_(iv) of
     (S)4.1; provided that no such Lien will extend to any property of the
     Borrower other than the specific items of equipment financed; or

           (vi) other Liens existing at the date hereof, but only to the extent
     and with the relative priorities set forth on item 4.2 of the attached
     Disclosure Schedule.

     Without limitation of the foregoing, the Borrower covenants and agrees that
it will not enter into (and will not suffer or permit any of its Subsidiaries to
enter into) any agreement or understanding (each, a "Restrictive Agreement")
with any Person other than the Bank which could prohibit or restrict in any
manner the right of the Borrower or any such Subsidiary to grant to the Bank any
Lien on any of its assets.  The Borrower represents and warrants that, at the
date of this letter agreement, neither the Borrower nor any such Subsidiary is
party to any such Restrictive Agreement.

     4.3. Guaranties.  The Borrower will not, without the prior written consent
          ----------
of the Bank, assume, guarantee, endorse or otherwise become directly or
contingently liable (including, without limitation, liable by way of agreement,
contingent or otherwise, to purchase, to provide funds for payment, to supply
funds to or otherwise invest in any debtor or otherwise to assure any creditor
against loss) (and will not permit any of its Subsidiaries so to assume,
guaranty or become directly or contingently liable) in connection with any
indebtedness of any other Person, except (i) guaranties by endorsement for
deposit or collection in the ordinary course of business and (ii) guaranties
existing at the date hereof and described on item 4.3 of the attached Disclosure
Schedule.

     4.4. Dividends.  The Borrower will not, without the prior written consent
          ---------
of the Bank, make any distributions to its shareholders, pay any dividends
(other than dividends payable solely in capital stock of the Borrower) or
redeem, purchase or otherwise acquire, directly or indirectly any of its capital
stock.

     4.5. Loans and Advances.  The Borrower will not make (and will not permit
          ------------------
any Subsidiary to make) any loans or advances to any Person, including, without
limitation, the Borrower's directors, officers and employees, except (i)
existing loans described in item 4.5 of the attached Disclosure Schedule, (ii)
loans made by the Borrower or by any Subsidiary of the Borrower which give rise
to Indebtedness permitted by clauses (vii), (viii) and (ix) of (S)4.1; and (iii)
advances to such directors, officers or employees with respect to expenses
incurred by them

                                      -15-
<PAGE>

in the ordinary course of their duties and advances against salary, all of which
advances will not exceed, in the aggregate, $100,000 outstanding at any one
time.

     4.6. Investments.  The Borrower will not, without the Bank's prior written
          -----------
consent, invest in, hold or purchase any stock or securities of any Person (nor
will the Borrower permit any of its Subsidiaries to invest in, purchase or hold
any such stock or securities) except (i) readily marketable direct obligations
of, or obligations guarantied by, the United States of America or any agency
thereof, (ii) other investment grade debt securities (including, without
limitation, rated investment grade fixed or variable rate tax-exempt securities)
and bankers' acceptances with ratings approved by the Bank, (iii) mutual funds,
the assets of which are primarily invested in items of the kind described in the
foregoing clauses (i) and (ii) of this (S)4.6, (iv) deposits with or
certificates of deposit issued by the Bank and any other obligations of the Bank
or the Bank's parent, (v) deposits in any other bank organized in the United
States having capital in excess of $100,000,000, (vi) contributions by the
Borrower to the capital of Securities Corp. representing the interest on loans
made by the Borrower to Securities Corp. and (vii) investments in any
Subsidiaries now existing or hereafter created by the Borrower pursuant to
(S)4.7 below; provided that in any event the Tangible Net Worth of the Borrower
alone (exclusive of its investment in Subsidiaries and any debt owed by any
Subsidiary to the Borrower) will not be less than 90% of the consolidated
Tangible Net Worth of the Borrower and Subsidiaries.

     4.7. Subsidiaries; Acquisitions.  Neither the Borrower nor any of its
          --------------------------
Subsidiaries will, without the prior written consent of the Bank, form or
acquire any Subsidiary or make any other acquisition of the stock of any other
Person or of all or substantially all of the assets of any other Person, except
that the Borrower may make acquisitions of the stock or assets of another Person
so long as the aggregate consideration (whether in cash, stock or other
property) for all such acquisitions consummated in any fiscal year of the
Borrower does not exceed $1,000,000 per fiscal year.  The Borrower will not
become a partner in any partnership.

     4.8. Merger.  The Borrower will not, without the prior written consent of
          ------
the Bank, merge or consolidate with any Person, or sell, lease, transfer or
otherwise dispose of any material portion of its assets (whether in one or more
transactions), other than sale of inventory in the ordinary course.

     4.9. Affiliate Transactions.  The Borrower will not, without the prior
          ----------------------
written consent of the Bank, enter into any transaction (other than an
investment in or loan to a Subsidiary of the Borrower to the extent expressly
permitted by this letter agreement), including, without limitation, the
purchase, sale or exchange of any property or the rendering of any service, with
any affiliate of the Borrower, except in the ordinary course of and pursuant to
the reasonable requirements of the Borrower's business and upon fair and
reasonable terms no less favorable to the Borrower than would be obtained in a
comparable arms'-length transaction with any Person not an affiliate; provided
that nothing in this (S)4.9 shall be deemed to prohibit the payment of salary or
other similar payments to any officer or director of the Borrower at a level
consistent with the salary and other payments being paid at the date of this
letter agreement and heretofore

                                      -16-
<PAGE>

disclosed in writing to the Bank, nor to prevent the hiring of additional
officers at a salary level consistent with industry practice, nor to prevent
reasonable periodic increases in salary, nor to prohibit any of the transactions
relating to Indebtedness permitted by clauses (vii), (viii) and/or (ix) of
(S)4.1. For the purposes of this letter agreement, "affiliate" means any Person
which, directly or indirectly, controls or is controlled by or is under common
control with the Borrower; any officer or director or former officer or director
of the Borrower; any Person owning of record or beneficially, directly or
indirectly, 5% or more of any class of capital stock of the Borrower or 5% or
more of any class of capital stock or other equity interest having voting power
(under ordinary circumstances) of any of the other Persons described above; and
any member of the immediate family of any of the foregoing. "Control" means
possession, directly or indirectly, of the power to direct or cause the
direction of the management or policies of any Person, whether through ownership
of voting equity, by contract or otherwise.

