| 摘要 |
A circuit for increasing the amplitude of signals transmitted through a bi-directional voice transmission line. A series amplifying network energized in accordance with the voltage across the line produces a signal voltage in aiding relationship to a transmitted signal. A shunt amplifying network energized in accordance with the current through the line produces a signal current in aiding relationship to that transmitted signal. A switching circuit controls the phase relationship between the input and output quantities of each amplifying network in accordance with the direction of transmission of the signal of highest amplitude at any given time, to amplify signals transmitted in that dominant direction and to suppress echo signals transmitted in the other or non-dominant direction. Circuitry is provided to vary the amplitudes of the input signals to the series and shunt amplifying networks as a function of the impedance of the line to provide stable amplification and fidelity of reproduced signal over a wide range of frequencies and transmission line impedances.
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