<PAGE>   1
                                                                   Exhibit 10


                              CREDIT LINE AGREEMENT


     Credit Line Agreement, dated as of June 25, 1997, by and between
BankBoston, N.A. (formerly known as The First National Bank of Boston), a
national banking association with its head office at 100 Federal Street, Boston,
Massachusetts 02110 (the "Bank"), and Dynatech Corporation, a Massachusetts
corporation, with its principal place of business at Three New England Executive
Park, Burlington, Massachusetts 01803 (the "Borrower").

     WHEREAS, the Borrower desires to enter into this Agreement so that it may
borrow funds from the Bank for general working capital and corporate purposes;

     WHEREAS, the Bank is willing to advance funds to the Borrower from time to
time on a demand discretionary basis on the terms set forth below;

     NOW THEREFORE, the parties hereto agree as follows:

     [SEC]1. DEFINITIONS. As used herein, the following terms shall have the
meanings assigned to them below:

     "Advance Request" has the meaning specified in [SEC]3.1 hereof.

     "Agreement" means this Credit Line Agreement, including the Schedules
hereto.

     "Articles of Organization" means the Articles of Organization of the
Borrower, dated November 21, 1968, with all amendments thereto.


     "Bank" has the meaning specified in the introductory paragraph hereof.

     "Borrower" has the meaning specified in the introductory paragraph hereof.

     "Domestic Business Day" means a day on which commercial banks are open for
the purpose of transacting business in Boston, Massachusetts.

     "Domestic Lending Office" means, initially, the office of the Bank
designated as such on SCHEDULE 1 attached hereto; thereafter, such other office
of the Bank, if any, located in the United States that shall be making or
maintaining M/M Rate Advances.

     "Federal Funds Effective Rate" means, for any day, the rate per annum equal
to the weighted average of the rates on overnight federal funds transactions
with members of the Federal Reserve System arranged by federal funds brokers, as
published for such day (or, if such day is not a Domestic Business Day, for the
next preceding Domestic 
<PAGE>   2
                                      -2-


Business Day) by the Federal Reserve Bank of New York, or, if such rate is not
so published for any day that is a Domestic Business Day, the average of the
quotations for such day on such transactions received by the Bank from three (3)
funds brokers of recognized standing selected by the Bank.

     "Interest Period" means, with respect to each M/M Rate Advance, the period
commencing on the date such M/M Rate Advance, as the case may be, is made and
ending not more than thirty (30) days thereafter; PROVIDED that:

            (i) any Interest Period with respect to a M/M Rate Advance which
      would otherwise end on a day which is not a Domestic Business Day shall be
      extended to the next succeeding Domestic Business Day; and

            (ii) any Interest Period with respect to any M/M Rate Advance which
      would otherwise end after either the Termination Date or the making of
      demand by the Bank for the repayment of such M/M Rate Advance shall end on
      the Termination Date or the date of demand, as the case may be.

     "Line of Credit" has the meaning specified in [SEC]2 hereof.

     "Loan Account" has the meaning specified in [SEC]3.6 hereof.

     "Maximum Amount" has the meaning specified in [SEC]2 hereof.

     "M/M Rate Advance" means any advance upon which interest will accrue based
on the Money Market Rate as set forth in [SEC]3.3 hereof.

     "Money Market Rate" means the fixed rate of interest quoted by the Bank on
the first day of any Interest Period which rate the Bank is willing to charge
with respect to a M/M Rate Advance to be made by the Bank during such Interest
Period.

     "Obligations" means all of the obligations (whether direct or indirect,
absolute or contingent, primary or secondary, due or to become due, now existing
or hereafter arising) of the Borrower to the Bank hereunder.

     "Regulation U" means Regulation U of the Board of Governors of the U.S.
Federal Reserve System, as in effect from time to time.

     "Revolver Agreement" means that certain Revolving Credit Agreement dated as
of April 29, 1997 by and among the Borrower, BankBoston, N.A. and certain other
lending institutions party thereto, and BankBoston, N.A. and Mellon Bank, N.A.
as agents for such banks, as the same may be amended, restated, modified and
supplemented from time to time, and, in the event the same ceases to exist prior
to the expiration of this Agreement, in such form as such agreement existed
immediately prior to its expiration.

