The motion picture projectionist (Nov 1931-Jan 1933)

34 Motion Picture Projectionist December, 1931 BE PREPARED! TELEVISION THOMAS BENSON TELEVISION For the PROJECTIONIST A COMPACT little book, complete with illustrations and diagrams, embracing the basic fundamentals of television instruments used in television today. It is a book both for the interested layman and for the craftsman who will shortly depend on television operation for his livelihood. It has been written especially for the motion picture projectionist who will unquestionably operate television in the theatre as he now does sound equipment. The serious projectionist will get a copy at once. Some of the Contents — Elements of Visual Communication — Light Sensitive Cells — Scanning Methods — The Television Signal and its Amplification — Transmission Channels for Television — Eight Sources for Television Reception — Reproducing the Image — Synchronizing Methods — Stereoscopic and Color Television — Experimental Television TELEVISION By Benson $2.00 SEND THIS COVPON TODAY Mancall Publishing Corp., 7 West 44th Street, New York City Enclosed find money order for .$2.00. Please send me Benson's Television. Name Address City and State. Theatre of the light beam is, effectively, reduced from the maximum obtained with the slit in the vertical position. As the slit is rotated back to its normal setting the width of the light beam grows narrower until, in its correct position, the light beam once more is but 0.001 inch wide. As the lens barrel was being rotated until the light beam was perpendicular, the cut-off of the slit and lens assembly was being reduced to lower and lower frequencies and the output of the reproducing system suffered in quality accordingly. Standardization of Picture Apertures (Continued from page 20) technical representatives was called to hear the report of the subcommittee and to decide between alternatives presented for several items of the specifications. The following studios were represented: Paramount-Publix, Universal, MetroGoldwyn-Mayer, Fox, RKO, Technicolor and Consolidated Film Industries. The specifications were approved and it was urged that they be submitted to the executives of the studios with a recommendation that the standardization be adopted. Technicolor Moves from Boston to Hollywood Technicolor has transferred all activities from Boston to its large Hollywood laboratories, it has been announced by Dr. Herbert T. Kalmus, President and General Manager of the Technicolor Corporation. Heretofore most of the Technicolor release prints have been manufactured m Boston. ' This move, which consolidates all Technicolor work — photography, printing of rushes and release prints, as wen as research — in the capital of the motion picture industry, means an economy of time in production that is important to the industry, Dr. Kalmus pointed out. Producers have expressed real satisfaction over the cnange, which is in keeping with the general policy of the industry, as it has developed in the last few years, to turn out release prints in Hollywood. Some forty Technicolor executives and technical men from the Boston plant already have arrived in Hollywood to augment the West Coast personnel. In addition to saving considerable time in the delivery of negatives to the laboratory the new arrangement will enable directors and other production executives to cooperate more closely with Technicolor in inspecting prints before they leave the plant. Technicolor opened its Hollywood laboratory in May, 1930. Theory and Fundamentals (Continued from page 29) speakers to the transformer. Diagram (a) Figure 5 shows a 30 ohm voice coil connected to terminals 1 and 3 of the transformer. The tube has a plate impedance of 1500 ohms. Since the equivalent load impedance (Zp) must equal 3000 ohms, the turns ratio N V3000 / -3y = V 100 = 10 Diagram (b) Figure 5 shows the same tube and transformer, but two loudspeakers in parallel are shown connected to terminals 2 and 3. Let it be required to find the turns ratio of the transformer for this connection in order to locate the position of the secondary tapped terminal 2. Since the two speakers are connected in parallel the total voice coil impedance is equal to 30 divided by two or 15 ohms. Having a total voice coil impedance (Zs) of 15 ohms, the turns ratio of the primary winding to terminals 2 and 3 of the secondary winding equals = 14.1 It is to be observed here that the above principles can be applied to the operation of push-pull circuits. Referring to Figure 4 the secondary of the transformer is tapped for two speakers operating in parallel in which case the turns ratio of the primary winding to terminals 2 and 3 of the secondary winding is 20 to 1. The calculations for determining this ratio will be left to the reader. Series Loudspeaker Connections Figure 6 shows the secondary terminal arrangement of the output transformer when it is desired to use either one speaker or to use two speakers connected in series. Diagram (a) of this figure shows one loudspeaker connected to terminals 2 and 3 of the secondary winding. Diagram (b) shows two speakers in series connected across the entire secondary winding (terminals 1 and 3). The turns ratio of 7.1 to 1 in the case of diagram (b) Figure 6 is determined as follows: The tube plate impedance is 1500 ohms and the equivalent load impedance (Zp) should be 3000 ohms. The total voice coil impedance (Zs) of the two speakers in series is equal to the sum of the voice coil impedance of the two speakers or 30 plus 30 or 60 ohms. The turns ratio then is N J3000 = J50 = y 60 " 7.1 It is to be noted that for one loudspeaker, diagram (a) Figure 6, the