This circuit with the NE602 was found in the February 1997 Electronics Now magazine. The NE602 integrated circuit is not very common these days.
With the configuration shown in the figure, we have the relay being activated when the microphone picks...
We found this circuit in a 1992 Poptronics. What it does is to activate LEDs sequentially,...
In the figure we have an application of a voltage comparator in a circuit that fires with the...