     4.10.  Change of Address, etc.  The Borrower will not change its name or
            ----------------------
legal structure, nor will the Borrower move its chief executive offices or
principal place of business from the address described in the first sentence of
(S)2.1(i) above, nor will the Borrower remove any books or records from such
address, nor will the Borrower keep any Collateral at any location other than
the premises described in (S)2.1(i), without, in each instance, giving the Bank
at least 30 days' prior written notice and providing all such financing
statements, certificates and other documentation as the Bank may request in
order to maintain the perfection and priority of the security interests granted
or intended to be granted pursuant to the Security Agreement.  The Borrower will
not change its fiscal year or methods of financial reporting unless, in each
instance, prior written notice of such change is given to the Bank and prior to
such change the Borrower enters into amendments to this letter agreement in form
and substance satisfactory to the Bank in order to preserve unimpaired the
rights of the Bank and the obligations of the Borrower hereunder.

     4.11.  Hazardous Waste.  Except as provided below, the Borrower will not
            ---------------
dispose of or suffer or permit to exist any hazardous material or oil on any
site or vessel owned, occupied or operated by the Borrower or any Subsidiary of
the Borrower, nor shall the Borrower store (or permit any Subsidiary to store)
on any site or vessel owned, occupied or operated by the Borrower or any such
Subsidiary, or transport or arrange the transport of, any hazardous material or
oil (the terms "hazardous material", "oil", "site" and "vessel", respectively,
being used herein with the meanings given those terms in Mass. Gen. Laws,
Ch. 21E or any comparable terms in any comparable statute in effect in any other
relevant jurisdiction). Except as otherwise expressly provided below, the
Borrower shall provide the Bank with written notice of (i) the storage or
transport of any hazardous material or oil by the Borrower or any Subsidiary of
the Borrower, (ii) any release or known threat of release of any hazardous
material or oil at or from any site or vessel owned, occupied or operated by the
Borrower or any Subsidiary of the Borrower, and (iii) any incurrence of any
expense or loss by any government or governmental authority in connection with
the assessment, containment or removal of any hazardous material or oil known to
the Borrower for which expense or loss the Borrower or any Subsidiary of the
Borrower may be liable. Notwithstanding the foregoing, the Borrower and its
Subsidiaries may use, store and transport and arrange for the transport or

                                      -17-
<PAGE>

disposal of, and need not notify the Bank of the use, storage, arrangement for
transport, disposal or transportation of, (x) oil as fuel for their respective
facilities or for vehicles or machinery used in the ordinary course of their
respective businesses and (y) hazardous materials that are solvents, cleaning
agents or other materials used in the ordinary course of the respective business
operations of the Borrower and its Subsidiaries, as long as in each case the
Borrower or the Subsidiary concerned (as the case may be) has obtained and
maintains in effect any governmental permits, licenses and approvals necessary
for such use, storage, transportation, arranging for transport or disposal,
complies with all requirements of federal, state and local law applicable to
such use, storage, transportation, arrangement for transport or disposal, and in
any event disposes of such materials (not consumed in the ordinary course) only
through licensed providers of hazardous waste removal services.

     4.12.  No Margin Stock.  No proceeds of any Revolving Loan shall be used
            ---------------
directly or indirectly to purchase or carry any margin security.

     4.13.  Subordinated Debt.  The Borrower will not directly or indirectly
            -----------------
make any optional or voluntary prepayment or purchase of Subordinated Debt or
modify, alter or add any provisions with respect to payment of Subordinated
Debt.  In any event, the Borrower will not make any payment of any principal of
or interest on any Subordinated Debt at any time when there exists, or if there
would result therefrom, any Event of Default hereunder.

     V.  DEFAULT AND REMEDIES
         --------------------

     5.1. Events of Default.  The occurrence of any one of the following events
          -----------------
shall constitute an Event of Default hereunder:

     (a) The Borrower shall fail to make any payment of principal of or interest
on the Revolving Note on or before the date when due; or the Borrower shall fail
to pay when due any amount owed to the Bank in respect of any letter of credit
now or hereafter issued by the Bank or in respect of any Foreign Exchange
Contract or in respect of any ACH transaction; or

     (b) Any representation or warranty of the Borrower contained herein shall
at any time prove to have been incorrect in any material respect when made or
any representation or warranty made by the Borrower in connection with any
Revolving Loan or letter of credit or any ACH transaction or any Foreign
Exchange Contract shall at any time prove to have been incorrect in any material
respect when made; or

     (c) The Borrower shall default in the performance or observance of any
agreement or obligation under any of (S)(S)3.1, 3.3, 3.6, 3.7, 3.8, 3.9 or 3.10
or Article IV; or

     (d) The Borrower shall default in the performance of any other term,
covenant or agreement contained in this letter agreement and such default shall
continue unremedied for 30 days after notice thereof shall have been given to
the Borrower; or

                                      -18-
<PAGE>

     (e) Any default on the part of the Borrower or any Subsidiary of the
Borrower shall exist, and shall remain unwaived or uncured beyond the expiration
of any applicable notice and/or grace period, under any other contract,
agreement or undertaking now existing or hereafter entered into with or for the
benefit of the Bank (or any affiliate of the Bank); or

