Abstract: A portable apparatus used for geophysical exploration for buried objects h as mines, relics and minerals utilizing a means to represent the endpoints of the apparatus sweep and means responsive thereto to blank data received at these points, thereby eliminating erroneous signals likely to occur when the search head is in a tilted position. The end-point representation may be achieved by either a metronome-type signal generator or by an accelerometer.

Abstract: Circuitry for detecting buried non-metallic and metallic land mines is diosed. A peak detector receives signals from a conventional search head. The output of the peak detector is amplified and this amplified signal is applied to a slope determination channel, to a pulse width determination channel and to a pulse amplitude determination channel. The output pulses from the slope determination channel, the pulse width determination channel and the pulse amplitude determination channel are all applied to different inputs of an AND gate. If pulses are coincidently present on all the inputs of the AND gate, the AND gate provides an output pulse which is applied to a field effect transistor (FET) switch. The FET switch controls the gain of an amplifier such that the gain of the amplifier is measurably increased when the AND gate applies a pulse to the FET switch.