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                                      -3-


     "Termination Date" means June __, 1998.

     [SEC]2. The Credit
             ----------

     [SEC]2.1 CREDIT LINE. Subject to the terms and conditions of this
Agreement, the Bank agrees to make available to the Borrower a line of credit (a
"Line of Credit") under which the Bank may from time to time in its sole and
absolute discretion make M/M Rate Advances to the Borrower. The maximum
principal amount of all M/M Rate Advances outstanding at any particular time
under the Borrower's Line of Credit shall not exceed $30,000,000.

As used herein, the term "Maximum Amount" means, at any particular time, the
maximum amount that the Borrower is permitted to borrow at such time in
accordance with the provisions of the preceding sentence.

     [SEC]3. Advances.
             --------

     [SEC]3.1. PROCEDURAL REQUIREMENTS. All M/M Rate Advances shall be requested
and funded in accordance with the procedures set forth below. Each request for a
M/M Rate Advance shall be referred to as an "Advance Request".

     [SEC]3.1.1. ADVANCE REQUESTS. In the event the Borrower desires to borrow
any M/M Rate Advance, the Borrower may request by telephone (a "Rate Request")
that the Bank on any Business Day give the Borrower a firm quotation of the
Money Market Rate which would be applicable to a M/M Rate Advance to be made on
such day for an Interest Period commencing on the date of such Rate Request.
Each Rate Request shall (a) specify the aggregate principal amount of the M/M
Rate Advance to which such rate quotation would apply (which shall be in
integral multiples of $100,000), (b) the Interest Period being requested for
such M/M Rate Advance and (c) be received by the Bank not later than 11:00 a.m.,
Boston time, on such day. At or before 12:00 noon, Boston time, the Bank shall
notify the Borrower by telephone, telex or telecopier of the Money Market Rate
which would apply to such M/M Rate Advance; PROVIDED, HOWEVER, that the Bank
may, in its sole and absolute discretion, decline to give any such quotation.
Such rate quotation shall remain in effect for one hour on such day. If the
Borrower wishes to accept the rate quotation from the Bank, and thereby request
such M/M Rate Advance, the Borrower shall give the Bank written notice of
acceptance (a "M/M Rate Acceptance"), no later than the expiration of such one
hour period. Each M/M Rate Acceptance may be given by telex or telecopier
(confirmed by letter), and shall confirm the Borrower's acceptance of such rate
quotation and the aggregate principal amount of the M/M Rate Advance requested.
Each Advance Request made by the Borrower shall

     (a) obligate the Borrower to borrow the principal amount of the M/M Rate
Advance requested thereby; and

     (b) constitute a representation and warranty by the Borrower to the Bank
that (i) the M/M Rate Advance requested thereby (A) is permitted under the
Borrower's
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                                      -4-


Articles of Organization and by-laws, in each case as then in effect
(B) will not, when made, cause the aggregate indebtedness of the Borrower
hereunder to exceed the Maximum Amount then in effect, and (C) will be used by
the Borrower only in accordance with the provisions of [SEC]3.7 hereof, and (ii)
all of the representations and warranties of the Borrower contained in [SEC]4
hereof are true and correct on and as of the date of such Advance Request (and,
if applicable, M/M Rate Acceptance) and the date of such M/M Rate Advance as
though made on and as of such dates.