     (f) Any default shall exist and remain unwaived or uncured with respect to
any Subordinated Debt of the Borrower or with respect to any instrument
evidencing, guaranteeing or otherwise relating to any such Subordinated Debt, or
any such Subordinated Debt shall not have been paid when due, whether by
acceleration or otherwise, or shall have been declared to be due and payable
prior to its stated maturity, or any event or circumstance shall occur which
permits, or with the lapse of time or the giving of notice or both would permit,
the acceleration of the maturity of any Subordinated Debt by the holder or
holders thereof; or

     (g) Any default shall exist and remain unwaived or uncured with respect to
any other Indebtedness of the Borrower or any Subsidiary of the Borrower in
excess of $100,000 in aggregate principal amount or with respect to any
instrument evidencing, guaranteeing, securing or otherwise relating to any such
Indebtedness, or any such Indebtedness in excess of $100,000 in aggregate
principal amount shall not have been paid when due, whether by acceleration or
otherwise, or shall have been declared to be due and payable prior to its stated
maturity, or any event or circumstance shall occur (and shall have continued
beyond the expiration of any applicable notice and/or grace period) giving the
holder or holders of such Indebtedness the right to accelerate the maturity
thereof; or

     (h) The Borrower shall be dissolved, or the Borrower or any Subsidiary of
the Borrower (other than WED after it transfers its assets to the Borrower)
shall become insolvent or bankrupt or shall cease paying its debts as they
mature or shall make an assignment for the benefit of creditors, or a trustee,
receiver or liquidator shall be appointed for the Borrower or any Subsidiary of
the Borrower (other than WED after it transfers its assets to the Borrower) or
for a substantial part of the property of the Borrower or any such Subsidiary
(other than WED after it transfers its assets to the Borrower), or bankruptcy,
reorganization, arrangement, insolvency or similar proceedings shall be
instituted by or against the Borrower or any such Subsidiary (other than WED
after it transfers its assets to the Borrower) under the laws of any
jurisdiction (except for an involuntary proceeding filed against the Borrower or
any Subsidiary of the Borrower which is dismissed within 60 days following the
institution thereof); or

     (i) Any attachment, execution or similar process in an amount of $50,000 or
more shall be issued or levied against any of the property of the Borrower or
any Subsidiary and such attachment, execution or similar process shall not be
paid, stayed, released, vacated or fully bonded within 10 days after its issue
or levy; or

     (j) Any final uninsured judgment in excess of $100,000 shall be entered
against the Borrower or any Subsidiary of the Borrower by any court of competent
jurisdiction; or

                                      -19-
<PAGE>

     (k) The Borrower or any Subsidiary of the Borrower shall fail to meet its
minimum funding requirements under ERISA with respect to any employee benefit
plan (or other class of benefit which the PBGC has elected to insure) or any
such plan shall be the subject of termination proceedings (whether voluntary or
involuntary) and there shall result from such termination proceedings a
liability of the Borrower or any Subsidiary of the Borrower to the PBGC which in
the reasonable opinion of the Bank may have a material adverse effect upon the
financial condition of the Borrower or any such Subsidiary; or

     (l) The Security Agreement or any other Loan Document shall for any reason
(other than due to payment in full of all amounts secured or evidenced thereby
or due to discharge in writing by the Bank) not remain in full force and effect;
or

     (m) The security interests and liens of the Bank in and on any of the
Collateral which is of a type that perfection may be had by filing UCC-1
financing statements shall for any reason (other than due to payment in full of
all amounts secured thereby or due to written release by the Bank) not be fully
perfected liens and security interests; or

     (n) At any time, 50% or more of the outstanding shares of any class of
equity securities of the Borrower shall be owned by any Person or by any "group"
(as defined in the Securities Exchange Act of 1934, as amended, and the
regulations thereunder); or

     (o) There shall occur any other material adverse change in the condition
(financial or otherwise), operations, properties, assets, liabilities or
earnings of the Borrower.

     5.2. Rights and Remedies on Default.  Upon the occurrence of any Event of
          ------------------------------
Default, in addition to any other rights and remedies available to the Bank
hereunder or otherwise, the Bank may exercise any one or more of the following
rights and remedies (all of which shall be cumulative):

     (a) Declare the entire unpaid principal amount of the Revolving Note then
outstanding, all interest accrued and unpaid thereon and all other amounts
payable under this letter agreement, and all other Indebtedness of the Borrower
to the Bank, to be forthwith due and payable, whereupon the same shall become
forthwith due and payable, without presentment, demand, protest or notice of any
kind, all of which are hereby expressly waived by the Borrower.

     (b) Terminate the revolving financing arrangements provided for by this
letter agreement; and the Bank may also terminate all facilities provided for
herein for letters of credit, ACH transactions and/or Foreign Exchange
Contracts.

     (c) Exercise all rights and remedies hereunder, under the Revolving Note,
under the Security Agreement, under the Intellectual Property Security
Agreement, under the Pledge and under each and any other agreement with the
Bank; and exercise all other rights and remedies which the Bank may have under
applicable law.

