| 摘要 |
Problems can be solved about reducing the maximum voltage, reducing the size and cost, and so on. According to the invention, three or more discharge units are connected in series between two conductors. Two or more clamping type overvoltage protective units (hereinafter referred to as “clamping units”) are connected in parallel to the discharge units except one or more of the discharge units. The overall operating voltage of the discharge units arranged in parallel to all the clamping units is set lower than any voltage obtained by subtracting from the operating voltage of each clamping unit, the spark-over voltages of the other discharge units connected in parallel to the clamping unit. The overall operating voltage of the discharge units connected in parallel to all the clamping units is set higher than the operating voltage of each discharge unit connected in series to any one of the clamping units.
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