This circuit, which can be used as a shield, was found in a 90s Electronic Design. The circuit uses a diac and the transistor can be general-purpose.
Found in documentation from the 1990s, this circuit drives an SCR with a delay that depends on C1...
The figure shows how to increase the output voltage of a 7812 IC with a zener diode. Other...
This super metal detector uses three coils, operating in differential form with two transmitter and...