     An Advance Request made by the Borrower shall be valid if given by an
officer or other agent of the Borrower identified as being an officer or agent
authorized by the Borrower to give such notices in a certificate executed by the
Clerk or Assistant Clerk of the Borrower and delivered to the Bank. The Bank is
authorized to accept any telephonic Advance Requests or Rate Requests if, in
good faith, it believes them to have been given by such an authorized person,
and the Borrower shall be obligated to borrow the amount of the M/M Rate Advance
requested thereby and repay all such M/M Rate Advances made by the Bank. Any
Advance Request or Rate Request made by an officer or other agent of the
Borrower identified as being an officer or agent authorized by the Borrower
shall be binding upon the Borrower until such time as the Bank has received
written notification from the Borrower in the form of a certificate executed by
the Clerk or Assistant Clerk of the Borrower and delivered to the Bank that such
officer or agent, as the case may be, is no longer authorized by the Borrower to
give such notices

     [SEC]3.1.2. FUNDING THE ADVANCES. If a M/M Rate Advance has been requested
by the Borrower pursuant to [SEC]3.1.1. hereof, and the Borrower has delivered
to the Bank all of the documents required to be delivered prior to such M/M Rate
Advance pursuant to [SEC]6 hereof, the Bank may, in its sole and absolute
discretion, make such M/M Rate Advance to the Borrower. Each M/M Rate Advance
made by the Bank to the Borrower shall be deposited or wired at the Borrower's
expense IN accordance with the wiring instructions set forth in Schedule 3.1.2
hereto, as amended and in effect from time to time, to the Borrower's account
maintained with the Bank.

     [SEC]3.1.3. LIMIT ON ADVANCES. No advance shall be made if the Interest
Period therefor would end after the Termination Date.

     [SEC]3.2. REPAYMENT OF ADVANCES. The principal amount of each M/M Rate
Advance shall be repaid by the Borrower upon the earlier of (a) thirty (30) days
(or such lesser period chosen by the Borrower when such M/M Rate Advance is
made) after the date such M/M Rate Advance is made to the Borrower pursuant to
[SEC]3.1.2, (b) demand by the Bank, or (c) termination of the Borrower's Line of
Credit pursuant to [SEC]3.9 hereof. All M/M Rate Advances, together with all
accrued interest thereon and any and all other amounts payable hereunder, shall
become immediately and automatically due and payable, without demand,
presentment, protest or notice of any kind, upon the insolvency, general
assignment, receivership, bankruptcy or dissolution of the Borrower. The
Borrower does hereby forever waive presentment, demand, protest, notice of
nonpayment or dishonor in connection with this Agreement.

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                                      -5-


     [SEC]3.3. Interest.

     (a) Subject to [SEC]3.3(b) hereof, each M/M Rate Advance shall bear
interest on the outstanding principal amount thereof, for the period commencing
with the date such M/M Rate Advance is made or continued through and including
the earlier to occur of the maturity of such M/M Rate Advance or the last day of
the Interest Period applicable thereto, at a rate per annum equal to the Money
Market Rate. Such interest shall be payable in arrears for each Interest Period
on the last day thereof.

     (b) Amounts overdue hereunder (including, without limitation, overdue
principal, and, to the extent permitted by law, overdue interest, fees, charges
and expenses) shall bear interest until paid in full (after as well as before
judgment) at a rate equal to the sum of two percent (2%) above the otherwise
applicable interest rate hereunder.

     [SEC]3.4. Prepayments. Subject to [SEC]3.10, M/M Rate Advances made
hereunder may be prepaid on any Domestic Business Day. If at any time during the
term hereof the total outstanding principal amount of all M/M Rate Advances made
to the Borrower hereunder exceeds the Maximum Amount then in effect, the
Borrower shall immediately repay to the Bank the amount of such excess. As
provided in [SEC]3.10, the Borrower shall indemnify the Bank for any and all
reasonable fees, expenses, penalties or other breakage costs associated with the
prepayment or repayment of any M/M Rate Advance other than on the last day of
the Interest Period with respect thereto.

