AMENDMENT NO. 4 TO CREDIT AGREEMENT


     THIS AMENDMENT NO. 4 TO CREDIT AGREEMENT (this "Amendment") is dated as of
September 28, 2006, among:

     LECROY CORPORATION, a Delaware corporation (hereinafter referred to as the
"Borrower");

     THE LENDERS PARTY HERETO; and

     THE BANK OF NEW YORK, as administrative agent for the Lenders referred to
below (in such capacity, the "Administrative Agent").

                                    RECITALS

     A. The Borrower, the Lenders party thereto (the "Lenders"), and The Bank of
New York, as Issuing Lender, Swingline Lender and Administrative Agent have
entered into a Credit Agreement, dated as of October 29, 2004 (as amended
pursuant to (i) a certain Amendment No. 1 and Consent, dated as of July 1, 2005,
(ii) a certain Amendment No. 2 to Credit Agreement, dated as of May 9, 2006, and
(iii) a certain Amendment No. 3 to Credit Agreement, dated as of September 26,
2006, and, as in effect on the date hereof, the "Credit Agreement").

     B. The Borrower has requested that the Lenders agree to amend the Credit
Agreement, among other things, to (a) amend Section 7.01 of the Credit Agreement
to permit the Borrower to incur indebtedness evidenced by the Senior Notes (as
hereinafter defined) and to require the prepayment of the Term Loans from the
proceeds thereof, (b) amend Section 7.04(e) of the Credit Agreement to permit
certain Acquisitions, and (c) amend certain other Sections of the Credit
Agreement.

     NOW, THEREFORE, in consideration of the agreements and provisions contained
herein, the parties hereto hereby agree as follows:

     1. DEFINITIONS. Capitalized terms used herein that are defined in the
Credit Agreement and not otherwise defined herein shall have the meanings
ascribed thereto therein.

     2. AMENDMENTS TO CREDIT AGREEMENT. The Credit Agreement is hereby amended,
as follows:

         2.1 Section 1.01 (Defined Terms) of the Credit Agreement is hereby
amended by adding the following Defined Terms in appropriate alphabetical order:

         "Amendment No. 4" means Amendment No. 4 to Credit Agreement, dated as
     of September 28, 2006.

<PAGE>

         "Refinance": means, in respect of any Indebtedness, to refinance,
     extend, renew, defease, redeem, amend, modify, supplement, restructure,
     replace, refund, prepay or repay, or to issue other indebtedness, in
     exchange or replacement for, such indebtedness in whole or in part.
     "Refinanced" and "Refinancing" shall have correlative meanings.

         "Senior Note Agreement": means the note purchase agreement or indenture
     to be executed between the Borrower and an indenture trustee, as amended,
     supplemented or otherwise modified from time to time to the extent
     permitted by this Agreement, including any agreement executed in connection
     with a Refinancing of the Senior Notes issued thereunder to the extent
     permitted by this Agreement.

         "Senior Note Holders": means the holders of the Senior Notes.

         "Senior Notes": means the unsecured convertible senior notes to be
     issued by the Borrower in an aggregate principal amount not to exceed
     $72,000,000 pursuant to the Senior Note Agreement, which notes are
     convertible into cash and, in certain circumstances, shares of Common Stock
     of the Borrower, and any Refinancing of such notes with senior notes or
     subordinated notes that are issued by the Borrower, and any subsequent
     Refinancings thereof that comply with the terms hereof, provided that (a)
     such Refinancing is on such customary terms and conditions as are then
     available in the market for issuers of similar credit profile, (b) the
     amount of such Refinancing is in a principal amount not to exceed (i) the
     outstanding principal amount of indebtedness so Refinanced plus (ii) unpaid
     accrued interest on such indebtedness being Refinanced plus (iii) premiums,
     penalties, fees and expenses actually incurred by the Borrower in
     connection with the Refinancing thereof, (c) such Refinanced notes shall
     have a final stated maturity that is no earlier than the date that is (12)
     twelve months after the Revolving Commitment Termination Date of this
     Agreement, and (d) the terms, covenants and conditions of such Refinancing
     are no more restrictive than the terms, covenants and conditions of the
     Senior Notes and the Senior Note Agreement.

         "Senior Note Documents": means the collective reference to the Senior
     Notes and the Senior Note Agreement.

