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TTYs and TTY Compatibility

TTYs (also called Telecommunication Devices for the Deaf (TDD) and text telephones) are terminals used for two-way text conversation over a telephone line. They are the primary tool used by deaf people (and some hard of hearing people) for telephone conversation. Other visual telecommunications technologies and services, such as Internet chat and messaging, email, e-paging, and fax and e-mail are also widely used in telecommunications by people who are deaf or hard of hearing.

Text telephones are abbreviated as "TTY" in the U.S. because they originated in technology used for teletypewriters.  (A book covering the TTY's early history,  A Phone of Our Own:  The Deaf Insurrection Against Ma Bell, by Dr. Harry Lang of RIT, was published by the Gallaudet Press in 2000.)

Frequently Asked Questions

Can a regular computer modem talk to a TTY?

  • If you have a compatible "voice" modem that includes digital signal processing (v.253 compatible), you can buy modestly priced software from NXi, Inc. or IDRT that will allow your computer to talk directly to TTYs.  Check each company's list of supported modems to see if this will work in your case. 
  • If you have a Macintosh G3-based computer (including the iMac, iBook, laptop, desktop, etc.), their internal modems are voice-capable and can be used with SoftTTY software to perform Baudot communication. SoftTTY also works with pre-G3 PowerPC Macintoshes or clones with a voice modem.
  • If you are on a computer network, typically at work, you may be able to take advantage of  another product by NXi, NXi Text Service.  This product allows you to put a TTY-compatible modem on a network server and access that modem from the desktop.  
  • There are specialized computer modems ("TTY modems") that permit the computer to talk to a TTY.  These cost more than a conventional modem, and they do not do well as ASCII modems as they do not support today's high speeds.  Links to vendors are shown below.
Read "Can I use a regular modem to talk to a TTY?" for more information.

Are there any technical standards for TTY?

ANSI/TIA/EIA 825, "A 45.45 Baud FSK Modem" is the U.S. standard for Baudot TTY signaling.  It can be obtained through the Telecommunication Industries Association.

ITU-T Recommendation V.18 specifies interworking procedures between data communications equipment (modems) and the world's various text telephone protocols.  It can be obtained through the International Telecommunications Union.  Take this link to more on V.18...

Note that there are also proprietary protocols used in North American TTYs.  The most widely used is TurboCode, by Ultratec, Inc.  The TTY manufacturer, Ameriphone, also has a protocol called HiSpeed, which is licensed by the company at no charge.

Other Information

A list of Telecommunications Standards Related to Accessibility     

TTY Basics
Information for engineers and product designers.

RIT's General TTY Information and Etiquette Tips
The Rochester Institute of Technology Wallace Library has developed an excellent Fact Sheet on how to use a TTY and general TTY etiquette.

Telecommunications Relay Service (TRS)
Visit TAP's page on TRS.  This contains links to other sites as well.


TTY Manufacturers

Ameriphone, Inc.
12082 Western Avenue
Garden Grove, CA  92841-2913
(800) 772-2889  TTY
(800) 874-3005  voice
(714) 897-4703  fax

P.O. Box 1265 
Provo, UT 84603-1265
(801) 465-1957 TTY
(801) 465-1958 fax

Krown Manufacturing, Inc.
3408 Indale Road
Fort Worth, TX 76116
(817) 738-2485  voice
(817) 738-8993  TTY
(817) 738-1970  fax

Ultratec, Inc.
450 Science Drive
Madison, WI  53711
(608) 238-5400  voice/TTY
(800) 482-2424  voice/TTY (US only)
(608) 238-3008  fax

TTY Modem and Software Manufacturers

Institute for Disabilities Research and Training, Inc.
11323 Amherst Avenue
Silver Spring, Maryland 20902
(301) 942-4326 (V/TTY)
(301) 942-4439 (FAX)

  • myTTY -- MS Windows-compatible TTY software for a PC

Microflip, Inc.
11211 Petworth Lane
Glenn Dale, MD  20769
(301) 262-6020  voice/TTY/ASCII
(301) 262-2607  voice only

  • Mic300i internal modem
  • Fulltalk software

NXi Communications, Inc.
4505 S. Wasatch Blvd., Suite 120
Salt Lake City, Utah  84124
(801) 274-6001  voice/TTY

  • NexCom 300 internal modem
  • NexTalk for Windows software
  • NexTalk-VM software for compatible voice modems
  • NXi Text Services LAN system software

Phone-TTY, Inc.
1246 Route 46 West
Parsippany, NJ  07054
(888) deaf-tty voice/TTY
(973) 299-6626  TTY
(973) 299-6627  voice
(973) 299-7768  fax

  • CM-4 modem
  • Futura-TTY software for CM-4, Intele-Modem, Krown SM-85H, NexCom 300, and Hayes modems.

Ultratec, Inc.
450 Science Drive
Madison, WI  53711
(608) 238-5400  voice/TTY
(800) 482-2424  voice/TTY (US only)
(608) 238-3008  fax

  • Intele-Modem

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