Practice code oscillator (CB21090E)

Found in Popular Electronics from the 90's, this circuit consists of an audio oscillator for Morse code practice.

Passive Tone Control (CB19183E)
This circuit appears in several versions on this site. It is designed to be used between the...
Ultrasonic Scarecrow (CB12342E)
This circuit uses a piezoelectric tweeter to emit a powerful continuous sound above the audible...
Touch Lamp Control (CB26132E)
This circuit is based on a Siemens S566B integrated circuit. The circuit is from a Radio...