It is driven by a toothed wheel called a sprocket. This target may contain magnets, or it may be a toothed wheel. A simple opisometer consists of a toothed wheel of known circumference on a handle. The cloth beam bears a toothed wheel which works a pinion. In 1811, John Blenkinsop patented a toothed wheel and rack rail system. Enclosing all this shall be a toothed wheel, symbolizing labor and industry. The rotor is a simple toothed wheel, with no windings or electrical components.