The OHMITE RHL350 is a wirewound rheostat, a type of variable resistor used for controlling electrical power. These rheostats are electro-mechanical devices, subject to mechanical wear and therefore have a finite life. They are commonly used in industrial applications where adjustable resistance is needed, such as motor speed control, lighting dimming, and volume adjustment. Models H, J, K, L, and N are listed under UL File No. E-10946 and CSA File No. 21309.