| 摘要 |
PURPOSE:To test a multichannel converter in a stand-by state as it is, by connecting an output and an input terminal in a loop when there is no call. CONSTITUTION:An input terminal 1-1 and an output terminal 16-1 are connected in a loop 20 through a switch 18. When there is no voice signal at the output terminal 16-1 and a detector 19 detects a noncalling state of 3.85KHz, its detection signal turns on the switch 18 to form the loop 20. At this time, an oscillator OSC is driven to send out an FDM test signal of frequency equivalent to 1KHz. The test signal is inputted to a receiving terminal 9 through a hybrid 22 and passed through a demodulation stage to output a 1KHz test signal from the output terminal 16-1. The 1KHz test signal is inputted to the input terminal 1-1 through the loop 20 and passed through a conversion stage to be outputted from a transmitting terminal 8 as a 63KHz signal. This output is read on a level meter. |