     [SEC]3.5. Repayment; Loan Accounts. The Borrower promises to pay upon the
earlier of (a) thirty (30) days (or such lesser period chosen by the Borrower
when such M/M Rate Advance is made) after the date such M/M Rate Advance is made
to the Borrower pursuant to [SEC]3.1.2, (b) demand by the Bank, or (c)
termination of the Borrower's Line of Credit pursuant to [SEC]3.9 hereof, and
there shall become absolutely due and payable on such date, all of the M/M Rate
Advances outstanding on such date, together with any and all accrued and unpaid
interest thereon. The Bank will maintain a separate account on its books for the
Borrower (a "Loan Account") on which will be recorded, in accordance with the
Bank's customary accounting practice, (a) all M/M Rate Advances made by the Bank
to the Borrower, (b) all payments of such M/M Rate Advances made to the Bank,
and (c) all other charges and expenses properly chargeable to the Borrower
hereunder. The debit balance of the Borrower's Loan Account shall reflect the
amount of the Borrower's indebtedness from time to time to the Bank hereunder.
Any written statement delivered by the Bank to the Borrower reflecting the
amount of the Borrower's indebtedness as of any time shall, in the absence of
manifest error, constitute prima facie evidence of the indebtedness of the
Borrower to the Bank hereunder as of such time.

     [SEC]3.6. COMPUTATIONS AND PAYMENTS. All computations hereunder shall be
computed on the basis of the actual number of days elapsed and a 360-day year.
All payments shall be made to the Bank's Loan Department at the address
specified on the first page hereof to the attention of Debra E. DelVecchio, Vice
President, High Technology Division. Whenever any payment of principal of, or
interest on, M/M Rate 

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                                      -6-


Advances or of fees shall be due on a day which is not a Domestic Business Day,
the date for payment thereof shall be extended to the next succeeding Domestic
Business Day. If the date for any payment of principal is extended by operation
of law or otherwise, interest thereon shall be payable for such extended time.
All payments by the Borrower hereunder shall be made in United States dollars
without setoff or counterclaims and free and clear of and without deduction for
any taxes, levies, imposts, duties, charges, fees, deductions, withholdings,
compulsory loans, restrictions or conditions of any nature now or hereafter
imposed or levied by any jurisdiction or any political subdivision thereof or
taxing or other authority therein unless the Borrower is compelled by law to
make such deduction or withholding. If any such obligation is imposed upon the
Borrower with respect to any amount payable by it hereunder, the Borrower will
pay to the Bank on the date on which such amount is due and payable hereunder
such additional amount in United States dollars as shall be necessary to enable
the Bank to receive the same net amount which the Bank would have received on
such due date had no such obligation been imposed upon the Borrower. The
Borrower will deliver promptly to the Bank certificates or other valid vouchers
for all taxes and other charges deducted from or paid with respect to payments
made by the Borrower hereunder.

     [SEC]3.7. USE OF PROCEEDS. THE proceeds of each M/M Rate Advance made
hereunder shall be used by the Borrower for working capital and general
corporate purposes . No portion of any M/M Rate Advance is to be used for the
purpose of purchasing or carrying any "margin stock" or "margin securities" as
such terms are used in Regulations U and Regulations X of the Board of Governors
of the Federal Reserve System, 12 C.F.R. Parts 221 and 224.

     [SEC]3.8. DISCRETIONARY DEMAND FACILITY. It is acknowledged and agreed by
the Borrower with the Bank that the Bank has no obligation to make any M/M Rate
Advance hereunder, and that the decision whether or not to make any M/M Rate
Advance requested by the Borrower under its Line of Credit is within the sole
and exclusive discretion of the Bank. It is further understood and agreed by the
Borrower that, notwithstanding any provision hereof to the contrary, each M/M
Rate Advance made by the Bank hereunder, and all interest and charges with
respect thereto, shall be payable as provided in [SEC][SEC]3.2 and 3.3 hereof.

     [SEC]3.9. TERMINATION OF LINE OF CREDIT. The Bank shall have the right, in
its sole and absolute discretion, to terminate the Borrower's Line of Credit
upon written notice of termination from the Bank to the Borrower. The foregoing
notwithstanding, the Line of Credit shall terminate automatically on the
Termination Date.

