**Exhibit 4.1**
**NOTATION OF GUARANTEE**
     For value received, the undersigned Guarantor (which term includes any successor Person underthe Indenture) has, jointly and severally, unconditionally guaranteed, to the extent set forth inthe Indenture and subject to the provisions in the Indenture dated as of December 20, 2001 (assupplemented by the First Supplemental Indenture, dated as of February 28, 2003, and the SecondSupplemental 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 dueand punctual payment of the principal of, premium and Special Interest (as defined in theIndenture), 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 overdueprincipal of and interest on the Notes, if any, if lawful, and the due and punctual performance ofall other obligations of the Company to the Holders or the Trustee all in accordance with the termsof the Indenture and (b) in case of any extension of time of payment or renewal of any Notes or anyof such other obligations, that the same will be promptly paid in full when due or performed inaccordance with the terms of the extension or renewal, whether at stated maturity, by accelerationor otherwise. The obligations of the Guarantors to the Holders of Notes and to the Trusteepursuant to the Subsidiary Guarantee and the Indenture are expressly set forth in Article 11 of theIndenture and reference is hereby made to the Indenture for the precise terms of the SubsidiaryGuarantee. Each Holder of a Note, by accepting the same, (a) agrees to and shall be bound by suchprovisions, (b) authorizes and directs the Trustee, on behalf of such Holder, to take such actionas 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*, thatthe Indebtedness evidenced by this Subsidiary Guarantee shall cease to be so subordinated andsubject in right of payment upon any defeasance of this Note in accordance with the provisions ofthe Indenture.         **ORBACOM SYSTEMS, INC.**          By: /s/ TIMOTHY WHELAN         Name: Timothy Whelan   Title: Treasurer  
 

 

**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*”), anindirect 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 datedas of December 20, 2001 (as supplemented by the First Supplemental Indenture, dated as of February28, 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 Subsidiaryshall execute and deliver to the Trustee a supplemental indenture pursuant to which theGuaranteeing Subsidiary shall unconditionally guarantee all of the Company’s Obligations under theNotes 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 anddeliver this Supplemental Indenture.
     NOW THEREFORE, in consideration of the foregoing and for other good and valuableconsideration, the receipt of which is hereby acknowledged, the parties mutually covenant and agreefor the equal and ratable benefit of the Holders of the Notes as follows:
     1. CAPITALIZED TERMS. Capitalized terms used herein without definition shall havethe meanings to them in the Indenture.
     2. AGREEMENT TO GUARANTEE. The Guaranteeing Subsidiary hereby agrees asfollows:
          (a) Along with all Guarantors named in the other Supplemental Indentures, to jointlyand severally Guarantee to each Holder of a Note authenticated and delivered by the Trustee and tothe Trustee and its successors and assigns, the Notes or the obligations of the Company hereunderor thereunder, that:
               (i) the principal of, and premium and Special Interest, if any, and interest on theNotes will be promptly paid in full when due, whether at maturity, by acceleration, redemption orotherwise, 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 willbe 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 ofsuch other obligations, that same will be promptly paid in full when due or performed in accordancewith the terms of the extension or renewal, whether at stated maturity, by acceleration orotherwise. Failing payment when due of any amount so guaranteed or any performance so guaranteedfor whatever reason, the Guarantors shall be jointly and severally obligated to pay the sameimmediately.
          (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 enforcethe same, any waiver or consent by any Holder of the Notes with respect to any provisions hereof orthereof, the recovery of any judgment against the Company, any action to enforce the same or anyother circumstance which might otherwise constitute a legal or equitable discharge or defense of aGuarantor.
          (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 torequire a proceeding first against the Company, protest, notice and all demands whatsoever.
          (d) This Subsidiary Guarantee shall not be discharged except by complete performanceof the obligations contained in the Notes and the Indenture, and the Guaranteeing Subsidiaryaccepts all obligations of a Guarantor under the Indenture.
          (e) If any Holder or the Trustee is required by any court or otherwise to return tothe Company, the Guarantors, or any custodian, trustee, liquidator or other similar official actingin relation to either the Company or the Guarantors, any amount paid by either to the Trustee orsuch Holder, this Subsidiary Guarantee, to the extent theretofore discharged, shall be reinstatedin full force and effect.
          (f) The Guaranteeing Subsidiary shall not be entitled to any right of subrogation inrelation to the Holders in respect of any obligations guaranteed hereby until payment in full ofall obligations guaranteed hereby.
          (g) As between the Guarantors, on the one hand, and the Holders and the Trustee, onthe other hand, (x) the maturity of the obligations guaranteed hereby may be accelerated asprovided in Article 6 of the Indenture for the purposes of this Subsidiary Guarantee,notwithstanding any stay, injunction or other prohibition preventing such acceleration in respectof the obligations guaranteed hereby, and (y) in the event of any declaration of acceleration ofsuch obligations as provided in Article 6 of the Indenture, such obligations (whether or not dueand payable) shall forthwith become due and payable by the Guarantors for the purpose of thisSubsidiary Guarantee.
          (h) The Guarantors shall have the right to seek contribution from any non-payingGuarantor so long as the exercise of such right does not impair the rights of the Holders under theSubsidiary Guarantee.
