Multi-frequency signal receiver

Abstract From the Canadian patent

Disclosed is a multi-frequency signal receiver adapted to receive a signal consisting of at least two frequency tones selected out of more-thantwo predetermined frequencies. The receiver comprises a filter having mutually independent pass bands at said frequencies a detector coupled with, the filter for sensing the presence of signal output at each of said frequencies, a variable threshold circuit for detecting the maximum value among the output signals of the filter and for generating a threshold value for the detector, an integrator circuit for integrating the input of the filter a circuit for effecting weighted comparison between the outputs of the variable threshold circuits and the …