Subscriber call signal circuit for digital telephone network

摘要

The subscriber call signal circuit for a digital telephone network uses two 2-stage amplifier circuits (VSTE,VSTA) for supplying and switching the call signal voltage and coupled via the coupling field (KN) of the telephone network to a digital tone generator used for providing both the audible tone signal and the call signals. The amplifier circuits (VSTE,VSTA) of the subscriber circuit (SLCA) have differing amplification factors on the input side and on the output side exhibit corresponding voltages (UV1,UV3). The switching from one voltage to the other is effected without a sharp variation in the voltage ratio between the speech wires (a,b) of the telephone line (TL).