     [SEC]3.10. INDEMNITY. The Borrower agrees to indemnify the Bank and to hold
the Bank harmless from and against any loss, cost or expense that the Bank may
sustain or incur as a consequence of (a) default by the Borrower in payment of
the principal amount of or any interest on any M/M Rate Advance as and when due
and payable, including any such loss or expense arising from interest or fees
payable by the Bank to lenders of funds obtained by it in order to maintain its
M/M Rate Advances M/M Rate Advances, (b) default by the Borrower in making a
borrowing after the Borrower has 

<PAGE>   7
                                      -7-


given an Advance Request or M/M Rate Acceptance or (c) the making of any payment
of a M/M Rate Advance on a day that is not the last day of the applicable
Interest Period with respect thereto, including interest or fees payable by the
Bank to lenders of funds obtained by it in order to maintain any such M/M Rate
Advances. A certificate setting forth any additional amounts payable pursuant to
this [SEC]3.10 and a brief explanation of such amounts which are due, submitted
by the Bank to the Borrower, shall be conclusive, absent manifest error, that
such amounts are due and owing.

     [SEC]4. REPRESENTATIONS AND WARRANTIES. The Borrower represents and
warrants to the Bank as follows:

     (a) The Borrower is Massachusetts corporation, validly existing and in good
standing under the laws of the Commonwealth of Massachusetts and is qualified to
do business in every other jurisdiction where lack of such qualification would
have a material adverse effect on the business, assets or condition (financial
or otherwise) of the Borrower, and has all corporate powers and all governmental
licenses, authorizations, consents and approvals required to carry on its
business as now conducted.

     (b) The execution, delivery and performance by the Borrower of this
Agreement (i) are within its powers, (ii) have been duly authorized by all
necessary action, and (iii) will not (A) contribute to or result in a breach of
or default under or conflict with any existing applicable law, order, regulation
or ruling of any governmental or regulatory agency or authority, or any order,
writ, injunction or ruling of any court or other tribunal, or any indenture,
lease, agreement, instrument or other undertaking to which the Borrower is a
party or by which it or its property or assets may be bound or affected, or (B)
result in the imposition of any liens or encumbrances on any property or assets
of the Borrower, or (C) violate any provision of the Borrower's Articles of
Organization or by-laws, as presently in effect.

     (c) This Agreement is a legally valid and binding obligation of the
Borrower, enforceable against the Borrower in accordance with its terms.

     (d) Except for approvals which the Borrower has obtained prior to the date
hereof and which are set forth on SCHEDULE 4(d)(i) hereto, no authorization,
approval, or other action by, and no notice to or filing with, any shareholder
of the Borrower, creditor, or governmental or regulatory body, agency or
authority is required for the due and valid execution, delivery and performance
of this Agreement by the Borrower or the exercise by the Bank of its rights and
remedies under this Agreement.

     (e) The Borrower is in compliance with all of the provisions of [SEC]5
hereof.

     (f) That each of the representations and warranties of the Borrower
contained in [SEC]8.3 - 8.22 of the Revolver Agreement are incorporated herein
by reference, with the intention that each of the representations contained in
[SEC]8.3 - 8.22 of the Revolver Agreement shall have the same effect in this
Agreement as if each such representation and warranty was set forth verbatim
herein, are true as of the date as of which they were made and shall also be
true at or as of the time of the making of any 

<PAGE>   8
                                      -8-


M/M Rate Advance, with the same effect as if made at and as of that time (except
to the extent of changes resulting from transactions contemplated or permitted
by this Agreement or the Revolver Agreement and changes occurring in the
ordinary course of business that singly or in the aggregate are not materially
adverse and to the extent that such representation and warranties relate
expressly to an earlier date).

     [SEC]5. Covenants
             ---------

     [SEC]5.1. Covenants in Effect until Termination of Agreement. Until all of
the Obligations have been performed in full and this Line of Credit has been
terminated as provided herein, the Borrower covenants that it will, and where
applicable cause each of its Subsidiaries to, perform, comply with and observe
each and every affirmative covenants contained in [SEC][SEC]9.2 - 9.12 and 9.14,
of the Revolver Agreement. The foregoing covenant in this [SEC]5.1 is made in
this Agreement by the Borrower to the Bank with the intention that each covenant
contained in [SEC][SEC]9.2 - 9.12 and 9.14 of the Revolver Agreement shall have
the same effect in this Agreement as if each such covenant was set forth
verbatim herein. The foregoing covenant in this [SEC]5.1 shall survive
termination, cancellation, or recession of the Revolver Agreement and shall not
be affected by the termination, cancellation or recession of the Revolver
Agreement.

