Abstract: A device used in a multimedia communication system is formed with a transceiver unit for transmitting and receiving information signal to and from the inside of a room and a base unit adapted to be mounted to a wall of the room to detachably support the transceiver unit. The transceiver unit has a plug surface on which a plug projects, a circular wall projecting on the plug surface to surround the plug, and a guide wall projecting on the plug surface inside the circular wall and around the plug. The base unit comprises a disk member which is provided with a receptacle exposed in a receptacle surface defined on the disk member. The disk member has a diameter slightly smaller than an inner diameter of the circular wall so that the disk member can fit within the circular wall when the transceiver unit is attached to the base.

Abstract: A plane antenna comprises a power-supply circuit, a radiator circuit and an earthing conductor which are stacked respectively with a dielectric layer interposed between them, in which the power-supply and radiator circuits are made independent of each other as electromagnetically coupled to each other and at least one of the dielectric layers is formed with a foamed resin, whereby insertion loss can be reduced to remarkably improve the antenna characteristics. Only with the interposition of the foamed resin dielectric layer or layers, an effective separation is achieved between at least the power-supply circuit and the earthing conductor or the power-supply circuit and the radiator circuit, for a large extent improvement in the assembling ability.