                                      -20-
<PAGE>

     5.3. Set-off.  In addition to any rights now or hereafter granted under
          -------
applicable law and not by way of limitation of any such rights, upon the
occurrence of any Event of Default, the Bank is hereby authorized at any time or
from time to time, without presentment, demand, protest or other notice of any
kind to the Borrower or to any other Person, all of which are hereby expressly
waived, to set off and to appropriate and apply any and all deposits and any
other Indebtedness at any time held or owing by the Bank or any affiliate
thereof to or for the credit or the account of the Borrower against and on
account of the obligations and liabilities of the Borrower to the Bank under
this letter agreement or otherwise, irrespective of whether or not the Bank
shall have made any demand hereunder and although said obligations, liabilities
or claims, or any of them, may then be contingent or unmatured and without
regard for the availability or adequacy of other collateral.  As further
security for the Obligations, the Borrower also grants to the Bank a security
interest with respect to all its deposits and all securities or other property
in the possession of the Bank or any affiliate of the Bank from time to time,
and, upon the occurrence of any Event of Default, the Bank may exercise all
rights and remedies of a secured party under the Uniform Commercial Code.  ANY
AND ALL RIGHTS TO REQUIRE THE BANK TO EXERCISE ITS RIGHTS OR REMEDIES WITH
RESPECT TO ANY OTHER COLLATERAL WHICH SECURES ANY OF THE OBLIGATIONS PRIOR TO
THE EXERCISE BY THE BANK OF ITS RIGHT OF SET-OFF UNDER THIS SECTION ARE HEREBY
KNOWINGLY, VOLUNTARILY AND IRREVOCABLY WAIVED.

     5.4. Letters of Credit.  Without limitation of any other right or remedy of
          -----------------
the Bank, (i) if an Event of Default shall have occurred and the Bank shall have
accelerated the Revolving Loans or (ii) if this letter agreement and/or the
revolving financing arrangements described herein shall have expired or shall
have been earlier terminated by either the Bank or the Borrower for any reason,
the Borrower will forthwith deposit with the Bank in cash a sum equal to the
total of all then undrawn amounts of all outstanding letters of credit issued by
the Bank for the account of the Borrower.  Upon the occurrence of any event
described in clause (i) or clause (ii) of the immediately preceding sentence,
the Bank may also require the Borrower to cash collateralize the outstanding F/X
Exposure and ACH Exposure.

     VI.  MISCELLANEOUS
          -------------

     6.1. Costs and Expenses.  The Borrower agrees to pay on demand reasonable
          ------------------
all costs and expenses (including, without limitation, reasonable legal fees) of
the Bank in connection with the preparation, execution and delivery of this
letter agreement, the Security Agreement, the Revolving Note and all other
instruments and documents to be delivered in connection with any Revolving Loan
or any letter of credit issued hereunder and/or any of the other Obligations and
any amendments or modifications of any of the foregoing, as well as the
reasonable costs and expenses (including, without limitation, the reasonable
fees and expenses of legal counsel) incurred by the Bank in connection with
preserving, enforcing or exercising, upon default, any rights or remedies under
this letter agreement, the Security Agreement, the Revolving Note and all other
instruments and documents delivered or to be delivered hereunder or in
connection herewith or in connection with any other Obligation, all whether or
not legal action is instituted.  In addition, the Borrower shall be obligated to
pay any and all stamp and

                                      -21-
<PAGE>

other taxes payable or determined to be payable in connection with the execution
and delivery of this letter agreement, the Security Agreement, the Revolving
Note and all other instruments and documents to be delivered in connection with
any Obligation. Any fees, expenses or other charges which the Bank is entitled
to receive from the Borrower under this Section shall bear interest from the
date of any demand therefor until the date when paid at a rate per annum equal
to the sum of (i) four (4%) percent plus (ii) the per annum rate otherwise
payable under the Revolving Note (but in no event in excess of the maximum rate
permitted by then applicable law).

     6.2. Capital Adequacy.  If the Bank shall have reasonably determined that
          ----------------
the adoption or phase-in after the date hereof of any applicable law, rule or
regulation regarding capital requirements for banks or bank holding companies,
or any change therein after the date hereof, or any change in the interpretation
or administration thereof by any governmental authority, central bank or
comparable agency charged with the interpretation or administration thereof, or
compliance by the Bank with any request or directive of such entity regarding
capital adequacy (whether or not having the force of law) has or would have the
effect of reducing the return on the Bank's capital with respect to the
Revolving Loans, the within-described revolving loan facility and/or letters of
credit issued for the account of the Borrower and/or any of the other
Obligations to a level below that which the Bank could have achieved (taking
into consideration the Bank's policies with respect to capital adequacy
immediately before such adoption, phase-in, change or compliance and assuming
that the Bank's capital was then fully utilized) but for such adoption, phase-
in, change or compliance by any amount deemed by the Bank to be material:
(i) the Bank shall promptly after its determination of such occurrence give
notice thereof to the Borrower; and (ii) the Borrower shall pay forthwith to the
Bank as an additional fee such amount as the Bank certifies to be the amount
that will compensate it for such reduction with respect to the Revolving Loans,
the within-described revolving loan facility and/or such letters of credit
and/or any of the other Obligations.

     A certificate of the Bank claiming compensation under this Section shall be
conclusive in the absence of manifest error.  Such certificate shall set forth
the nature of the occurrence giving rise to such compensation, the additional
amount or amounts to be paid to it hereunder and the method by which such
amounts were determined.  In determining such amounts, the Bank may use any
reasonable averaging and attribution methods.  No failure on the part of the
Bank to demand compensation on any one occasion shall constitute a waiver of its
right to demand such compensation on any other occasion and no failure on the
part of the Bank to deliver any certificate in a timely manner shall in any way
reduce any obligation of the Borrower to the Bank under this Section.

     6.3. Facility Fees.  With respect to the within arrangements for Revolving
          -------------
Loans, the Borrower will pay to the Bank, on the date of this letter agreement
and thereafter on the first day of each calendar quarter (commencing January 1,
1999), a non-refundable quarterly facility fee of $6,250 per calendar quarter
(appropriately pro-rated for any partial calendar quarter), payable in advance.
In addition, if the within-described revolving financing arrangements are

                                      -22-
<PAGE>

terminated by the Borrower for any reason or by the Bank as the result of the
Borrower's default, the Borrower shall forthwith upon such termination pay to
the Bank a sum equal to all of the fees which would have become due pursuant to
the immediately preceding sentence from the date of such termination through the
Expiration Date.  The fees described in this Section are in addition to any
balances and fees required by the Bank or any of its affiliates in connection
with any other services now or hereafter made available to the Borrower.