     [SEC]5.2. Covenants in Effect While Advances Are Outstanding. The Borrower
covenants that, so long as any principal of or interest on any M/M Rate Advance
made to it hereunder is outstanding:

     (a) It will not permit the aggregate outstanding principal amount of all
M/M Rate Advances made to it hereunder to exceed at any particular time the
Maximum Amount in effect at such time.

     (b) It will not, so long as any M/M Rate Advance is outstanding hereunder,
create or permit to exist any encumbrance or lien in favor of any person or
entity other than the Bank upon any of the Borrower's assets other than
encumbrances permitted pursuant to the Revolver Agreement.

     (c) It will not create, incur, permit to exist, or be or remain liable for
any indebtedness, other than indebtedness owed to the Bank hereunder and
indebtedness permitted by the Revolver Agreement.

     (d) It will notify the Bank promptly of (i) any material change in its
method of business and (ii) the occurrence of any event which would make any of
the representations and warranties contained herein, or in any document,
instrument or certificate delivered in connection herewith, untrue or inaccurate
in any material respect.

     [SEC]6. DOCUMENTS TO BE DELIVERED AT SIGNING. The Borrower shall deliver to
the Bank simultaneously with the signing of this Agreement the following
documents (and this Agreement shall not become effective until such time as the
Bank receives the following or waives the delivery requirement in writing):


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                                      -9-


     (a) a Clerk or Assistant Clerk's Certificate certifying that no changes
have occurred to the Borrower's Articles of Organization and by-laws since the
date previously delivered to the Bank pursuant to the Revolver Agreement;

     (b) copies, certified as of a recent date by the Clerk of the Borrower, of
all resolutions of the Borrower's Board of Directors authorizing this Agreement
and the transactions contemplated hereby;

     (c) an incumbency certificate, executed by the Clerk of the Borrower,
setting forth the names and specimen signatures of each person authorized to
request Advances, give notices, sign or act on behalf of the Borrower in
connection with the transactions contemplated hereby; and

     (d) certificate of the Secretary of State of the Commonwealth of
Massachusetts as to the legal existence and good standing of the Borrower.

     [SEC]7. Change in Circumstances.
             -----------------------
  
     [SEC]7.1. INCREASED COST AND REDUCTION OF RETURN. (a) If any change in any
existing applicable law, rule or regulation, or any new law, rule or regulation,
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 (or its
Domestic Lending Office) with any request or directive (whether or not having
the force of law) of any such authority, central bank or comparable agency in
connection therewith:

            (i) shall subject the Bank (or its Domestic Lending Office) to any
      tax, duty, levy, impost, fee, deduction, withholding of any nature or
      other charge with respect to its Advances, or shall change the basis of
      taxation of payments to any Bank (or its Domestic Lending Office) of the
      principal of or interest on its Advances or any other amounts due under
      this Agreement, in each case except for any tax on, or changes in the rate
      of tax on the overall net income of the Bank or its Domestic Lending
      Office imposed by the jurisdiction in which the Bank's principal executive
      office or Domestic Lending Office is located; or

            (ii) shall impose, modify or deem applicable any reserve (including,
      without limitation, any such requirement imposed by the Board of Governors
      of the Federal Reserve System), special deposit, reserve, liquidity,
      capital adequacy, insurance assessment or similar requirement against
      assets of, deposits with or for the account of, or credit extended by, the
      Bank (or its Domestic Lending Office) or shall impose on the Bank (or its
      Domestic Lending Office) any other condition affecting its M/M Rate
      Advances;

and the result of any of the foregoing is to increase the cost to the Bank (or
its Domestic Lending Office) of making, funding, issuing, renewing, extending or
maintaining any M/M Rate Advance, or to reduce the amount of any sum received or
receivable by the 

<PAGE>   10
                                      -10-


Bank (or its Domestic Lending Office) under this Agreement with respect thereto,
or require the Bank to make any payment or to forego any interest or other sum
by an amount deemed by the Bank to be material, then, within fifteen (15) days
after demand by the Bank, the Borrower shall pay to the Bank such additional
amount or amounts as will compensate the Bank for such increased cost or
reduction.

