A variable speed control system is provided for use with a heat pump heatingcooling system having a variable speed compressor. The molding material mixture contains 0. The cam is engageable with the at least one stop of the housing to stop rotation of the cam when the slider moves to the retracted position andor to stop rotation of the cam when the slider moves to the extended position. Thereby, sum of radiation performance reduction due to pressure loss inside tube and radiation performance reduction due to air flow resistance is reduced, thereby attaining high radiation performance. The electrical isolator is located to inhibit induced eddy current loops due to inductive coupling of the first cooling coil with eddy current inducing field sources. The first stretch roller has a circumferential surface formed into a normal crown shape in which a straight area where a diameter of the first stretch roller is constant is provided at a center part in a direction of axis of rotation.