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Old 21st Apr 2017, 5:08 am   #2
TonyDuell
Dekatron
 
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,190
Default Re: ASR33 Teletype nostalga question

There are dozens of official Teletype versions of the Model 33. A look at the parts list will show versions with a separate keyboard, sprocket feed (with top-of-form setting), various control code optios, various type cylinders, etc. There was even a numeric-only keyboard. Remote reader control (XON/XOFF characters), that was a standard option too.

As for the 'call control unit' (the electronics chassis to the right of the printer mechanism there were many versions of that too, including versions with punch-card operated pulse or tone autodialers for US lines.

The normal Teletype call control unit used with computers gave you a 20mA or 60mA current loop interface. The connections were a barrier strip inside (with 115V mains on 2 of the terminals just to catch the unwary!). The only user control was a knob on the front of the teleprinter, local/off/remote.

To complicated matters further, in the UK the Data Dynamics company made a series of teleprinters using Model 33 mechanicals (keyboard, printer, punch, reader) and their own electronics in a metal (rather than plastic-top) case. Their electronics often added extra features like an RS232 interface, single-stepping the reader, etc.

And there were many 'unofficial' modifications. Just about every computer manufactuer who used the Model 33 locally connected to their machine added a relay to allow the computer to directly control the tape reader. DEC, Intel and HP all did, the modificatons are pretty similar.

To get back to your question, Teletype never used the Plug 420, but it was commonly used in the UK. I've seen it used at universities for teletype current loop connections. I don't think Teletype used the 80V line directly, but there could well have been an interface in the stand or something. The illuminated buttons sound more Data Dynamics than Teletype to me. The reader control and motor time-out could have been Teletype options or something custom.
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