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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

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.

대표청구항 ▼

A security alarm apparatus for warning of attempted siphoning of gasoline in an automotive vehicle having a battery, an electrically energizeable sonic alarm, and a first variable resistor whose resistance is varied by a gas tank float, said apparatus comprising: a window comparator means having fir

A security alarm apparatus for warning of attempted siphoning of gasoline in an automotive vehicle having a battery, an electrically energizeable sonic alarm, and a first variable resistor whose resistance is varied by a gas tank float, said apparatus comprising: a window comparator means having first and second input terminals and an output terminal, a resistive voltage divider means including said first resistor and a second manually adjustable resistor; means for connecting said voltage divider means across said battery; said voltage divider means having output signal means coupled without inversion to the first terminal of said window comparator means to form a first signal at said first input terminal, an inverting amplifier means fed by said output signal means of said voltage divider means and feeding the second input terminal of said window comparator means to form a second signal at said second input terminal; said second resistor being variable to initially set said alarm apparatus in a manner that said first and second signals are substantially equal, said window comparator means being configured in a manner that said output terminal has a predetermined output signal state in response to the absolute value of the difference between said first and second signals being greater than a predetermined constant, and means responsive to the output of said window comparator means for coupling said sonic alarm across said battery in response to said predetermined state.