If you ‘suspected’ Mrs Mcgilicuddy was listening in, just say something ‘dramatic’ about her and wait for the gasp from HER and all the others..then the ‘click’...
Without thinking I will STILL say ice box and am a tad older than 30....
Of course, all us USN types (well military) can have a conversation using the ‘old’ words and it is sort of cryptic... (Don’t pull a Clark Gable saying I had a ‘gay old time’ last night in the 1930s reruns)
wait for the gasp from HER and all the others..then the click...
The pay phone in the back was for calling out, but someone figured out that dial phones transmitted a number of clicks based on the number you dialed. A seven, for example, had seven clicks which set a stepper relay at the phone company to that number.
So we would tap the receiver cradle on the dial-less phone to generate the numbers we wanted, and called out for free.
I don’t think we ever got caught.