| 摘要 |
<p>The impedance matching appts. is used to obtain faithful audibility of all participants in a conference circuit and to avoid reverberations due to feedback. The internal telephones connected to the switching circuit over two-wire lines, are connectable to the Four-Wire Conference circuit via attenuation members and two-to four forking translators. The latter consist of directional amplifiers in each branch and their ground connections are coupled over transformers. The attenuation member consists of a T-network with cross connected capacitors. The a-b line is terminated by two symmetrically connected transformer windings with a pair of serially connected secondary windings being connected to a line imaging termination having an attenuation member identical to that in the a-b line and terminated by a line imaging impedance of 600 Ohms. A second pair of symmetrically arranged secondary windings are connected to the four line conference circuit.</p> |
