When they have increased in resistance to a point at which they supply 30,000 watts, they will be on 100% of the time.A SCR (silicon controlled rectifier) or thyrister can also be used.

• 当电阻阻值增大到一个临界值及输出功率为30；000瓦时，这个百分比刚好达到100%25.；也可以用可控硅整流器或者是半导体闸流管。