International projectionist (Jan-Dec 1948)

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the line pulses, so that the sync separator circuit will be able to distinguish between the two types of pulses and thus be able to separate the vertical sync pulses from the horizontal sync pulses. At the same time the edges of the serrations at half-line intervals provide the necessary control for maintenance of horizontal synchronization. The serrations are required at half-line intervals because of the interlacing; the reasoning used in connection with the equalizing pulses also applies here. (3) It was explained previously that in order to provide identical conditions for the two successive fields preceding the vertical sync pulses, six equalizing pulses were inserted in front of the vertical sync pulse in each field. It is just as necessary to keep the conditions following the vertical syncpulse interval the same for the two successive fields (A) and (B) : for this reason six lagging equalizing pulses appear in both (A) and (B) after the vertical sync pulse. Examining the vertical sync-pulse interval in both (A) and (B), you will see that although the lines in the two fields are displaced by onehalf line because of the interlacing, nevertheless the conditions in the neighborhood of the vertical sync-pulse interval are the same for both fields. Note that the lagging equalizing pulses are also one-half line apart so that line synchronization is maintained for both the "odd" and "even" fields. Blanking Period 7 to 12 Lines (4) The lagging equalizing pulse interval is terminated before the end of the vertical blanking period so as to prepare the line oscillator for the normal horizontal sync pulses which are to follow. In practice, the video signal is blanked out for a period of from 7 to 12 lines following the last equalizing pulse so that the bne oscillator (which may have been operating at double line frequency during the preceding period) has a chance to settle down to being under control of the normal type of sync signal. At the end of the vertical blanking interval the blanking is of course removed, and the video portion of the signal again controls the intensity of the beam in the picture tube. [To be Continued] Estimated Movie Gross in 1948 Gross take of U. S. film theatres will approximate $1,530,000,000 during 1948, according to an estimate by the Internal Revenue Bureau based on a projection to the whole year of figures for the first half. This figure is about 2% less than the record 1947 take, but would be well ahead of 1945 income. Theatres were held to have reached lowest point of their slump during June, with attendance climbing slowly but steadily since then. 20 Years of Theatre Sound System Servicingf By EDWARD S. SEELEY Chief Engineer, Altec Service Corporation The history of the sound motion picture industry is told from the point of view of the service organization. Particular emphasis is given to the part played by the service forces in the steady improvement of sound quality to its present standard. Also discussed are possible theatre problems of the future which national service organizations will help solve. ON AUGUST 6, 1926, the sound motion picture was officially born. On that date the world premier of the Vitaphone was held at Warners Theatre, New York, the program consisting of "Don Juan" with a synchronized sound-on-disc score and a group of Vitaphone musical shorts. Revolution seized the industry. The equipment companies were besieged with thousands of exhibitors begging for equipment. Many were glad to obtain a nine-month delivery promise. This sudden demand for equipment placed a heavy strain on the principal manufacturers, W. E. and RCA, despite their great facilities. But the greatest strain was placed on the new organizations whose role it was to install the equipment. These organizations mushroomed. For some time all sources of the required type of personnel were scoured for men of suitable abilities and background at the rate of 75 to 100 per month for one of these organizations alone. Because of the urgent need for men in the field, the training period was all too brief for these men to master the technical mysteries of the sound systems, the mechanics of good installation practices, and the lore of the theatre. t J. Soc. Mot. Pict. Eng., May, 1947. Altec's chief engineer Ed Seeley at the controls of the Altec Flutter Bridge which eliminates guesswork and individual "experting" from the evaluation of flutter in film reproduction. This unit permitted the establishment of standards for various types of reproducers. To add to the burden, it immediately became evident that the new equipment had a perverse tendency to break down when the house was packed with expectant patrons. It was soon apparent that in order to ensure continuous and satisfactory operation it would be necessary to establish an additional corps of trained specialists to service this new complex electrical and mechanical apparatus. Service Inaugurated in 7927 It was felt that the security of the future of sound pictures depended upon continued satisfactory operation, and consequently in the Spring of 1927 a service department was organized by Erpi in order to maintain the equipment in operation without interference with the high-pressure installation schedule. The service department gradually emerged from its lowly beginnings and in 1937 became separated from Erpi to be known as Altec Service Corp., with the sole functions of maintaining and improving quality performance in theatres. Inevitable growing pains were experienced by the young Erpi organization. The new men, rushed into the field to handle sometimes three installations at a time, often without help from their own supervisors, could not achieve completely what we consider the full standard of installation practice, and improper conditions were sometimes left behind them. The new art of theatre sound projection was growing rapidly and the problem of applying the latest knowledge in the field developed. Furthermore, as the need for new men began to moderate somewhat, it was considered necessary to recontact the field personnel to supply some of the training which it was not possible to give them when the pressure was most intense. Technical Inspectors Group Formed To accomplish these several purposes a new group was formed known as Technical Inspectors. These inspectors, selected on the basis of special technical ability, were given more advanced schooling in all parts of the sound systems. They then contacted the installation and service inspectors to further the training of the latter, and made detailed inspec(Continued on page 32) INTERNATIONAL PROJECTIONIST • October 1948 15