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 > >
