<PAGE>

                     SUPPLEMENTAL INDENTURE TO BE DELIVERED
                          BY GUARANTEEING SUBSIDIARIES

         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 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 "Guaranteeing Subsidiary", and collectively, the "Guaranteeing
Subsidiaries") each a subsidiary of L-3 Communications Corporation (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").

                                   WITNESSETH

         WHEREAS, the Company has heretofore executed and delivered to the
Trustee an indenture (the "Indenture"), dated as of May 22, 1998 providing for
the issuance of an aggregate principal amount of up to $250,000,000 of 8 1/2%
Senior Subordinated Notes due 2008 (the "Notes");

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

         WHEREAS, pursuant to Section 4.13 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
Guaranteeing Subsidiaries and the Trustee mutually covenant and agree for the
equal and ratable benefit of the Holders of the Notes as follows:

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

         2.   AGREEMENT TO GUARANTEE. Each Guaranteeing Subsidiary hereby agrees
              as follows:


<PAGE>


                                                                               2


              (a)  Such Guaranteeing Subsidiary, jointly and severally with any
                   other current or future guarantors of the Notes
                   (collectively, "the Guarantors" and each, a "Guarantor"),
                   Guaranteeing Subsidiaries, 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 and interest 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 and interest 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
                   Subsidiary Guarantee would constitute or result in a
                   violation of any applicable fraudulent conveyance or similar
                   law of any relevant jurisdiction, the liability of such
                   Guaranteeing Subsidiary under this Supplemental Indenture and
                   its Subsidiary Guarantee shall be reduced to the maximum
                   amount permissible under such fraudulent conveyance or
                   similar law.

         3.   EXECUTION AND DELIVERY OF SUBSIDIARY GUARANTEES.

              (a)  To evidence its Subsidiary Guarantee set forth in this
                   Supplemental Indenture, each Guaranteeing Subsidiary hereby
                   agrees that a notation of such Subsidiary Guarantee
                   substantially in the form of Exhibit C to the Indenture shall
                   be endorsed by an officer of such Guaranteeing Subsidiary on
                   each Note authenticated and delivered by the Trustee after
                   the date hereof.

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


<PAGE>


                                                                               3


              (c)  If an Officer whose signature is on this Supplemental
                   Indenture or on the Subsidiary Guarantee no longer holds that
                   office at the time the Trustee authenticates the Note on
                   which a Subsidiary Guarantee is endorsed, the Subsidiary
                   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 Subsidiary Guarantee set forth in this
                   Supplemental Indenture on behalf of each Guaranteeing
                   Subsidiary.

              (e)  Each Guaranteeing Subsidiary 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 Guaranteeing Subsidiary 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 Subsidiary 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 Guaranteeing
                   Subsidiary, or any Custodian, Trustee, liquidator or other
                   similar official acting in relation to either the Company or
                   such Guaranteeing Subsidiary, any amount paid by either to
                   the Trustee or such Holder, the Subsidiary Guarantee made
                   pursuant to this Supplemental Indenture, to the extent
                   theretofore discharged, shall be reinstated in full force and
                   effect.

              (h)  Each Guaranteeing Subsidiary 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
                   Guaranteeing Subsidiary further agrees that, as between such
                   Guaranteeing Subsidiary, on the one hand, and the Holders and
                   the Trustee, on the other hand:


<PAGE>


                                                                               4


                   (i)  the maturity of the obligations guaranteed hereby may be
                        accelerated as provided in Article 6 of the Indenture
                        for the purposes of the Subsidiary Guarantee made
                        pursuant to this Supplemental Indenture, notwithstanding
                        any stay, injunction or other prohibition preventing
                        such acceleration in respect of the obligations
                        guaranteed hereby; and

                   (ii) in the event of any declaration of acceleration of such
                        obligations as provided in Article 6 of the Indenture,
                        such obligations (whether or not due and payable) shall
                        forthwith become due and payable by such Guaranteeing
                        Subsidiary for the purpose of the Subsidiary Guarantee
                        made pursuant to this Supplemental Indenture.

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

         4.   GUARANTEEING SUBSIDIARIES MAY CONSOLIDATE, ETC. ON CERTAIN TERMS.

              (a)  Except as set forth in Articles 4 and 5 of the Indenture,
                   nothing contained in the Indenture, this Supplemental
                   Indenture or in the Notes shall prevent any consolidation or
                   merger of any Guaranteeing Subsidiary with or into the
                   Company or any Guarantor or shall prevent any transfer, sale
                   or conveyance of the property of any Guaranteeing Subsidiary
                   as an entirety or substantially as an entirety, to the
                   Company or any other Guarantor.

              (b)  Except as set forth in Article 4 of the Indenture, nothing
                   contained in the Indenture, this Supplemental Indenture or in
                   the Notes shall prevent any consolidation or merger of any
                   Guaranteeing Subsidiary with or into a corporation or
                   corporations other than the Company or any other Guarantor
                   (in each case, whether or not affiliated with the
                   Guaranteeing Subsidiary), or successive consolidations or
                   mergers in which a Guaranteeing Subsidiary or its successor
                   or successors shall be a party or parties, or shall prevent
                   any sale or conveyance of the property of any Guaranteeing
                   Subsidiary as an entirety or substantially as an entirety, to
                   a corporation other than the Company or any other Guarantor
                   (in each case, whether or not affiliated with the
                   Guaranteeing Subsidiary) authorized to acquire and operate
                   the same; provided, however, that each Guaranteeing
                   Subsidiary hereby covenants and agrees that (i) subject to
                   the Indenture, upon


<PAGE>


                                                                               5


                   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 Guaranteeing
                   Subsidiary, shall be expressly assumed (in the event that
                   such Guaranteeing Subsidiary 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 Guaranteeing Subsidiary
                   shall have been merged, or by the corporation which shall
                   have acquired such property and (ii) immediately after
                   giving effect to such consolidation, merger, sale or
                   conveyance no Default or Event of Default exists.