         2.2 Section 1.01 (Defined Terms) of the Credit Agreement is hereby
amended by deleting the Defined Term Material Indebtedness and substituting
therefor the following:

         "Material Indebtedness" means Indebtedness (other than Indebtedness
     under the Loan Documents) or obligations in respect of one or more Hedging
     Agreements, of any one or more of the Borrower and the Subsidiaries in an
     aggregate principal amount exceeding $1,000,000, including without
     limitation, Indebtedness under the Senior Notes and the Saleh Note. For
     purposes of determining Material Indebtedness, the "principal amount" of
     the obligations of the Borrower or any Subsidiary in respect of any Hedging
     Agreement at any time shall be the maximum aggregate amount (giving effect
     to any netting agreements) that the Borrower or such Subsidiary, as
     applicable, would be required to pay if such Hedging Agreement were
     terminated at such time.


                                       2
<PAGE>


         2.3 Section 2.01 (Revolving Commitment) of the Credit Agreement is
hereby amended by deleting the text of clause 2.01(a)(ii) and substituting
therefor the following:

     "(ii) with regard to the Lenders collectively, the sum of the aggregate
     amount of outstanding Revolving Loans plus Swingline Loans plus LC
     Obligations shall not exceed the Revolving Committed Amount."

         2.4 Section 6.08 (Use of the Proceeds) of the Credit Agreement is
hereby amended by deleting the text of such Section and substituting therefor
the following:

             "Section 6.08 (Use of the Proceeds) . The proceeds of the Loans
     will be used only (a) to finance the acquisition of the Acquired Company
     pursuant to the Merger Agreement, (b) to pay transaction fees and expenses
     related to the Merger, (c) provided that the conditions precedent set forth
     in Section 2 of Amendment No. 3 have been satisfied, (i) to finance the
     Catalyst Merger pursuant to the Catalyst Merger Agreement, and (ii) to pay
     transaction fees and expenses related to the Catalyst Merger and (d) for
     general corporate purposes not inconsistent with the terms hereof. No part
     of the proceeds of any Loan will be used, whether directly or indirectly,
     and whether immediately, incidentally or ultimately, to (i) purchase,
     acquire or carry any Margin Stock or for any purpose that entails a
     violation of any of the regulations of the Board, including Regulations T,
     U and X or (ii) repay or retire or redeem or purchase all or any portion of
     the Senior Notes, including a repayment or retirement or redemption or
     purchase pursuant to a "conversion" or the occurrence of a "designated
     event" (as such terms are described in the Senior Note Documents)."

         2.5 Section 7.01 (Indebtedness) of the Credit Agreement is hereby
amended by deleting the "." at the end of clause 7.01(a)(x) and substituting
therefor "; and" inserting the following clause (xi):

             "(xi) unsecured Indebtedness evidenced by the Senior Notes,
     provided that the proceeds thereof are used to prepay the Term Loans and
     any accrued interest thereon and any amount due under Section 3.06 as a
     result of such prepayment."

         2.6 Section 7.01 (Indebtedness) of the Credit Agreement is hereby
amended by deleting the text of Section 7.01(b) and substituting therefor the
following:


                                       3
<PAGE>



             "(b) The Borrower will not, and it will not permit any Subsidiary
     to, (i) issue any preferred equity securities unless the issuance of such
     preferred equity securities is on terms and conditions reasonably
     satisfactory to the Administrative Agent, or (ii) be or become liable in
     respect of any obligation (contingent or otherwise) to purchase, redeem,
     retire, acquire or make any other payment in respect of any shares of
     Capital Stock of the Borrower or any Subsidiary or any option, warrant or
     other right to acquire any such shares of Capital Stock other than Capital
     Stock of the Borrower pursuant to any employee benefit plan, except (i) as
     permitted under Section 7.08, (ii) as required under the terms of the
     Senior Note Documents, and (iii) repurchases of the Capital Stock of the
     Borrower in an aggregate amount not to exceed 20% of the gross proceeds
     realized from the issuance of the Senior Notes and made within three (3)
     Business Days after the issuance of, and from the proceeds of, the Senior
     Notes."

