Parking valve for a commercial vehicle trailer

The parking valve (14) has an output terminal (34) for compressed air pressurization of a spring-loaded parking brake (16). A supply port (35) is connected to an output terminal in a ventilation position. A pressure safety valve (31) is interposed in the ventilation position between the supply port and output terminal. An actuating member (24) is provided to put a pressure on the output terminal relative to a pressure drop at the supply port.