Eli5: Why does the coin drop after hanging up the pay phone

Question

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?

In: 244

Answer 1

Other people have mentioned how you could fool a US payphone into thinking the call was not completed.

Here in the UK for a period there was a much more mechanical way than using tones. Way back in the 1990s, you could take a metal kebab stick and put it in the coin return slot and push up. We used to ring competition lines and use the same pound over and over again.