This circuit triggers an alarm in the event of a power failure. The circuit is from an 80's documentation, being powered by 9 V battery. The parts are common today.
We found this configuration in an American technical documentation of 1977. The circuit can...
This simple circuit can drive a reed-relay when light falls onto the photo-transistor. The...
In the figure we have the way to obtain an adjustable constant current source of 2 mA. The...