In this day in 1872, George Westinghouse patents the air brake.

In the air brake’s simplest form, referred to as a straight air system, compressed air is directed to a brake cylinder, causing its piston to apply force to mechanical linkage, which linkage is conventionally referred to as the brake rigging. The brake rigging, in turn, is connected to brake shoes that are pressed against the car’s wheel treads (some types of passenger cars instead use disc brakes). The resulting friction slows the car by dissipating its kinetic energy as heat.
The brake rigging is often quite elaborate, as it is designed to evenly distribute the brake cylinder’s force to multiple wheels.