     (b) The Bank will promptly notify the Borrower of any event of which it has
knowledge, occurring after the date hereof, which will entitle the Bank to
compensation pursuant to this [SEC]7. A certificate of the Bank claiming
compensation under this [SEC]7 and setting forth the additional amount or
amounts to be paid to it hereunder and THE calculations used in determining such
additional amount or amounts shall be conclusive in the absence of manifest
error. In determining such amount, the Bank may use any reasonable averaging and
attribution methods.

     [SEC]8. SETOFF. Regardless of the adequacy of any collateral, during the
continuance of any Event of Default, any deposits, balances or other sums
credited by or due from the Bank to the Borrower may be, at any time or from
time to time, set off and applied by the Bank, in such order as the Bank in its
sole discretion may determine, against all or any part of the Obligations.

     [SEC]9. EXPENSES. (a) The Borrower shall pay to the Bank promptly upon
demand all reasonable costs, fees, expenses and disbursements (including,
without limitation, any taxes and legal and other professional fees) incurred by
the Bank in connection with the preparation, negotiation, execution, amendment,
administration and/or enforcement of this Agreement and the other documents and
agreements referred to herein including the reasonable fees and out-of-pocket
expenses of counsel for the Bank with respect thereto. The Borrower shall
indemnify the Bank against any transfer taxes, documentary taxes, assessments or
charges made by any governmental authority by reason of the execution and
delivery of this Agreement.

     (b) The Borrower agrees to indemnify the Bank and hold the Bank harmless
from and against any and all liabilities, losses, damages, costs and expenses of
any kind, including, without limitation, the reasonable fees and disbursements
of counsel, which may be incurred by the Bank in connection with any
investigative, administrative or judicial proceeding (whether or not the Bank
shall be designated a party thereto) relating to or arising out of this
Agreement or any actual or proposed use of proceeds of Advances hereunder,
provided that the Bank shall not have the right to be indemnified hereunder for
its own gross negligence or willful misconduct as finally determined by a court
of competent jurisdiction.

     [SEC]10. NOTICE. Except as otherwise expressly provided herein, all notices
hereunder to any party shall be in writing and shall be delivered in hand,
mailed by United States registered or certified first-class mail, postage
prepaid, sent by overnight courier or sent by telegraph, telex, facsimile or
telecopy and confirmed by delivery via courier or postal service, addressed to
such party to the attention of the person specified in the following sentence at
the address set forth on the first page hereof, or to such other person or
address as such party may designate to the other party hereto by notice


<PAGE>   11
                                      -11-


delivered in accordance with this [SEC]10. All NOTICES to the Borrower shall be
addressed to the attention of the Chief Financial Officer at the Borrower, at
Three New England Executive Park, Burlington, Massachusetts 01803, and all
notices from the Borrower to the Bank shall be addressed to the attention of
Debra E. DelVecchio, Vice President, 100 Federal Street, Boston, Massachusetts
02110. Any such notice sent by hand or by telegraph, telex or telecopy shall be
deemed delivered to such party on the day such notice was sent; and any such
notice mailed as set forth above shall be deemed delivered to such party two (2)
Domestic Business Days after the posting thereof.

     [SEC]11. AMENDMENTS. Neither this Agreement nor any provision hereof may be
modified or amended in any respect except by a statement in writing executed by
the Bank and the Borrower.

     [SEC]12. ASSIGNMENT; PARTICIPATIONS. All of the terms of this Agreement
shall be binding upon and inure to the benefit of and be enforceable by the
parties hereto and their respective successors and assigns; provided, that the
Borrower may not assign or transfer any of its rights or obligations hereunder
without the prior written consent of the Bank. The Borrower acknowledges and
agrees that the Bank may assign or transfer, either directly or through loan
participations, all or a portion of its rights and obligations hereunder to
other persons or entities selected by the Bank in its sole discretion.

