Electrical control system

Claim 1

IN AN ELECTRICAL CONTROL SYSTEM FOR SMOKE DETECTING APPARATUS INCLUDING A PLURALTIY OF CONDUITS FOR SUPPLYING AIR SAMPLES FROM SPACES IN WHICH SMOKE IS TO BE DETECTED, A DETECTOR FOR GIVING AN INDICATION IN RESPONSE TO THE PRESENCE OF SMOKE, A SELECTOR VALVE FOR CONNECTING THE DETECTOR TO EACH OF THE CONDUITS, AND MOTOR MEANS FOR DRIVING SAID VALVE TO SEQUENTIALLY CONNECT THE DETECTOR TO EACH OF THE CONDUIT; THE COMBINATION OF TIMING MEANS FOR CONTROLLING SAID MOTOR MEANS TO CONNECT EACH OF SAID LINES TO SAID DETECTOR FOR A PREDETERMINED INTERVAL OF TIME, AND INDICATION HOLD-OFF MEANS UNDER THE CONTROL OF SAID TIMING MEANS FOR RENDERING SAID DETECTOR INEFFECTIVE DURING A PREDETERMINED INITIAL PORTION OF SAID INTERVAL OF TIME WHEREBY SAID DETECTOR IS PREVENTED FROM GIVING AN INDICATION AFTER SAID DETECTOR IS DISCONNECTED FROM A CONDUIT TRANSMITTING SMOKE.