     6.4. Other Agreements.  The provisions of this letter agreement are not in
          ----------------
derogation or limitation of any obligations, liabilities or duties of the
Borrower under any of the other Loan Documents or any other agreement with or
for the benefit of the Bank.  No inconsistency in default provisions between
this letter agreement and any of the other Loan Documents or any such other
agreement will be deemed to create any additional grace period or otherwise
derogate from the express terms of each such default provision.  No covenant,
agreement or obligation of the Borrower contained herein, nor any right or
remedy of the Bank contained herein, shall in any respect be limited by or be
deemed in limitation of any inconsistent or additional provisions contained in
any of the other Loan Documents or in any such other agreement.

     6.5. Governing Law.  This letter agreement and the Revolving Note shall be
          -------------
governed by, and construed and enforced in accordance with, the laws of The
Commonwealth of Massachusetts.

     6.6. Addresses for Notices, etc.  All notices, requests, demands and other
          --------------------------
communications provided for hereunder shall be in writing and shall be mailed or
delivered to the applicable party at the address indicated below:

          If to the Borrower:

          Aseco Corporation
          500 Donald Lynch Boulevard
          Marlborough, MA  01752
          Attention:  Mary R. Barletta, Chief Financial Officer

          If to the Bank:

          Fleet National Bank
          High Technology Group
          Mail Code:  MA OF D07A
          One Federal Street
          Boston, MA  02110
          Attention:  Lucie Burke, Vice President

or, as to each of the foregoing, at such other address as shall be designated by
such Person in a written notice to the other party complying as to delivery with
the terms of this Section.  All

                                      -23-
<PAGE>

such notices, requests, demands and other communications shall be deemed
delivered on the earlier of (i) the date received or (ii) the date of delivery,
refusal or non-delivery indicated on the return receipt if deposited in the
United States mails, sent postage prepaid, certified or registered mail, return
receipt requested, addressed as aforesaid.

     6.7. Binding Effect; Assignment; Termination.  This letter agreement shall
          ---------------------------------------
be binding upon the Borrower, its successors and assigns and shall inure to the
benefit of the Borrower and the Bank and their respective permitted successors
and assigns.  The Borrower may not assign this letter agreement or any rights
hereunder without the express written consent of the Bank.  The Bank may, in
accordance with applicable law, from time to time assign or grant participations
in this letter agreement, the Revolving Loans, the Revolving Note and/or the
letters of credit issued hereunder and/or any of the other Obligations.  Without
limitation of the foregoing generality:

          (i)  The Bank may at any time pledge all or any portion of its rights
               under the Loan Documents (including any portion of the Revolving
               Note) to any of the 12 Federal Reserve Banks organized under
               Section 4 of the Federal Reserve Act, 12 U.S.C. Section 341. No
               such pledge or the enforcement thereof shall release the Bank
               from its obligations under any of the Loan Documents.

          (ii) The Bank shall have the unrestricted right at any time and from
               time to time, and without the consent of or notice to the
               Borrower, to grant to one or more banks or other financial
               institutions (each, a "Participant") participating interests in
               the Bank's obligation to lend hereunder and/or any or all of the
               Revolving Loans held by the Bank hereunder. In the event of any
               such grant by the Bank of a participating interest to a
               Participant, whether or not upon notice to the Borrower, the Bank
               shall remain responsible for the performance of its obligations
               hereunder and the Borrower shall continue to deal solely and
               directly with the Bank in connection with the Bank's rights and
               obligations hereunder. The Bank may furnish any information
               concerning the Borrower in its possession from time to time to
               prospective assignees and Participants; provided that the Bank
               shall require any such prospective assignee or Participant to
               agree in writing to maintain the confidentiality of such
               information to the same extent as the Bank would be required to
               maintain such confidentiality.

     The Borrower may terminate this letter agreement and the financing
arrangements made herein by giving written notice of such termination to the
Bank together with payment of the sum described in the second sentence of
(S)6.3; provided that no such termination will release or waive any of the
Bank's rights or remedies or any of the Borrower's obligations under this letter
agreement or any of the other Loan Documents unless and until the Borrower has
paid in full the Revolving Loans and all interest thereon and all fees and
charges payable in connection therewith and all letters of credit issued
hereunder have been terminated.

                                      -24-
<PAGE>

     6.8. Consent to Jurisdiction.  The Borrower irrevocably submits to the non-
          -----------------------
exclusive jurisdiction of any Massachusetts court or any federal court sitting
within The Commonwealth of Massachusetts over any suit, action or proceeding
arising out of or relating to this letter agreement and/or the Revolving Note
and/or any of the other Obligations.  The Borrower irrevocably waives, to the
fullest extent permitted by law, any objection which it may now or hereafter
have to the laying of venue of any such suit, action or proceeding brought in
such a court and any claim that any such suit, action or proceeding has been
brought in an inconvenient forum.  The Borrower agrees that final judgment in
any such suit, action or proceeding brought in such a court shall be enforced in
any court of proper jurisdiction by a suit upon such judgment, provided that
service of process in such action, suit or proceeding shall have been effected
upon the Borrower in one of the manners specified in the following paragraph of
this (S)6.8 or as otherwise permitted by law.

