Adaptive braking modulator for air-braked vehicles

An adaptive braking modulator is disclosed for use in a vehicle having brake actuated by pressurized air. The modulator includes a housing having an inlet port, an outlet port, and an exhaust port. Differential pressure responsive valve means within the housing normally permits uninhibited flow of fluid between the inlet and outlet ports and prevents flow of fluid to the exhaust port, but terminates fluid communication between the inlet and outlet ports and permits communication between the outlet and the exhaust port at a controlled rate when an adaptive braking cycle is initiated. Electrically operated valve means are provided which reduces the pressure on one side of the differential pressure valve means to actuate the latter.