     [SEC]13. SECTION HEADINGS. The descriptive section headings on this
Agreement have been inserted for ease of reference only and shall not be deemed
to limit or otherwise affect the construction of any provision thereof or
hereof.

     [SEC]14. COUNTERPARTS. This Agreement and the documents contemplated hereby
may be executed simultaneously in any number of counterparts each of which when
so executed and delivered shall be an original; but all of which shall together
constitute but one and the same document.

     [SEC]15. SEPARABILITY. If any of the provisions of this Agreement or any
instrument delivered hereunder or the application thereof to any party hereto or
to any person or circumstances is held invalid, the remainder of this Agreement
or such instrument and the application thereof to any party hereto or to any
other person or circumstances shall not be affected thereby.

     [SEC]16. GOVERNING LAW; SUBMISSION TO JURISDICTION; CHOICE OF FORUM; WAIVER
OF JURY TRIAL. (A) THIS AGREEMENT IS A CONTRACT UNDER THE LAWS OF THE
COMMONWEALTH OF MASSACHUSETTS AND SHALL FOR ALL PURPOSES BE CONSTRUED IN
ACCORDANCE WITH AND GOVERNED BY THE LAWS OF SAID COMMONWEALTH OF MASSACHUSETTS
(EXCLUDING THE LAWS APPLICABLE TO CONFLICTS OR CHOICE OF LAW). THE BORROWER
AGREES THAT ANY SUIT FOR THE ENFORCEMENT OF THIS AGREEMENT OR ANY OTHER ACTION
BROUGHT BY THE BORROWER ARISING HEREUNDER OR IN ANY WAY RELATED TO THIS
AGREEMENT WHETHER SOUNDING IN CONTRACT, TORT, EQUITY OR OTHERWISE, SHALL BE
BROUGHT IN THE COURTS OF THE 

<PAGE>   12
                                      -12-


COMMONWEALTH OF MASSACHUSETTS OR ANY FEDERAL COURT SITTING THEREIN, AND CONSENTS
TO THE NONEXCLUSIVE JURISDICTION OF SUCH COURT AND THE SERVICE OF PROCESS IN ANY
SUIT BEING MADE UPON THE BORROWER BY MAIL AT THE ADDRESS SPECIFIED IN CLAUSE (B)
HEREOF. THE BORROWER HEREBY WAIVES ANY OBJECTION THAT IT MAY NOW OR HEREAFTER
HAVE TO THE VENUE OF ANY SUIT OR ANY COURT OR THAT A SUIT IS BROUGHT IN AN
INCONVENIENT COURT.

     (b) THE BORROWER, AS AN INDUCEMENT TO THE BANK TO ENTER INTO THIS
AGREEMENT, HEREBY WAIVES ITS RIGHT TO A JURY TRIAL WITH RESPECT TO ANY ACTION
ARISING IN CONNECTION HEREUNDER.

     [SEC]17. ENTIRE AGREEMENT. This Agreement and the other documents
contemplated hereby and executed in connection herewith express the entire
understanding of the parties with respect to the transactions contemplated
hereby.

<PAGE>   13
                                      -13-


     IN WITNESS WHEREOF, each of the parties hereto has caused this Agreement to
be duly executed as an instrument under seal by its duly authorized officer as
of the date first written above.

                              BANKBOSTON, N.A.



                              By: Debra E. DelVecchio
                                  --------------------------------- 
                              Title: Vice President


                              DYNATECH CORPORATION


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


<PAGE>   14
                                      -13-

     IN WITNESS WHEREOF, each of the parties hereto has caused this Agreement to
be duly executed as an instrument under seal by its duly authorized officer as
of the date first written above.

                              BANKBOSTON, N.A.



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


                              DYNATECH CORPORATION


                              By: Allan M. Kline
                                  -----------------------------------------
                              Title: Allan M. Kline, Vice President,
                                     Chief Financial Officer, and Treasurer