This circuit uses a crystal phone and can be built with more modern transistors like the BC548. The original circuit is from a 1979 publication and is powered with only two AA or AAA batteries.
In the figure we have the photo-conductive way of using a photocell to control a small motor with...
Pressing S1 the LED glows by a time interval depending on the capacitor. Time intervals in the...
This is a protection circuit in which, under excess current in the load, the SCR trips by shorting the...