EX-4.1: THIRD SUPPLEMENTAL INDENTURE

Exhibit 4.1

NOTATION OF GUARANTEE

     For value received, the undersigned Guarantor (which term includes any successor Person under the Indenture) has, jointly and severally, unconditionally guaranteed, to the extent set forth in the Indenture and subject to the provisions in the Indenture dated as of December 20, 2001 (as supplemented by the First Supplemental Indenture, dated as of February 28, 2003, and the Second Supplemental Indenture, dated as of May 13, 2003, the “Indenture”) among IPC Acquisition Corp. (the “Company”), the other Guarantors and The Bank of New York, as trustee (the “Trustee”), (a) the due and punctual payment of the principal of, premium and Special Interest (as defined in the Indenture), if any, and interest on the Notes (as defined in the Indenture), whether at maturity, by acceleration, redemption or otherwise, the due and punctual payment of interest on overdue principal of and interest on the Notes, if any, if lawful, and the due and punctual performance of all other obligations of the Company to the Holders or the Trustee all in accordance with the terms of the Indenture and (b) in case of any extension of time of payment or renewal of any Notes or any of such other obligations, that the same will be promptly paid in full when due or performed in accordance with the terms of the extension or renewal, whether at stated maturity, by acceleration or otherwise. The obligations of the Guarantors to the Holders of Notes and to the Trustee pursuant to the Subsidiary Guarantee and the Indenture are expressly set forth in Article 11 of the Indenture and reference is hereby made to the Indenture for the precise terms of the Subsidiary Guarantee. Each Holder of a Note, by accepting the same, (a) agrees to and shall be bound by such provisions, (b) authorizes and directs the Trustee, on behalf of such Holder, to take such action as may be necessary or appropriate to effectuate the subordination as provided in the Indenture and (c) appoints the Trustee attorney-in-fact of such Holder for such purpose; provided, however, that the Indebtedness evidenced by this Subsidiary Guarantee shall cease to be so subordinated and subject in right of payment upon any defeasance of this Note in accordance with the provisions of the Indenture.

THIRD SUPPLEMENTAL INDENTURE

     THIRD SUPPLEMENTAL INDENTURE (this “Supplemental Indenture”), dated as of December 9, 2004, among Orbacom Systems, Inc., a New Jersey corporation (the “Guaranteeing Subsidiary”), an indirect subsidiary of IPC Acquisition Corp. (or its permitted successor), a Delaware corporation (the “Company”), the Company, the other Guarantors (as defined in the Indenture referred to herein) 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 dated as of December 20, 2001 (as supplemented by the First Supplemental Indenture, dated as of February 28, 2003, and the Second Supplemental Indenture, dated as of May 13, 2003, the “Indenture”) providing for the issuance of 11.50% Senior Subordinated Notes due 2009 (the “Notes”);

     WHEREAS, the Indenture provides that under certain circumstances the Guaranteeing Subsidiary shall execute and deliver to the Trustee a supplemental indenture pursuant to which the Guaranteeing Subsidiary 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 parties 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 to them in the Indenture.

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

          (a) Along with all Guarantors named in the other Supplemental Indentures, to jointly and severally Guarantee to each Holder of a Note authenticated and delivered by the Trustee and to the Trustee and its successors and assigns, the Notes or the obligations of the Company hereunder or thereunder, that:

               (i) the principal of, and premium and Special Interest, if any, and interest 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 and interest on the Notes, if any, if lawful, and all other obligations of the Company to the Holders or the Trustee hereunder or thereunder will be promptly paid in full or performed, all in accordance with the terms hereof and thereof; and

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               (ii) in case of any extension of time of payment or renewal of any Notes or any of such other obligations, that same will be promptly paid in full when due or performed in accordance with the terms of the extension or renewal, whether at stated maturity, by acceleration or otherwise. Failing payment when due of any amount so guaranteed or any performance so guaranteed for whatever reason, the Guarantors shall be jointly and severally obligated to pay the same immediately.

          (b) The obligations hereunder shall be unconditional, irrespective 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.

          (c) The following is hereby waived: 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.

          (d) This Subsidiary Guarantee shall not be discharged except by complete performance of the obligations contained in the Notes and the Indenture, and the Guaranteeing Subsidiary accepts all obligations of a Guarantor under the Indenture.

          (e) If any Holder or the Trustee is required by any court or otherwise to return to the Company, the Guarantors, or any custodian, trustee, liquidator or other similar official acting in relation to either the Company or the Guarantors, any amount paid by either to the Trustee or such Holder, this Subsidiary Guarantee, to the extent theretofore discharged, shall be reinstated in full force and effect.

          (f) The Guaranteeing Subsidiary 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.

          (g) As between the Guarantors, on the one hand, and the Holders and the Trustee, on the other hand, (x) the maturity of the obligations guaranteed hereby may be accelerated as provided in Article 6 of the Indenture for the purposes of this Subsidiary Guarantee, notwithstanding any stay, injunction or other prohibition preventing such acceleration in respect of the obligations guaranteed hereby, and (y) 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 the Guarantors for the purpose of this Subsidiary Guarantee.

          (h) The Guarantors shall have the right to seek contribution from any non-paying Guarantor so long as the exercise of such right does not impair the rights of the Holders under the Subsidiary Guarantee.

