SPEECH LEVEL CONTROL DEVICE FOR TWO-WIRE TELEPHONE LINE REPEATER

摘要

PURPOSE:To discriminate exactly whether call voltages Va, Vb are high or low, by providing a variable attenuating element on an input side of an auxiliary amplifying circuit of the call voltages Va, Vb of east bound and west bound, and giving the same attenuation quantity to each call voltage Va, Vb. CONSTITUTION:Call voltages Va, Vb are attenuated by variable attenuating elements 11a, 11b, amplified, rectified and smoothed, become DC voltages, and applied to a capacitor 9. This voltage is inputted to an amplifier 10, the voltage is proportional to Va+Vb, and a current being proportional to it is supplied in parallel to a control terminal (q) of the attenuating elements 11a, 11b from an output terminal. Accordingly, the total gain of the cascaded attenuating elements and an auxiliary amplifying circuit is the same with regard to both channels. In case when a value of one or both of the call voltages Va, Vb is large remarkably, a large control current from the amplifier 10 flows in from the terminal (q) of the attenuating elements 11a, 11b and its attenuation quantity drops, auxiliary amplifying circuits 1a, 1b can be operated within a linear range, and whether the call voltages Va, Vb are high or low can be discriminated exactly.