Every computer MICROPHONE INPUT jack, has its own voltage and current that is already built inside it, in order to power Electret Mics. By modifying a very simple and low voltage square wave generator circuit to make use of this MIC VOLTAGE, a very simple and NO BATTERY NEEDED - EVER - code practice oscillator can be made using this circuit, the MIC JACK, and an AUDIO to MIDI technique to regenerate the original input cw tone from this LM3909 and convert it to an amazing sine wave shaped cw note.
Here is the circuit used for this:
- HERE IS WHAT THIS OSCILLATOR SOUNDS LIKE -
Just like it sounds with no filtering and then by using AUDIO to MIDI technique to regenerate the tone