| 摘要 |
<p>A system for detecting the direction of speech transmission between a telephone communication device and a telephone line connected thereto comprises an apparatus for detecting coincidence in the phase of speech signals developed across respective impedances and an impedance network by means of which said device is coupled to the telephone line. The apparatus for detecting the phase coincidence of the signals comprises a pulse generating device for generating trains of pulses in response to excursions of the respective signals across a reference level, and a gating device responsive to the coincidence of pulses of the respective trains. In a system with separate amplification of talk and listen channels, the amplifier providing the output to the line is preferably an operational amplifier connected to have substantially zero output impedance, which makes possible a simple configuration of an impedance network of which respective impedances are effectively connected either in series or in parallel, in accordance with the direction of speech transmission. Such impedance network thus provides for the appropriate change in the phase relationship of signals developed across the respective impedance.</p> |
