Abstract: A system for detecting a leak in a line consists of an apparatus for detecting a drop to a predetermined pressure in the line; and, once the predetermined pressure is reached, an output is developed by the pressure-sensing apparatus. A bi-state circuit responsive to the output from the detecting apparatus has a first state when no leak is present and a second state when the predetermined pressure is detected. A switching circuit has its input connected through the bi-state circuit. A timing circuit develops a signal at its output after a predetermined time and applies this signal to a bi-state gate circuit. A nonleak detector is coupled to the output of the bi-stable gate circuit to indicate that no leak is present in the system.