SUPPLEMENTAL INDENTURE TO BE DELIVERED BY GUARANTEEING SUBSIDIARIES

SUPPLEMENTAL INDENTURE TO BE DELIVERED

BY GUARANTEEING SUBSIDIARIES

Supplemental Indenture (this "Supplemental Indenture"), dated as of

February 20, 2007, 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

1

(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

2

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:

(iii) 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

(iv) 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

3

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 Gu