The "Top Secret" consists of a spinning
top with a radially oriented magnetic field and an associated base that
houses a conductive coil. When the top spins past the center of
the base, its changing magnetic field induces a current in the coil which momentarily
opens the switch to the battery resulting in powering up the electromagnet.
The electromagnet then delivers enough torque to the spinning top to allow
it to speed up and spin away from the center. Since the
electromagnet is only engaged when the top crosses near the center of the base,
one 9 volt battery can last for over a week of continual use!