<PAGE>



                          SUPPLEMENTAL INDENTURE TO BE
                             DELIVERED BY GUARANTORS

     SUPPLEMENTAL INDENTURE (this "Supplemental Indenture"), dated as of
November 9, 2001, among Coleman Research Corporation, a Florida corporation, EER
Systems, Inc., a Virginia corporation, Electrodynamics, Inc., an Arizona
corporation, Henschel Inc., a Delaware corporation, Hygienetics Environmental
Services, Inc., a Delaware corporation, Interstate Electronics Corporation, a
California corporation, KDI Precision Products, Inc., a Delaware corporation,
L-3 Communications Corporation, a Delaware corporation, L-3 Communications Aydin
Corporation, a Delaware corporation, L-3 Communications DBS Microwave, Inc., a
California corporation, L-3 Communications ESSCO, Inc., a Delaware corporation,
L-3 Communications ILEX Systems, Inc., a Delaware corporation, L-3
Communications SPD Technologies, Inc., a Delaware corporation, L-3
Communications Storm Control Systems, Inc., a California corporation, Microdyne
Corporation, a Maryland corporation, MPRI, Inc., a Delaware corporation, Pac Ord
Inc., a Delaware corporation, Power Paragon, Inc., a Delaware corporation,
Southern California Microwave, Inc., a California corporation, SPD Electrical
Systems, Inc., a Delaware corporation, SPD Holdings, Inc., a Delaware
corporation and SPD Switchgear Inc., a Delaware corporation, (each, a
"Guarantor," and collectively, the "Guarantors"), each an indirect subsidiary of
L-3 Communications Holdings, Inc. (or its permitted successor), a Delaware
corporation (the "Company"), the Company and The Bank of New York, as trustee
under the indenture referred to below (the "Trustee").

                              W I T N E S S E T H:

     WHEREAS, the Company has heretofore executed and delivered to the Trustee
an indenture (the "Indenture"), dated as of November 21, 2000 providing for the
issuance of an aggregate principal amount of up to $300,000,000 of 5 1/4%
Convertible Senior Subordinated Notes due 2009 (the "Notes");

     WHEREAS, the Indenture provides that under certain circumstances the
Guarantors shall execute and deliver to the Trustee a supplemental indenture
pursuant to which the Guarantors shall unconditionally guarantee all of the
Company"s Obligations under the Notes and the Indenture on the terms and
conditions set forth herein (the "Guarantee"); and

     WHEREAS, pursuant to Section 14.7 of the Indenture, the Trustee is
authorized to execute and deliver this Supplemental Indenture.

     NOW THEREFORE, in consideration of the foregoing and for other good and
valuable consideration, the receipt of which is hereby acknowledged, the
Guarantors and the Trustee mutually covenant and agree for the equal and ratable
benefit of the Holders of the Notes as follows:

<PAGE>
                                       2


     1. CAPITALIZED TERMS. Capitalized terms used herein without definition
shall have the meanings assigned to them in the Indenture.

     2. AGREEMENT TO GUARANTEE. Each Guarantor hereby agrees as follows:

     (a)  Each Guarantor, jointly and severally with all other current and
          future guarantors of the Notes (collectively, the "Guaranteeing
          Subsidiaries" and each, a "Guaranteeing Subsidiary"), unconditionally
          guarantees to each Holder of a Note authenticated and delivered by the
          Trustee and to the Trustee and its successors and assigns, regardless
          of the validity and enforceability of the Indenture, the Notes or the
          Obligations of the Company under the Indenture or the Notes, that:

          (i)  the principal of, premium, interest and additional amounts, if
               any, on the Notes will be promptly paid in full when due, whether
               at maturity, by acceleration, redemption or otherwise, and
               interest on the overdue principal of, premium, interest and
               Liquidated Damages, if any, on the Notes, to the extent lawful,
               and all other Obligations of the Company to the Holders or the
               Trustee thereunder or under the Indenture will be promptly paid
               in full, all in accordance with the terms thereof; and

          (ii) in case of any extension of time for payment or renewal of any
               Notes or any of such other Obligations, that the same will be
               promptly paid in full when due in accordance with the terms of
               the extension or renewal, whether at stated maturity, by
               acceleration or otherwise.

