GB1400679A - Control system for a plurality of loads - Google Patents

Abstract

1400679 Door etc control systems HOCHIKI KK 14 Sept 1973 [22 Sept 1972] 43253/73 Heading E2A In a control system for sequentially operating a plurality of loads, such as firepreventing doors, smoke exhaust fans, automatic water sprinklers alarms etc installed in buildings, sequentially connected in parallel across the supply conductors CL, L, each load is connected across the supply conductors through a switching circuit SC which is closed a predetermined interval after application of an operating voltage, the loads in the second and succeeding states being connected across the supply conductors through transfer switches MS which are operated in response to the operation of the loads in the proceeding stages. There is a relay contact a connected in parallel with each switch MS, and relay means A is provided for each stage for opening the contact when the load and switching circuit in each stage are energised and for closing the contact after a predetermined interval, and a terminal impedance element RL connected across the end terminals of the supply conductors. As shown in Fig 2, particularly for door unlocking circuits DL 1 , and DL 2 , a door DR has secured thereto an armature PT which is attracted by the permanent magnet M to secure the door in closed position; when electrical current flows through the coil L the armature is released and the door is biassed by springs to an open position, a plunger PG being moved outwardly by a spring SP so that the end of the plunger actuates the transfer switch MS whereby the circuit DL 1 is de-energised and the next circuit DL 2 is energised. A normal operating voltage for the loads is supplied by a source E 1 and a second source E 2 supplies a lower voltage, the current flowing through the conductors CL, L being indicated by a meter M whereby if one of the conductors is interrupted the meter will indicate a resistance which is higher than that of the element RL.