Exhibit 4.15
 
  W I T N E S S E T H
       (a)
    
    Such Guaranteeing Subsidiary, jointly and
severally with all other current and future guarantors of the CODES
(collectively, the Guarantors and each, a Guarantor),
unconditionally guarantees to each Holder of a CODE 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 CODES or the Obligations of the Company under the
Indenture or the CODES, that:
 (i)
    
    the principal of and interest
(including Contingent Interest and Additional Interest, if
any) on the CODES will be promptly paid in full when due,
whether at maturity, by acceleration, redemption or otherwise,
and interest on the overdue principal of and interest
(including Contingent Interest and Additional Interest, if
any) on the CODES, 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 CODES 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.
  (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 A to the Indenture shall be endorsed by an Officer
of such Guaranteeing Subsidiary on each CODE 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 CODE 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 CODE on which a
Subsidiary Guarantee is endorsed, the Subsidiary Guarantee shall be
valid nevertheless.(d)
    
    The delivery of any CODE 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, to the extent permitted by applicable
law, be unconditional, regardless of the validity, regularity or
enforceability of the CODES or the Indenture, the absence of any action
to enforce the same, any waiver or consent by any Holder of the CODES
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, to the extent
permitted by applicable law, 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
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Subsidiary Guarantee made pursuant to this Supplemental Indenture
will not be discharged except by complete performance of the
Obligations contained in the CODES 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 4 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;(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 Guaranteeing Subsidiary for the purpose of the Subsidiary
Guarantee made pursuant to this Supplemental Indenture; and(iii)
    
    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.
  (a)
    
    Except as set forth in Articles 6 and 9 of the
Indenture, nothing contained in the Indenture, this Supplemental
Indenture or in the CODES shall prevent (i) any consolidation or merger
of any Guaranteeing Subsidiary with or into the Company or any other
Guarantor, (ii) 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 or (iii) any merger of a
Guarantor with or into with an Affiliate of that Guarantor that has not
significant assets or liabilities and was incorporated solely for the
purpose of reincorporating such Guarantor in another State of the
United States so long as the amount of
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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 CODES shall prevent any consolidation or merger of
any Guaranteeing Subsidiary with or into any Person organized under the
laws of the United States of America, any state thereof, the District
of Columbia or any territory thereof 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 any Person organized under the laws of the United
States of America, any state thereof, the District of Columbia or any
territory thereof 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 any Person formed by such consolidation, or into which such
Guaranteeing Subsidiary shall have been merged, or by any Person 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 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 of the Indenture (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
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 Person 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 Person
thereupon may cause to be signed any or all of the Subsidiary
Guarantees to be endorsed upon the CODES 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
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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.
  (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. If the assets sold in such sale or
other disposition (including by way of merger or consolidation) 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. 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, 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
(including Contingent Interest and Additional Interest, if any) on the
CODES 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 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 of the
Indenture (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 Guaranteeing Subsidiary
shall be released and relieved of all 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 and the indentures
governing , the Outstanding Senior Subordinated Notes as the same are
in effect on the date of the Indenture (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),
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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 CODES and for the other obligations of any
Guaranteeing Subsidiary under the Indenture as provided herein.
 (c)
    
    Upon any Guarantor being released from its
guarantees of, and all pledges and security interests granted in
connection with, Indebtedness of the Company or any of its Subsidiaries
(other than a Foreign Subsidiary), such Guarantor shall be released and
relieved of its obligations under this Supplemental Indenture.
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Dated: February 20, 2009
    
    L-3 COMMUNICATIONS HOLDINGS, INC.By:
    
    /s/
Steven M. PostName: Steven M. PostTitle: Senior Vice President, General Counsel and
Corporate Secretary




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As Guaranteeing SubsidiariesBy:
    
    /s/
Steven M. PostName: Steven M. PostTitle: Vice President and Secretary
  By:
    
    /s/
Steven M. PostName: Steven M. PostTitle: Senior Vice President, General Counsel and
Corporate Secretary
  By: L-3 COMMUNICATIONS
AIS GP CORPORATION, as General PartnerBy:
    
    /s/
Steven M. PostName: Steven M. PostTitle: Vice President and Secretary
 
 By: L-3 COMMUNICATIONS
VERTEX AEROSPACE LLC, as Sole MemberBy: L-3 COMMUNICATIONS INTEGRATED SYSTEMS L.P., as Sole
MemberBy: L-3 COMMUNICATIONS
AIS GP CORPORATION, as General PartnerBy:
    
    /s/
Steven M. PostName: Steven M. PostTitle: Vice President and Secretary




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By: L-3 COMMUNICATIONS INTEGRATED SYSTEMS L.P., as Sole
MemberBy: L-3 COMMUNICATIONS
AIS GP CORPORATION, as General PartnerBy:
    
    /s/
Steven M. PostName: Steven M. PostTitle: Vice President and Secretary
  By: L-3 COMMUNICATIONS CORPORATION, as Sole MemberBy:
    
    /s/
Steven M. PostName: Steven M. PostTitle: Senior Vice President, General Counsel and
Corporate Secretary
  By: L-3 COMMUNICATIONS CORPORATION, as Sole MemberBy:
    
    /s/
Steven M. PostName: Steven M. PostTitle: Senior Vice President, General Counsel and
Corporate Secretary




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Dated: February 20, 2009
    
    THE BANK OF NEW YORK
MELLON,
as TrusteeBy:
    
    /s/ Franca FerreraName: Franca FerreraTitle: Assistant Vice President




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Supplemental Indenture Guarantor Guarantors Trustee




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As Guaranteeing SubsidiariesBy:
    
    /s/
Steven M. PostName: Steven M. PostTitle: Vice President and Secretary
  By:
    
    /s/
Steven M. PostName: Steven M. PostTitle: Senior Vice President, General Counsel and
Corporate Secretary
  By: L-3 COMMUNICATIONS
AIS GP CORPORATION, as General PartnerBy:
    
    /s/
Steven M. PostName: Steven M. PostTitle: Vice President and Secretary
 
 By: L-3 COMMUNICATIONS
VERTEX AEROSPACE LLC, as Sole MemberBy: L-3 COMMUNICATIONS INTEGRATED SYSTEMS L.P., as Sole
MemberBy: L-3 COMMUNICATIONS
AIS GP CORPORATION, as General PartnerBy:
    
    /s/
Steven M. PostName: Steven M. PostTitle: Vice President and Secretary




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By: L-3 COMMUNICATIONS INTEGRATED SYSTEMS L.P., as Sole
MemberBy: L-3 COMMUNICATIONS
AIS GP CORPORATION, as General PartnerBy:
    
    /s/
Steven M. PostName: Steven M. PostTitle: Vice President and Secretary
  By: L-3 COMMUNICATIONS CORPORATION, as Sole MemberBy:
    
    /s/
Steven M. PostName: Steven M. PostTitle: Senior Vice President, General Counsel and
Corporate Secretary
  By: L-3 COMMUNICATIONS CORPORATION, as Sole MemberBy:
    
    /s/
Steven M. PostName: Steven M. PostTitle: Senior Vice President, General Counsel and
Corporate Secretary