     (b)  Notwithstanding the foregoing, in the event that this Guarantee would
          constitute or result in a violation of any applicable fraudulent
          conveyance or similar law of any relevant jurisdiction, the liability
          of each Guarantor under this Supplemental Indenture and its Guarantee
          shall be reduced to the maximum amount permissible under such
          fraudulent conveyance or similar law.

     3. EXECUTION AND DELIVERY OF GUARANTEES.

     (a)  To evidence its Guarantee set forth in this Supplemental Indenture,
          each Guarantor hereby agrees that a notation of such Guarantee, the
          form of which is included in the Form of Security attached as Exhibit
          A to the Indenture, shall be endorsed by an officer of such Guarantor
          on each Note authenticated and delivered by the Trustee after the date
          hereof.

     (b)  Notwithstanding the foregoing, each Guarantor hereby agrees that its
          Guarantee set forth herein shall remain in full force and effect
          notwithstanding any failure to endorse on each Note a notation of such
          Guarantee.
<PAGE>
                                       3


     (c)  If an Officer whose signature is on this Supplemental Indenture or on
          the Guarantee no longer holds that office at the time the Trustee
          authenticates the Note on which a Guarantee is endorsed, the Guarantee
          shall be valid nevertheless.

     (d)  The delivery of any Note by the Trustee, after the authentication
          thereof under the Indenture, shall constitute due delivery of the
          Guarantee set forth in this Supplemental Indenture on behalf of each
          Guarantor.

     (e)  Each Guarantor hereby agrees that its obligations hereunder shall be
          unconditional, regardless of the validity, regularity or
          enforceability of the Notes or the Indenture, the absence of any
          action to enforce the same, any waiver or consent by any Holder of the
          Notes with respect to any provisions of the Notes or the Indenture,
          the recovery of any judgment against the Company, any action to
          enforce the same or any other circumstance which might otherwise
          constitute a legal or equitable discharge or defense of a guarantor.

     (f)  Each Guarantor hereby waives diligence, presentment, demand of
          payment, filing of claims with a court in the event of insolvency or
          bankruptcy of the Company, any right to require a proceeding first
          against the Company, protest, notice and all demands whatsoever and
          covenants that its Guarantee made pursuant to this Supplemental
          Indenture will not be discharged except by complete performance of the
          obligations contained in the Notes and the Indenture.

     (g)  If any Holder or the Trustee is required by any court or otherwise to
          return to the Company or any Guarantor, or any Custodian, Trustee,
          liquidator or other similar official acting in relation to either the
          Company or such Guarantor, any amount paid by either to the Trustee or
          such Holder, the Guarantee made pursuant to this Supplemental
          Indenture, to the extent theretofore discharged, shall be reinstated
          in full force and effect.

     (h)  Each Guarantor agrees that it shall not be entitled to any right of
          subrogation in relation to the Holders in respect of any obligations
          guaranteed hereby until payment in full of all obligations guaranteed
          hereby. Each Guarantor further agrees that, as between such Guarantor,
          on the one hand, and the Holders and the Trustee, on the other hand:

          (i)  the maturity of the obligations guaranteed hereby may be
               accelerated as provided in Article 4 of the Indenture for the
               purposes of the Guarantee made pursuant to this Supplemental
               Indenture, notwithstanding any stay, injunction or other
               prohibition preventing such acceleration in respect of the
               obligations guaranteed hereby;
<PAGE>
                                       4


          (ii) in the event of any declaration of acceleration of such
               obligations as provided in Article 4 of the Indenture, such
               obligations (whether or not due and payable) shall forthwith
               become due and payable by such Guarantor for the purpose of the
               Guarantee made pursuant to this Supplemental Indenture; and

         (iii) each Guarantor shall have the right to seek contribution from
               any other non-paying Guarantor so long as the exercise of such
               right does not impair the rights of the Holders or the Trustee
               under the Guarantee made pursuant to this Supplemental Indenture.

