Abstract: A system for detecting the position of an object within a body of biological tissue includes a resonant circuit attached to the object and a probe including a receiver/transmitter that operates at the resonant frequency of the object. The resonant circuit rings in response to pulses transmitted from the probe thereby activating receiver circuits which control a visual display indicating the direction the probe should be moved to center it over the object. When the object is centered a second visual display provides confirmation.

Abstract: A system for detecting the position of an object within a body of biological tissue includes a resonant circuit attached to the object and a probe including a receiver/transmitter that operates at the resonant frequency of the object. The resonant circuit rings in response to pulses transmitted from the probe thereby activating receiver circuits which control a visual display indicating the direction the probe should be moved to center it over the object. When the object is centered a second visual display provides confirmation.

Abstract: A synchronous demodulator subsystem produces a ground balance pulse and a discriminate pulse each time a detector head housing the receive coil and an associated transmit coil passes over a metallic object (e.g., a target) buried in the ground. In one form, a pair of synchronous demodulators produce V.sub.X and V.sub.R signals, each of which includes a pulse each time the detector head passes over a target. The V.sub.X and V.sub.R signals are combined to produce the ground balance and discriminate pulses. Alternatively, a pair of synchronous demodulators are used to directly produce the ground balance and discriminate pulses. The polarity of the discriminate pulse is dependent upon on whether the target is a desirable or an undesirable target. Contrariwise, the polarity of the ground balance pulse is always the same.