冲击始终存在于电力系统中，但由于近年来广泛使用VCR和PC机，才使这种冲击开始引起注意。
Surges have always existed on power systems, but it is only in recent years, with the advent of extensive VCR and PC use, that they have received attention.
电接触广泛存在于电子和电力系统中，元件之间、电路之间、设备之间乃至元件内部之间都需要可靠的电子连接。
There are numerous electric contacts in electronics, electric-power and automatic control system. Their capability affects the reliability of electric and electronic devices directly.
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