         2.7 Section 7.04 (Investments, Loans, Advances, Guarantees and
Acquisitions) of the Credit Agreement is hereby amended by deleting in its
entirety the text of Section 7.04(e) and substituting therefor the following:

             "(e) (i) Acquisitions consummated prior to the effective date of
     Amendment No. 3;

                 (ii) the Catalyst Merger provided that (1) all conditions set
     forth in Section 3 of Amendment No. 3 shall have been satisfied and (2) the
     aggregate consideration paid by the Borrower for the Catalyst Merger does
     not exceed the amounts set forth in the form of Catalyst Merger Agreement
     submitted to the Lenders on the date of Amendment No. 3; and

                 (iii) Acquisitions (whether by purchase of stock or assets,
     merger or consolidation) by the Borrower and/or the Subsidiaries after the
     effective date of Amendment No. 4 and not otherwise permitted by this
     Section, provided that:

                      (1) such Acquisition shall be within the same industry and
         line of business as that conducted by, or contemplated to be conducted
         by, the Borrower and/or the Subsidiaries on the Effective Date;

                      (2) the aggregate consideration paid by the Borrower
         and/or the Subsidiaries in connection with all such Acquisitions with
         borrowed money and/or internally generated funds shall not exceed
         $10,000,000;

                      (3) the aggregate consideration paid by the Borrower
         and/or the Subsidiaries in connection with all such Acquisitions, shall
         not exceed $26,500,000;


                                       4
<PAGE>


                      (4) the Borrower shall furnish the Administrative Agent
         with written notice of such Acquisition not less than thirty (30) days
         prior to the closing of such Acquisition;

                      (5) in the event any Acquisition is of Capital Stock, the
         Borrower shall, pursuant to the Security Agreement, grant to the
         Administrative Agent a first priority security interest in all of the
         Capital Stock of such new Subsidiary if such new Subsidiary is a
         Domestic Subsidiary, and 65% of the Capital Stock of such new
         Subsidiary if such new Subsidiary is a Material Foreign Subsidiary, and
         each new Subsidiary shall, at the time it becomes a new Subsidiary,
         execute such certifications, opinions, resolutions and documents as the
         Administrative Agent may reasonably require (consistent with the
         requirements of this Agreement) to cause such new Subsidiary (if a
         Domestic Subsidiary) to become a party to the Guarantee Agreement and
         to cause such new Subsidiary to become a party to the Security
         Agreement in order for such new Subsidiary to grant to the
         Administrative Agent a first priority security interest in the assets
         of such new Subsidiary, subject to the Permitted Encumbrances; and

                      (6) the Borrower shall have delivered to the
         Administrative Agent a certificate of a Financial Officer of the
         Borrower demonstrating that, on a pro forma basis, after giving effect
         to such Acquisition, (A) the Borrower would be in compliance with
         Sections 7.12, 7.13, 7.14 and 7.15 (such covenants to be determined as
         if such Acquisition had been consummated on the first day of the period
         for which such covenants are being calculated) and (B) no Default or
         Event of Default would exist.

         2.8 Section 7.05 (Asset Sales) of the Credit Agreement is hereby
amended by deleting the text of Section 7.05(d) and substituting therefor the
following:

     "(d) Intentionally Omitted;"

         2.9 Section 7.08 (Restricted Payments) of the Credit Agreement is
hereby amended by deleting the "." at the end of such Section and substituting
therefor ";" and inserting the following new Section 7.08(d) as follows:

     "(d) as required under the terms of the Senior Note Documents; and".

         2.10 Section 7.08 (Restricted Payments) of the Credit Agreement is
hereby amended by adding a new Section 7.08(e) as follows:

     "(e) and other repurchases to the extent permitted under Section
7.01(b)(iii)."


                                       5
<PAGE>


         2.11 Article 7 of the Credit Agreement is hereby amended by adding the
following Section 7.17:

         "Section 7.17 Optional Payments and Modifications of Certain Debt
     Instruments (a) The Borrower will not make or offer to make any optional or
     voluntary payment, prepayment, repurchase or redemption of or otherwise
     optionally or voluntarily defease or segregate funds with respect to the
     Senior Notes other than pursuant to a Refinancing permitted under the
     definition of Senior Notes, or (b) amend, modify, waive or otherwise
     change, or consent or agree to any amendment, modification, waiver or other
     change to, any of the terms of the Senior Notes Documents (other than any
     such amendment, modification, waiver or other change that (i) would extend
     the maturity or reduce the amount of any payment of principal thereof or
     reduce the rate or extend any date for payment of interest thereon and (ii)
     does not involve the payment of a consent fee)."

     3. CONDITIONS PRECEDENT TO EFFECTIVENESS.

         Upon the fulfillment of the following conditions precedent, this
Amendment and the amendments contained in Section 2 hereof shall become
effective:

         3.1 Amendment. The Administrative Agent shall have received this
Amendment, duly executed by a duly authorized officer or officers of the
Borrower, the Administrative Agent and the Lenders.

