INTELLECTUAL PROPERTY SECURITY AGREEMENT

Exhibit 10.6

INTELLECTUAL PROPERTY SECURITY AGREEMENT

THIS INTELLECTUAL PROPERTY SECURITY AGREEMENT is entered into as of this 18th day of October, 2006 by and among VERTICAL COMMUNICATIONS, INC., a Delaware corporation (“VCI”), VERTICAL COMMUNICATIONS ACQUISITION CORP., a Delaware corporation (“VCAC” and together with VCI, the “Borrowers” and each a “Borrower”), and COLUMBIA PARTNERS, L.L.C. INVESTMENT MANAGEMENT, as agent and investment manager (“Investment Manager”), for the benefit of itself and NEIPF, L.P. (“Lender”).

RECITALS

WHEREAS, Borrowers, Lender and Investment Manager entered into a certain Credit Agreement of even date herewith (as amended, restated, supplemented or otherwise modified from time to time, the “Credit Agreement”) pursuant to which Lender has agreed to lend to Borrowers up to Thirty Million Dollars ($30,000,000) to be evidenced by Borrowers’ issuance to Lender of certain senior secured promissory notes. As a condition of the loans, Lender required that Borrowers grant to Investment Manager, for the benefit of Lender a security interest in certain copyrights, trademarks and patents to secure the Obligations (as defined in the Credit Agreement); and

WHEREAS, pursuant to the terms of the Security Agreement (as defined in the Credit Agreement), Borrowers have granted to Investment Manager a security interest in all of Borrowers’ right, title and interest, whether presently existing or hereafter acquired, in, to and under all of the Collateral (as defined in the Security Agreement).

NOW, THEREFORE, for good and valuable consideration, receipt of which is hereby acknowledged, and intending to be legally bound, as collateral security for the prompt and complete payment when due of the Obligations, Borrowers hereby jointly and severally represent, warrant, covenant and agree as follows:

AGREEMENT

To secure the Obligations, each Borrower grants and pledges to Investment Manager, as agent for the benefit of Investment Manager and Lender, a security interest in all of such Borrower’s right, title and interest in, to and under its Intellectual Property (as defined in the Credit Agreement), including without limitation those copyrights, patents and trademarks listed on Exhibits A, B and C hereto, and including without limitation all proceeds thereof (such as, by way