This ingenious circuit was found in a 1990s Popular Electronics. The oscillator is a 555 and the keyer uses an optocoupler in the configuration shown.
This circuit is from 1999 documentation. However, it can still be easily assembled, as all...
This circuit was found in 1978 documentation, using the National Semiconductor's LM380. The...
This simple circuit that activates a buzzer was found in the July 1971 Radio Electronics magazine. The...