Clock consisting of a motor (weight or spring), a transmission mechanism, and a moving display (the hands). The weight ensures a more uniform force and is usually employed in large clocks in fixed locations. The spring, on the other hand, is suitable for small and portable time-pieces. Isochronous motion is provided by a regulating mechanism, either a pendulum (weight suspended from a non-extensible cord) or a balance (small crown flywheel connected to a spiral spring).