| 摘要 |
A metal locator apparatus the preferred practice of which includes two electromagnetic field radiating inducers, which serve to act upon a metal object deposited in a covert medium from distinctly separate positions, including two separate search oscillators one of which is connected to each of the inducers thereby producing two output signals, each of which include distinctive frequency perturbations introduced by the proximal relationship of the metal object with the responsive inducer. The two signals are then each individually combined, or mixed with a common beat oscillator which action results in two output sets of sum and difference frequencies. By way of suitable filtering, the two difference frequencies come out as distinctly separate audio frequency signals the pitch of which fluctuates in direct accordance with the frequency perturbations appearing on the individual search oscillator combinative signals. The two thus produced audio difference frequencies are amplified, whereupon they serve to drive two sensory indicators, for example a dual headset arrangement, whereby a stereotonic or otherwise multisensible positional indicative signal is conveyed to an operator which will serve to narrowly localize the concealed object. Pronounced improvement in the average operator's ability to differentiate between subtle, or slight, differences in the indicative audio frequencies is brought forth in the locator through the use of a very low, subaudible frequency which operates so as to switch the sensory indicators alternatingly back and forth between the audio difference frequencies thereby enhancing the recognition of even slight pitch differences.
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