a pcm decoder for converting to an analog voice signal an 8 - bit pcm signal the first bit of which is a polarity specifying bit , the pcm decoder comprising a capacitor array having binary - weighted capacitors and a resistor string circuit having plural resistors for dividing a reference voltage to obtain different tap voltages , wherein the tap voltages corresponding to the four lower bits of the pcm signal are derived from the resistor string circuit and the combination of the reference voltage and each of the tap voltages , made according to the contents of the second , third and fourth bits of the pcm signal is applied to the corresponding one of the capacitors in the capacitor array circuit whereby the capacitor array circuit delivers an analog voltage signal corresponding to the received signal , the resistor string circuit having two groups of intermediate taps so that the conversion characteristic for obtaining voltages in the signalling frame may be different from that in the non - signalling frame .