“,..If you did it fast enough hitting it 5 times was the same as dialing a 5.”
Actually you do the off-on thing 6 times to dial a 5. Still works in many areas. I’ve literally dialed hundreds of numbers this way. Have to add 1 and that’s the clicks.
Origin traces to the original switching relay systems. First on-off-on signal tells the equipment a number is coming, and the central relay bank switches that line to the incoming counting relays.
I worked in a relay farm for awhile. “Inside Plant,” they call it. Mainframe full of a gazillion chattering rotary and linear relays. Noisiest thing you ever heard.
ATT (Bell Labs) Redbank invented the transistor switching equipment relacement, called ESS. Electronic Switching System. My dad installed the first one in a Central Office. Military got the 2nd one, just outside DC. Blew the top off a mountain, put in a massive, hardened, gigantic facility, buried it back up. Gargantuan blast gates. I was there as a tyke when my Dad and buds put that one in. Impressive. Hush hush.
He knew Schotky, and other inventors of the transistor. Told stories. Characters, all of them. Brilliant guys. With sliderules and pocket protectors.
I knew a guy who heard one abruptly go quiet. They thought something went wrong, then it built up to a crescendo.
They knew something VERY bad had happened, but not what.
JFK was assassinated.