Automotive burglar alarm with gas siphoning detector

TLDR: In this paper, an automotive burglar alarm system receives an input from a gasoline float responsive potentiometer, which is included in a voltage divider with a manually adjustable resistor, and the output of the window comparator operates an SCR coupled, via a selector switch, for controlling the energization of either a test light or the horn of the automotive vehicle.

Abstract: An automotive burglar alarm system receives an input from a gasoline float responsive potentiometer. The potentiometer is included in a voltage divider with a manually adjustable resistor. The divider has one output signal connected, without inversion, to one input of a window comparator formed by a pair of PUT's. The other comparator input terminal is fed via an inverter from another output of the voltage divider thus forming a bridge circuit with the window comparator as an unbalance defector. The output of the window comparator operates an SCR coupled, via a selector switch, for controlling the energization of either a test light or the horn of the automotive vehicle. The manually adjustable potentiometer is initially calibrated using the test light, to bring the comparator input signals into substantial equality. Then the horn is selected for energization to signal any change in the resistance of the float potentiometer.