GB1429180A - Alarm circuits - Google Patents

Abstract

1429180 Protective arrangements GENT & CO Ltd 13 Aug 1973 [18 Aug 1972] 38679/72 Heading H2K In a battery operated alarm circuit including a battery charger 3 permanently connected to the battery 1, a portion of the circuit including the battery 1 and terminal connections of the output conductors 31, 32 from the battery is connected in an impedance sensitive circuit supplied with a fluctuating current, a warning or indicating device 10 being operated when the impedance of this portion of the circuit increases above a predetermined value. As shown, pulse generator 21 energized by a supply circuit 20 causes pulses to flow in the portion of the circuit including the conductors 31, 32 and the battery 1 which normally has a low impedance. Should this circuit portion have a high impedance due to a faulty connection, a faulty battery, or an open circuit, then the pulse voltage rises sufficiently to cause a voltage sensor 22 to provide an output to a warning circuit 23 to effect the operation of the warning or indicator device 10. The alarm 2 of the alarm circuit is isolated from. the pulses by a choke 45 and a capacitor 47. In an alternative arrangement the fluctuating current is an alternating current and the portion of the circuit in question is connected to form one arm of an A.C. bridge.