| 摘要 |
<p>PURPOSE:To generate a folding loop with resupply of power to a repeater even if there is not a signal break detection signal of a down repeater, by providing a power supply detecting part consisting of a rise voltage detector, an RS flip flop circuit, and an AND gate circuit of negative logic. CONSTITUTION:When power is supplied again to a repeating installation, a power source voltage rise detector 41 detects a certain rise voltage to generate a pulse, and a pulse (a) (in the high level for a negative logic input) is supplied to a terminal S of an RSFF42. Since a state (c) of a reset terminal R bar of the RSFF42 is in the low level, a state (d) of a terminal Q bar of the output is in the high level. As the result, an output (e) of an AND gate circuit 43 of negative logic is in the high level no matter whether an output (b) of a signal break detecting circuit OD of a down repeater 20 is in the high level to indicate signal break or in the low level to indicate signal existence. This output (e) is inverted in a monitor control circuit 30 and is applied to a gate A. Since a main signal is outputted to the gate A from a terminal Q of a discriminating part DEC in an up repeater 10, the main signal is inverted and is outputted to the output of the gate A. Meanwhile, the high level of the output (e) stops passage of a down main signal in a gate C.</p> |