     4. GUARANTORS MAY CONSOLIDATE, ETC. ON CERTAIN TERMS.

     (a)  Except as set forth in Articles 6 and 9 of the Indenture, nothing
          contained in the Indenture, this Supplemental Indenture or in the
          Notes shall prevent (a) any consolidation or merger of any Guarantor
          with or into the Company or any other Guaranteeing Subsidiary, (b) any
          transfer, sale or conveyance of the property of any Guarantor as an
          entirety or substantially as an entirety, to the Company or any other
          Guaranteeing Subsidiary or (c) any merger of a Guarantor with or into
          an Affiliate of that Guarantor in another State of the United States
          so long as the amount of Indebtedness of the Company and the domestic
          non-Guarantor subsidiaries is not increased thereby.

     (b)  Except as set forth in Article 9 of the Indenture, nothing contained
          in the Indenture, this Supplemental Indenture or in the Notes shall
          prevent any consolidation or merger of any Guarantor with or into a
          corporation or corporations other than the Company or any other
          Guaranteeing Subsidiary (in each case, whether or not affiliated with
          the Guarantor), or successive consolidations or mergers in which a
          Guarantor or its successor or successors shall be a party or parties,
          or shall prevent any sale or conveyance of the property of any
          Guarantor as an entirety or substantially as an entirety, to a
          corporation other than the Company or any other Guaranteeing
          Subsidiary (in each case, whether or not affiliated with the
          Guarantor) authorized to acquire and operate the same; provided,
          however, that each Guarantor hereby covenants and agrees that (i)
          subject to the Indenture, upon any such consolidation, merger, sale or
          conveyance, the due and punctual performance and observance of all of
          the covenants and conditions of the Indenture and this Supplemental
          Indenture to be performed by such Guarantor, shall be expressly
          assumed (in the event that such Guarantor is not the surviving
          corporation in the merger), by supplemental indenture satisfactory in
          form to the Trustee, executed and delivered to the Trustee, by the
          corporation formed by such consolidation, or into which such Guarantor
          shall have been merged, or by the corporation which shall have
          acquired such property, (ii) immediately after giving effect to such
          consolidation, merger, sale or conveyance no Default or Event of
          Default exists, and (iii) such transaction will only be


<PAGE>
                                       5


          permitted under the Indenture and this Supplemental Indenture if it
          would be permitted under the terms of all of the indentures governing
          the Outstanding Senior Subordinated Notes as the same are in effect on
          the date hereof (whether or not those indentures are subsequently
          amended, waived, modified or terminated or expire and whether or not
          any of these notes continue to be outstanding).

     (c)  In case of any such consolidation, merger, sale or conveyance and upon
          the assumption by the successor corporation, by supplemental
          indenture, executed and delivered to the Trustee and satisfactory in
          form to the Trustee, of the Guarantee made pursuant to this
          Supplemental Indenture and the due and punctual performance of all of
          the covenants and conditions of the Indenture and this Supplemental
          Indenture to be performed by each Guarantor, such successor
          corporation shall succeed to and be substituted for such Guarantor
          with the same effect as if it had been named herein as one of the
          Guarantors. Such successor corporation thereupon may cause to be
          signed any or all of the Guarantees to be endorsed upon the Notes
          issuable under the Indenture which theretofore shall not have been
          signed by the Company and delivered to the Trustee. All the Guarantees
          so issued shall in all respects have the same legal rank and benefit
          under the Indenture and this Supplemental Indenture as the Guarantees
          theretofore and thereafter issued in accordance with the terms of the
          Indenture and this Supplemental Indenture as though all of such
          Guarantees had been issued at the date of the execution hereof.

