Fail-safe electro=pneumatic braking control for the rear-axle brakes of bus or tram

摘要

The relay valve (1) for the rear brakes of the vehicle has a supply line input (4) and a brake circuit output (13). One control input (8) from the electrically controlled proportional valve (2) and one control input (12) from the brake control system (3) control the relay valve with a select-high control. The control input from the brake control system is normally lower than that from the proportional control valve. This ensures that direct braking control is selected if the electronic control fails or if the electronic control provides a faulty, low signal.