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                                                                   EXHIBIT 10.58

                          SUPPLEMENTAL INDENTURE TO BE
                             DELIVERED BY GUARANTORS

     SUPPLEMENTAL INDENTURE (this "Supplemental Indenture"), dated as of
February 25, 2004, among L-3 Communications Holdings, Inc. (or its permitted
successor), a Delaware corporation (the "Company"), each subsidiary of the
Company signatory hereto (each, a "Guarantor", and collectively, the
"Guarantors"), 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:

     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

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                    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 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

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               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 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

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                         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
               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

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               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 pursuant
               hereto. If the Guarantor is not released from its obligations
               under its Guarantee, it shall

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               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.

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     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.

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

Dated: February 25, 2004                  L-3 COMMUNICATIONS HOLDINGS, INC.

                                          By:
                                             -----------------------------------
                                             Name:
                                             Title:

Dated: February 25, 2004        APCOM, INC., a Maryland corporation
                                BROADCAST SPORTS INC., a Delaware 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 AEROMET, INC., an Oregon
                                   corporation
                                L-3 COMMUNICATIONS VERTEX AEROSPACE LLC, a
                                   Delaware limited liability company
                                L-3 COMMUNICATIONS AIS GP CORPORATION, a
                                   Delaware corporation
                                L-3 COMMUNICATIONS AVIONICS SYSTEMS, INC., a
                                   Delaware corporation
                                L-3 COMMUNICATIONS AYDIN CORPORATION, a
                                   Delaware corporation
                                L-3 COMMUNICATIONS CORPORATION, a Delaware
                                   corporation
                                L-3 COMMUNICATIONS CSI, INC., a California
                                   corporation
                                L-3 COMMUNICATIONS ESSCO, INC., a Delaware
                                   corporation
                                L-3 COMMUNICATIONS FLIGHT INTERNATIONAL AVIATION
                                   LLC, a Delaware limited liability company
                                L-3 COMMUNICATIONS FLIGHT CAPITAL LLC, a
                                   Delaware limited liability company
                                L-3 COMMUNICATIONS GOVERNMENT SERVICES, INC., a
                                   Virginia corporation
                                L-3 COMMUNICATIONS ILEX SYSTEMS, INC., a
                                   Delaware corporation
                                L-3 COMMUNICATIONS INTEGRATED SYSTEMS L.P., a
                                   Delaware limited partnership
                                L-3 COMMUNICATIONS INVESTMENTS INC., a Delaware
                                   corporation
                                L-3 COMMUNICATIONS KLEIN ASSOCIATES, INC., a
                                   Delaware corporation
                                L-3 COMMUNICATIONS MAS (US) CORPORATION, a
                                   Delaware corporation
                                L-3 COMMUNICATIONS SECURITY AND DETECTION
                                   SYSTEMS CORPORATION CALIFORNIA, a California
                                   corporation
                                L-3 COMMUNICATIONS SECURITY AND DETECTION
                                   SYSTEMS CORPORATION DELAWARE, a Delaware
                                   corporation

                                L-3 COMMUNICATIONS SECURITY SYSTEMS CORPORATION,
                                   a Delaware corporation
                                L-3 COMMUNICATIONS STORM CONTROL SYSTEMS, INC.,
                                   a California corporation
                                L-3 COMMUNICATIONS VECTOR INTERNATIONAL AVIATION
                                   LLC, a Delaware limited liability company
                                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
                                SPD ELECTRICAL SYSTEMS, INC., a Delaware
                                   corporation
                                SPD SWITCHGEAR INC., a Delaware corporation
                                SYCOLEMAN CORPORATION, a Florida corporation
                                TROLL TECHNOLOGY CORPORATION, a California
                                   corporation
                                WESCAM AIR OPS INC., a Delaware corporation
                                WESCAM AIR OPS LLC, a Delaware limited
                                   liability company
                                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
                                WOLF COACH, INC., a Massachusetts corporation
                                   As Guaranteeing Subsidiaries

                                          By:
                                             -----------------------------------
                                             Name:
                                             Title:

Dated:  February 25, 2004                 THE BANK OF NEW YORK,
                                          as Trustee

                                          By:
                                             -----------------------------------
                                             Name:
                                             Title:
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