What is Telecommunications Display Device (TDD)? - Definition from Whatis.com

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Telecommunications Display Device (TDD)

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Telecommunications Display Device (TDD)

A Telecommunications Display Device (TDD), also known as a text telephone, is a telephone equipped with a keyboard and a display for people who are hearing- or speech-impaired. A TDD allows individuals to send and receive typed messages using its keyboard. Both home and public telephones can be equipped with a TDD. Public TDD pay phones have a keyboard drawer that slides out only after a call has been placed to and answered from another TDD phone so that the keyboard is protected from vandalism or other damage.

Related glossary terms: virtual area network (VAN), 10-high-day busy period (10HD busy period), graceful degradation, online, softswitch, maximum transmission unit (MTU), traffic shaping (packet shaping), Dialed Number Identification Service (DNIS), WATS (wide-area telephone service), mail user agent (MUA)

Contributor(s): Martha Pogue

This was last updated in October 2002

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- Union Station in Seattle, WA briefly explains TDD on their Sound Transit site.

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