求翻译：由于它们的时间常数不同，导致在不同时刻只有一种反馈起主导作用，周期交往替，造成输出光强时起时伏的复现脉动现象。是什么意思？

Because of their different time constants, at different times, only a feedback plays a dominant role, periodic alternating, resulting in the output light intensity from time to time a repetition of pulsation.

Because of their constant different, resulting in at different times there is only one feedback plays a dominant role, alternately, causes the output light intensity from time to time the pulse.

Because their time-constant is different, causes to feed back the leading role frequently differently in only then one kind, the periodicity takes turn, creates the reappearance pulsation phenomenon which the output luminous intensity experiences ups and downs.

Because of their different time constants, resulting in a different moment only a feedback play a leading role, cyclical alternating, resulting in recurrence fluctuation phenomenon of the output light intensity have ups and downs.

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