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                                                                   EXHIBIT 10.55

                     SUPPLEMENTAL INDENTURE TO BE DELIVERED
                          BY GUARANTEEING SUBSIDIARIES

     Supplemental Indenture (this "Supplemental Indenture"), dated as of
February 24, 2006, among L-3 Communications Corporation (or its permitted
successor), a Delaware corporation (the "Company"), each subsidiary of the
Company signatory hereto (each, a "Guaranteeing Subsidiary", and collectively,
the "Guaranteeing Subsidiaries"), and The Bank of New York, as trustee under the
indenture referred to below (the "Trustee").

                                   WITNESSETH

          WHEREAS, the Company has heretofore executed and delivered to the
Trustee an indenture (the "Indenture"), dated as of June 28, 2002 providing for
the issuance of an aggregate principal amount of up to $750,000,000 of 7 5/8%
Senior Subordinated Notes due 2012 (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 9.01 of the Indenture, the Trustee is
authorized to execute and deliver this Supplemental Indenture.

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

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

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

               (a)  Such 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, 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 Additional Amounts,
                         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
                    Subsidiary Guarantee would constitute or result in a
                    violation of any applicable fraudulent conveyance or similar
                    law of any relevant jurisdiction, the liability of such
                    Guaranteeing Subsidiary under this Supplemental Indenture
                    and its Subsidiary Guarantee shall be reduced to the maximum
                    amount permissible under such fraudulent conveyance or
                    similar law.

          3. EXECUTION AND DELIVERY OF SUBSIDIARY GUARANTEES.

               (a)  To evidence its Subsidiary Guarantee set forth in this
                    Supplemental Indenture, such 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, such 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.

               (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 hereof or thereof, 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

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                    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 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 SUBSIDIARY 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

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                    corporation or corporations other than the Company or any
                    other Guarantor (in each case, whether or not affiliated
                    with the Guaranteeing Subsidiary), or successive
                    consolidations or mergers in which a Guaranteeing Subsidiary
                    or its successor or successors shall be a party or parties,
                    or shall prevent any sale or conveyance of the property of
                    any Guaranteeing Subsidiary as an entirety or substantially
                    as an entirety, to a corporation other than the Company or
                    any other Guarantor (in each case, whether or not affiliated
                    with the Guaranteeing Subsidiary) authorized to acquire and
                    operate the same; provided, however, that each Guaranteeing
                    Subsidiary hereby covenants and agrees that (i) subject to
                    the Indenture, upon 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 Subsidiaries, shall be expressly assumed (in
                    the event that such Guaranteeing Subsidiary is not the
                    surviving corporation in the merger), by supplemental
                    indenture satisfactory in form to the Trustee, executed and
                    delivered to the Trustee, by the corporation formed by such
                    consolidation, or into which such Guaranteeing Subsidiary
                    shall have been merged, or by the corporation which shall
                    have acquired such property and (ii) immediately after
                    giving effect to such consolidation, merger, sale or
                    conveyance no Default or Event of Default exists.

               (c)  In case of any such consolidation, merger, sale or
                    conveyance and upon the assumption by the successor
                    corporation, by supplemental indenture, executed and
                    delivered to the Trustee and satisfactory in form to the
                    Trustee, of the Subsidiary Guarantee made pursuant to this
                    Supplemental Indenture and the due and punctual performance
                    of all of the covenants and conditions of the Indenture and
                    this Supplemental Indenture to be performed by such
                    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

                                        4

                    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 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.

               (c)  Each Guaranteeing Subsidiary shall be released and relieved
                    of its obligations under this Supplemental Indenture in
                    accordance with, and subject to, Section 4.18 of the
                    Indenture.

          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

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the Notes. Such waiver may not be effective to waive liabilities under the
federal securities laws and it is the view of the SEC that such a waiver is
against public policy.

          7. SUBORDINATION OF SUBSIDIARY GUARANTEES; ANTI-LAYERING. No
Guaranteeing Subsidiary 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 Guaranteeing Subsidiary and senior in
any respect in right of payment to any of the Subsidiary Guarantees.
Notwithstanding the foregoing sentence, the Subsidiary Guarantee of each
Guaranteeing Subsidiary shall be subordinated to the prior payment in full of
all Senior Debt of that Guaranteeing Subsidiary (in the same manner and to the
same extent that the Notes are subordinated to Senior Debt), 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.

