A system for controlling a braking force applied to a trailer, said system comprising:
- said trailer having an air brake located on an axle, said air brake including a service brake chamber including a diaphragm located within said service brake chamber and a service brake pushrod connected to said diaphragm so that said diaphragm extends said service brake pushrod to an extended position when pressurized air is introduced into said service brake chamber and said service brake chamber including a return spring to retract said service brake pushrod to a retracted position when air is removed from said service brake chamber, said air brake including a spring brake chamber including a spring brake diaphragm located within said spring brake chamber and a spring brake pushrod adjacent said spring brake diaphragm so that when pressurized air is introduced into said spring brake chamber, said spring brake pushrod is retracted to a retracted position and said spring brake diaphragm compresses a spring brake spring, when air is removed from said spring brake chamber, said spring brake spring moves said spring brake pushrod to an extended position and movement of said spring brake pushrod to said extended position causing movement of said service brake pushrod to its said extended position;
- movement of said service brake pushrod to its said extended position actuating a foundation brake;
- said trailer including an air compressor in fluid communication with a supply tank said air compressor providing pressurized air to said supply tank;
- an electrically actuated valve in fluid communication with said supply tank and in fluid communication said service brake chamber, said electrically actuated valve for releasing air from said supply tank at a controlled rate;
- an air line connecting said supply tank and said spring brake chamber in fluid communication;
- a release valve in fluid communication with said supply tank and having an energized state corresponding to said release valve receiving electrical current and a non-energized state in the absence of electrical current, said release valve being open in said non-energized state and releasing said pressurized air from said supply tank in said non-energized state;
- a controller for receiving a proportional braking signal from a towing vehicle, said proportional braking signal moveable between a signal representing no braking force from said towing vehicle and a signal representing full braking force from said towing vehicle, said controller electrically connected to said electrically actuated valve, when said controller receives said proportional braking signal from said towing vehicle representing no braking force, said controller actuates said electrically actuated valve to provide no air pressure to said service chamber of said air brake and when said controller receives said proportional braking signal from said towing vehicle representing full braking force, said controller actuates said electrically actuated valve to provide air to said service chamber of said air brake corresponding to full braking force of said brake on said axle of said trailer.