Master Controller are the small devices with a rigid and compact design and are equipped within the main crane control system. These are used to control or stop the large machineries in case of power failure to prevent any accident. The components used to build the mechanism are housed in a hard and rigid metal casing to avoid any contact with dust particles. Master Controller are considered as one of the most important controlling equipment of heavy electrical overhead cranes. These are also provided with a spring return mechanism which returns the handle to the neutral position when it is released.