              (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 Subsidiary
                   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 Guaranteeing Subsidiary, such
                   successor corporation shall succeed to and be substituted for
                   such Guaranteeing Subsidiary with the same effect as if it
                   had been named herein as the Guaranteeing Subsidiary. Such
                   successor corporation thereupon may cause to be signed any or
                   all of the Subsidiary 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 Subsidiary Guarantees so issued shall in all
                   respects have the same legal rank and benefit under the
                   Indenture and this Supplemental Indenture as the Subsidiary
                   Guarantees theretofore and thereafter issued in accordance
                   with the terms of the Indenture and this Supplemental
                   Indenture as though all of such Subsidiary 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 Guaranteeing
                   Subsidiary), all Liens, if any, in favor of the Trustee in
                   the assets sold thereby shall be released; provided that in
                   the event of an Asset Sale, the Net Proceeds from such sale
                   or other disposition are treated in accordance with the
                   provisions of Section 4.10 of the Indenture. If the assets
                   sold in such sale or other disposition include all or
                   substantially all of the assets of a Guaranteeing Subsidiary
                   or all of the Capital Stock of a Guaranteeing Subsidiary,
                   then the Guaranteeing Subsidiary (in the


<PAGE>


                                                                               6


                   event of a sale or other disposition of all of the Capital
                   Stock of such Guaranteeing Subsidiary) 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 Guaranteeing Subsidiary) shall be released from and
                   relieved of its obligations under this Supplemental
                   Indenture and its Subsidiary Guarantee made pursuant hereto;
                   provided that in the event of an Asset Sale, the Net
                   Proceeds from such sale or other disposition are treated in
                   accordance with the provisions of Section 4.10 of the
                   Indenture. 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 Guaranteeing
                   Subsidiary, as the case may be, in accordance with the
                   provisions of the Indenture and this Supplemental Indenture,
                   including without limitation, Section 4.10 of the Indenture,
                   the Trustee shall execute any documents reasonably required
                   in order to evidence the release of the Guaranteeing
                   Subsidiary from its obligations under this Supplemental
                   Indenture and its Subsidiary Guarantee made pursuant hereto.
                   If the Guaranteeing Subsidiary is not released from its
                   obligations under its Subsidiary Guarantee, it shall remain
                   liable for the full amount of principal of and interest on
                   the Notes and for the other obligations of such Guaranteeing
                   Subsidiary under the Indenture as provided in this
                   Supplemental Indenture.

              (b)  Upon the designation of a Guaranteeing Subsidiary as an
                   Unrestricted Subsidiary in accordance with the terms of the
                   Indenture, such Guaranteeing Subsidiary shall be released and
                   relieved of its obligations under its Subsidiary Guarantee
                   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
                   Guaranteeing Subsidiary as an Unrestricted Subsidiary was
                   made by the Company in accordance with the provisions of the
                   Indenture, including without limitation Section 4.07 of the
                   Indenture, the Trustee shall execute any documents reasonably
                   required in order to evidence the release of such
                   Guaranteeing Subsidiary from its obligations under its
                   Subsidiary Guarantee. Any Guaranteeing Subsidiary not
                   released from its obligations under its Subsidiary Guarantee
                   shall remain liable for the full amount of principal of and
                   interest on the Notes and for the other obligations of any
                   Guaranteeing Subsidiary 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
              Guaranteeing Subsidiary, as such, shall have any liability for any
              obligations of the Company or any Guaranteeing Subsidiary under
              the Notes, any Subsidiary


<PAGE>


                                                                               7


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

         8.   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.

         9.   EFFECT OF HEADINGS. The Section headings herein are for
              convenience only and shall not affect the construction hereof.

         10.  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
              Guaranteeing Subsidiaries 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.

                              L-3 COMMUNICATIONS CORPORATION



                              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 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 SUBSIDIARY GUARANTEE


         Pursuant to the Supplemental Indenture (the "Supplemental Indenture")
dated as of November 9, 2001 among L-3 Communications Corporation, 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 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 Guaranteeing Subsidiary (i) has jointly and
severally unconditionally guaranteed (a) the due and punctual payment of the
principal of, premium and interest 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 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 Subsidiary Guarantee.

         Notwithstanding the foregoing, in the event that the Subsidiary
Guarantee of any Guaranteeing Subsidiary would constitute or result in a
violation of any applicable fraudulent conveyance or similar law of any relevant
jurisdiction, the liability of such Guaranteeing Subsidiary under its Subsidiary
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 Guaranteeing Subsidiary, as such,
shall have any liability for any obligations of the Company or any Guaranteeing
Subsidiary under the Notes, any Subsidiary Guarantee, Indenture, any
supplemental indenture delivered pursuant to the Indenture by such Guaranteeing
Subsidiary or any Subsidiary 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 Subsidiary Guarantee shall be binding upon each Guaranteeing
Subsidiary 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


<PAGE>


extend to and be vested in such transferee or assignee, all subject to the terms
and conditions hereof.

         This Subsidiary Guarantee shall not be valid or obligatory for any
purpose until the certificate of authentication on the Note upon which this
Subsidiary 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.



                            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:



                                      C-2