Internet Protocol Captioned Telephone Service

Definition
Internet Protocol Captioned Telephone Service (also called IP Captioned Telephone Service or IP CTS)) is

"[a] telecommunications relay service that permits an individual who can speak but who has difficulty hearing over the telephone to use a telephone and an Internet Protocol-enabled device via the Internet to simultaneously listen to the other party and read captions of what the other party is saying. With IP CTS, the connection carrying the captions between the relay service provider and the relay service user is via the Internet, rather than the public switched telephone network."