DIGITAL SIGNALLING RECEIVER FOR RECEIVING PCM TONES

摘要

A digital signalling receiver translates pulse code modulated (PCM) tone signalling into a signal format compatible with a controller in an associated time division multiplex (TDM) telephone switching facility. In the receiver, steering signals are generated in synchronism with the operation of the switching facility to direct the operation of a time shared filter. The filter performs a plurality of filter functions with a series of PCM signals received from the TDM switching facility and generates therefrom series of filter signals relative each of the filter functions. A translator identifies two filter signals having larger amplitudes than the others and if the two signals persist substantially uninterrupted (a) through a predetermined period of time, (b) within a predetermined relative amplitude range and(c) one of the two signals having at least a predetermined signal to noise ratio relative another filter signal corresponding to an allpass filter function, the translator indicates the receipt of multifrequency signalling by generating the appropriate signals in the required signal format. - i