It's been a long time, but I'm fairly sure it was 110 baud RS232, 7 bit ASCII, all upper case. I think it was an ASR 33, or at least I recall it looking like t

It's been a long time, but I'm fairly sure it was 110 baud RS232, 7 bit ASCII, all upper case. I think it was an ASR 33, or at least I recall it looking like this: https://en.wikipedia.org/wiki/Teletype_Model_33 https://en.wikipedia.org/wiki/Teletype_Model_33 Unfortunately I don't have it any more - my parents threw it out a few years after I left home. Wikipedia certainly implies the ASR 33 used current loop. If I recall correctly, mine had a DB25 connector, which likely indicates RS232, and is probably how I figured out it was RS232 in the first place, as information was hard to come by back then. I do know I used a 24V power supply from a cash machine, using a potential divider to create a +/- 12V signal, which is consistent with the model I had having an RS232 interface. Getting the timing right in software was a lot of trial and error. Edit: this page indicates that RS232 was available as an option on the ASR-33 teletype: http://bytecollector.com/asr_33.htm http://bytecollector.com/asr_33.htm