Power supply for loudspeaking telephone - has delay circuit blocking receiving amplifier when loudspeaker amplifier is on

摘要

The power supply is for a loudspeaking telephone station, where the speech circuit contains a receiving and a transmitting amplifier. The two amplifiers are regulated by a control circuit. The supply voltage is derived from a double Graetz bridge with a bridge rectifier with common branches for the two bridges. There is a delay circuit (V) which blocks the receiving amplifier (EV) when the loudspeaking amplifier is switched on. The receiving amplifier is blocked until a second capacitor (C2) has been charged.