Patent ID: 8170198

Claim:
A tone signal detector, comprising: a frequency-signal generator that generates a frequency signal for shifting a frequency of a tone signal to a predetermined frequency band; a frequency converter that generates a frequency-converted signal by shifting a frequency of an input signal containing the tone signal by a frequency of the frequency signal generated by the frequency-signal generator; a normalizer that generates a normalized signal by determining a reference value indicative of an intensity of the frequency-converted signal generated by the frequency converter based on an amplitude of the frequency-converted signal, and then dividing the frequency-converted signal by the reference value and thus normalizing the amplitude of the frequency-converted signal; a filter whose pass band is set in a frequency band of the tone signal contained in the normalized signal generated by the normalizer, the filter filtering the normalized signal; and a tone signal detection unit that detects the tone signal based on the signal filtered by the filter.