Access for 9-1-1 and Telephone Emergency Services

B. TTYs & Telephone Relay Services

A TTY is a device that is used in conjunction with a telephone to communicate with persons who are deaf, who are hard of hearing, or who have speech impairments, by typing and reading text. To communicate by TTY, a person types his or her conversation, which is read on a TTY display by the person who receives the call. Both parties must have TTYs to communicate. When typing on a TTY, each letter is transmitted by an electronic code called Baudot, which is sent from the TTY on the sending end of the call through the telephone line in the form of tones to the TTY on the receiving end of the call, the same way voiced communications occur between two parties. The receiving TTY transforms the tones back to letters on a small display screen.

Communication between two persons using standard TTYs can only occur in one direction at a time. Thus, both persons who are conversing cannot type to each other at the same time; they must take turns sending and receiving. A person sending a communication by TTY indicates that he or she has finished transmitting by typing the letters "GA," which stand for "go ahead."

A person can also use a computer with a TTY modem and related software to communicate with someone who has a TTY or who has a computer with TTY software and a modem. Computers generally operate in American Standard Code for Information Interexchange (ASCII), an electronic "language." A person who uses ASCII must use an ASCII/Baudot modem and related software to convert the ASCII code into Baudot code, in order to communicate with another person who is using a Baudot-based system. Similarly, a person who is using a Baudot-based TTY must utilize conversion software to communicate with a person using an ASCII-based computer.

Telephone relay services are provided by States, as required by Title IV of the ADA, and are regulated by the Federal Communications Commission. Relay services involve a communications assistant who uses both a standard telephone and a TTY to type voice communication to a TTY user and read a TTY user's typed communication to a voice telephone user. Telephone relay services are not as effective for emergencies, because they are far more time-consuming than calls between two TTYs.

Q: Does Title II require that telephone emergency service systems be compatible with all codes used for TTY communications?

A: No. At present, telephone emergency services must only be compatible with the Baudot format. Until it can be technically proven that communications in another format can operate in a reliable and compatible manner in a given telephone emergency environment, a State or local government agency is not required to provide direct access to computer modems using formats other than Baudot.

Q: Can PSAPs rely on State relay services to answer emergency calls from persons who are deaf, hard of hearing, or who have speech impairments?

A: No. The Title II regulation specifically prohibits emergency telephone service providers from relying on relay services. Relay services do not provide "direct access," because they require the services of a third party and are far more time-consuming than direct TTY calls. However, if a person placing a call to a PSAP voluntarily chooses to rely on a telephone relay service, the PSAP must answer and respond appropriately to such a call.