     The Borrower hereby consents to process being served in any suit, action or
proceeding of the nature referred to in the preceding paragraph of this (S)6.8
either (i) by mailing a copy thereof by registered or certified mail, postage
prepaid, return receipt requested, to it at its address set forth in (S)6.6
(as such address may be changed from time to time pursuant to said (S)6.6) or
(ii) by serving a copy thereof upon it at its address set forth in (S)6.6
(as such address may be changed from time to time pursuant to said (S)6.6).

     6.9. Severability.  In the event that any provision of this letter
          ------------
agreement or the application thereof to any Person, property or circumstances
shall be held to any extent to be invalid or unenforceable, the remainder of
this letter agreement, and the application of such provision to Persons,
properties or circumstances other than those as to which it has been held
invalid and unenforceable, shall not be affected thereby, and each provision of
this letter agreement shall be valid and enforced to the fullest extent
permitted by law.

     6.10. Replacement Note.  Upon receipt of an affidavit of an officer of the
           ----------------
Bank as to the loss, theft, destruction or mutilation of the Revolving Note or
of any other Loan Document which is not of public record and, in the case of any
such mutilation, upon surrender and cancellation of such Revolving Note or other
Loan Document, the Borrower will issue, in lieu thereof, a replacement Revolving
Note or other Loan Document in the same principal amount (as to the Revolving
Note) and in any event of like tenor.

     6.11. Usury.  All agreements between the Borrower and the Bank are hereby
           -----
expressly limited so that in no contingency or event whatsoever, whether by
reason of acceleration of maturity of the Revolving Note or otherwise, shall the
amount paid or agreed to be paid to the Bank for the use or the forbearance of
the Indebtedness represented by the Revolving Note exceed the maximum
permissible under applicable law. In this regard, it is expressly agreed that it
is the intent of the Borrower and the Bank, in the execution, delivery and
acceptance of the Revolving Note, to contract in strict compliance with the laws
of The Commonwealth of Massachusetts. If, under any circumstances whatsoever,
performance or fulfillment of any

                                      -25-
<PAGE>

provision of the Revolving Note or any of the other Loan Documents at the time
such provision is to be performed or fulfilled shall involve exceeding the limit
of validity prescribed by applicable law, then the obligation so to be performed
or fulfilled shall be reduced automatically to the limits of such validity, and
if under any circumstances whatsoever the Bank should ever receive as interest
an amount which would exceed the highest lawful rate, such amount which would be
excessive interest shall be applied to the reduction of the principal balance
evidenced by the Revolving Note and not to the payment of interest. The
provisions of this (S)6.11 shall control every other provision of this letter
agreement and of the Revolving Note.

     6.12.  WAIVER OF JURY TRIAL.  THE BORROWER AND THE BANK HEREBY KNOWINGLY,
            --------------------
VOLUNTARILY AND INTENTIONALLY MUTUALLY WAIVE THE RIGHT TO A TRIAL BY JURY IN
RESPECT OF ANY CLAIM BASED HEREON, ARISING OUT OF, UNDER OR IN CONNECTION WITH
THIS LETTER AGREEMENT, THE REVOLVING NOTE OR ANY OTHER LOAN DOCUMENTS OR OUT OF
ANY COURSE OF CONDUCT, COURSE OF DEALING, STATEMENTS (WHETHER ORAL OR WRITTEN)
OR ACTIONS OF ANY PARTY.  THIS WAIVER CONSTITUTES A MATERIAL INDUCEMENT FOR THE
BANK TO ENTER INTO THIS LETTER AGREEMENT AND TO MAKE REVOLVING LOANS AND EXTEND
OTHER CREDIT AS CONTEMPLATED HEREIN.

     6.13.  Amendment and Restatement.  This letter agreement amends and
            -------------------------
restates in its entirety the Prior Agreement, and any and all defaults under the
Prior Agreement are hereby waived.  Upon the execution and delivery of this
letter agreement, neither the Borrower nor the Bank will have any further
obligations to each other under the Prior Agreement; provided that the Borrower
shall remain obligated to pay all interest, fees and other charges accruing
under the Prior Agreement to the date of this letter agreement, whether or not
same are presently due and payable.  All loans outstanding under the Prior
Agreement at the date hereof will be deemed at this date (without any
requirement for further documentation) to become Revolving Loans for the
purposes of this letter agreement and to be evidenced by the Revolving Note.
All letters of credit outstanding under the Prior Agreement at the date hereof
will be deemed at this date (without any requirement for further documentation)
to become letters of credit issued under this letter agreement.

     VII.  DEFINED TERMS
           -------------

     7.1. Definitions.  In addition to terms defined elsewhere in this letter
          -----------
agreement, as used in this letter agreement, the following terms have the
following respective meanings:

     "ACH Exposure" - As defined in (S)1.6.

     "Aggregate Bank Liabilities" - At any time, the sum of (i)_the principal
amount of all Revolving Loans then outstanding, plus (ii) all then undrawn
                                                ----
amounts of letters of credit issued by the Bank for the account of the Borrower
(other than the Existing L/C described in the first

                                      -26-
<PAGE>

paragraph of (S)1.5), plus (iii) all amounts then drawn on any such letter of
credit which at said date shall not have been reimbursed to the Bank by the
Borrower.

     "Borrowing Base" - As determined at any date, 80% of the aggregate
principal amount of the Qualified Receivables of the Borrower then outstanding.

     "Business Day" - Any day which is not a Saturday, nor a Sunday nor a public
holiday under the laws of the United States of America or The Commonwealth of
Massachusetts applicable to a national bank.

     "Capital Base" - At any time, the sum of (i) the consolidated Tangible Net
Worth of the Borrower and Subsidiaries then existing, plus (ii) the principal
amount of Subordinated Debt of the Borrower then outstanding (nothing contained
herein being deemed to authorize the incurrence of any additional Subordinated
Debt).

