Document:

<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 a 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 October 24, 2001 providing for the
issuance of an aggregate principal amount of up to $420,000,000 of 4.00% Senior
Subordinated Convertible Contingent Debt Securities (CODES) due 2011 (the
"Securities");

     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 Securities 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 Securities 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 Securities (collectively, the "Guaranteeing
          Subsidiaries" and each, a "Guaranteeing Subsidiary"), unconditionally
          guarantees to each Holder of a Security 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
          Securities or the Obligations of the Company under the Indenture or
          the Securities, that:

          (i)  the principal of, premium, interest (including Contingent
               Interest, if any) and Additional Amounts, if any, on the
               Securities 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 (including
               Contingent Interest, if any) and Additional Amounts, if any, on
               the Securities, 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
               Securities 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,
          substantially in the form included as Exhibit B to the Indenture,
          shall be endorsed by an Officer of such Guarantor on each Security
          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

<PAGE>

                                                                               3

          notwithstanding any failure to endorse on each Security a notation of
          such Guarantee.

     (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 Security on which a Guarantee is endorsed, the
          Guarantee shall be valid nevertheless.

     (d)  The delivery of any Security 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 Securities or the Indenture, the absence of any
          action to enforce the same, any waiver or consent by any Holder of the
          Securities with respect to any provisions of the Securities 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 Securities 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

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                                                                               4

               preventing such acceleration in respect of the Obligations
               guaranteed hereby;

          (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
               Securities shall prevent (a) any consolidation or merger of any
               Guarantor with or into the Company or any 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
               Securities 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

<PAGE>

                                                                               5

               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 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 Securities 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 Securities 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

<PAGE>

                                                                               6

               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 (including Contingent
               Interest, if any) and Additional Amounts, if any, on the
               Securities and for the other obligations of such Guarantor under
               the Indenture as provided herein.

          (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 Securities 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 expire and whether or not any of
               those Securities 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 Securities 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 Securities, 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 Securities by accepting a
Security waives and releases all such liability. The waiver and release are part
of the consideration for issuance of the Securities. Such waiver may not be
effective to waive liabilities under the federal securities laws and it is the
view of the Securities and Exchange 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 (in the same manner and to the same extent that the Securities
are subordinated to Senior Debt), which shall include all guarantees of Senior
Debt.
<PAGE>

                                                                               7

     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.

     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 CONVERTIBLE CONTINGENT DEBT SECURITY
                              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
(including Contingent Interest, if any) and Additional Amounts, if any, on the
Security, 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 (including Contingent Interest,
if any) and Additional Amounts, if any, on the Security, and (c) in case of any
extension of time of payment or renewal of any Security 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
Security, 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 Security 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

<PAGE>

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.

     This Guarantee shall not be valid or obligatory for any purpose until the
certificate of authentication on the Security 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 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>

                          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").

                              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 December 11, 1998
providing for the issuance of an aggregate principal amount of up to
$300,000,000 of 8% 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:

<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 Guaranteeing Subsidiary hereby
agrees as follows:

                  (a)      Each Guaranteeing Subsidiary, jointly and severally
                           with all other current and future guarantors of the
                           Notes (collectively, the "Guarantors" and each, a
                           "Guarantor"), 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 each 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 F 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:

                           (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

<PAGE>

                                                                              4

                                    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 other
                           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 such
                           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 such 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 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

<PAGE>

                                                                              5

                           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 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

<PAGE>

                                                                              6

                           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
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.

<PAGE>

                                                                              7

                  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.

Dated: November 9, 2001

                                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 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 Subsidiary Guarantee.

                  Notwithstanding the foregoing, in the event that the
Subsidiary 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 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 Guarantor, as such, shall have any
liability for any obligations of the Company or any Guarantor under the Notes,
any Subsidiary Guarantee, the Indenture, any supplemental indenture delivered
pursuant to the Indenture by such Guarantor 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 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 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.

<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:

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