3 ms·

Why? The use of TTYs for computing interfaces is very different to using them as teletypes on comms links. I thought the control characters for that sort of us

by rswail 1y ago

Why? The use of TTYs for computing interfaces is very different to using them as teletypes on comms links. I thought the control characters for that sort of use were the DC1-4 characters? RS-485 uses polling but my understanding is that the characters for polling usually involve like "FF" (hex) and some sort of device ID. I just read a TTY model 28 manual about the stunt box and I didn't see anything specific about FS/GS/RS there. How were messages delimited in the polled multidrop environment?

varjag 1y ago
TTY interfaces initially were teletypes on comms links.
- rswail 1y ago
  Yes, but they were character based, not message based as being discussed. The ones I used were ASR-33s on 20mA current loop interfaces.
dfox 1y ago
Modern protocols running over RS-485 UART usually use some kind of HDLC-inspired framing scheme with flag characters and byte stuffing. But still there is a lot of stuff that uses ASCII STX/ETX and then some kind of field separators inside otherwise human readable message. Things like industrial scales, industrial barcode readers and what not usually use something like that as default output format.
Animats 1y ago
> I just read a TTY model 28 manual about the stunt box and I didn't see anything specific about FS/GS/RS there. The Model 28 was a 5-bit Baudot (ITA2 code) machine with a stunt box. The Model 35, an ASCII machine, had a similar system, with different coding.[1] The term "Selective calling" replaced "stunt box". ASCII-67 is modern ASCII, but there was previously ASCII-63.[2] That keyboard has special keys for selective calling. WRU, RU, EOT, EOA, TAPE, ~TAPE, etc. Codes didn't become standardized industry-wide until ASCII-67. Before that, there were lots of variations. Here's a popular view of the process in the Baudot era.[3] That big switching center is essentially Sendmail built from of relays and paper tape equipment. It was called "Plan 55-A".[4] [1] https://www.smecc.org/teleprinters/35selcall001.pdf https://www.smecc.org/teleprinters/35selcall001.pdf [2] https://lostbits.net/blog/the-teletype-model-35-character-set.html https://lostbits.net/blog/the-teletype-model-35-character-se... [3] https://youtu.be/PKJyGuhCQdQ?t=369 https://youtu.be/PKJyGuhCQdQ?t=369 [4] https://en.wikipedia.org/wiki/Plan_55-A https://en.wikipedia.org/wiki/Plan_55-A

by rswail 1y ago

varjag 1y ago

TTY interfaces initially were teletypes on comms links.

rswail 1y ago
Yes, but they were character based, not message based as being discussed. The ones I used were ASR-33s on 20mA current loop interfaces.

dfox 1y ago

Modern protocols running over RS-485 UART usually use some kind of HDLC-inspired framing scheme with flag characters and byte stuffing. But still there is a lot of stuff that uses ASCII STX/ETX and then some kind of field separators inside otherwise human readable message. Things like industrial scales, industrial barcode readers and what not usually use something like that as default output format.

Animats 1y ago

> I just read a TTY model 28 manual about the stunt box and I didn't see anything specific about FS/GS/RS there. The Model 28 was a 5-bit Baudot (ITA2 code) machine with a stunt box. The Model 35, an ASCII machine, had a similar system, with different coding.[1] The term "Selective calling" replaced "stunt box". ASCII-67 is modern ASCII, but there was previously ASCII-63.[2] That keyboard has special keys for selective calling. WRU, RU, EOT, EOA, TAPE, ~TAPE, etc. Codes didn't become standardized industry-wide until ASCII-67. Before that, there were lots of variations. Here's a popular view of the process in the Baudot era.[3] That big switching center is essentially Sendmail built from of relays and paper tape equipment. It was called "Plan 55-A".[4] [1] https://www.smecc.org/teleprinters/35selcall001.pdf https://www.smecc.org/teleprinters/35selcall001.pdf [2] https://lostbits.net/blog/the-teletype-model-35-character-set.html https://lostbits.net/blog/the-teletype-model-35-character-se... [3] https://youtu.be/PKJyGuhCQdQ?t=369 https://youtu.be/PKJyGuhCQdQ?t=369 [4] https://en.wikipedia.org/wiki/Plan_55-A https://en.wikipedia.org/wiki/Plan_55-A