rpm of device increases or decreases. Centrifugal switches are designed to minimize frictional contact between the rotating speed sensor and the non-rotating switch body. In most cases, this is done by having contact at low speed, which is pulled away at operating speed, so there is friction only during brief periods of start-up and slow-down. However, overspeed switches work the other way, making contact at high speed, but avoiding contact at normal operating speed. See also Centrifugal governor Transfer switch References Switches