A door closer comprises a spindle journaled in a housing and connected to turn with a door. The apparatus incorporates, among other elements, a display, a display article, a cap, and a base. The apparatus also includes a receiver for receiving the transmitted data by obtaining a diversity gain based on the maximum order of the diversity in order to effectively detect the data. A portion of the aperture plate between the inner edge and the outer edge of the aperture plate is positioned more outward from the cylindrical portion than the inner edge and the outer edge are.