Found in an American publication of 1968, this circuit makes use of a pilot light of the time. It can be replaced with LED with appropriate series resistor. Transistors may be modern equivalents.
This simple metronome, from 1985 documentation uses only transistors and has two settings. For...
This circuit is suitable for modulating AM transmitters. The circuit is from a 1977 radio amateur...
This flasher was found in an old Hands On, but uses common components. The optocoupler can be...