               (i) Each Guarantor, and by its acceptance of Notes, each Holder hereby confirms thatit 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 federalor state law to the extent applicable to any Subsidiary Guarantee. To effectuate the foregoingintention, the Trustee, the Holders and the Guarantors hereby irrevocably agree that theobligations of the Guaranteeing Subsidiary will, after giving effect to any maximum amount and allother contingent and fixed liabilities that are relevant under any applicable Bankruptcy orfraudulent conveyance laws, and after giving effect to any collections from, rights to receivecontribution from or payments made by or on behalf of any other Guarantor in respect of theobligations of such other Guarantor under the Indenture, this new Subsidiary Guarantee shall belimited to the maximum amount permissible such that the obligations of the Guaranteeing Subsidiaryunder this Subsidiary Guarantee shall not constitute a fraudulent transfer or conveyance.
     3. EXECUTION AND DELIVERY. The Guaranteeing Subsidiary agrees that theSubsidiary Guarantees shall remain in full force and effect notwithstanding any failure to endorseon 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 allsubstantially all of its assets to, or consolidate with or merge with or into (whether or not theGuaranteeing Subsidiary is the surviving Person) another Person, other than the Company or anotherGuarantor unless:
               (i) immediately after giving effect to such transaction, no Default or Event ofDefault exists; and
               (ii) either (A) subject to Section 11.06 of the Indenture, the Person acquiring theproperty in any such sale or disposition or the Person formed by or surviving any suchconsolidation 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 ortherein; or (B) the Net Proceeds of such sale or other disposition are applied in accordance withthe 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 theassumption by the successor Person, by supplemental indenture, executed and delivered to theTrustee and satisfactory in form to the Trustee, of the Subsidiary Guarantee endorsed upon theNotes and the due and punctual performance of all of the covenants and conditions of the Indentureto be performed by the Guaranteeing Subsidiary, such successor Person shall succeed to and besubstituted for the Guaranteeing Subsidiary with the same effect as if it had been named herein asthe Guaranteeing Subsidiary. Such successor Person thereupon may cause to be signed any or all ofthe Subsidiary Guarantees to be endorsed upon all of the Notes issuable under the Indenture whichtheretofore shall not have been signed by the Company and delivered to the Trustee. All theSubsidiary 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 issuedin accordance with the terms of the Indenture as though all of such Subsidiary Guarantees had beenissued at the date of the execution hereof.
          (c) Notwithstanding the foregoing, any Guarantor may consolidate or merge with orinto another Guarantor or into the Company, and the Company may consolidate or merge with or intoany Guarantor.
     5. RELEASES.
          (a) In the event of any sale or other disposition of all or substantially all of theassets of any Guarantor, by way of merger, consolidation or otherwise, or a sale or otherdisposition 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 theCompany designates any Restricted Subsidiary that is a Guarantor as an Unrestricted Subsidiary inaccordance with Section 4.18 of the Indenture, then such Guarantor (in the event of a sale or otherdisposition, by way of merger, consolidation or otherwise, of all of the capital stock of suchGuarantor 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 suchGuarantor) 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 theapplicable 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 Counselto the effect that such sale or other disposition was made by the Company in accordance with theprovisions of the Indenture, including without limitation Section 4.10 of the Indenture, theTrustee shall execute any documents reasonably required in order to evidence the release of anyGuarantor from its obligations under its Subsidiary Guarantee.
          (b) Any Guarantor not released from its obligations under its Subsidiary Guaranteeshall remain liable for the full amount of principal of and interest on the Notes and for the otherobligations 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 underthe Notes, any Subsidiary Guarantees, the Indenture or this Supplemental Indenture or for any claimbased on, in respect of, or by reason of, such obligations or their creation. Each Holder of theNotes by accepting a Note waives and releases all such liability. The waiver and release are partof the consideration for issuance of the Notes.
     7. NEW YORK LAW TO GOVERN. THE INTERNAL LAW OF THE STATE OF NEW YORK SHALL GOVERNAND BE USED TO CONSTRUE THIS SUPPLEMENTAL INDENTURE BUT WITHOUT GIVING EFFECT TO APPLICABLEPRINCIPLES OF CONFLICTS OF LAW TO THE EXTENT THAT THE APPLICATION OF THE LAWS OF ANOTHERJURISDICTION WOULD BE REQUIRED THEREBY.
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     8. COUNTERPARTS. The parties may sign any number of copies of thisSupplemental Indenture. Each signed copy shall be an original, but all of them together representthe same agreement.
     9. EFFECT OF HEADINGS. The Section headings herein are for convenienceonly and shall not affect the construction hereof.
     10. THE TRUSTEE. The Trustee shall not be responsible in any mannerwhatsoever for or in respect of the validity or sufficiency of this Supplemental Indenture or foror in respect of the recitals contained herein, all of which recitals are made solely by theGuaranteeing Subsidiary and the Company.
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     IN WITNESS WHEREOF, the parties hereto have caused this Supplemental Indenture to be dulyexecuted and attested, all as of the date first above written.         ORBACOM SYSTEMS, INC.          By: /s/ TIMOTHY WHELAN         Name: Timothy Whelan   Title: Treasurer           IPC ACQUISITION CORP.          By: /s/ TIMOTHY WHELAN         Name: Timothy Whelan   Title: Chief Financial Officer           IPC INFORMATION SYSTEMS, LLC