On the pay phone at boarding school in South Africa in the 60's we used to have an earthed "tickey-wire" (a tickey being three pence).
When the pips sounded to insert your coins, the tickey-wire was inserted into a small hole in the mouthpiece, where the ensuring connection made a sound/signal like a coin had been inserted.
Caused difficulty when telco takings from that phone were significantly short of what they should have been.

Lived in the CBD for the 10 years. Suddenly felt all grown up when we moved in - waking distance to the whole CBD and only minutes from buses, trains and ferries. I love it. Only downside is suburban screamers who descend on Saturday and Sunday nights.