Found in a 90s Electronic Design, this circuit can be used as a shield in current projects. The circuit provides three levels of signals for triggering loads.
A narrow range of frequencies around 1 kHz is rejected by the high Q filter shown in the figure,...
This simple converter does not use a transformer and the transistor can be the BD135 for currents up...
This is a circuit from the time when some still called the transistor a crystal triode. It...