     5. RELEASES.

     (a)  Concurrently with any sale of assets (including, if applicable, all of
          the Capital Stock of a Guarantor), all Liens, if any, in favor of the
          Trustee in the assets sold thereby shall be released. If the assets
          sold in such sale or other disposition include all or substantially
          all of the assets of a Guarantor or all of the Capital Stock of a
          Guarantor, then the Guarantor (in the event of a sale or other
          disposition of all of the Capital Stock of such Guarantor) or the
          Person acquiring the property (in the event of a sale or other
          disposition of all or substantially all of the assets of such
          Guarantor) shall be released from and relieved of its obligations
          under this Supplemental Indenture and its Guarantee made pursuant
          hereto. Upon delivery by the Company to the Trustee of an Officers"
          Certificate to the effect that such sale or other disposition was made
          by the Company or the Guarantor, as the case may be, in accordance
          with the provisions of the Indenture and this Supplemental Indenture,
          the Trustee shall execute any documents reasonably required in order
          to evidence the release of the Guarantor from its obligations under
          this Supplemental Indenture and its Guarantee made pursuant hereto. If
          the Guarantor is not released from its obligations under its
          Guarantee, it shall remain liable for the full amount of principal of
          and interest on the Notes and for the other obligations of such
          Guarantor under the Indenture as provided in this Supplemental
          Indenture.
<PAGE>
                                       6


     (b)  Upon the designation of a Guarantor as an Excluded Subsidiary in
          accordance with the terms of the Indenture and the indentures
          governing the Outstanding Senior Subordinated Notes as the same are in
          effect on the date hereof (whether or not those indentures are
          subsequently amended, waived, modified or terminated or expire and
          whether or not any of those notes continue to be outstanding), such
          Guarantor shall be released and relieved of its obligations under the
          Indenture and this Supplemental Indenture. Upon delivery by the
          Company to the Trustee of an Officers" Certificate and an Opinion of
          Counsel to the effect that such designation of such Guarantor as an
          Excluded Subsidiary was made by the Company in accordance with the
          provisions of the Indenture and the indentures governing the
          Outstanding Senior Subordinated Notes as the same are in effect on the
          date hereof (whether or not those indentures are subsequently amended,
          waived, modified, terminated or expired and whether or not any of
          those notes continue to be outstanding), the Trustee shall execute any
          documents reasonably required in order to evidence the release of such
          Guarantor from its obligations under its Guarantee. Any Guarantor not
          released from its obligations under its Guarantee shall remain liable
          for the full amount of principal of and interest on the Notes and for
          the other obligations of any Guarantor under the Indenture as provided
          herein.

     6. NO RECOURSE AGAINST OTHERS. No past, present or future director,
officer, employee, incorporator, stockholder or agent of any Guarantor, as such,
shall have any liability for any obligations of the Company or any Guarantor
under the Notes, any Guarantees, the Indenture or this Supplemental Indenture or
for any claim based on, in respect of, or by reason of, such obligations or
their creation. Each Holder of the Notes by accepting a Note waives and releases
all such liability. The waiver and release are part of the consideration for
issuance of the Notes. Such waiver may not be effective to waive liabilities
under the federal securities laws and it is the view of the Commission that such
a waiver is against public policy.

     7. SUBORDINATION OF GUARANTEES; ANTI-LAYERING. No Guarantor shall incur,
create, issue, assume, guarantee or otherwise become liable for any Indebtedness
that is subordinate or junior in right of payment to any Senior Debt of a
Guarantor and senior in any respect in right of payment to any of the
Guarantees. Notwithstanding the foregoing sentence, the Guarantee of each
Guarantor shall be subordinated to the prior payment in full of all Senior Debt
of that Guarantor, which shall include all guarantees of Senior Debt.

     8. THIS SUPPLEMENTAL INDENTURE SHALL BE GOVERNED BY, AND CONSTRUED IN
ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK.

