| 摘要 |
PURPOSE:To decide the start of a network control device, by applying the power source to a call signal detecting circuit only when a circuit has reversed in its polarity and at the same time the voltage of the circuit is within a range of the 1st and 2nd prescribed voltages. CONSTITUTION:When the working voltage is supplied through the terminals 111 and 112, an overvoltage detecting part 11 and a voltage detecting part 12 work through a rectifier 17 to control a switch 14. Then a power source is applied to a detecting circuit 15 for data terminal call signal from a power source 13. Receiving a call signal from a center, the circuit 15 controls a connecting circuit 16 to connect the next data terminal 7 to the terminals 113 and 114. A start deciding circuit 10 consists of the rectifier 17, the part 11, the part 12, the power source 13 and the switch 14. And said parts 11 and 12 check whether the voltage is within a range of a prescribed level. Then a power source is applied to said circuit 15 only when the voltage is within a prescribed level. |
