False target warning system

Claim 1

A false target warning system for a target designator, comprising: detector means for detecting electromagnetic energy from the target designator that is reflected back thereto and which defines a path of optical transmission; an amplifier connected to the output of said detector means; a threshold circuit having first and second inputs, said first input connected to the output of said amplifier, said threshold circuit configured to have a signal output whenever the signal applied to said first input exceeds the threshold level; a sensitivity control circuit for controlling the threshold level of said threshold circuit, comprising: an integrator having the output thereof connected to said second input of said threshold circuit; a one-shot multivibrator connected to the negative input of said integrator, said one-shot multivibrator configured to be triggered by a pulse of energy from the target detector; a source of positive voltage connected to the positive input of said integrator, the integrator output being equal to said positive voltage minus the integrated signal from said one-shot multivibrator, thereby supplying a voltage that decreases with time to said second threshold input to cause the threshold level of said threshold circuit to decrease with time; a timing circuit triggered by pulses of energy from the target designator, connected to the output of said threshold circuit and configured to be triggered simultaneously with said one-shot multivibrator; and indicator means, connected to said timing means, for warning the operator of the target designator whenever said timing circuit receives a signal from said threshold circuit in a time less than a predetermined interval.