Cam wheel. Coloured scanning electron micrograph (SEM) of a microscopic cam wheel. This mechanical device is used to transform circular motion into irregular or intermittent motion. This is achieved by the protruding ribs moving another device (not seen). They might raise and release a hammer four times per revolution. This cam wheel is from the voice-activated mechanism of a voice-activated computer. Magnification: x14 at 6x7cm size.