I'm looking for a schematic for a code practice oscillator that can be hooked up to a keyer. I have a Picokeyer so I'd like to be able to just plug the oscillator into the key jack of the Picokeyer. Output would be to an 8 ohm speaker. Tone should be adjustable. Power could be a 9v battery. I've found lots of references to square wave code oscillator circuits. I found only one for a sine wave oscillator. Unfortunately, I can't remember where I saw it and haven't been able to find it again. I'd settle for a square wave oscillator but I find the tone a bit annoying so I'd prefer a sine wave output. Any input would be appreciated.