This specification covers the general requirements for semi-precision, wirewound, variable, resistors having a resistance element of wire, wound on an arc shaped insulated form, so that a contact bears uniformly on the resistance element, when adjusted by a contact shaft. The electrical output (in terms of percent of applied voltage) is linear with respect to the angular position of the contact arm. These resistors are capable of full-load operation (when the maximum resistance is engaged) at a maximum ambient temperature of 85OC, and are suitable for continuous operation, when properly derated, at a maximum temperature of 135OC. These resistors have a tolerance of å±5 percent.