Automatic on/off circuit with time delay

In combination with an automotive vehicle having an engine and an electric system including a battery, and in which a cigarette lighter plug is electrically connected to said battery and a radar warning receiver for supplying a D.C. electrical input signal and such that whenever said engine is running said D.C. electric input signal has superimposed thereon a varying electrical noise signal, whereas whenever said engine is not running said varying electrical noise signal is absent from said D.C. electrical input signal, an off/off circuit adapted to receive said D.C. electrical input signal from said battery via said cigarette lighter plug for operation of said radar warning reciver, said on/off circuit comprising:

• a solid-state switch electrically connected between said cigarette lighter plug and said radar warning receiver for receiving said D.C. electrical input signal from said battery, said solid-state switch being electrically switchable between "on" and "off" electrical states to correspondingly transmit and not transmit said D.C. electrical output signal to said radar warning receiver for turning it "on" and "off";
• a signal integrator electrically connected to said batter via said cigarette lighter plug for receiving said D.C. electrical input signal therefrom and sensing the presence or absence of said varying electrical noise signal superimposed thereon, said signal integrator being operable to produce a first electrical output signal when the presence of said varying electrical noise signal is sensed and a second electrical output signal when the absence of said varying electrical noise signal is sensed;
• and
• time delay means electrically connected between said signal integrator and said solid-state switch for receiving said respective first and second electrical output signals from said signal integrator and being actuated in response thereto to corresponding first and second output states after lapse of a preset period of time, said time delay means when actuated to said first state from said second state after lapse of said present time period causing said solid-state switch to switch from said "off" to "on" state and when actuated to said second state from said first state after lapse of said present time period causing said solid-state switch to switch from said "on" to "off" state.

An on/off circuit for controlling the application of power from a vehicle electric powersupply system to a radar warning device, for applying said system to said device automatically when the vehicle's engine is running and for disconnecting said system after said engine is turned off, comprising:

• noise detecting means connected to vehicle's power supply system providing a signal in a first state when noise is present in the power supply system indicating that the engine is running, and providing a signal in the second state when no noise is present indicating that the engine is not running, time delay means connected to receive said signal states from said noise detector and operable to produce a first signal after a predetermined time delay following the application of said first state thereto and operable to produce a second signal after a predetermined time delay following the application of said second signal state thereto, and electrically controllable on/off switch means connected to apply power from said vehicle power system to said warning device and having a controllable input connected to said time delay means for applying power to said device when said first output is applied thereto, indicating that noise is present in said power system and said engine is running and operable to remove power therefrom upon receipt of said second output indicating that the vehicle engine is not running.