     9. COUNTERPARTS. The parties may sign any number of copies of this
Supplemental Indenture. Each signed copy shall be an original, but all of them
together represent the same agreement.

     10. EFFECT OF HEADINGS. The Section headings herein are for convenience
only and shall not affect the construction hereof.
<PAGE>
                                       7


     11. THE TRUSTEE. The Trustee shall not be responsible in any manner
whatsoever for or in respect of the validity or sufficiency of this Supplemental
Indenture or for or in respect of the recitals contained herein, all of which
recitals are made solely by the Guarantors and the Company.



<PAGE>
                                       8




     IN WITNESS WHEREOF, the parties hereto have caused this Supplemental
Indenture to be duly executed and attested, all as of the date first above
written.

Dated: November 9, 2001


                                 L-3 COMMUNICATIONS HOLDINGS, INC.


                                 By: ______________________________________
                                     Name:
                                     Title:

                                 COLEMAN RESEARCH CORPORATION
                                 EER SYSTEMS, INC.
                                 ELECTRODYNAMICS, INC.
                                 HENSCHEL INC.
                                 HYGIENETICS ENVIRONMENTAL SERVICES,
                                         INC.
                                 INTERSTATE ELECTRONICS CORPORATION
                                 KDI PRECISION PRODUCTS, INC.
                                 L-3 COMMUNICATIONS CORPORATION
                                 L-3 COMMUNICATIONS AYDIN
                                        CORPORATION
                                 L-3 COMMUNICATIONS DBS MICROWAVE,
                                        INC.
                                 L-3 COMMUNICATIONS ESSCO, INC.
                                 L-3 COMMUNICATIONS ILEX SYSTEMS, INC.
                                 L-3 COMMUNICATIONS SPD
                                        TECHNOLOGIES, INC.
                                 L-3 COMMUNICATIONS STORM CONTROL
                                        SYSTEMS, INC.
                                 MICRODYNE CORPORATION
                                 MPRI, INC.
                                 PAC ORD INC.
                                 POWER PARAGON, INC.
                                 SOUTHERN CALIFORNIA MICROWAVE, INC.
                                 SPD ELECTRICAL SYSTEMS, INC.
                                 SPD HOLDINGS, INC.
                                 SPD SWITCHGEAR INC.
                                        As Guaranteeing Subsidiaries

                                 By: ______________________________________
                                     Name:
                                     Title:

<PAGE>
                                       9





Dated:  November 9, 2001          THE BANK OF NEW YORK
                                  as Trustee


                                  By: ______________________________________
                                      Name:
                                      Title:


















<PAGE>


                      NOTATION ON SENIOR SUBORDINATED NOTE
                             RELATING TO GUARANTEE

     Pursuant to the Supplemental Indenture (the "Supplemental Indenture") dated
as of November 9, 2001 among L-3 Communications Holdings, Inc., a Delaware
corporation, Coleman Research Corporation, a Florida corporation, EER Systems,
Inc., a Virginia corporation, Electrodynamics, Inc., an Arizona corporation,
Henschel Inc., a Delaware corporation, Hygienetics Environmental Services, Inc.,
a Delaware corporation, Interstate Electronics Corporation, a California
corporation, KDI Precision Products, Inc., a Delaware corporation, L-3
Communications Corporation, a Delaware corporation, L-3 Communications Aydin
Corporation, a Delaware corporation, L-3 Communications DBS Microwave, Inc., a
California corporation, L-3 Communications ESSCO, Inc., a Delaware corporation,
L-3 Communications ILEX Systems, Inc., a Delaware corporation, L-3
Communications SPD Technologies, Inc., a Delaware corporation, L-3
Communications Storm Control Systems, Inc., a California corporation, Microdyne
Corporation, a Maryland corporation, MPRI, Inc., a Delaware corporation, Pac Ord
Inc., a Delaware corporation, Power Paragon, Inc., a Delaware corporation,
Southern California Microwave, Inc., a California corporation, SPD Electrical
Systems, Inc., a Delaware corporation, SPD Holdings, Inc., a Delaware
corporation and SPD Switchgear Inc., a Delaware corporation, and The Bank of New
York, each Guarantor (i) has jointly and severally unconditionally guaranteed
(a) the due and punctual payment of the principal of, and premium, interest and
Liquidated Damages on the Notes, whether at maturity or an interest payment
date, by acceleration, call for redemption or otherwise, (b) the due and
punctual payment of interest on the overdue principal and premium of, and
interest and Liquidated Damages on the Notes, and (c) in case of any extension
of time of payment or renewal of any Notes or any of such other obligations, the
same will be promptly paid in full when due in accordance with the terms of the
extension or renewal, whether at stated maturity, by acceleration or otherwise
and (ii) has agreed to pay any and all costs and expenses (including reasonable
attorneys" fees) incurred by the Trustee or any Holder in enforcing any rights
under this Guarantee.

