| 摘要 |
PURPOSE:To obtain a specific load current even if either of feeding devices of both terminal stations of a relay system is disabled from feeding by adjusting the resistance value of a resistor for protection according to variation in station feed voltage and controlling the feed current to the relay system to a constant value. CONSTITUTION:The feeding devices 10 and 20 of the same constitution are connected mutually through the relay system 30. In a both-terminal feed state, the voltage detector 14 in the feeding device 10 generates no output, the switch 16 in a switch circuit 15 is on, and the resistance value for protection is equal to the resistance value R1 of the resistor 121. The inside of the device 20 is the same. The feeding of the constant current supply part 21 in the device 20 is stopped from this balanced both-terminal feeding state and when a one-terminal feeding state is entered, a feed current Ia from the device 10 is returned through the diode 23 in the device 20 to return the constant current supply part 11, the feed current to the relay system 30 is maintained, and a partial charge voltage Va attains to a maximum load voltage VM, and a partial charge voltage Vb falls to ''0''. When the voltage Va attains to VM, a relay coil 17 is fed with the output of the voltage detector 14 and the switch 16 is opened, so that the one- terminal feeding to the relay system 30 from the device 10 having a resistance value R1+R2 is performed. |
