| 摘要 |
PURPOSE:To execute transmission by switching a PCM system with an ADPCM system by the same transmission channel in accordance with a transmission purpose, by executing a multiplexing in accordance with a transmission line frame, and having a transmitting device provided with a converting interface circuit in a transmission line signal. CONSTITUTION:A 64 kbps PCM signal 21 applied to a terminal 1 is inputted to the first ADPCM encoder 5 and the first switching device 6. In the first ADPCM encoder 5, in response to the inputted PCM signal 21, 8kHz sampling and 4-bit ADPCM encoding are executed, and said signal is converted to an ADPCM signal 25 of 32 KBPS and sent out to the first switching device 6. As for a terminal 3, a control signal 22 as to whether a PCM transmission is executed or an ADPCM transmission is executed in accordance with a transmission purpose is applied, and a switching controller 4 converts said control signal 22 to a mode switching signal 23, and applies it to the first switching device 6 and a control signal converter 7. In a transmitting transmission line interface circuit 8, a multiplexing operation is switched in accordance with a control signal 71 from the control signal converter 7. In case of a PCM mode, the third switching device 17 selects a 64 kbps PCM signal in a signal 32 from a receiving transmission line interface circuit 11, and sends it out as a receiving PCM signal of a signal 36 to an output terminal 19. |