         3.2 Senior Note Documents. The Administrative Agent shall have (a)
received, reviewed and approved the Senior Note Documents and (b) confirmed that
the Senior Notes shall become effective pursuant thereto concurrently with the
effectiveness of this Amendment.

         3.3 Term Loans. The Administrative Agent shall have confirmed that the
Term Loans and all accrued interest thereon and any amounts due under Section
3.06 of the Credit Agreement have been paid in full from the proceeds of the
issuance of the Senior Notes.

         3.4 Secretary's Certificate. The Administrative Agent shall have
received a certificate, dated the date hereof, duly executed by the Secretary,
Assistant Secretary, or other analogous counterpart of the Borrower:

             (a) attaching a true and complete copy of the resolutions of its
Managing Person and of all other documents evidencing all necessary corporate
action (in form and substance satisfactory to the Administrative Agent) taken to
authorize this Amendment and the other transactions contemplated hereby;

             (b) certifying that no amendment or modification of its
Organizational Documents has occurred since the date of delivery thereof to the
Administrative Agent in connection with the Credit Agreement; and


                                       6
<PAGE>


             (c) setting forth the incumbency of its officer or officers who may
sign this Amendment and the other documents to be executed by it in connection
herewith, including therein a signature specimen of such officer or officers.

         3.5 Guaranty Confirmation. The Administrative Agent shall have received
a counterpart of the Guaranty Confirmation, substantially in the form attached
hereto as Exhibit C, duly executed by each of the Guarantors.

         3.6 Security Agreement Confirmation. The Administrative Agent shall
have received a counterpart of the Security Agreement Confirmation,
substantially in the form attached hereto as Exhibit D, dated the date hereof,
duly executed by the Borrower and each Guarantor.

         3.7 Financial Covenant Compliance Certificate. The Administrative Agent
shall have received a certificate, dated the date of the issuance of the Senior
Notes and signed by a Financial Officer of the Borrower, setting forth
reasonably detailed calculations demonstrating that, on a pro forma basis, after
giving effect to the issuance of the Senior Notes, the Borrower is and will be
in compliance with Sections 7.12 (such covenant to be determined as if the
Senior Notes had been issued on the first day of the period for which such
covenant is being calculated).

         3.8 Financial Officer's Certificate. The Administrative Agent shall
have received a certificate signed by a Financial Officer of the Borrower, in
such Financial Officer's capacity as an officer of the Borrower, in all respects
reasonably satisfactory to the Administrative Agent, dated the date hereof,
certifying that immediately before and after giving effect to the issuance of
the Senior Notes on a pro forma basis the representations and warranties
contained in the Loan Documents that are qualified as to materiality are and
will be true and correct in all respects, that the representations and
warranties contained in the Loan Documents that are not so qualified are and
will be true and correct in all material respects, and that no Default exists or
will exist.

         3.9 Fees. The Administrative Agent shall have received all fees and
other amounts due and payable to the Administrative Agent and the Lenders under
the Loan Documents upon the execution of this Amendment, including, to the
extent invoiced, reimbursement or payment of the fees and disbursements of
Special Counsel and all other out-of-pocket expenses required to be reimbursed
or paid by the Borrower hereunder, all of which fees shall be earned and
non-refundable whether or not the other conditions in this Section have been or
are satisfied and notwithstanding the termination of this Amendment after the
execution thereof.


                                       7
<PAGE>


         3.10 Other Documents. The Administrative Agent shall have received all
other documents that the Administrative Agent may reasonably request with
respect to any matter relevant to this Amendment.

         In the event the conditions in this Section have not been satisfied on
or before October 31, 2006 this Amendment shall terminate and shall be of no
effect.

     4. REPRESENTATIONS AND WARRANTIES. The Borrower represents and warrants to
the Lenders and the Administrative Agent that:

         4.1 No Default. After giving effect to this Amendment, no Default or
Event of Default shall have occurred or be continuing.

         4.2 Existing Representations and Warranties. As of the date hereof and
after giving effect to this Amendment, each and every one of the representations
and warranties set forth in the Loan Documents is true, accurate and complete in
all respects and with the same effect as though made on the date hereof, and
each is hereby incorporated herein in full by reference as if restated herein in
its entirety, except for any representation or warranty limited by its terms to
a specific date and except for changes in the ordinary course of business which
are not prohibited by the Credit Agreement (as amended hereby) or changes which
do not, either singly or in the aggregate, have a Material Adverse Effect.

