TTY Relay Service

A telecommunications service that enables people who are deaf, hard of hearing, or have speech disabilities to communicate by telephone through a relay operator who converts between text and voice. Users type messages on a TTY (teletypewriter) device, and the relay operator reads them aloud to the hearing party, then types the hearing party's spoken responses back. TTY relay services were among the earliest forms of interactive crowdsourcing for accessibility, predating modern internet-based approaches by decades. They have been largely supplanted by Video Relay Services and IP-based relay services.