ASR-33 Teletype
The Teletype Corporation introduced the Model 33 in 1963. There were 3 versions: Model 33 ASR (Automatic Send Receive) which includes a paper tape reader and puncher; Model 33 KSR (Keyboard Send Receive) which lacks the paper tape reader/puncher; Model 33 RO (Receive Only) which lacks both the paper tape reader/puncher and the keyboard. The Model 33 was one of the first products to employ the ASCII code.
Main Characteristics
- Speed up to 100 words/minute (60 wpm, 66 wpm, 100 wpm)
- Four-row keyboard generating an eight-level code
- The SHIFT key is used to transmit printing characters (such as &, %, and #)
- The CTRL key is used to transmit control functions (such as WRU, BELL, and TAB)
- Transmission code: 8-level start-stop signals with 11-unit transmission pattern
- Paper 8-1/2 inches wide; max 5 inch diameter roll
- 10 characters/inch, max 74 characters/line
- Uppercase characters only
- Tape specifications: 5 or 8 levels; width 11/16 inch (17 mm) for 5 levels, 1 inch (25 mm) for 8 levels; 10 code combinations per inch; feed hole diameter 0.0465 inch
- Communication via current loop (a modern RS-232 adapter card exists; details here)
Java System Simulator
- ASR-33 teletype simulation implementation in Java here
- Details about the ASR33Teletype virtual device here
Useful resources
- Technical Manual Model 32 and 33
- https://en.wikipedia.org/wiki/Teletype_Model_33
- https://www.pdp8online.com/asr33/asr33.shtml
- https://www.curiousmarc.com/mechanical/teletype-asr-33