Matsushita Electric Industrial Co., which produces consumer-electronics items under the Panasonic brand name in the U.S., plans to begin selling a 103-inch plasma-display-panel television set by the end of the year, the company said Wednesday. It noted that the screen width is comparable to the size of a double bed. In a statement, the company said that it hoped that the TV set, the world's largest flat-panel model, will "impress the marketplace" with its technological excellence.