This type of brakes, though not very popular, as a service brakes, have been commonly used on trailers. One such example is Warner electric brake.

The current from the battery is utilized to energize an Electromagnet within brake drum, which in turn actuates the mechanism (usually a cam) to expand the brake shoes. When current stops, the cam and brake shoes are returned to the release position by retractor springs. The severity of braking is controlled by means of a rheostat, which is operated by the driver through the foot pedal.

As an alternative to the foot operated rheostat, hydraulic pressure has also been used to apply electric brakes. As pedal is pressed more, hydraulic pressure actuates the roasted to increase current to the Electromagnet. Still another method uses an inertia weight to uncover a light. As the brakes are applied for the main vehicle, it slows down due to which the weight or pendulum in the trailer brake control device moves forward, exposing a light sensitive diode to more of the light beam. This increases the current to the Electromagnet in the trailer brake, there by applying these breaks.

Advantage of electric brakes

1.) The operating linkage is much simplified in electric brakes. Instead of complicated linkage as in mechanical brakes or pipelines as in Hydraulic brakes, these require only one cable for each drum.

2.) Being electrically operated there is much less time lag between the pressing of the brake pedal and application of brakes at the wheels, as compared to other systems.

3.) For trailer brakes, this type offers much simplified connections, simply one cable has to be carried to the trailer side.