2010 ADA Standards for Accessible Design Pocket Guide

TTY.

An abbreviation for teletypewriter. Machinery that employs interactive text-based communication through the transmission of coded signals across the telephone network. TTYs may include, for example, devices known as TDDs (telecommunication display devices or telecommunication devices for deaf persons) or computers with special modems. TTYs are also called text telephones. [S.H. 3.5 Text Telephone]