     "Collateral" - All property now or hereafter owned by the Borrower or in
which the Borrower now or hereafter has any interest which is described as
"Collateral" in the Security Agreement or in the Pledge or in (S)7.2(b) below.

     "Current Liabilities" - All liabilities of the Borrower and/or any
Subsidiary of the Borrower which would properly be shown as current liabilities
on a consolidated balance sheet of the Borrower prepared in accordance with
generally accepted accounting principles consistently applied.  Further,
"Current Liabilities" will in any event be deemed to include all Revolving
Loans.

     "Determination Date" - As defined in (S)3.7.

     "ERISA" - The Employee Retirement Income Security Act of 1974, as amended.

     "Existing L/C" - As defined in (S)1.5.

     "Expiration Date" - September 1, 1999, unless extended pursuant to (S)1.3,
which extension may be given or withheld by the Bank in its sole discretion.

     "F/X Exposure" - As defined in (S)1.7.

     "Indebtedness" - All obligations of a Person, whether current or long-term,
senior or subordinated, which in accordance with generally accepted accounting
principles would be included as liabilities upon such Person's balance sheet at
the date on which Indebtedness, is to be determined, and shall also include
guaranties, endorsements (other than for collection in the ordinary course of
business) or other arrangements whereby responsibility is assumed for the
obligations of others, whether by agreement to purchase or otherwise acquire the
obligations of others, including any agreement, contingent or otherwise, to
furnish funds through the purchase of goods, supplies or services for the
purpose of payment of the obligations of others.

                                      -27-
<PAGE>

     "Liabilities" - All Indebtedness of the Borrower and/or any of its
Subsidiaries which would properly be shown as liabilities on the face of a
consolidated balance sheet of the Borrower prepared in accordance with generally
accepted accounting principles consistently applied, and not merely in the
footnotes to such balance sheet.

     "Loan Documents" - Each of this letter agreement, the Revolving Note, the
Security Agreement, the Intellectual Property Security Agreement, the Pledge and
each other instrument, document or agreement evidencing, securing, guaranteeing
or relating in any way to any of the Revolving Loans or any of the letters of
credit issued hereunder or to any Foreign Exchange Contract or ACH transaction,
all whether now existing or hereafter arising or entered into.

     "Maximum Revolving Amount" - At any date as of which same is to be
determined, the amount by which (x) $5,000,000 exceeds (y) the sum of (i) all
then undrawn amounts of letters of credit issued by the Bank for the account of
the Borrower (other than the Existing L/C described in the first paragraph of
(S)1.5), plus (ii) all amounts then drawn on any letter of credit which at said
date shall not have been reimbursed to the Bank by the Borrower.

     "Net Current Assets"  -  Such current assets of the Borrower as consist of
cash, cash-equivalents, Receivables (less an allowance for bad debt consistent
with the Borrower's prior experience) and inventory (including finished goods
inventory, raw materials and work-in-process, net of a reserve for damaged,
obsolete or returned inventory and any other reserves required by generally
accepted accounting principles consistently applied).

     "Net Income" (or "Net Loss") - The book net income (or book net loss, as
the case may be) of a Person for any period, after all taxes actually paid or
accrued and all expenses and other charges determined in accordance with
generally accepted accounting principles consistently applied.

     "Obligations" - All Indebtedness, covenants, agreements, liabilities and
obligations, now existing or hereafter arising, made by the Borrower with or for
the benefit of the Bank or owed by the Borrower to the Bank in any capacity.
"Obligations" includes, without limitation, the Revolving Loans and obligations
with respect to ACH transactions, letters of credit and Foreign Exchange
Contracts issued hereunder.

     "PBGC" - The Pension Benefit Guaranty Corporation or any successor thereto.

     "Person" - An individual, corporation, limited liability company,
partnership, joint venture, trust or unincorporated organization, or a
government or any agency or political subdivision thereof.

     "Pledge" - As defined in (S)1.1 above.

     "Prior Agreement" - As defined in the introductory paragraph of this letter
agreement.

                                      -28-
<PAGE>

     "Qualified Receivables" - Only those Receivables of the Borrower which
arise out of bona fide sales made to customers of the Borrower (which customers
are located in the United States and are unrelated to the Borrower) in the
ordinary course of the Borrower's business and which remain unpaid no more than
90 days past the respective invoice dates of such Receivables, the payment of
which is not in dispute.  Unless the Bank in its sole discretion otherwise
determines with respect to any Receivable, a Receivable which would otherwise be
a Qualified Receivable shall be deemed not to be a Qualified Receivable (i) if
the Bank does not have a fully perfected first priority security interest in
such Receivable; (ii) if such Receivable is not free and clear of all interests
in favor of any Person other than the interests of the Borrower and the Bank;
(iii) if such Receivable is subject to any deduction, off-set, contra account,
counterclaim or condition; (iv) if a field examination made by the Bank fails to
confirm that such Receivable exists and satisfies all of the criteria set forth
herein to be a Qualified Receivable; (v) if such Receivable is not properly
invoiced at the date of sale; (vi) if the customer or account debtor has
disputed liability or made any claim with respect to the Receivable or the
merchandise covered thereby or with respect to any other Receivable due from
said customer to the Borrower; (vii) if the customer or account debtor has filed
a petition for bankruptcy or any other application for relief under the
Bankruptcy Code or has effected an assignment for the benefit of creditors, or
if any petition or any other application for relief under the Bankruptcy Code
has been filed against said customer or account debtor, or if the customer or
account debtor has suspended business, become insolvent, ceased to pay its debts
as they become due, or had or suffered a receiver or trustee to be appointed for
any of its assets or affairs; (viii) if the customer or account debtor has
failed to pay other Receivables so that an aggregate of 25% of the total
Receivables owing to the Borrower by such customer or account debtor has been
outstanding for more than 90 days past their respective due dates; (ix) if such
Receivable is owed by the United States government or any agency or department
thereof (unless assigned to the Bank under the Federal Assignment of Claims
Act); or (x) if the Bank reasonably believes that collection of such Receivable
is insecure or that it may not be paid by reason of financial inability to pay
or otherwise, or that such Receivable is not for any reason suitable for use as
a basis for borrowing hereunder (provided that no Receivable which would
otherwise be a Qualified Receivable will be deemed not to be a Qualified
Receivable due to the application of this clause (x) unless the Bank shall have
given the Borrower at least 30 days' prior notice that the Receivable in
question (or all Receivables owed by the same account debtor) will not be
considered to be Qualified Receivables due to the application of this clause
(x)).  Notwithstanding the first sentence of this definition, the Borrower may
include within "Qualified Receivables" any Receivable which meets all of the
criteria set forth above to be a Qualified Receivable except that the relevant
customer is located outside the United States; provided that such Receivable is
secured by a letter of credit in form and substance satisfactory to the Bank and
issued by a financial institution satisfactory to the Bank or is insured by
Eximbank credit insurance or other credit insurance satisfactory to the Bank.
Further, if credit insurance meeting the criteria of the immediately preceding
sentence becomes applicable to any Receivable during the month of December 1998
and such insurance is retroactive to December 1, 1998, the Borrower may at any
time thereafter prior to January 15, 1999 deliver to the Bank a pro forma
Borrowing Base certificate as at December 1, 1998 giving effect to such
retroactive