         4.3 Authority; Enforceability. (i) The execution, delivery and
performance by the Borrower of this Amendment are within its corporate powers
and have been duly authorized by all necessary corporate action, (ii) this
Amendment is the legal, valid and binding obligation of the Borrower,
enforceable against the Borrower in accordance with its terms, subject to
applicable bankruptcy, insolvency, reorganization, moratorium or other laws
affecting creditors' rights generally and (iii) this Amendment and the
execution, delivery and performance by the Borrower hereof does not: (A)
contravene the terms of the Borrower's organizational documents; (B) conflict
with or result in any breach or contravention of, or the creation of any Lien
(other than Liens under the Loan Documents) under, any document evidencing any
contractual obligation to which the Borrower is a party or any order,
injunction, writ or decree to which it or its respective property is subject; or
(C) violate any requirement of law.

5. REFERENCE TO AND EFFECT UPON THE CREDIT AGREEMENT.

         5.1 Effect. Except as specifically amended hereby, the Credit Agreement
and the other Loan Documents shall remain in full force and effect in accordance
with their terms and are hereby ratified and confirmed.

         5.2 No Waiver; References. The execution, delivery and effectiveness of
this Amendment shall not operate as a waiver of any right, power or remedy of
the Administrative Agent or any Lender under the Credit Agreement, or constitute
a waiver of any provision of the Credit Agreement, except as specifically set
forth herein. Upon the effectiveness of this Amendment, each reference in:


                                       8
<PAGE>

             (i) the Credit Agreement to "this Agreement", "hereunder",
         "hereof", "herein" or words of similar import shall mean and be a
         reference to the Credit Agreement as amended hereby;

             (ii) the other Loan Documents to the term "the Credit Agreement"
         shall mean and be a reference to the Credit Agreement as amended
         hereby; and

             (iii) the Loan Documents to the term "the Loan Documents" shall be
         deemed to include this Amendment.

6.       MISCELLANEOUS.

         6.1 Expenses. The Borrower agrees to pay the Administrative Agent upon
demand for all reasonable expenses, including reasonable attorneys' fees and
expenses of the Administrative Agent, incurred by the Administrative Agent in
connection with the preparation, negotiation and execution of this Amendment.

         6.2 Headings. Section headings in this Amendment are included herein
for convenience of reference only and shall not constitute a part of this
Amendment for any other purposes.

         6.3 Law; Waiver of Trial by Jury. THIS AMENDMENT SHALL BE CONSTRUED IN
ACCORDANCE WITH AND GOVERNED BY THE INTERNAL LAWS OF THE STATE OF NEW YORK
WITHOUT REGARD TO PRINCIPLES OF CONFLICT OF LAWS. THE PARTIES HERETO HEREBY
WAIVE THE RIGHT TO TRIAL BY JURY IN ANY ACTION OR PROCEEDING BASED UPON, ARISING
OUT OF OR IN ANY WAY CONNECTED TO THIS AMENDMENT.

         6.4 Successors. This Amendment shall be binding upon the Borrower, the
Lenders and the Administrative Agent and their respective successors and
assigns, and shall inure to the benefit of the Borrower, the Lenders and the
Administrative Agent and the successors and assigns of the Lenders and the
Administrative Agent.

         6.5 Execution in Counterparts. This Amendment may be executed in any
number of counterparts and by different parties hereto in separate counterparts,
including counterparts executed and delivered by facsimile, each of which when
so executed and delivered shall be deemed to be an original and all of which
taken together shall constitute one and the same instrument.




                           [Signature Page to Follow]



                                       9
<PAGE>




                   Amendment No. 4 to LeCroy Credit Agreement
         IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
executed and delivered by their respective duly authorized officers on the date
first written above.


                                LECROY CORPORATION



                                By:
                                      ------------------------------------
                                      Name:   Sean B. O'Connor
                                      Title:  Vice President and
                                              Chief Financial Officer





                                       10
<PAGE>




                                THE BANK OF NEW YORK,
                                as Administrative Agent, as Issuing Lender
                                and as a Lender



                                By:
                                      ------------------------------------
                                Name:   Patrick M. Trask
                                Title: Vice President





                                       11
<PAGE>




                                WEBSTER BANK, NATIONAL ASSOCIATION, as a Lender


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





                                       12
<PAGE>




                                LASALLE BANK NATIONAL ASSOCIATION, as a Lender


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





                                       13
<PAGE>




                                MANUFACTURERS AND TRADERS TRUST
                                COMPANY, as a Lender


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





                                       14
<PAGE>




                                GENERAL ELECTRIC CAPITAL CORPORATION,
                                as a Lender


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



                                       15