Let's read,guess and draw.What is it?

Let's read,guess and draw.What is it?
I've got a round face,but it never smiles.
I've got no mouth,but I talk day and night.
I've got no eyes,but I can see you every day.
I've got no nose,no ears,and no feet,
but I've got three hands and they can walk.
The shortest one walks very slow,
the long ones walk faster.
What am