[anigbrowl]

Well, if you think of it in terms of voltage rather than switching, the audio transient will cause similar spikes in the voltage amplitude. I think that the analog circuits in exchange hardware are only interested in the shape rather than the origin of the pulse but as I said I've never looked at such equipment directly.

I have a modular synth here and have managed to rig up a patch that counts audio pulses (incoming signal goes through a rectifier and an envelope follower and on to an accumulator) and generates an appropriate tone for the counted number after a ~1/4 second pause, and doesn't much care whether I'm opening and closing the circuit or just tapping the front of the microphone. It's not a very complex circuit so maybe analog exchange switching works on a similar principle.