| 摘要 |
<p>A subscriber's line equipment for a telephone exchange for replacing equipment comprising a telephone transformer or chopper, comprises a telphone line supply circuit comprised of two constant d.c. voltage sources, a transistor functioning as a constant current generator, a transformer connected to rectifying means, two transmitters connected to the primary winding of the transformer, a closed loop detecting circuit and receiving and transmitting circuits connected to receive and transmit signals to the telephone exchange.</p> |
