normt@ihlpy.att.com (Norman R Tiedemann) (06/04/90)
Index Number: 8586 I am looking for information on TDD communication. Namely I need the technical information on the communication protocol. Carrier tone frequency, encoding algorithm, baudot coding and digit frequencies, etc. I have contacted a few manufacturers, but they are reluctant to part with this. If there is anyone who know where I can find this information or has some references, I would very much appreciate hearing about it. Thanks in Advance. Norm Tiedemann AT&T Bell Labs IH 2G-419 att!ihlpy!normt 2000 Naperville Rd. normt@ihlpy.att.com Naperville, IL 60566
wtm@bunker.uucp (Bill McGarry) (06/04/90)
Index Number: 8587
Well, I've read enough articles about TDD's in this newsgroup so
I should be able to answer this one. If I leave anything out or
give a wrong answer, there are enough TDD-experienced people reading
this to correct me. (In particular, Dick Barth who is the
sysop of HEX (the Handicapped Education Exchange BBS) which was the
first BBS to allow both TDD and Ascii callers. Phone numbers for
the HEX BBS are: (301) 593-7033 (TDD or 300 baud Ascii)
(301) 593-7357 (1200 baud Ascii only)
TDD's run in 2 way simplex mode at 45.45 baud. Frequencies are the
same in both directions and are 1400 Hz for Mark and 1800 Hz for space.
The Baudot coding used consists of one start bit, five data bits and
roughly 1.5 stop bits.
Bill McGarry
(203) 337-1518
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