          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 Guaranteeing Subsidiaries 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 24, 2006                   L-3 COMMUNICATIONS CORPORATION

                                           By: /s/ Christopher C. Cambria
                                               ---------------------------------
                                               Name: Christopher C. Cambria
                                               Title: Senior Vice President,
                                                      Secretary and General
                                                      Counsel

Dated: February 24, 2006                APCOM, INC., a Maryland corporation
                                        BROADCAST SPORTS INC., a Delaware
                                           corporation
                                        D.P. ASSOCIATES INC., a Virginia
                                           corporation
                                        ELECTRODYNAMICS, INC., an Arizona
                                           corporation
                                        HENSCHEL INC., a Delaware corporation
                                        HYGIENETICS ENVIRONMENTAL SERVICES,
                                           INC., a Delaware corporation
                                        INTELLIGENCE DATA SYSTEMS, INC., a
                                           Virginia corporation
                                        INTERNATIONAL SYSTEMS, LLC, a California
                                           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 AIS GP CORPORATION, a
                                           Delaware corporation
                                        L-3 COMMUNICATIONS ADVANCED LASER
                                           SYSTEMS TECHNOLOGY, INC., a Florida
                                           corporation
                                        L-3 COMMUNICATIONS APPLIED SIGNAL AND
                                           IMAGE TECHNOLOGY, INC., a Maryland
                                           corporation
                                        L-3 COMMUNICATIONS AVIONICS SYSTEMS,
                                           INC., a Delaware corporation
                                        L-3 COMMUNICATIONS AVISYS CORPORATION, a
                                           Texas corporation
                                        L-3 COMMUNICATIONS CSI, INC., a
                                           California corporation
                                        L-3 COMMUNICATIONS AYDIN CORPORATION, a
                                           Delaware corporation
                                        L-3 COMMUNICATIONS CE HOLDINGS, INC., a
                                           Delaware corporation
                                        L-3 COMMUNICATIONS CINCINNATI
                                           ELECTRONICS CORPORATION, an Ohio
                                           corporation
                                        L-3 COMMUNICATIONS ELECTRON
                                           TECHNOLOGIES, INC., a Delaware
                                           corporation
                                        L-3 COMMUNICATIONS EO/IR, INC., a
                                           Florida corporation
                                        L-3 COMMUNICATIONS EOTECH, INC., a
                                           Delaware 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 INFRAREDVISION
                                           TECHNOLOGY CORPORATION, a California
                                           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 MOBILE-VISION, INC.,
                                           a New Jersey corporation
                                        L-3 COMMUNICATIONS SECURITY AND
                                           DETECTION SYSTEMS, INC., a Delaware
                                           corporation
                                        L-3 COMMUNICATIONS SONOMA EO, INC., a
                                           California corporation
                                        L-3 COMMUNICATIONS TITAN CORPORATION, a
                                           Delaware corporation
                                        L-3 COMMUNICATIONS VECTOR INTERNATIONAL
                                           AVIATION LLC, a Delaware limited
                                           liability company
                                        L-3 COMMUNICATIONS VERTEX AEROSPACE LLC,
                                           a Delaware limited liability company
                                        L-3 COMMUNICATIONS WESTWOOD CORPORATION,
                                           a Nevada corporation
                                        LINCOM WIRELESS, INC., a Delaware
                                           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
                                        PROCOM SERVICES, INC., a California
                                           corporation
                                        SHELLCO, INC., a Delaware corporation
                                        SPD ELECTRICAL SYSTEMS, INC., a Delaware
                                           corporation
                                        SPD SWITCHGEAR INC., a Delaware
                                           corporation
                                        SYCOLEMAN CORPORATION, a Florida
                                           corporation
                                        TITAN FACILITIES, INC., a Virginia
                                           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 LLC, a Delaware limited liability
                                           company
                                        WOLF COACH, INC., a Massachusetts
                                           corporation

                                           As Guaranteeing Subsidiaries

                                           By: /s/ Christopher C. Cambria
                                               ---------------------------------
                                               Name: Christopher C. Cambria
                                               Title: Vice President and
                                                      Secretary

Dated: February 24, 2006                   THE BANK OF NEW YORK,
                                           as Trustee

                                           By: /s/ Robert A. Massimillo
                                               ---------------------------------
                                               Name: Robert A. Massimillo
                                               Title: Vice President

      NOTATION ON SENIOR SUBORDINATED NOTE RELATING TO SUBSIDIARY GUARANTEE

          Pursuant to the Supplemental Indenture (the "Supplemental Indenture")
dated as of February 24, 2006 among L-3 Communications Corporation, a Delaware
corporation, the Guarantors party thereto (each a "Guarantor" and collectively
the "Guarantors") and The Bank of New York, as trustee (the "Trustee"), each
Guarantor (i) has jointly and severally unconditionally guaranteed (a) the due
and punctual payment of the principal of, and premium, interest and Additional
Amounts 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 Additional
Amounts 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 the
Subsidiary Guarantee (as defined in the Supplemental Indenture).

          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 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.

