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

摘要

The invention relates to a reference rectifier in a multifrequency signal receiver in order to obtain 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 comprises a first signal path including a first circuit for example, a peak rectifier for creating a first signal level in dependence on the incoming signal level. This signal level is compared with the signal component having the frequency equal to one tone in the incoming voice frequency signal. The rectifier also comprises a second signal path including a second circuit for example, 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.