BIDIRECTIONAL VOICE-FREQUENCY AMPLIFIER Russian patent published in 1999 - IPC

FIELD: telephone communications. SUBSTANCE: device depends for its operation on operating time division of two single-ended amplifiers 9, 19 connected in parallel opposition. Their connection to lines is effected by means of two matching transformers 10, 16 through two pairs of switches 1,2 and 3,4 and two variable-frequency clock generators 5, 6. Digital signal picked off amplifier circuits is filtered off to ensure amplification of input signals within voice-frequency band. Capacitors 11, 12, 15, 17 connected to transformers 10, 16 cause flow of variable-polarity transient current during switching intervals which enables compensation of energy stored in transformers 10, 16 by integration thereby suppressing return signals. Adjustment to communication line impedance is made by varying sampling frequency of respective clock generator. EFFECT: provision for simultaneous double-ended amplification of voice-frequency signals in narrow-band two- wire communication lines. 3 dwg