Teletypewriter (TTY) and Telecommunications Device for the Deaf (TDD)

A teletypewriter (TTY) and telecommunications device for the Deaf (TDD) are both types of assistive technology. TTY and TDD are often used to refer to the same type of device.  TTY is more commonly used now, since it isn’t limited to Deaf individuals.

Teletypewriter (TTY)

A teletypewriter, or teletype, is a device that allows for typed messages to be communicated over the telephone. TTY devices often use a relay service with a TTY relay service communication assistant (CA). The relay service connects those who use TTY with those who use a telephone.

While the original TTY technology used a typewriter and a printer, modern versions are fully electronic and involve the use of a screen.

TTY helps people who are Deaf or have communication disabilities communicate with businesses and governments via a phone line.

Telecommunications Device for the Deaf (TDD)

A telecommunications device for the deaf (TDD) is a device for text communications via telephone lines. It is used by people who cannot use a regular telephone due to a hearing or speech disability. A TDD is usually the size of a small laptop computer that includes a keyboard and small screen. By typing the message, a TDD user is able to send a message to another TDD device. A relay service can be used with TDD in the case of communication between a TDD user and a telephone user.


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