International projectionist (Jan-Dec 1950)

THE CATHODE-RAY TUBE: BASIC DATA (Continued from page 28) possible to classify the uses of the cathode-ray tube into three major groups. These are: 1. Cathode-ray tubes used as display devices in receiving systems. 2. Cathode-ray tubes used as generators. 3. Cathode-ray tubes used in measuring equipment. Cathode-Ray Tube in Receivers An appreciation of the first use is easy. Millions of television receivers employ the cathode-ray tube either as the viewing screen on which the picture appears, or as the source of the picture which is enlarged for projection onto a separate viewing screen. Another example is the radar receiver. A pulse is sent out into space from a transmitter. One or more target objects reflect some of this electromagnetic energy, and the reflections are picked up by a receiver adjacent to the transmitter. The reflected signal appears on the calibrated screen of a cathode-ray tube, and specific information concerning the location of the reflecting target, relative to the receiver, is determined from the trace on the cathode-ray-tube screen. A type of radar equipment which is enjoying expanding peacetime application is the device which develops a map of the land or sea area being scanned by the equipment. In this system, a shortduration pulse is repeatedly transmitted from an antenna which is located above the area being examined. The antenna rotates azimuthally several times per minute, scanning the given area by small sectors. A reflected signal returns from each small sector, and, after the usual handling by the receiving equipment, appears as a spot, or a series of spots, of light on the screen of the cathode-ray tube. The net result is a map of the area scanned. A display device of this kind used for Armed Forces or civilian pursuits is called a PPI, or Plan Position j Indicator. Another important use of the cathoderay tube is in the panoramic receiver also known as a Panalyzer, or Panadaptor, which has been used by amateurs for many years. During the war, it proved to be a very valuable piece of communications equipment. The Tube as a Generator The second category of uses mentioned above is not as clearly defined as the first. The equipment as a rule is still experimental in nature. Tubes other than those using luminescent screens, although properly classified as cathode-ray devices, are used as generators of electrical energy of various kinds and have become commercial realities. These devices utilize the electron beam for purposes other than to make a screen fluoresce. The beam may be rotated by suitable means and in that way be made to complete alternately electrical circuits with a series of stationary metallic seg ments, which, in turn, may control other circuits. The beam now acts as an electronic commutator. Because it is almost inertialess, the frequency of commutation can far exceed that of any conceivable mechanical device. In another use, the beam may excite a resonant cavity, thus producing extremely high frequency oscillations, as in a manner not unlike the magnetron. There are ANSWER TO YOUR TECHNICAL PROBLEMS... The Altec Service Man and the organization behind him 161 Sixth Avenue, New York 13, N. Y. PROTECTING THE THEATRE FIRST PLACE IN ENTERTAINMENT n nrto ESSENTIAL THERE IS A LORRAINE CARION TAILORED FOR YOUR SPECIFIC PROJECTION REQUIREMENT Send necessary projection equipment data to guide us in recommending the Lorraine Carbons that will do your theatre or drive-in projection job better and More Economically. SLOW BURNING SAVINGS IN POWER CONSUMPTION SAVINGS IN MAINTENANCE ECONOMIZE ^WuUmC carbons, inc.. ioonton. n. J. INTERNATIONAL PROJECTIONIST • December 1950 15