| 摘要 |
PURPOSE:To ensure relay when a return stand-by period is variable by detecting the return stand-by period of a supervisory data based on a reproduced output of a transmission signal transmitted from a central control device so as to control a gate of a relay amplifier means for a return signal. CONSTITUTION:When a transmission signal Vs of the variable length mode is received, since outputs Q1, Q2 of a latch circuit R go to '1', '1' after output of data output terminals OUT3, OUT2 outputted synchronously with the timing pulse outputted at first when a start pulse is obtained go to '1', '1', an output of an AND circuit AND1 goes to '1' and an output of an inverter circuit I2 goes to '0'. Thus, an output Q of a D-FF is outputted as a gate control pulse Pg' of the variable length mode, and a gate 6 is opened for a time corresponding to a return stand-by period of the variable length mode.
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