scottp@AMSAA.arpa (AWD) (09/25/86)
I have a friend who has had severe hearing loss. She has started a local chapter of SHHH (Self Help for the Hard of Hearing). With her hearing problems coordinating activities is a bear. She has a Sanyo MB 550 PC and was told all she needed was a MODEM and she could use the TDD/TTY communications that many hearing impaired have. She got a Hayes 1200 MODEM and now has been looking for software. The companies she has been able to contact want to sell their hardware (their own MODEM, etc.) and software. Is their anyone familiar with these devices and communications software that can advise what the best approach is? Is there software available for a standard MODEM? Scott Phillips
BARTH@AI.AI.MIT.EDU (Richard Barth) (09/26/86)
In a net msg, Scott Phillips (AWD) <scottp@AMSAA.arpa> writes:
Quote
I have a friend who has had severe hearing loss. She has started a
local chapter of SHHH (Self Help for the Hard of Hearing). With her
hearing problems coordinating activities is a bear. She has a Sanyo
MB 550 PC and was told all she needed was a MODEM and she could use the
TDD/TTY communications that many hearing impaired have. She got a Hayes
1200 MODEM and now has been looking for software. The companies she has
been able to contact want to sell their hardware (their own MODEM, etc.)
and software. Is their anyone familiar with these devices and
communications software that can advise what the best approach is? Is
there software available for a standard MODEM?
....
A TTY, also known as a TDD, is not compatible with a Bell-103, a -212,
or any other kind of ASCII modem. A TTY is compatible only with another TTY.
Anybody who tries to tell you a Hayes only needs software to talk to a TTY is
either talking through his hat or, as you suggested, "...want(s) to sell their
hardware (their own MODEM, etc."
A TDD modem uses Frequency Shift Keying, like a 103, but the tones are
different. Mark freq is 1400 Hz, Space is 1800 Hz. Same freqs are used in each
direction. The TDD is a half-duplex device and only one end can type at a time.
The TDD also uses Baudot code, not ASCII. Any communications software
that wants to talk TDD had better know how to do code conversion. Baud rate for
Baudot is 45.45 baud, or 60 wpm.
There are a very few TTYs (e.g. Ultratech Superphone, Krown Porta-
Printer Plus) that handle both normal TTY as described above, and ASCII.
This ASCII uses Bell-103 tones and isusually 110 baud, although 300 is
sometimes provided.
There are, two my knowledge, three commercial TTY modems on the
market. One is the Model CM-4 by Phone-TTY Inc. of Hackensack, NJ. It
provides both TTY capability and Bell-103 originate and answer. Its data
input is via an RS-232 port, so it is usable with almost any computer. It
comes with software for MS-DOS which allows TTY and ASCII commo, and also takes
messages over the phone in either mode. Callers may also read messages left
for them by the system operator. It is not a full-blown BBS, as callers may
not leave messages for each other.
A second device by Krown provides its own code conversion, and
is thus usable with a dumb terminal. It also provides TTY, and ASCII
in 7E1 format only, so is not usable for XMODEM file transfers.
A third modem is a plug-in for the IBM-PC bus, provides TTY/ASCII
originate and ASCII answer. Comes with software. Source is Integrated Micro-
computer Systems of Rockville MD.
A TTY modem is a relatively simple device, and you can build one
using Exar 2206 and 2211 modem chips from Radio Shack. Signetics MF-10
switched capacitor filters from the same source match well.
A VADIC -103 modem card is available through the Amateur Radio
R&D Corporation (AMRAD) for $25 or so. It comes with instructions for
modifying it to TTY operation. The Handicapped Educational Exchange BBS,
which is sponsored by AMRAD and operated by me, uses one of these to provide
the ability to answer TTY as well as ASCII calls. HEX is on (301) 593-7033
and provides files with further information on all of this.
There is public domain software for the IBM-PC and PCjr, and for
the Radio Shack Color Computer, that permits these machines to talk to TTYs
without using a modem. The cassette port hardware is used to emulate the
modem and a Radio Shack telephone amplifier (modified according to
instructions provided) couples the computer to the phone line,
legally. This software is available from some BBS systems, the latest
version being in an ARC file called TDD54. The file, as I distribute it,
contains source, listing and executable for the PC/PCjr, and source for
the CoCo. A user's manual is also provided. If the file isn't on your
favorite BBS, send me a blank floppy and return postage and I'll load 'er
up and return 'er. Address is:
Handicapped Educational Exchange
11523 Charlton Drive
Silver Spring MD 20902
Further distribution of the above info, and the software, is welcomed.
The programs mentioned are by John Spalding of Atlanta, GA.BillW@SU-SCORE.arpa (William Chops Westfield) (09/27/86)
Contact KLH@SRI-NIC.ARPA - he did work on DEAFNet (which I think currently is a Tandy UNIX PC), and is no doubt an excellant source of information... BillW