Was it? I've dialed like that a few times and I always clicked N times.

Here's the code for the phone, BTW, as I forgot to include it in the article:

https://github.com/skorokithakis/dialogue/blob/master/src/ma...

I remember it being N at least in ex-Yu. But now that I think about it I forget if it was a reverse-click i.e. the pulse was created by releasing the pressure plate briefly. In that case we'd have a fencepost thing and there would be N+1 physical presses maybe