The deaf telecommunications network began in
the early 1960's. Surplus Teletype machines
became available, and a deaf physicist named
Robert Weitbrecht invented a modem that
enabled these machines to communicate over
the telephone lines. These machines coupled
with the Weitbrecht modem became the first
Telecommunications Devices for the Deaf
(TDDs). These Teletype machines used 5-level
Baudot code, and established the foundation for
today's extensive deaf Baudot TTY network.
TTYs today are small electronic typewriter-like
devices that use built-in Weitbrecht-type
modems to communicate in Baudot code. They
are used by people who are deaf or hearing or
speech impaired to access the telephone
network.
Please note:
In this manual TTY, TDD and text
telephone all refer to the same device.
1
About TTYs
and the TDD Detector
About TTYs and
the Deaf TTY
Network
The Ultratec
TDD Detector
connects directly
to the telephone line. It monitors the line,
listening for the sounds of incoming TTY
(Baudot code) signals. Incoming TTY signals
mean that someone is typing to you on a
TTY (text telephone).
When the TDD Detector hears TTY signals
on the phone line, it responds in two ways.
First, a built-in voice "announces" the
incoming TTY call to you by repeating, "TDD
CALL… TDD CALL." Second, the TDD
Detector sends a TTY message for your caller
to read on his or her TTY display. The
standard TTY message says, "911 HERE
PLEASE HOLD."
The Ultratec TDD
Detector
announces
incoming TTY
calls
