This test circuit was found in the PE Hobbyst Handbook in a 1990s edition. The circuit tests the battery under load. The load, as the battery is selected by the switch.
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...