A transceiver system employing vector feedback to linearize the transmitter over a narrowband channel to support concurrent low-rate subchannels, each providing a low bit error rate. An image display device according to an exemplary embodiment of the present invention includes a display panel displaying an image, and a diffractive lens for the image of the display panel to be recognized as a two-dimensional image or a three-dimensional image, wherein the diffractive lens modifies a path of light by using an optical principle of a Fresnel zone plate. The flap is moveable between a closed position in which the flap blocks a lower window bordered by the frame and an open position in which the flap allows passage through the lower window. The camper shell also may include a right post connected to the right rear side near a rear most bottom corner of the right rear side. Separating out the group assignment indication and the car assignment indication is accomplished in one example by providing separate interfaces at different locations within a building.