| 摘要 |
PURPOSE: To provide a switch opening/closing device, including a supply circuit for securing simple and cost effective protection against an excessive current on a subscriber's line to his terminal unit. CONSTITUTION: 1st and 2nd limiter circuits 6 and 11 are provided. The 1st limiting circuit 6 is equipped with a 1st serial combination of a 1st supply transistor device 8 and a 1st supply resistor device R1, for limiting a supply current to flow through the 1st serial combination. The 2nd limiting circuit 11 is equipped with a 2nd serial combination of a 2nd supply transistor device 13 and a 2nd supply resistor device R2, for limiting a supply current Is to flow through the 2nd serial combination. A potential V0 on the control input terminal of the 2nd supply transistor device 13 depends on a voltage Ur on the 1st serial combination. |
