Solar intercom (CB20503E)

This circuit can be used in demonstrations or science fairs. The circuit uses headphones and can be powered by solar cells.

4 to 20 mA loop (CB8707E)
Found in a 90s EDN, this circuit is indicated for power control through a 4-20 mA line. The...
Voltage variation for the 7812 (CB24809E)
In the figure we have an improved method of varying the voltage of a 7812 regulator. The circuit is...
Busy line indicator (CB9111E)
This circuit was found in an Electronic Engineering of the 80s. The circuit indicates when a...