| 摘要 |
<p>PURPOSE:To remote-control the execution of a loop back test for ADPCM transmission line in a voice transfer system with two ADPCM transcoders connected opposite. CONSTITUTION:A control ADPCM transcoder 1 sends an error signal alternately outputting the maximum amplitude value of the positive/negative difference in the ADPCM signal to a transmission line 301 by selecting the output of an error signal generation circuit 13 by a first selection circuit 12 at the loop- back control and sends a fixed value signal with the continuous constant differential values to the transmission line 301 by selecting the output of a fixed value generation circuit 14 at the loop-back release control. On the other hand, an ADPCM transcoder 2 to be controlled detects an error signal and fixed value signal by the signal detection circuit 22. At the error signal reception, the second selection circuit 23 returns the branch input from the transmission line 301 to the other transmission line 302 by the second selection circuit 23, and releases this loop-back state at receiving the fixed value signal.</p> |
