Ip-relay

A telecommunications relay service, also known as TRS, relay service, or IP-relay, or Web-based relay service, is an operator service that allows people who are deaf, hard of hearing, deafblind, or have a speech disorder to place calls to standard telephone users via a keyboard or assistive device. Originally, relay services were designed to be connected through a TDD, teletypewriter (TTY) or other assistive telephone device. Services gradually have expanded to include almost any real-time text capable technology such as a personal computer, laptop, mobile phone, PDA, and many other devices. The first TTY was invented by deaf scientist Robert Weitbrecht in 1964. The first relay service was established in 1974 by Converse Communications of Connecticut.

Depending on the technical and physical abilities and physical environments of users, different call types are possible via relay services.

Once the most common type of TRS call, TTY calls involve a call from a deaf or hard-of-hearing person who utilizes a TTY to a hearing person. In this type of call, typed messages are relayed as voice messages by a TRS operator, (also known as Communication Assistant (CA),Relay Operator (RO),Relay Assistant (RA), or relay agent (agent)), and vice versa. This allows callers who are unable to use a regular telephone to be able to place calls to people who use a regular telephone and vice versa. When the person who is hearing is ready for a response, it is customary to say "go ahead" or "GA" to indicate that it is the TTY (teletypewriter) user's turn to talk and "stop keying", "SK", or "ready to hang up" when ending the call and vice versa. This mode of communication has largely been superseded by other modes of communications, including the utilization of IP relay, VPs, VRS, and VRI.

A common type of call is voice carry over, VCO. This allows a person who is hard of hearing or deaf but can speak to use their voice while receiving responses from a person who is hearing via the operator's typed text. There are many variations of VCO, including two-line VCO and VCO with privacy.

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