RECEIVER APPARATUS FOR DETECTION OF TWO VOICE FREQUENCIES IN A MULTIFREQUENCY TONE SIGNAL

摘要

The invention relates to a reference rectifier in a multifrequency signal receiver for obtaining a correct detection of the two signalling frequencies in an incoming voice frequency signal independently of disturbing signals of varying frequency and duration. The rectifier has a first signal path including a peak rectifier for creating a first signal level in dependence on the incoming signal level which is compared with the signal component having a frequency equal to one tone in the incoming voice frequency signal. The rectifier also has a second signal path including a mean value creating circuit which, in dependence on the incoming signal gives a second signal whose level is smaller than said first signal level. A number of diodes is connected between the outputs of the receiver and the first signal path to inhibit the output signal from this signal path in dependence on the comparison between the signal level from the first signal path and the signal component having the frequency equal to one tone in the incoming voice frequency signal.