Check out the video below from Marc where he works on his Model 19 Teletype. Teletypes used a serial to parallel converter comprised of a solenoid and a multi-

Check out the video below from Marc where he works on his Model 19 Teletype. Teletypes used a serial to parallel converter comprised of a solenoid and a multi-lobe camshaft that converted an incoming electrical signal (serial) into 5 individual bits (mechanical). Timing was important, so the motor on the Teletype had to be running at a known speed. You used a tuning fork that had a slot cut in it to look through to check it periodically. Marc mentions how Teletypes would commonly run with one or 1.5 stop bits. You need this to tell the mechanical parts to "lock up" at the end of a character. Preferred would be to run with 1.5 stop bits so that the machines became self-synchronizing -- if the wire got reconnected in the middle of a character they would start producing readable output again after only a few garbled characters. The way the camshaft worked was each bit had a window of time where it could be set or cleared (marking vs spacing) by the solenoid. For letter H the bits are 10100 [0]. So the first lobe of the camshaft would come around and the solenoid would be in it's marking position (1) so the 1st bail would be selected. The second lobe would come around a few milliseconds later and the solenoid would be in it's spacing position (0) and the 2nd bail would NOT be selected. A few milliseconds later the third lobe would come around and the solenoid would be in it's marking position (1) so the 3rd bail would be selected. This would continue for the next two bits (spacing) and then the stop bit would arrive and the machine would use the values stored in the bails to print the letter H and/or punch an H (10100) into the paper tape. https://www.youtube.com/watch?v=ug5lUI-hs3s https://www.youtube.com/watch?v=ug5lUI-hs3s Ever wonder why carriage return and line feed are different codes in Baudot, ASCII, and Unicode? It's because Teletypes needed the time to physically move the printing carriage back to column 1. Operators were trained to hit CR CR LF in case the Teletype at the other end was a little slow in returning from column 80 so the next line would start in column 1. [0] Assuming you were in Letters. Because you only had 5 bits, alphabetic (Letters) and numbers/symbols (Figures) were alternately selected by 11111 and 11011. So 10100 could produce either an H or a # depending on whether you were in Letters or Figures mode.