Found in Ferranti's 1968 documentation, this circuit uses a Darlington photo transistor to drive a 12V relay. The circuit can be implemented with modern equivalent components.
Found in Popular Electronics this circuit will trigger a buzzer if the ignition key is removed...
Found in Popular Electronics, this sophisticated short-wave receiver requires a lot of skill from...
This circuit is from an old American documentation using LEDs in the rectification. The circuit...