This circuit is from American documentation from the 1980s. The circuit can make use of any common NPN transistor and the power comes from two small batteries.
This circuit allows 220 / 240V shavers to be used in the 110V network. The diodes can be general...
Used with telephones at the time, this circuit was found in Popular Electronics from the 90s. The...
This circuit was obtained from an American 80's documentation. It can be implemented with modern...