Direct current proximity detector having switching means which provide on two distinct outputs, signals when the target is located beyond or within a predetermined range

A proximity detector comprising:

• a source of direct current supply having first and second terminal;
• first and second load circuits;
• first and second diodes having a common point, the first diode and the first load circuit being serially connected between the common point and the second terminal and the second diode and the second load circuit being serially connected between the common point and the second terminal;
• a voltage stabilising transistor having a current input, a current output and a control input, the said current output being connected to the said common point;
• a first Zener diode connecting the first terminal of the source to the said control input;
• an oscillator power supplied between the first terminal of the source and the current input of the voltage stabilising transistor and having a high frequency output;
• a detector power supplied between the first terminal of the source and the current input of the voltage stabilising transistor and having an input connected to the high frequency output of the oscillator and an output on which a control signal is generated when the oscillator is in an oscillating state;
• inverter means power supplied between the first terminal of the source and the current input of the voltage stabilising transistor and having an input connected to the output of the detector and first and second control outputs, said inverter means providing a signal on the first output thereof when the said control signal is present and a signal on the second output thereof when the said control signal is absent;
• first and second switching transistors each having a current input, a current output and a control input;
• a second Zener diode connecting the first terminal of the source to the current inputs of the first and second switching transistors, the current output of the first switching transistor being connected to the junction point between the serially connected first diode and first load circuit and the current output of the second switching transistor being connected to the junction point between the serially connected second diode and second load circuit, means connecting the control inputs of the first and second switching transistors respectively to the first and second control outputs of the inverter means;
• and first and second resistors respectively connecting the control input of the voltage stabilising transistor to the respective junction points between the serially connected first and second diodes and first and second load circuits.