Exhibit 10.13

AMENDMENT TO SUBLEASE

THIS AMENDMENT TO SUBLEASE (this “Amendment”) is made and entered into as of the 28^th day of December, 2011 by and between TRANSWITCH CORPORATION, a Delaware corporation, having an office at 3 Enterprise Drive, Shelton, Connecticut 06484 (hereinafter referred to as “Sublandlord”) and SIKORSKY AIRCRAFT CORPORATION, a Delaware corporation, having an office at 6900 Main Street, P.O. Box 9729, Mail Stop 427A, Stratford, Connecticut 06615 (hereinafter referred to as “Subtenant”).

WITNESSETH:

WHEREAS, on February 24, 2009, Subtenant and Sublandlord entered into a Sublease (the “Sublease”) for 92,880 square feet of space located on the sixth, seventh and eighth floors (the “Premises”) in the building known as 6 Corporate Drive (formerly known as 4 Enterprise Drive), Shelton, as more particularly described in the Sublease;

WHEREAS, the parties hereto desire to amend and extend the term of the Sublease as set forth herein;

NOW, THEREFORE, for and in consideration of the mutual covenants contained herein and other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the parties agree as follows:

Subtenant agrees to indemnify, defend and hold Sublandlord harmless from and against any and al1 1iabilities, damages, costs and expenses (including reasonable attorneys’ fees and legal expenses) which Sublandlord may suffer or incur relating to or arising, directly or indirectly, out of any (i) breach by Subtenant of any representation, covenant or warranty of Subtenant set forth herein, (ii) resulting from a breach of Subtenant’s obligations under this Amendment, or (iii) any claim by USRI for any fee, commission or compensation whatsoever, or (iv) any claim by any broker, finder, person or entity, (excepting C&W, which has entered into an agreement with Sublandlord and/or USRI, for which Sublandlord is entitled to indemnification under subsection (iii)), claiming to have been engaged by or has an agreement with Subtenant for any commission, reimbursement, fee, payment, remuneration or compensation arising out of the Sublease, this Amendment or any extension and/or renewal of the Sublease. Sublandlord shall promptly notify Subtenant of any claim made against it for any claim under this Paragraph 2. Subtenant shall have the right to undertake, conduct and control, through counsel of its own choosing, the defense and settlement of any such claim, so long as such settlement does not impose any obligations on Sublandlord, except for any obligations to which Sublandlord has consented in writing. Sublandlord shall have the right to be represented by counsel of its own choosing, but at its own expense. So long as Subtenant is contesting any such claim in good faith, Sublandlord shall not pay or settle any claim.

IN WITNESS WHEREOF, the parties hereto set their hands as an instrument under seal on the day and year first written above.