Also, those older plugs were more or less not hot-pluggable. The computer had to be off (really off, not standby) before you plugged/unplugged a cable, or you'd

Also, those older plugs were more or less not hot-pluggable. The computer had to be off (really off, not standby) before you plugged/unplugged a cable, or you'd risk damaging the port and/or the device. The only exception I know of is that Apple Desktop Bus (mini-DIN) had been designed (by Woz !) to be supposed to be hot-pluggable but Apple cheaped out on overcurrent protection so it never was. Edit: I forgot: in a MIDI connection there is an opto-coupler behind the receiving end, to electrically separate devices.