The brass c p Guide rod carrying contact block is tightened with brass screw. The slider is provided with phosphorous bronze brush contact. Made from 4 4 cm Or 5 6 cm Dia. special insulating porcelain tube wound with heavily oxidised eureka wire according to the required length, tubes are mounted on heavy aluminium feet duly powder coated with rod and brass nuts to provide more durability. Three lock type brass socket terminals with proper insulation are provided. One terminals being connected to the sliding contact and other two are contacted to the ends of winding enabling the instrument to be used as rheostat or potentiometer. These have double contact system and moves smoothly on the sliding rod. Total resistance and maximum current capacity is clearly marked on the slider.