摘要 |
A tractor/trailer vehicle fluid pressure braking control system enabling two line control of trailer service and secondary braking includes for tractor braking a service brake control valve for controlling the fluid pressure applied both to service brake actuators and to a trailer service brake control line, a secondary control valve which controls the magnitude of a counteracting pressure applied to tractor spring brakes and also to a relay valve which controls a pressure in a trailer secondary spring brake control line. |