Chuck My error, you said 20 mA current loop, I bowdlerised it as parallel port. I have a punch with a parallel interface ... I can't recollect ever using a current loop interface on equipment, although I have met many in old documents. 4 .. 20 mA current loops reporting e.g. pressure actuated potentiometers are however old friends, if that is the correct term. As you observe current loop has good noise immunity.
Martin -----Original Message----- From: Chuck Guzis [mailto:ccl...@sydex.com] Sent: 10 April 2022 20:08 To: Martin Bishop <mjd.bis...@emeritus-solutions.com> Cc: CCtalk <cctalk@classiccmp.org> Subject: Re: Fanuc PPR - Paper Tape Punch, Printer and Reader : Not quite working On 4/10/22 11:08, Martin Bishop wrote: > Chuck > > Thank you for the parallel port suggestion. I followed it up by opening the > D-25 and reviewing the wiring. It looks very RS232 to me, the pin out I > found is detailed in my 10 1314A Apr 22. That the punch and reader respond > to RS232 input I think settles the issue - I was briefly optimistic ... No, not parallel port, but 20 ma current loop. Used extensively in teletype/industrial work. Still serial, but suited to long-haul or noisy environments. The original IBM PC serial card could be configured for CL. The advantage is that it's not voltage-sensitive per se, but rather to the current flowing through the loop. On long hauls, one could raise the voltage until the proper current level was obtained. RS232C, on the other hand is strictly voltage-sensitive. https://en.wikipedia.org/wiki/Current_loop for details. But it sounds as if you have a bog-standard RS232C setup. Very old teletype setups used, I believe 60 ma. CL. --Chuck
