TTYs for the deaf

Tom Jennings wrote: John C. Ellingboe wrote: AFAIK, the model 28 and 32 use the same five-level code as the 15 and 19. The model 32 is the five-level version of the better-known model 33. Tom's point is that contrary to popular belief, the five-level Teletype code is NOT actually the Baudot code. His web page on the history of character codes explains this in great detail with references: http://www.wps.com/projects/codes/index.html Years ago my friend Jim Philips interfaced a model 28RO to his semi-homebrew 6502-based TLB computer. He wired up some sort of circuit to turn off the motor when the line when idle (spacing) for more than a minute or so. I wrote a driver for the APEX operating system, which normally used ASCII. The driver performed the necessary code conversion. The tricky part was what to do about printing characters that had no five-level equivalent. I decided to use overstrikes (somewhat like APL in principle). The driver kept track of whether any characters on the current print line needed overstrikes, and if so, would print one pass, carriage return, second pass, then another CR and a line feed. I think that's the oldest piece of code I've written for which I still have source. I doubt that it's of use to anyone, but there are two versions of it on my web site: http://www.brouhaha.com/~eric/software/ttyhan/ I'm still hoping to recover my program from the same era to format eight-inch disks on a 1771-based controller. Eric