We can also use digital electronics in circuits to make unusual sounds.

This Project uses the counter circuit along with a familiar oscillator circuit.

Look at the schematic for this Project.

You'll notice that the output of the oscillator goes into the counter circuit instead of the Speaker. The oscillator circuit generates pulses (similar to the raindrops sound in Project 103).

Since digital circuits operate "on" or "off", they can make use of these pulses.

Do circuits like amplifiers and oscillators have a special term for themselves like digital circuits do?

Yes — it's called analog.

Analog circuits are those we can vary continuously in some way — their volume, tone, etc. (Digital circuits, as you remember, are either "on" or "off" — there's no "in-between"!)

Turn the Control Knob clockwise to switch power ON.

What do you hear from the Speaker?

What are the LEDs doing?

Now press push botton.

What do you hear now from the Speaker?

Do the LEDs change in any way?

Rotate the Control Knob and see what effect this has on the circuit's operation.

Make some notes about how you think this Project works.

Before long you'll be able to explain how this works.