| 摘要 |
PURPOSE:To prevent mis-connection between a communication unit and a modulator-demodulator at system building by displaying the presence of a transmission element timing signal from the modulator-demodulator to the communication control unit and informing the result of display to a communication control equipment. CONSTITUTION:When the modulator-demodulator 3 is of synchronizing type, a transmission element timing signal ST2 is fed to the communication control unit via a cable 101, and when the modulator-demodulator 3 is of start-stop type, the signal is not supplied. A transmission signal element timing detecting circuit 22 in the communication control unit 2 detects the presence of the transmission element timing signal of the cable 101 and sends the result to a notice circuit 23. The notice circuit 23 informs the presence of the transmission element timing signal to the communication control equipment 1.
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