> > Wikipedia says it was defined in 1960 although their cite links don’t seem > to work.
Their cite link worked for me, which led to a basically a text-file version of the following document (which is from Oct. 1976): https://archive.org/details/standardsforcom7610evan_0/page/18/mode/2up (page 18, item 7) With a blanket statement of "7. Standardization Status: RS-232, May 1960; RS-232-A, October 1963; RS-232-B," So I was just looking for more evidence to back up that statement - as in, actual copies of those standards, or other publications/products/manuals that refer to RS-232-A or RS-232-B (prior to 1969). I'm not doubting the statement! When you look at a physical Bell Model 103A, you see the DB25 connector, and its manual describing the pin usage match the modern one (pin 1 as a protective ground, pin 2 for TX, pin 3 for RX, on up to Ring Indicator as pin 22). The earliest copy of its manual I find is marked from 1967, but the ad-images are a few years earlier, and I suspect there were earlier copies of its manual (of around 1963). And as I mentioned earlier, I found Datamation talking "RS-232" as early as 1966. Just I was curious to see the actual "RS-232-A" (and B) documents, that an engineer at the time (mid-1960s) might refer to. Yes, the later -C ought to be the 3rd revision of these said docs. Per Datamation, I see some quite capable minicomputers even by 1964 (even at $30K) - if I were Joe Engineer at one of those minicomputer companies and wanted to hook my system up to a Bell DataSet 103A, would I just read the 103A's manual? Or would I seek out "RS-232-B"? Then to even know such a standard or revision existed, surely it would be mentioned/discussed in some publication (like Datamation). -Steve On Sun, Apr 20, 2025 at 12:01 PM Wayne S via cctalk <[email protected]> wrote: > Wikipedia says it was defined in 1960 although their cite links don’t seem > to work. > If that helps! > Sent from my iPhone > > > On Apr 20, 2025, at 08:01, Chuck Guzis via cctalk <[email protected]> > wrote: > > > > On 4/20/25 04:11, Steve Lewis via cctalk wrote: > > > >> Anyway, just poking around, no specific question here :) Wel, except a > >> related/unrelated question -- why does MIDI use 5mA current loop? And > is > >> that why MIDI adopted the joystick port? (IBM original joystick card > spec, > >> didn't it involve measuring electrical discharge? so it is effectively a > >> current-loop port? is that somewhat accurate?) > > > > Having occupied an adjacent building to Sequential Circuits on N. First > > Street, right after the orchards were bulldozed, my guess is that 5 ma > > was completely satisfactory for the relatively short haul that MIDI > > required sometime around 1980. > > > > Note that old (<Model 15) TTYs used 60 ma current loop and were strictly > > mechanical devices. 60 ma could adequately power the selector magnets > > in 1930, > > > > --Chuck > > > > >