     Notwithstanding the foregoing, in the event that the Guarantee of any
Guarantor would constitute or result in a violation of any applicable fraudulent
conveyance or similar law of any relevant jurisdiction, the liability of such
Guarantor under its Guarantee shall be reduced to the maximum amount permissible
under such fraudulent conveyance or similar law.

     No past, present or future director, officer, employee, agent,
incorporator, stockholder or agent of any Guarantor, as such, shall have any
liability for any obligations of the Company or any Guarantor under the Notes,
any Guarantee, the Indenture, any supplemental indenture delivered pursuant to
the Indenture by such Guarantor or any Guarantees, or for any claim based on, in
respect of or by reason of such obligations or their creation. Each Holder by
accepting a Note waives and releases all such liability.

     This Guarantee shall be binding upon each Guarantor and its successors and
assigns and shall inure to the benefit of the successors and assigns of the
Trustee and the Holders and, in the event of any transfer or assignment of
rights by any Holder or the Trustee, the rights and privileges herein conferred
upon that party shall automatically extend to and be vested in such transferee
or assignee, all subject to the terms and conditions hereof.
<PAGE>

     This Guarantee shall not be valid or obligatory for any purpose until the
certificate of authentication on the Note upon which this Guarantee is noted
have been executed by the Trustee under the Indenture by the manual signature of
one of its authorized officers. Capitalized terms used herein have the meaning
assigned to them in the Indenture.



<PAGE>





                                    COLEMAN RESEARCH CORPORATION
                                    EER SYSTEMS, INC.
                                    ELECTRODYNAMICS, INC.
                                    HENSCHEL INC.
                                    HYGIENETICS ENVIRONMENTAL SERVICES,
                                           INC.
                                    INTERSTATE ELECTRONICS CORPORATION
                                    KDI PRECISION PRODUCTS, INC.
                                    L-3 COMMUNICATIONS AYDIN
                                           CORPORATION
                                    L-3 COMMUNICATIONS DBS MICROWAVE,
                                           INC.
                                    L-3 COMMUNICATIONS ESSCO, INC.
                                    L-3 COMMUNICATIONS ILEX SYSTEMS, INC.
                                    L-3 COMMUNICATIONS SPD
                                           TECHNOLOGIES, INC.
                                    L-3 COMMUNICATIONS STORM CONTROL
                                           SYSTEMS, INC.
                                    MICRODYNE CORPORATION
                                    MPRI, INC.
                                    PAC ORD INC.
                                    POWER PARAGON, INC.
                                    SOUTHERN CALIFORNIA MICROWAVE, INC.
                                    SPD ELECTRICAL SYSTEMS, INC.
                                    SPD HOLDINGS, INC.
                                    SPD SWITCHGEAR INC.
                                             As Guaranteeing Subsidiaries

                                    By: ______________________________________
                                           Name:
                                           Title: