Cable detection apparatus with a comb filter

Abstract

An apparatus that uses harmonics of the power line frequency at which electrical power is distributed is presented. The apparatus includes a sensor antenna to detect an electromagnetic field produced by a cable. The output of the sensor is fed to a mixer together with a signal from a sine wave generator at less than the fundamental power frequency to frequency shift the signals from the sensor. The mixed output is then amplified to provide an audible output. A single comb filter receives signals from the mixer and outputs a filtered signal removing non-harmonic frequencies but preferably passing both odd and even harmonics. The output of the comb filter is then integrated at and displayed to indicate the detection of a cable based on the filtered signal.

Dependencies are inferred from the claim text.