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一对交替闪烁的发光二极管(LED)可以构成相当不错的视觉报警器。其中的一个LED保持发光,所以几乎总是能够看到报警,甚至偶而看一眼也能发现。有几种电路具
A pair of alternating flashing light-emitting diode (LED) can form a very good visual alarm. One of the LEDs stays lit, so an alarm can almost always be seen and even occasionally seen. There are several circuits