This circuit was found in a 90's Electronic Design. The circuit can be adapted to use modern components. The power supply is made with 5 V which allows its use as a shield sensor.
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...