Photograph. "Lighthouse" tubes for generating high-frequency radio waves developed by General Electric. Official Caption: "Rome, 6/9/45--'Lighthouse' tubes for microwaves--Development in the United States by General Electric Company of the new disk-seal tubes for generating high-frequency radio waves of considerable power may speed conquering a new range of the radio spectrum. The disk tubes, one of which is called the 'lighthouse' tube because of its shape, provide a novel means of producing very short radio waves. They have played an important war role and may play a vital part in the postwar creation and expansion of microwave industries, such as television and navigation. A disk-seal tube is similar in principal to the three-element tubes used in radio sets: it has the heated cathode for emitting electrons, the grid which controls their passage, and the anode which receives them. However, it is built differently, from simple disks and cylinders. With the high frequencies for which these tubes are used, the shape has an importance which it lacks in tubes for lower frequencies, such as those of ordinary broadcasting stations. In the microwave field it becomes necessary to think of a microwave oscillator as an electrical system having one section walled off and evacuated to house the electronic activity. That is why the shape of these very-short-wave tubes is so different from ordinary radio tubes.--FF Photo—serviced by Rome OWI (A List out) ++ Approved by appropriate military authority. 6533-8." United States. 9 June 1945