Directional pickup coil and oscillator apparatus for the location of buried electrically conducting elements

Claim 1

A locator for a buried conductor having alternating current passing there-through, comprising a directional pickup coil having a center tap, an operational amplifier having negative and positive input terminals connected across said pickup coil, an output terminal, offset voltage terminals and a first and a second amplifier power terminal, a power supply having first and second power supply terminals, said first or positive power supply terminal connected to said first amplifier power terminal and to said center tap, said second or negative power supply terminal connected to said second amplifier power terminal, a first resistor connected to said output terminal, a second resistor connected between said first resistor and said second power supply terminal, a capacitor having one side connected to the juncture between said resistors and another side connected to said positive input terminal, said resistors and said capacitor comprising a feedback circuit for said amplifier for establishing a one-shot multivibrator amplifier output dependent on coil signal input of said coil created by the alternating current through said conductor, the frequency of said one-shot multi-vibrator amplifier output increasing with closer proximity of said coil to the magnetic field of said conductor, an offset voltage potentiometer across said offset voltage terminals and having a movable contact, said movable contact connected to said second power supply terminal, movement of said movable contact adjusting the threshold sensitivity of said amplifier, an indicator connected to said output terminal and to said second power supply terminal for producing observable indications of the frequency of said one-shot multi-vibrator amplifier outputs, and a casing enclosing all of the foregoing elements except said conductor.