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 Phase-Shift Oscillator produces sine low frequency signals suitable for many applications. It...
This circuit is from an 80's technical newsletter. The circuit can use any general purpose...
This circuit is from American documentation from the 1980s. The circuit can make use of any common...