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
