| 摘要 |
PURPOSE:To eliminate the need of a terminal ordered terminal setting operation and to prevent a fault caused by a mistake in the setting of the ordered terminal by detecting a voltage in a trunk circuit and automatically setting a battery/ earth (BG) power supplying system and a battery/battery(BB) power supplying system according to the voltage value. CONSTITUTION:According to the line resistance 16 of a relay line, a voltage generated in a trunk resistance 3 is detected in voltage detectors 4, 5 by a current passing through the trunk circuit 2 and the detected voltage is added by a voltage adder 6. This added voltage is compared with threshold Vth1, Vth2 levels respectively in voltage comparators 7, 8, and when the output of the voltage comparators 7, 8 goes to the state of a positive logic '1', the output of an AND circuit 9 goes to '1' to operate a transistor 11 and a relay 10 and switch from the BG power supplying system to the BB power supplying system. The threshold Vth1 level is a threshold not to shift to the BB power supplying system at the time of the inoperative state of the trunk circuit 2 such as a monitor state and the threshold Vth2 level is a threshold at the time of switching from the BG power supplying system to the BB power supplying system.
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