Electric-Brake Controller

• For the brakes to work, trailers must be connected to a tow vehicle equipped with an electric-brake controller. Unlike surge brakes on a trailer, electric brakes are not independent of the tow vehicle. When you step on the brake pedal in the tow vehicle, the controller receives a signal from the brake-light switch that the brake has been applied. This causes the controller to switch higher current power to the trailer brake. The degree to which the trailer brake is applied is determined by the adjustments the driver makes to the controller.
  
  

Mechanics

• When the controller sends current to the electric brake, the magnet is energized, causing the magnet to be attracted to the inside of the brake drum. This attraction makes the magnet try to turn with the brake drum. Because the magnet is attached to the actuator arm, the rotation of the brake drum forces the brake shoes out against the friction area of the brake drum, slowing the trailer.
  
  

Breakaway Switch

• Trailers equipped with electric brakes have a breakaway switch. This switch automatically applies full power to the brakes in the event the trailer becomes detached from the tow vehicle during driving. The 12 volts required to do this come from a small battery mounted on the trailer for this purpose.