Abstract: A rotor of a motor has a bearing mounted thereon, the bearing having a tab which is urged in one direction by the fluid friction of the lubricant in the bearing, the tab being urged against a spring, the tab actuating a micro-switch. The force exerted by the tab on the spring is a function of the rotor speed. Upon reduction of rotor speed the spring urges the tab rearwardly so that the micro-switch open circuits in turn disconnecting power from the motor which comes to a standstill.