MULTIFREQUENCY TONE DETECTION

摘要

A method and apparatus for detecting multifrequency tones in a received signal by summing aperiodic samples and without using bandpass filters. In a receiver capable of detecting m different tones each comprised of n different frequencies, the apparatus performs m parallel summations each of 2n samples of the received signal. Each summation corresponds to a different detectable tone. In each summation, an initial sample is followed by samples delayed from it by respective half-periods of the frequencies comprising the corresponding tone and by samples delayed from the initial sample by combinations of different ones of such half-periods. The detection of a particular tone is indicated when the corresponding sum is zero and all other sums have finite values.