From How Stuff Works
A visit to the facilities, especially when abroad, can be highly perplexing. The traveler can often spend at least 10 minutes trying to figure out how to operate the flushing mechanisms, as every single toilet seems to be different.
I was first introduced to the concept of pay toilets in Europe in the 1980s. It was not wise to go on the cheap and go into a stall before inserting change, as one could get trapped inside! — Jenny Bleiholder