               (i) Each Guarantor, and by its acceptance of Notes, each Holder hereby confirms that it is the intention of all such parties that the Subsidiary Guarantee of each such

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Guarantor not constitute a fraudulent transfer or conveyance for purposes of Bankruptcy Law, the Uniform Fraudulent Conveyance Act, the Uniform Fraudulent Transfer Act or any similar federal or state law to the extent applicable to any Subsidiary Guarantee. To effectuate the foregoing intention, the Trustee, the Holders and the Guarantors hereby irrevocably agree that the obligations of the Guaranteeing Subsidiary will, after giving effect to any maximum amount and all other contingent and fixed liabilities that are relevant under any applicable Bankruptcy or fraudulent conveyance laws, and after giving effect to any collections from, rights to receive contribution from or payments made by or on behalf of any other Guarantor in respect of the obligations of such other Guarantor under the Indenture, this new Subsidiary Guarantee shall be limited to the maximum amount permissible such that the obligations of the Guaranteeing Subsidiary under this Subsidiary Guarantee shall not constitute a fraudulent transfer or conveyance.

     3. EXECUTION AND DELIVERY. The Guaranteeing Subsidiary agrees that the Subsidiary Guarantees shall remain in full force and effect notwithstanding any failure to endorse on each Note a notation of such Subsidiary Guarantee.

     4. GUARANTEEING SUBSIDIARY MAY CONSOLIDATE, ETC. ON CERTAIN TERMS.

          (a) The Guaranteeing Subsidiary may not sell or otherwise dispose of all substantially all of its assets to, or consolidate with or merge with or into (whether or not the Guaranteeing Subsidiary is the surviving Person) another Person, other than the Company or another Guarantor unless:

               (i) immediately after giving effect to such transaction, no Default or Event of Default exists; and

               (ii) either (A) subject to Section 11.06 of the Indenture, the Person acquiring the property in any such sale or disposition or the Person formed by or surviving any such consolidation or merger unconditionally assumes all the obligations of the Guaranteeing Subsidiary, pursuant to a supplemental indenture in form and substance reasonably satisfactory to the Trustee, under the Notes, the Indenture and the Subsidiary Guarantee on the terms set forth herein or therein; or (B) the Net Proceeds of such sale or other disposition are applied in accordance with the applicable provisions of the Indenture, including without limitation, Section 4.10 thereof.

          (b) In case of any such consolidation, merger, sale or conveyance and upon the assumption by the successor Person, by supplemental indenture, executed and delivered to the Trustee and satisfactory in form to the Trustee, of the Subsidiary Guarantee endorsed upon the Notes and the due and punctual performance of all of the covenants and conditions of the Indenture to be performed by the Guaranteeing Subsidiary, such successor Person shall succeed to and be substituted for the 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 all of 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

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and benefit under the Indenture as the Subsidiary Guarantees theretofore and thereafter issued in accordance with the terms of the Indenture as though all of such Subsidiary Guarantees had been issued at the date of the execution hereof.

          (c) Notwithstanding the foregoing, any Guarantor may consolidate or merge with or into another Guarantor or into the Company, and the Company may consolidate or merge with or into any Guarantor.

     5. RELEASES.

          (a) In the event of any sale or other disposition of all or substantially all of the assets of any Guarantor, by way of merger, consolidation or otherwise, or a sale or other disposition of all of the capital stock of any Guarantor, in each case to a Person that is not (either before or after giving effect to such transaction) a Subsidiary of the Company or if the Company designates any Restricted Subsidiary that is a Guarantor as an Unrestricted Subsidiary in accordance with Section 4.18 of the Indenture, then such Guarantor (in the event of a sale or other disposition, by way of merger, consolidation or otherwise, of all of the capital stock of such Guarantor or designation as an Unrestricted Subsidiary) or the corporation 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 and relieved of any obligations under its Subsidiary Guarantee; provided that the Net Proceeds of such sale or other disposition are applied in accordance with the applicable provisions of the Indenture, including without limitation Section 4.10 of the Indenture. Upon delivery by the Company to the Trustee of an Officers’ Certificate and an Opinion of Counsel to the effect that such sale or other disposition was made by the Company in accordance with the provisions of the 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 any Guarantor from its obligations under its Subsidiary Guarantee.

          (b) Any Guarantor 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 Guarantor under the Indenture as provided in Article 11 of the Indenture.

     6. NO RECOURSE AGAINST OTHERS. No past, present or future director, officer, employee, incorporator, stockholder or agent of the 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 the Notes.

     7. NEW YORK LAW TO GOVERN. THE INTERNAL LAW OF THE STATE OF NEW YORK SHALL GOVERN AND BE USED TO CONSTRUE THIS SUPPLEMENTAL INDENTURE BUT WITHOUT GIVING EFFECT TO APPLICABLE PRINCIPLES OF CONFLICTS OF LAW TO THE EXTENT THAT THE APPLICATION OF THE LAWS OF ANOTHER JURISDICTION WOULD BE REQUIRED THEREBY.

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     8. 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.

     9. EFFECT OF HEADINGS. The Section headings herein are for convenience only and shall not affect the construction hereof.

     10. 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 Subsidiary and the Company.

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

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Schedule I

IPC Funding Corp.

IPC Information Systems Far East, Inc.

V Band Corp.

IPC Information Systems Holdings, Inc.

IPC Information Systems Holdings USA, Inc.

IPC Information Systems Services, Inc.

Gains Acquisition Corp.

IPC Network Services, Inc.

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Schedule II

IPC Information Systems Holdings, L.L.C.

IPC Information Systems Holdings USA, L.L.C.

IPC Information Systems Services, L.L.C.

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