Abstract: The trailer brake control system for use in a trailer which is adapted to be towed by a towing vehicle. The trailer includes an electrically operated braking mechanism and the towing vehicle includes a brake pedal, at least one brake light, and a brake switch operated by the brake pedal to energize the brake light. The control system includes a short circuit indicator circuit to provide a short circuit signal when a short circuit condition is detected in the trailer brake mechanism. A manual switch is also provided to manually actuate the trailer brake mechanism and to provide a manual brake actuation signal. A second circuit including a NOR gate provides a variable amplitude brake actuation signal in response to the concurrent closure of the brake switch, the absence of a manual brake actuation signal, and the absence of a short circuit signal. An indicator light is responsive to the brake actuation signal to provide a signal indicative of brake actuation.