clock is actually comprised of two seperate clock
s with a button or switch on each side. They are either digital
After you make your move, you press the button on your side of the clock. This stops the clock on your side and starts the one on the opposite side. Your opponent
is now free to mull over his move while his clock tick
The digital ones are quite costly
, and can run for about $100. The analog ones can be found for about $40-$60.
See Also: Chess - Time Controls