US Patent 7699406 Towed vehicle brake actuator assembly

A system for actuating brakes in a towed vehicle in response to actuation of brakes in a towing vehicle comprising a cylinder including an inner cylindrical wall attached to a brake pedal in the towed vehicle and an outer cylindrical wall attached to the firewall in the towed vehicle. An air line supplies positive airflow from the towing vehicle to the cylinder and to a venturi to create a vacuum in response to the airflow. The vacuum is supplied to a brake booster in the towed vehicle while the airflow is supplied to the air cylinder to move the brake pedal in the towed vehicle in proportion to the amount of braking is the towing vehicle.