This highly sensitive light sensor was found in a 1970 General Electric documentation. The circuit can use the 2N2646 for the UJT and the phototransistor can be of any type.
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...