The Bumpers or 'mushrooms' are most often three in number and placed at the very top of the playfield.
The pinball ball goes from bumper to bumper making as much noise as possible.
This is an element that contributes to the sensations restored by your Pincab to make it as close as possible to a real pinball machine.
The Bumpers are controlled with a Freescale KLZ25 PCB, a mosfet card and the Pinscape Config Tool software.