Exhibit 10.57

                          SUPPLEMENTAL INDENTURE TO BE
                             DELIVERED BY GUARANTORS

         SUPPLEMENTAL INDENTURE (this "Supplemental Indenture"), dated as of May
5, 2003, among AMI Instruments, Inc., an Oklahoma corporation, Apcom, Inc., a
Maryland corporation, Broadcast Sports Inc., a Delaware corporation, Celerity
Systems Incorporated, a California corporation, EER Systems, Inc., a Virginia
corporation, Electrodynamics, Inc., an Arizona corporation, Goodrich Aerospace
Component Overhaul & Repair, Inc., a Delaware corporation, Goodrich Avionics
Systems, Inc., a Delaware corporation, Goodrich FlightSystems, Inc., an Ohio
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 AIS GP Corporation, a California corporation, L-3
Communications Analytics Corporation, a California corporation, L-3
Communications Atlantic Science and Technology Corporation, a New Jersey
corporation, L-3 Communications Aydin Corporation, a Delaware corporation, L-3
Communications Corporation, a Delaware corporation, L-3 Communications ESSCO,
Inc., a Delaware corporation, L-3 Communications ILEX Systems, Inc., a Delaware
corporation, L-3 Communications IMC Corporation, a Connecticut corporation, L-3
Communications Integrated Systems L.P., a Delaware limited partnership, L-3
Communications Investments, Inc., a Delaware corporation, L-3 Communications
Security and Detection Systems Corporation Delaware, a Delaware corporation, L-3
Communications Security and Detection Systems Corporation California, a
California corporation, L-3 Communications SPD Technologies, Inc., a Delaware
corporation, L-3 Communications Storm Control Systems, Inc., a California
corporation, L-3 Communications TMA Corporation, a Virginia corporation, L-3
Communications Westwood Corporation, a Nevada corporation, MCTI Acquisition
Corporation, a Maryland Corporation, Microdyne Communications Technologies
Incorporated, a Maryland corporation, Microdyne Corporation, a Maryland
corporation, Microdyne Outsourcing Incorporated, a Maryland corporation, MPRI,
Inc., a Delaware corporation, Pac Ord Inc., a Delaware corporation, Power
Paragon, Inc., a Delaware corporation, Ship Analytics, Inc., a Connecticut
corporation, Ship Analytics International, Inc., a Delaware corporation, Ship
Analytics USA, Inc., a Connecticut corporation, Southern California Microwave,
Inc., a California corporation, SPD Electrical Systems, Inc., a Delaware
corporation, SPD Holdings, Inc., a Delaware corporation, SPD Switchgear Inc., a
Delaware corporation, SYColeman Corporation, a Florida corporation, Telos
Corporation, a California corporation, Troll Technology Corporation, a
California corporation, Wescam Air Ops Inc., a Delaware corporation, Wescam Air
Ops LLC, a Delaware limited liability, Wescam Holdings (US) Inc., a Delaware
corporation, Wescam Incorporated, a Florida corporation, Wescam LLC, a Delaware
limited liability company, Wescam Sonoma Inc., a California corporation and Wolf
Coach, Inc., a Massachusetts corporation (each, a "Guarantor", and collectively,
the "Guarantors"), each an indirect subsidiary of L-3 Communications Holdings,
Inc. (or its permitted successor), a Delaware corporation (the "Company"), the
Company and The Bank of New York, as trustee under the indenture referred to
below (the "Trustee").

                              W I T N E S S E T H:
                              - - - - - - - - - -

         WHEREAS, the Company has heretofore executed and delivered to the
Trustee an indenture (the "Indenture"), dated as of November 21, 2000 providing
for the issuance of an


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aggregate principal amount of up to $300,000,000 of 5 1/4% Convertible Senior
Subordinated Notes due 2009 (the "Notes");

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

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

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


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

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

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

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

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

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

         3. EXECUTION AND DELIVERY OF GUARANTEES.

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

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

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

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

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

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

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

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

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

                   (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.

