| 摘要 |
PURPOSE:To supervise a fault of a talkie sound source, a talkie trunk, and a coder depending on the level of a supervisory signal by superimposing a supervisory signal having a frequency at the out-band of the talkie tone on the talkie tone and allowing the incoming side to detect the supervisory signal from the talkie tone. CONSTITUTION:A signal S3 comprising a supervisory signal S2 superimposed on a talkie tone S1 is subjected to analog/digital conversion by a high-speed encoder 11, which outputs an input signal string 27 having a frequency of 1/4f0 and the string 27 is distributed into two signal lines 28, 29. When a decoder 25 applies D/A conversion in the decoding speed of frequency 2f0 to the string, the signal of the talkie tone S1 is obtained mainly. On the other hand, the input signal string 27 on the line 29 is subjected to D/A conversion in the decoding speed of frequency 4f0 by a high-speed decoder 28, the supervisory signal S2 having a frequency 2f0 is extracted by using a filter and the level of the S2 is supervised by a supervisory signal detector 19. |
