JAJZ801@calstate.bitnet (12/22/90)
Regarding TDD's and modems, the following is the DOC file from a
rather old s/w package that allows use of a true-blue IBM PC (not XT,
AT, or PS/2): REQUIRES the cassette port of the original PC although
appropriate TDD modems are possible. I can send the who file (ARC'ed
and uuencoded to some internet addresses or provide it for the telecom
library.
Jeff Sicherman
HANDICAPPED EDUCATIONAL EXCHANGE
11523 Charlton Drive
Silver Spring MD 20902
Computer: (301) 593-7033 MCI Mail: "RBARTH"
Home: (301) 681-7372 January 7, 1985 TELEX: 650 248-8912
TDD54
This software permits the IBM-PC and PC-Jr to function as TDDs, or
Telecommunications Devices for the Deaf. These devices are also known as
TTYs. This (TDD5.4) is the fourth generation of IBM-PC software by the
same author, and is the first to provide for operation with the PC Jr.
This software was written by John Spalding of Atlanta Georgia and placed
by him in the public domain.
The TDD was originally a mechanical teleprinter used with a unique
modem which employed the same tone pair (1400 Hz mark and 1800 Hz space)
in each direction. The modem was developed by Dr. Robert Weitbrecht, a
deaf physicist, and was unfortunately incompatible with any industry
standard modem. The TDD also uses the Baudot code rather than ASCII, and
so in order for a computer to talk to a TTY is has been necessary both
to include code conversion in the computer software and to provide a
separate modem.
Adaptive software has been developed for a number of home
computers. Details on this work are available from HEX. Two computers,
the IBM-PC and the Radio Shack Color Computer, incorporate hardware that
permits them to emulate a modem, permitting their cassette ports to be
connected to the phone line via an inexpensive telephone amplifier. This
amplifier may be built by the user, or is available at cost (forty
dollars) from John E. Steele, 2100 N. New Road, Waco, Texas 76707. The
same amplifer is plug compatible with either the PC or the CoCo.
Similar software for the Apple, Smoke Signal Broadcasting 6800 and
6809 machines, Atari, Pet, TRS-80 Model I, VIC-20 and Commodore 64
computers can be obtained from the AMRAD, the sponsor of the HEX. These
machines require addition of modems and interface circuitry. Complete
details can be obtained by writing to the letterhead address, or by
calling the HEX BBS at the number above. Calls will be accepted either
from an ASCII device (300 baud, 8 bits, no parity, one stop bit) or from
a standard TDD.
[Moderator's Note: If you wish to do so, send along the code for this
and it will be placed in the archives with related files. PAT]