          The 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.

          The Subsidiary Guarantee shall not be valid or obligatory for any
purpose until the certificate of authentication on the Note upon which the
Subsidiary Guarantee is noted has 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, dated as
of June 28, 2002, among L-3 Communications Corporation, the Guarantors party
thereto and the Trustee.

Dated: February 24, 2006                APCOM, INC.
                                        BROADCAST SPORTS INC.
                                        D.P. ASSOCIATES INC.
                                        ELECTRODYNAMICS, INC.
                                        HENSCHEL INC.
                                        HYGIENETICS ENVIRONMENTAL SERVICES, INC.
                                        INTELLIGENCE DATA SYSTEMS, INC.
                                        INTERNATIONAL SYSTEMS, LLC
                                        INTERSTATE ELECTRONICS CORPORATION
                                        KDI PRECISION PRODUCTS, INC.
                                        L-3 COMMUNICATIONS AEROMET, INC.
                                        L-3 COMMUNICATIONS AIS GP CORPORATION
                                        L-3 COMMUNICATIONS ADVANCED LASER
                                           SYSTEMS TECHNOLOGY, INC.
                                        L-3 COMMUNICATIONS APPLIED SIGNAL AND
                                           IMAGE TECHNOLOGY, INC.,
                                        L-3 COMMUNICATIONS AVIONICS SYSTEMS,
                                           INC.
                                        L-3 COMMUNICATIONS AVISYS CORPORATION
                                        L-3 COMMUNICATIONS CSI, INC.
                                        L-3 COMMUNICATIONS AYDIN CORPORATION
                                        L-3 COMMUNICATIONS CE HOLDINGS, INC.
                                        L-3 COMMUNICATIONS CINCINNATI
                                           ELECTRONICS CORPORATION
                                        L-3 COMMUNICATIONS ELECTRON
                                           TECHNOLOGIES, INC.
                                        L-3 COMMUNICATIONS EO/IR, INC.
                                        L-3 COMMUNICATIONS EOTECH, INC.
                                        L-3 COMMUNICATIONS ESSCO, INC.
                                        L-3 COMMUNICATIONS FLIGHT INTERNATIONAL
                                           AVIATION LLC
                                        L-3 COMMUNICATIONS FLIGHT CAPITAL LLC
                                        L-3 COMMUNICATIONS GOVERNMENT
                                           SERVICES, INC.,
                                        L-3 COMMUNICATIONS ILEX SYSTEMS, INC.
                                        L-3 COMMUNICATIONS INFRAREDVISION
                                           TECHNOLOGY CORPORATION
                                        L-3 COMMUNICATIONS INTEGRATED
                                           SYSTEMS L.P.
                                        L-3 COMMUNICATIONS INVESTMENTS INC.
                                        L-3 COMMUNICATIONS KLEIN ASSOCIATES,
                                           INC.
                                        L-3 COMMUNICATIONS MAS (US) CORPORATION
                                        L-3 COMMUNICATIONS MOBILE-VISION, INC.
                                        L-3 COMMUNICATIONS TITAN CORPORATION
                                        L-3 COMMUNICATIONS SECURITY AND
                                           DETECTION SYSTEMS, INC.
                                        L-3 COMMUNICATIONS SONOMA EO, INC.
                                        L-3 COMMUNICATIONS VECTOR INTERNATIONAL
                                           AVIATION LLC
                                        L-3 COMMUNICATIONS VERTEX AEROSPACE LLC
                                        L-3 COMMUNICATIONS WESTWOOD CORPORATION
                                        LINCOM WIRELESS, INC.
                                        MCTI ACQUISITION CORPORATION
                                        MICRODYNE COMMUNICATIONS TECHNOLOGIES
                                           INCORPORATED

                                        MICRODYNE CORPORATION
                                        MICRODYNE OUTSOURCING INCORPORATED
                                        MPRI, INC.
                                        PAC ORD INC.
                                        POWER PARAGON, INC.
                                        PROCOM SERVICES, INC.
                                        SHELLCO, INC.
                                        SPD ELECTRICAL SYSTEMS, INC.
                                        SPD SWITCHGEAR INC.
                                        SYCOLEMAN CORPORATION
                                        TITAN FACILITIES, INC.
                                        TROLL TECHNOLOGY CORPORATION
                                        WESCAM AIR OPS INC.
                                        WESCAM AIR OPS LLC
                                        WESCAM HOLDINGS (US) INC.
                                        WESCAM LLC
                                        WOLF COACH, INC.

                                           As Guaranteeing Subsidiaries

                                           By: /s/ Christopher C. Cambria
                                               ---------------------------------
                                               Name: Christopher C. Cambria
                                               Title: Vice President and
                                                      Secretary
```