Abstract: A quasifixed variable resistor includes a resistor substrate with a resistor mounted thereon, a stopper plate rotatably retained about an axis on the substrate, and a knob having a slider fixed to an end of the stopper plate, the slider, sliding on the resistor. In a flat portion located at a bottom end of a cylindrical section of the stopper plate, a screwdriver engaging section having an adjusting groove is folded and is integrally formed therein. A wing piece branched by the adjusting groove is tapered in a direction toward the flat portion and a tip end of the screwdriver can be engaged with an end portion of the wing piece for adjustment.

Abstract: A fader controlling variable resistor adapted to adjust the balance in sound volume of the right and left loudspeakers, or the front and rear loudspeakers. When abnormal heat is generated in a variable resistor in a fader control circuit, the sliding piece of the variable resistor is disconnected from the resistance member by the utilization of a thermo-plastic resin of a low-melting-point material is readily deformed or molten by heat, to prevent a fire attributed to the generation of heat therein. In one embodiment of the invention, the sliding piece is maintained in contact with the resistance member against its elastic force by a protrusion of thermo-plastic resin. When abnormally high heat is generated in the variable resistor, the protrusion is molten, and the sliding piece is disconnected from the resistance member or the conductor.