Title: Telephone station with automatic switch-over between pulse code dialling and multifrequency code dialling

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Abstract: A keyboard type telephone station connected to a telephone subscriber's line comprises a dial pulse train generator and a dialling multifrequency signal generator. The telephone station includes a control unit connected to at least one current threshold detector for the power level of supervisory or so-called tone signals. The supervisory signals are transmitted from the linking exchange on the telephone subscriber's line and indicate the beginnings of various call dialling phases in setting up a telephone communication. In response to the detection of the supervisory signal, the control unit blocks transmission of the pulse generator and releases transmission of the multifrequency generator, so that only the multifrequency generator transmits only the dialling multifrequency signal associated with the first key of the dialling phase. Then under automatical control of the control unit only the pulse generator transmits the dial pulse trains associated with said first key and with the subsequent keys of the dialling phase in response to further detection of the supervisory signal, or only the multifrequency generator transmits the dialling multifrequency signals associated only with the subsequent keys in response to the non-detection of the supervisory signal.


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