Abstract: In a fixture for ascertaining pressure losses in a pressure line (3) which can be blocked for a selectable unit of time by means of shut-off valves (11, 13), in which the consumers (4, 5) are connected to the pressure line (3) and the pressure line (3) is provided with a pressure watchdog (15), the blocked pressure line (3) can have an adjustable quantity of the enclosed pressurised medium supplied into it via a branch line (24) for a unit of time, and the pressure watchdog (15) is provided with a circuit (31) by means of which the pressure line (3) can be controlled depending on the operating status of the pressure watchdog (15). By means of this embodiment, it is possible with only a very minor scope of circuitry to test the pressure line (3) at any time or at selectable time intervals and, depending on the measurement result, to resume the supply to the consumers (4, 5) or to deactivate the pressure line (3).