| 摘要 |
PURPOSE:To realize a power supply circuit with low cost and high durability and reliability by providing a switch turned on at the application of a power voltage to supply a current to a feeder line and a switch interrupting the power voltage of the former switch in the event of occurrence of an excess current. CONSTITUTION:A base current enough to saturate a transistor(TR) 1 is given to a base of the TR 1 with respect to a maximum supply current to a terminal equipment TERM at normal power supply. If a short-circuit between feeder lines takes place and an overcurrent flows, a TR 2 is turned on and the collector current of the TR 2 absorbs the base current of the TR 1, then the base current supply to the TR 1 is stopped, the TR 1 is turned off and the power supply to the TERM is stopped. When the two feeder lines are opened, since the resistance rz of the insulation resistance Rz of the two wires is sufficiently larger than the resistance r11 of a resistor R11, the TR 2 is turned off and the TR 11 is turned on to complete the standby of re-power supply. |
