This is a small switch inside the controller connected to the full on power and full off brake. Gives positive contact, and eliminates the resistor from the circuit. A very efficient way of handling power, even in the newer electronic controllers.

Micro switch Diagram

A micro switch is a generic term used to refer to an electric switch that is designed to be actuated by the physical motion of mechanical devices and is generally packaged in a small form factor to allow placement in small spaces. They are very common due to their low cost and extreme durability, typically greater than 1 million cycles and up to 10 million cycles for heavy duty models. This durability is a natural consequence of the design.