                                      -29-
<PAGE>

credit insurance and such pro forma certificate will be deemed to replace any
Borrowing Base certificate as at December 1, 1998 theretofore delivered pursuant
to clause (iv) of (S)3.6.

     "Receivables" - All of the Borrower's present and future accounts and
accounts receivable representing a right to payment for goods sold or for
services rendered.

     "Revolving Note" - As defined in (S)1.1.

     "Senior Liabilities" - All Liabilities which are not Subordinated Debt.

     "Subordinated Debt" - Any Indebtedness of the Borrower which is expressly
subordinated, pursuant to a subordination agreement in form and substance
satisfactory to the Bank, to all Indebtedness now or hereafter owed by the
Borrower to the Bank.

     "Subsidiary" - Any corporation or other entity of which the Borrower and/or
any of its Subsidiaries, directly or indirectly, owns, or has the right to
control or direct the voting of, fifty (50%) percent or more of the outstanding
capital stock or other ownership interest having general voting power (under
ordinary circumstances).

     "Tangible Net Worth" - An amount equal to the total assets of any Person
(excluding (i) the total intangible assets of such Person and (ii) any assets
representing amounts due from any officer or employee of such Person or from any
Subsidiary of such Person) minus the total liabilities of such Person.  Total
intangible assets shall be deemed to include, but shall not be limited to, the
excess of cost over book value of acquired businesses accounted for by the
purchase method, formulae, trademarks, trade names, patents, patent rights and
deferred expenses (including, but not limited to, unamortized debt discount and
expense, organizational expense, capitalized software costs and experimental and
development expenses).

     "WED" - Western Equipment Developments (Holdings) Ltd., a Subsidiary of the
Borrower.

     Any defined term used in the plural preceded by the definite article shall
be taken to encompass all members of the relevant class.  Any defined term used
in the singular preceded by "any" shall be taken to indicate any number of the
members of the relevant class.

     7.2. Security Agreement.  (a)  The Borrower acknowledges and agrees that
          ------------------
the "Obligations" described in and secured by the Security Agreement include,
without limitation, all of the obligations of the Borrower under the Revolving
Note and/or this letter agreement and/or with respect to any letter of credit
which may be issued by the Bank for the account of the Borrower, as well as
obligations in respect of ACH transactions and Foreign Exchange Contracts.

     (b) The Security Agreement is hereby modified to provide as follows:

                                      -30-
<PAGE>

         (i) That the "Collateral" subject thereto includes, without limitation
     and in addition to the Collateral described therein, all of the Borrower's
     files, books and records (including, without limitation, all electronically
     recorded data) all whether now owned or existing or hereafter acquired,
     created or arising. The Borrower hereby grants to the Bank a security
     interest in all such Collateral in order to secure the full and prompt
     payment and performance of all of the Obligations.

         (ii) That, upon the occurrence of any Event of Default (as defined in
     (S)5.1 of this letter agreement), the Bank may, at any time, notify account
     debtors that the Collateral has been assigned to the Bank and that payments
     by such account debtors shall be made directly to the Bank. At any time
     after the occurrence of an Event of Default, the Bank may collect the
     Borrower's Receivables, or any of same, directly from account debtors and
     may charge the collection costs and expenses to the Borrower.

                                      -31-
<PAGE>

    This letter agreement is executed, as an instrument under seal, as of the
day and year first above written.

                                    Very truly yours,

                                    ASECO CORPORATION


                                    By: /s/Mary R. Barletta
                                        ------------------------------------
                                        Name:
                                        Title: Chief Financial Officer
Accepted and agreed:

FLEET NATIONAL BANK


By: /s/Thomas W. Davies
    ---------------------------
    Its Senior Vice President

                                      -32-
<PAGE>

                              DISCLOSURE SCHEDULE



Item 2.1(a)      Jurisdictions in which Borrower is qualified; Subsidiaries

Item 2.1(d)      Litigation

Item 2.1(i)      Collateral locations; record owners

Item 2.1(j)      Intellectual property

Item 4.1         Existing Indebtedness

Item 4.2         Existing Liens

Item 4.3         Existing Guaranties

Item 4.5         Existing Loans

                                      -33-