Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!utgpu!water!watmath!clyde!rutgers!ucla-cs!sdcrdcf!trwrb!felix!fritz!dennisg From: dennisg@fritz.UUCP Newsgroups: comp.dcom.modems Subject: Re: Converting a modem+terminal to TTY/TTD Message-ID: <4262@fritz.UUCP> Date: Wed, 22-Apr-87 11:47:18 EST Article-I.D.: fritz.4262 Posted: Wed Apr 22 11:47:18 1987 Date-Received: Sat, 25-Apr-87 04:35:25 EST References: Reply-To: dennisg@fritz.UUCP (Dennis Griesser) Distribution: world Organization: FileNet Corp., Costa Mesa, CA Lines: 26 In article SASHA@THINK.COM (Sarah Ferguson) writes: >Does anyone out there know how to convert a standard modem+terminal >setup for use as a TTY/TTD machine (phone for the deaf)? > >I am told it can be done, but no one I know seems to know how. A TTD uses BAUDOT coding, and a strange bit rate. Since BAUDOT has a small number of bits per character, half of the characters must be accessed via an escape mechanism ("letters" and "figures" shift). This means that the problem is a bit more difficult than a pair of UARTs with an EPROM in between. You will need some latches and comparators. And you want it bidirectional, so we need two EPROMs. This is getting messy. Sounds like the optimum outboard solution is a single-board micro, with two serial ports and some minimal software. Do you really want to convert an existing terminal? The simplest other way to do this would involve a cheap computer, say a Radio Shack Color Computer, bunning a BAUDOT terminal emulator. If you can't find such a thing in amateur radio periodicals, it would be easy to write. If you want a TTD for the use of a deaf associate, go to the phone company! They have been collecting money for years. The line on my bill reads something like "communications equipment for the deaf". This should make such a device cheap or free to a qualified user.