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

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

              (c)  In case of any such consolidation, merger, sale or conveyance
                   and upon the assumption by the successor corporation, by



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

         5. RELEASES.

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

              (b)  Upon the designation of a Guarantor as an Excluded Subsidiary
                   in accordance with the terms of the Indenture and the
                   indentures

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

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

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

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

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

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         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.




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                  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: May 5, 2003                  L-3 COMMUNICATIONS HOLDINGS, INC.


                                    By:/s/ Christopher C. Cambria
                                    -------------------------------
                                    Name:
                                    Title:




                                                                              10

Dated: May 5, 2003        AMI INSTRUMENTS, INC.
                          APCOM, INC.
                          BROADCAST SPORTS INC.
                          CELERITY SYSTEMS INCORPORATED
                          EER SYSTEMS, INC.
                          ELECTRODYNAMICS, INC.
                          GOODRICH AEROSPACE COMPONENT OVERHAUL & REPAIR, INC.
                          GOODRICH AVIONICS SYSTEMS, INC.
                          GOODRICH FLIGHTSYSTEMS, INC.
                          HENSCHEL INC.
                          HYGIENETICS ENVIRONMENTAL SERVICES, INC.
                          INTERSTATE ELECTRONICS CORPORATION
                          KDI PRECISION PRODUCTS, INC.
                          L-3 COMMUNICATIONS AIS GP CORPORATION
                          L-3 COMMUNICATIONS ANALYTICS CORPORATION
                          L-3 COMMUNICATIONS ATLANTIC SCIENCE AND TECHNOLOGY CORPORATION
                          L-3 COMMUNICATIONS AYDIN CORPORATION
                          L-3 COMMUNICATIONS CORPORATION
                          L-3 COMMUNICATIONS ESSCO, INC.
                          L-3 COMMUNICATIONS ILEX SYSTEMS, INC.
                          L-3 COMMUNICATIONS IMC CORPORATION
                          L-3 COMMUNICATIONS INTEGRATED SYSTEMS L.P.
                          L-3 COMMUNICATIONS INVESTMENTS, INC.
                          L-3 COMMUNICATIONS SECURITY AND DETECTION SYSTEMS CORPORATION DELAWARE
                          L-3 COMMUNICATIONS SECURITY AND DETECTION SYSTEMS CORPORATION CALIFORNIA
                          L-3 COMMUNICATIONS SPD TECHNOLOGIES, INC.
                          L-3 COMMUNICATIONS STORM CONTROL SYSTEMS, INC.
                          L-3 COMMUNICATIONS TMA CORPORATION
                          L-3 COMMUNICATIONS WESTWOOD CORPORATION
                          MCTI ACQUISITION CORPORATION
                          MICRODYNE COMMUNICATIONS TECHNOLOGIES INCORPORATED
                          MICRODYNE CORPORATION
                          MICRODYNE OUTSOURCING INCORPORATED
                          MPRI, INC.
                          PAC ORD INC.




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                          POWER PARAGON, INC.
                          SHIP ANALYTICS, INC.
                          SHIP ANALYTICS INTERNATIONAL, INC.
                          SHIP ANALYTICS USA, INC.
                          SOUTHERN CALIFORNIA MICROWAVE, INC.
                          SPD ELECTRICAL SYSTEMS, INC.
                          SPD HOLDINGS, INC.
                          SPD SWITCHGEAR INC.
                          SYCOLEMAN CORPORATION
                          TELOS CORPORATION
                          TROLL TECHNOLOGY CORPORATION
                          WESCAM AIR OPS INC.
                          WESCAM AIR OPS LLC
                          WESCAM INCORPORATED
                          WESCAM LLC
                          WESCAM SONOMA INC.
                          WESCAM HOLDINGS (US) INC.
                          WOLF COACH, INC.
                          As Guaranteeing Subsidiaries

                          By:/s/ Christopher C. Cambria
                          --------------------------------
                          Name:
                          Title:







Dated:  May 5, 2003       THE BANK OF NEW YORK,
                          as Trustee


                          By:/s/ Kisha A. Holder
                          ------------------------
                          Name:
                          Title: