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４７５．扩展的ＰＣ驱动器ＬＥＤ指示器当无法观察计算机磁盘驱动器的指示灯时，（由于计算机放在桌子一边或桌下），该电路可能有用。当出现问题时，计算机显示器旁也可多一个扩展指示器。该电路并不复杂。它可由一个Ｐ－ｎ－Ｐ晶体管、一个发光二极管和两个电阻组成；也...
475. Extended PC Drive LED Indicator This circuit may be useful when you are unable to see the indicator lights on your computer’s disk drive (because your computer is on the side of a table or under a table). When there is a problem, there may be an extra indicator next to the computer monitor. This circuit is not complicated. It consists of a P-n-P transistor, a light-emitting diode and two resistors; also ...