| 摘要 |
PURPOSE:To eliminate the generation of howling in case of executing a loopback test by a telephone set, by adding a signal delay switching means provided with a prescribed function. CONSTITUTION:A multiple PCM signal from a multiplexing device 1 has (n) pieces of channels constituted of (p) bits and one piece of frame pulse. In a signal delay switching means 10, with regard to this multiple PCM signal, a frame pulse is loopbacked without a bit delay, each channel signal is subjected to an (m)X(p) bit delay, and also, as for (m) pieces of tail channels, they are further delayed excessively by the number of bits which have added the number of bits of a frame pulse. In such a way, the number of bits in a frame is not varied, and the frame pulse is moved between two pieces of optional and adjacent channel signals. By sending it back to a separating device 2 through a loopback switching circuit 3, a loopback signal can be returned to an optional channel being different from that of the time of sending out. Since the channels are switched in such a way, the generation of howling is eliminated at the time of a loopback test by a telephone set. |
