This photoelectric sensor that triggers a relay was found in an English book from 1989. The transistor is a general-purpose type, and the integrated circuit consists of an operational amplifier.
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...