Frequency Shift Oscillator
Many of the oscillators we've played with so far have used the Key to turn them on or off. This one is different ... can you tell what it does just by looking at the schematic?
When you turn the power ON, you'll hear a tone from the Speaker, Now press the Key, What happens to the tone?
Can you explain why this happens? (C'mon! By now this should be duck soup for you!)
When you press the Key, you add another resistor in parallel to the 47K resistor. Remember from Project Parallel Resistors in Resistor Section that connecting two resistors in parallel decreases the total resistance. When this happens, the tone become higher just like you heard.
Try adding different resistors in place of the 220K value. What effect do higher and lower values have on the tone when the Key is pressed?
Be sure to make notes of your results.