Melvin J. Zahnow Library

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Zahnow Library Disability Accommodations

TDD Contact Information - 964.7091 | Campus Disability Services Home Page

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TDD - A telecommunications device for the deaf (TDD) is an electronic device for text communication via a telephone line, used when one or more of the parties has hearing or speech difficulties. Other names for TDD include TTY (telephone typewriter or teletypewriter, although TTY is also a term used for teletypes in general), textphone (Common in Europe and the UK), and minicom (United Kingdom).

The typical TDD is a device about the size of a small laptop computer with a QWERTY keyboard and small screen that uses LEDs or an LCD screen to display typed text electronically. In addition, TDDs commonly have a small spool of paper on which text is also printed - old versions of the device had only a printer and no screen. The text is transmitted live, via a telephone line, to a compatible device, i.e. one that uses a similar communication protocol. In certain countries there are Telecommunications Relay Services, so that a deaf person can communicate with a hearing person on an ordinary voice phone using a human relay operator. There are also "carry-over" services, enabling people who can hear but cannot speak ("hearing carry-over," a.k.a. "HCO"), or people who cannot hear but are able to speak ("voice carry-over," a.k.a. "VCO") to use the telephone.