When I was a kid, I noticed two odd things about public buses.
When a bus came to a stop, it invariably make a hissing sound–almost a fart–which I later figured out had to do with the air brakes. Now, of course–I ride the buses quite often–I no longer hear buses farting.
The old mechanical fare box, with the glass chamber at the top, would accept your money and some part of it below the top would rotate–making a click-a-click, click-a-click sound. Was that a primitive coin counter? And what do they use in place of it now?
Dunno about the brakes, but the old busblender* has been replaced by fairly sophisticated equipment that counts coins, accepts currency, and on some, processes stored-value tickets or passes.
When I was a kid, I remember the glass dome, and it was simply up to the driver to watch what you dropped in. They’d hit a lever to dump the coins into the vault, which also made it easier to view the next passenger’s payment.
When the brake pedal is released, the air that was used to apply pressure to the brake pads is released to the atmosphere. This is what makes that hissing sound.
The handbrake works in quite the opposite way. When the handbrake is used, pressure on the brake pads is applied by springs. When it is released, air pressure is applied to retract the springs. So you should hear a hissing sound whenever the handbrake is applied. This means that in case a truck loses air pressure due to malfunction, the handbrake will still work. Also, when you start a truck in the morning, you have to wait 2-3 minutes until there’s enough pressure to release the handbrake.
Why you don’t hear those hissing sounds anymore? My WAG is that these buses are designed in such a way to create as little noise as possible.