Pneumatic fire alarm system

Claim 1

A PNEUMATIC FIRE ALARM SYSTEM COMPRISING, A SOURCE OF COMPRESSED AIR, A PLURALITY OF ZONE DETECTORS POSITIONED IN ZONES IN WHICH FIRE DETECTION IS DESIRED, SAID ZONE DETECTORS EACH INCLUDING AN AUDIBLE WARNING MEANS AND A PRESSURE RESPONSIVE VALVE MEANS FOR CONTROLLING THE OPERATION OF SAID WARNING MEANS, A SINGLE PIPE LINE CONNECTED TO ALL OF SAID DETECTORS AND TO SAID SOURCE OF COMPRESSED AIR INCLUDING A PIPE MEANS CONNECTING SAID AUDIBLE WARNING MEANS AND SAID VALVE MEANS OF THE DETECTOR TO SAID PIPE LINE, A PRESSURE REDUCING VALVE AND A RESTRICTION INCLUDED IN SAID SINGLE PIPE LINE NEAR SAID COMPRESSED AIR SOURCE AND ESTABLISHING A PREDETERMINED LOW PRESSURE IN SAID LINE TO EACH DETECTOR, A PRESSURE RESPONSIVE VALVE MEANS CONNECTED TO SAID SOURCE AND SAID PIPE LINE AND ADAPTED TO BYPASS SAID PRESSURE REDUCING VALVE AND SAID RESTRICTION, SAID PRESSURE RESPONSIVE VALVE BEING RESPONSIVE TO A DROP IN PRESSURE IN SAID PIPE LINE BELOW SAID PREDETERMINED LOW PRESSURE TO OPEN SAID PRESSURE RESPONSIVE VALVE AND APPLY A HIGHER THAN SAID PREDETERMINED LOW PRESSURE TO SAID PIPE LINE AND SAID DETECTORS, A PLURALITY OF THERMAL ELEMENTS CONNECTED TO SAID DETECTORS AND RESPONSIVE TO A RAPID RISE IN TEMPERATURE IN SAID ZONES, SAID THERMAL ELEMENTS INCLUDING VALVE MEANS CONNECTING SAID PIPE LINE TO A VENTED CHAMBER OF SAID DETECTORS TO DROP THE PRESSURE IN SAID PIPE LINE AND CAUSE SAID PRESSURE RESPONSIVE VALVE MEANS TO BE OPERATED AND BYPASS SAID PRESSURE REDUCING VALVE TO RAISE THE PRESSURE IN SAID PIPE LINE, THE PRESSURE RESPONSIVE VALVE MEANS IN SAID DETECTORS RESPONDING TO THE INCREASE IN PRESSURE IN SAID PIPE LINE TO OPERATE SAID AUDIBLE WARNING DEVICE AND CLOSE THE VENTED CHAMBER OF SAID DETECTORS.