I recall many years ago in Spain, the well patronised single decker urban buses had no bells, but the conductor had a piercing whistle permanently in their mouth on a short string, which they would blow, particularly for the driver to start.
Russia came back to conductors around year 2000, when fares started moving away from Soviet-era trivial amounts which were just deposited in a box by the door, known as a "trust the passenger" system. Self-appointed old ladies used to sit in the adjacent seats and enjoy scowling at the glass-fronted box device for each entrant, to see a coin had actually gone in. Those with season tickets (a large proportion) would hold them up high on entry for all, but particularly the old ladies, to see.
San Francisco's famous cablecars still have conductors, and traditional Fare Registers which apparently were once universal in the USA. Handles the length of the car are connected to a large dial device under the roof, and a loud bell, there are no tickets but for every flat fare paid the conductor reaches up, pulls the handle, resounding ding, and the dial advances by one. Presumably the conductor has to pay in at the end of the shift what the Register shows.