| 摘要 |
PROBLEM TO BE SOLVED: To provide a protector when a high voltage is impressed between the terminals of a DC circuit consisting of a bidirectional signal transfer circuit. SOLUTION: The serial circuit of positive characteristic thermistors 7 and 8 and Zener diodes 9 and 10 is connected between the terminals of connection terminals 5a, 5b, 6a and 6b for signal transfer at the bidirectional signal transfer circuit. Thus, the DC circuit connected between the terminals is protected from the high voltage impressed by the erroneous connection of connection lines 14a, 14b, 15a, 15b, etc., by the Zener diodes 9 and 10 and these Zener diodes 9 and 10 are protected by suppressing an excessive current at the time of high voltage impression while using the positive characteristic thermistors 7 and 8 so that the DC current can be prevented from being destroyed by impressing the high voltage. Besides, since a resistor having a fuse function is used in place of the positive characteristic thermistor, the resistor cuts off the excessive current so that the destruction of the DC circuit can be similarly prevented as well. Further, by sharing the connection lines for signal transfer and power, the device can be provided at low cost. |
