Telephone subscriber's appts. circuitry with call signal generating circuit - has cradle switch contact disconnecting rectifier bridge from call tone circuit and supplying speech circuit

摘要

The call circuit supplies a signal to an electro-acoustic transducer for ringing in dependence on the AC call signal received from the telephone exchange. A rectifier bridge (GR) and a preceding KC element (R1, C1) are used to provide the operating voltage for the call tone circuit and the electroacoustic transducer. The RC element (R1, C1) is bridged by a cradle switch contact (GU1) when the telephone handset is lifted, a second cradle switch contact (GU2) being coupled to the DC side of the rectifier bridge (GR), for breaking the connection between the latter and the call tone circuit (TR) and coupling the rectifier bridge (GR) to the speech circuit (SP). ADVANTAGE - Reduced current supply for microprocessor.