| 摘要 |
PURPOSE:To send properly a reception state display signal at the reception side at the transmission preparation period just before data transmission by utilizing a terminal device ready signal, a transmission request signal and a transmission enable signal at the transmission side even in the time division multiplex system. CONSTITUTION:Pattern detectors 51, 52 detect the 1st and 2nd patterns respectively at the receiver side. At first, the 1st pattern is detected by the pattern detector 51, a flip-flop 53 is reset in response to the detection and the 2nd pattern is detected succeedingly by the pattern detector 52 and the flip-flop 53 is set in response to the detection. The set state of the flip-flop 53 is continued even during the data transmission period after the 2nd pattern is lost and a carrier is detected by a carrier detector 46 during this period. Thus, the gate 54 is opened and a reception state display signal CD is generated just before the start of the transmission data.
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