Britain Shows Her Radio Brains Electronic Private Show - One of the valves developed for hearing aids is so small that three will fit into a thimble. Here seen are two of the valves compared with a threepenny piece. Engineers and industry experts from 18 countries ware expected at Grosvenor House, London today (Monday) when Sir Robert Ranwick opened a three day exhibition organised by the Radio and Component Manufacturers Federation, of which he it president. The radio, TV and electronic davices seen at this private showing were, during the war only shown in strictest secrecy, Countries sending representatives included Australia, Poland, Czechoslovakia, and the U.S. April 17, 1950. (Photo by Fox Photos).