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                                                                   EXHIBIT 10.57

                          SUPPLEMENTAL INDENTURE TO BE
                             DELIVERED BY GUARANTORS

         SUPPLEMENTAL INDENTURE (this "Supplemental Indenture"), dated as of
March 10, 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, 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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                                                                               2


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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                                                                               3

                             (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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                                                                               4

                        (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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                                                                               5

                        (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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                                                                               6

                             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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                                                                               7

                             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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                                                                               8

                  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: March 10, 2003        L-3 COMMUNICATIONS HOLDINGS, INC.


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















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Dated: March 10, 2003        AMI INSTRUMENTS, INC.
                             APCOM, INC.
                             BROADCAST SPORTS INC.
                             CELERITY SYSTEMS INCORPORATED
                             EER SYSTEMS, INC.
                             ELECTRODYNAMICS, 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.
                             POWER PARAGON, INC.
                             SHIP ANALYTICS, INC.
                             SHIP ANALYTICS INTERNATIONAL, INC.
                             SHIP ANALYTICS USA, INC.



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                                                                              11

                             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:












<PAGE>



Dated:  March 10, 2003       THE BANK OF NEW YORK,
                             as Trustee


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