TNS, Inc. entered into a definitive merger agreement to be acquired by an investor group led by Siris Capital Group in a transaction valued at approximately $862 million.

Siris secured committed financing consisting of equity and debt. The equity financing will be provided by an investor group led by Siris. The debt financing will be arranged by SunTrust Robinson Humphrey and Macquarie Capital (USA).

Siris will acquire all of the outstanding common shares of TNS for $21 per share in cash, representing a premium of approximately 44% over the closing price on Dec. 10, 2012 and 47% over TNS’ volume weighted average share price during the 30 days ended Dec. 10, 2012. The transaction is expected to close in the first quarter of 2013.

Upon completion of the acquisition, TNS will become a private company, wholly owned by an affiliate of Siris. It is expected that members of the TNS senior management team will continue to lead the company.

Greenhill & Co. is acting as financial advisor to the Special Committee of the Board of Directors of TNS. Gibson, Dunn & Crutcher is acting as legal advisor to the Special Committee of the Board of Directors of TNS. UBS Securities and Macquarie Capital are acting as financial advisors to Siris. Simpson Thacher & Bartlett LLP is acting as legal advisor to Siris.

“Siris believes in the investments that we are making,” TNS CEO Henry H. Graham, Jr., said. “We will continue our product initiatives that can either help our customers cost-effectively navigate the complexities of network evolution or create new revenue opportunities, while providing the same level of exceptional customer service that we are known for.”

TNS offers a range of networks and innovative value-added services which enable transactions and the exchange of information in the retail, banking, payment processing and telecommunications industries and the financial markets.

Siris Capital Group is a private equity firm focused on complex, control equity investments in the telecom, technology and technology-enabled business service sectors.