lorien@dartvax.UUCP (Lorien Y. Pratt) (05/11/84)
I posted a note recently asking about telecommunications facilities for
the deaf to help my grandfather, who has a deaf friend with whom he'd
like to communicate. I'd like to thank everybody who contributed to my
large number of responses. Here is a summary of the results:
It seems that very many people in the deaf community use terminals that
communicate in an arcane and outdated 5 bit baudout code. This
protocol is completely incompatible with the ASCII that 99% of
terminals speak today. I've given the details of this baudout code at
the end of the article for you hardware freaks. Seems the reason for
this is that the companies that produced machines that ran the
soon-to-be outdated protocol found enthusiastic buyers in hams and the
deaf and gave them substantial discounts on hardware. California also
recently passed some sort of law that forced the phone company go give
one free TDD to each deaf person.
Small TDD's are available that still speak baudout. They are simple
terminals that simply plug into an existing phone system via a modular
plug. They have no intelligence. A cheap version is the MINICOM by
Ultratech. They run around $240. You can write to:
Weitbrecht Communications, Inc.
666 Skyway Suite 230
San Carlos, CA 64070
(415) 592-1622
If you'd like to speak baudout using your home computer, there are
several options available. Novations Apple CAT modem (which I seem to
recall is very inexpensive, but one of my responders says costs $495)
has as one of its options TDD compatibility. Also there's a package
called Apple Express. It seems that an Apple IIC with one of these
packages would be just *perfect* for someone who wanted communication
ability plus some computing power. And at under $1400, it's a pretty
cheap.
Rumors of something called DeafNet, which was rumored to be a project
aimed at a USENET-like network for the deaf. No detailed followup
information on that, but I did receive some pointers to groups that
help deaf people with telecommunications. They are:
Telecommunications for the Deaf, Inc.
Barry Strassler, Executive Director
814 Thayer Avanue
Silver Springs, MD 20910
(301) 589-3006
Deafnet (provides assistance to local deaf communities)
Hal Huntley
SRI International
Menlo Park, CA
HAL@SRI-NIC
(415) 859-2236
Hardware info for 5-bit baudout
-------------------------------
a) Teletype units use a 5 unit Baudot Code. The character is always
preceded by a 1 bit duration start bit (space or 0) and is always
followed by a 1.42 to bit stop bit (Mark or 1). [sic: probably meant
1.42 to 2 bit]
b) Teletype units transmit data at 45.45 baud +- 0.45 bauds.
c) Other information:
Transmission Characteristics:
Mark (1) 1400Hz +- 1% -9 dB (Level at tip and ring, dBM)
Space(0) 1800Hz +- 1% -9 dB
Receive Characteristics:
Mark (1) 1400Hz +- 1% 72 dB (level, dB SPL) -0dB+43dB tolerance
Space(0) 1800Hz +- 1% 72 dB -0dB+44dB