system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5: Why does the coin drop after hanging up the pay phone

I always see in the movies that when they hang up a pay phone, you hear a coin drop. What’s the reason for this?
gpt
The coin goes into a sort of “escrow” holding. That is it doesn’t fall all the way into the bank, in case the call isn’t completed. Instead it’s held in this escrow feature until after the call, when the coin is dropped into the bank. If a call doesn’t complete, the coin falls into a different mechanism for the coin return.