| 摘要 |
PURPOSE:To prevent a TIP side feeding resistor and a ring side feeding resistor from being broken down, even if an overvoltage is applied in case a commercial power source line touches a subscriber's line, etc. CONSTITUTION:This two-wire subscriber's circuit is provided with photocouplers 19, 20 inserted between an overvoltage protective varistor 9 and a ground, a relay control circuit 22 for receiving outputs of these photocouplers, and protective relays 17, 18 for receiving a control signal from the control circuit 22 and cutting off the circuit at the time when overvoltage is applied. |
