Apparatus for picking up signal currents flowing through signal lines

Claim 1

An apparatus for discriminating an operated sensor and attached to an alarm system in which a plurality of sensors are connected in parallel between signal lines led from a receiving panel of said alarm system for short-circuiting said signal lines so that a signal current passes through said signal lines when said sensor has detected an abnormal condition, said apparatus comprising an annular magnetic core wound with a pickup coil linked with one of said signal lines for picking up said signal current flowing through said signal lines, thyristor means connected to be turned ON by the voltage induced in said pickup coil, a programmable unijunction transistor connected to said pickup coil and said thyristor for increasing the load impedance of said pickup coil thereby positively turning ON said thyristor, the output of said pickup coil being connected to the gate input of said programmable unijunction transistor, the output of said programmable unijunction transistor being connected to the gate input of said thyristor means, a capacitor connected to be charged from a source of direct current, a discharge circuit connected to said capacitor for discharging said capacitor, said discharge circuit comprising the anode-cathode circuit path of said transistor and the gate-cathode circuit path of said thyristor connected to said anode-cathode circuit path, and to discharge through a discharge circuit including the anode-cathode circuit of said transistor and the gate-cathode circuit of said thyristor, said signal lines having signal and return conductors connected to said sensor, said conductors forming a loop, one of said conductors being magnetically coupled with said magnetic core corresponding to each of the sensors whereby when said respective sensor is operated, the currents flowing through the signal and return conductors being unequal and thereby inducing a voltage across said pickup coil.

Claim 2

An apparatus for discriminating an operated sensor and attached to an alarm system in which a plurality of sensors are connected in parallel between signal lines led from a receiving panel of said alarm system for short-circuiting said signal lines so that a signal current passes through said signal lines when said sensor has detected an abnormal condition, said apparatus comprising an annular magnetic core wound with a pickup coil linked with one of said signal lines for picking up said signal current flowing through said signal lines, thyristor means connected to be turned ON by the voltage induced in said pickup coil, a programmable unijunction transistor connected to said pickup coil and said thyristor for increasing the load impedance of said pickup coil thereby positively turning ON said thyristor, the output of said pickup coil being connected to the gate input of said programmable unijunction transistor, the output of said programmable unijunction transistor being connected to the gate input of said thyristor means, a capacitor connected to be charged from a source of direct current, a discharge circuit connected to said capacitor for discharging said capacitor, said discharge circuit comprising the anode-cathode circuit path of said transistor and the gate-cathode circuit path of said thyristor connected to said anode-cathode circuit path, and to discharge through a discharge circuit including the anode-cathode circuit of said transistor and the gate-cathode circuit of said thyristor, said signal lines having signal and return conductors connected to said sensor, said conductors forming a loop, one of said conductors being magnetically coupled with said magnetic core corresponding to each of the sensors whereby when said respective sensor is operated, the currents flowing through the signal and return conductors being unequal and thereby inducing a voltage across said pickup coil.