What Is the Difference Between TTY and TDD?

by Diana O'gilvie

Technology has made leaps and bounds in providing communication options for the disabled. TTY and TDD enable hearing-impaired and speech-impaired individuals to communicate over the telephone. TTY and TDD work in conjunction--there is no distinguishing difference.

What is TDD?

TDD, or Telecommunications Device for the Deaf, is a software program that enables deaf or mute individuals to communicate over the telephone with TTY devices.

What is TTY?

TTY--or telephone typewriter, teletypewriter or text phone--is a device used by deaf or mute individuals to communicate over telephone lines. The device is a "QWERTY" keyboard that is similar to a computer's but smaller. A screen attached to device shows words as they are being typed.


The TTY is connected to a phone line. The Direct Connect ensures that the phone cord is plugged directly into the phone jack. A flashing light alerts when there is an incoming call.

Technological Advances

TTY/TDD is available as a portable device and is used in place of a land line. Some TTY/TDD devices can be attached to hearing aids.


Callers must take turns when sending messages. You cannot interrupt as in a normal conversation. To facilitate proper protocol, codes are used at the end of each transmission to let the other person know when it's his turn.


About the Author

Diana has been a freelance writer for five years now. She enjoys writing about travel, health and fitness. Diana holds a Master of Arts degree from Long Island University in Media Arts. She currently lectures for the Communication Arts Department at Dowling College in Long Island, New York.

More Articles