Attenuation control circuit for hands-free telephone station - has extra second comparator, whose minus input is coupled to tap for meter value

摘要

The telephone station has a reception and a transmission amplifier, and a measuring device for the reception and tranmsission signal voltage each. The two signal voltages are processed by a comparator (K1). A beat control is provided for the reception signal and transmission signal attenuation. The station has also a cradle circuit. There is a second comparator (K2) whose minus input is coupled to the tap for the measured value (UE) for the reception voltage (EM). Its second plus input is coupled to the tap for the measured value (US) of the transmission signal voltage (SM) via a differential voltage source (UR). The comparator output is linked to an extra control input (S) of the first comparator via a charge current resistor (RL) and diode (D). ADVANTAGE - Improved beat extent with a e simple cradle circuit.