The motion picture projectionist (Nov 1930-Oct 1931)

38 Motion Picture Projectionist February, 1931 the theatre from which sound reception can be safely judged. Certainly the projectionist in the projection room cannot determine if and when more or less volume of sound is needed to please the patrons. His monitor horn tells him only that there is sound emanating from the screen. The quality of the reception is not within his power of determination. But with remote control from downstairs points, the manager or some attendant delegated to do so may not only regulate accurately the quantity of sound volume but the quality as well, actually "playing the picture," giving it the proper touch and tone for every set or scene, just as the producer intended the exhibition should be made. While several remote stations may be installed, located at as many points in the house as desired, one station is usually sufficient, this located at the rear of the seats in the auditorium. An inconspicuous double toggle switch with "up" and "down" positions marked enables one to instantly regulate the volume, step by step, up or down as desired. And further, the device does not in any manner interfere with the work of the projectionist who still retains his same means of control and operation. It is pointed out that buzzer signals, cue sheets, telephone calls and other methods heretofore employed in trying to direct the sound reception from downstairs may be dispensed with when the new system is installed. The manager directly controls the sound of his program with the new device which does not in any way interfere with the work of the projectionist. Installations are now being made in RCA equipped theatres and, according to Mr. Strong, within a very short time the devices will be ready for adaptation to all other makes of sound equipment amplifiers. Fundamentals of Television The scanning disc is a vital element in present-day television broadcasting and reception. Its action is extremely interesting. The disc is made of metal, as a rule, and is thin and rigid, a foot or more in diameter. There is a spirally located series of tiny holes drilled through the disc, and the disc is rotated by an electric motor which must be maintained at exactly the same speed as the corresponding motor at the broadcasting station. The holes are placed a certain distance apart horizontally, that is, in the direction of rotatio'n, and . also a certain distance apart vertically, that is, toward the center of the disc. The horizontal distance between the holes determines the width of the picture, usually about 1% inches. The holes are spaced apart vertically a distance equal to the diameter of the hole, (usually very slightly less). The Scanning Disc In back of the disc we have a neon tube which blinks bright and dim in accordance with the impulses from the transmitting station. In front of the disc we have a small ground glass screen on which we view the images. The disc passes between, so that no light from the neon tube may reach the screen except through a hole in the disc. And only one hole at a time can be between the bulb and the screen. The top hole traces its path along the top of the screen, and during this brief passage, the neon tube may brighten and dim a number of times, making flashes of light at different places along the path of this hole. Next comes the second hole, starting its quick trip across the picture just as the first hole leaves at the other side. Again the neon bulb flashes up and off, sending further shots of light. Each hole in succession traces its path, each path slightly lower down than its predecessor, until all the holes have passed and "swept" the picture complete. Persistence of Vision Your eye retains the image of each flash of light some time after it has gone. This is known as persistence of vision. The whole process occurs a number of times every second, perhaps ten times or more. The eye does not realize that the light flashes which compose themselves together really come only one at a time in a series of flashes. The eye sees the complete picture. If there are only twentyfour holes in the disc, the picture is less detailed, but the neon tube does not have to respond so fast. When wider bands are allowed for television purposes, larger and better pictures may be transmitted. Naturally, the accuracy of speed control is highly important, for the picture would break up into a meaningless jumble of distorted light and dark spots should the disc get out of synchronism with that in the television broadcasting station. Hence the best drive for the disc is a synchronous motor, with mechanical braking device as second choice. A. P. S. Chap. 7 Holds Annual Frolic in Hollywood Tuesday, Dec. 16, or rather, Wednesday morning, Dec. 17, saw one of the most interesting events in the Hollywood film colony's social activities, when the American Projection Society, California Chapter No. 7, of Los Angeles, entertained at its second annual dinner dance and frolic. The affair took place in the Elks' Temple, at Sixth and Park View. The great ballroom, specially decorated for the occasion, was given a modernistic aspect through the use of unique lighting effects, shifting color combinations and odd effects, designed after the fashion of the theatre and being used to enhance the effectiveness of the decorations. The frolic was informal in nature. Gene Morgan, famous master of ceremonies in movie houses, acted in a like capacity and introduced the acts, as well as Miss Raquel Torres, heroine of "White Shadows of the South Seas," who made the presentations. The recent celebration and dinner dance marks the completion of one of the most active years in the history of the society, with many developments in sound projection having been studied and investigated. The dinner dance was handled by a committee headed by Otto Felts, assisted by "Chuck" Fowler and Louis Wutke. The affair incidentally aided in welcoming the newly-elected officers of the chapter : Sydney Burton, president; Fred L. Borch, secretary, and Harry Cage, treasurer. This is Burton's third term as president. The retiring officers are: Vice President J. B. Kenton, Secretary D. H. Koskoff, Treasurer Al Feinstein, Sergeant-atArms D. B. Levitt, Board of Governors A. C. Schroeder, Wallace G. Crowley. H. & S. Solderless Lug Up to the present time the connecting of the lead wires to rheostats for motion picture projectors has been a source of general annoyance, both to projectionists and electricians, and very often the contacts effected were of a necessity faulty. This trouble has been due to the large variation in the sizes of wires used on the different installations, particularly now when rheostats of higher amperage are being installed. In view of this condition, Hoffman & Soons, makers of the Perfection rheostat, have developed a new type solderless lug which has solved this vexing problem. These lugs are of extra heavy construction, are adjustable and will accommodate any size wire from No. 4 B & S to a No. 4/0 B & S with equal efficiency. An added feature is the supports which prevent the lugs from turning and becoming loose. These new lugs are now being installed on all H. & S. Perfection rheostats. These lugs are adjudged to be the best adjustable lug yet developed. They are now available at all dealers. Series and Parallel Dry cells used in battery sets illustrate series and parallel connections nicely. Dry cells are used to light the filaments of dry cell type radio sets. With tubes like the 199, three dry eels in series are required. The voltage is then tripled (each cell is 1% volts; total is therefore 4% volts). The current capacity of the cell remains the same as that of one cell, however. For other tubes, such as the WD11, only 1% volts are required, but one cell does not have enough current capacity to light all the tubes of the set. Therefore a number of dry cells, any number desired, is connected in parallel, that is, with their positive terminals joined together, and their negative terminals joined together. This acts as a single dry cell, still of 1V2 volts, but of greater current capacity.