The speedometer allows easy reading of the speed of a motor vehicle. It is connected by means of a flexible cable attached to the gears inside the transmission system. The speed shown on the device is determined by the rotation of a magnet. A drum is mounted around the magnet which also moves as the magnet does. The pointer of the speedometer rotates when the drum is in motion, but if the speed is kept consistent, then the pointer is stabilized by a hair spring. The hair spring's function is to balance the magnet's force and retain the pointer's stationary position on the face of the dial.
