International projectionist (Jan-Dec 1936)

34 INTERNATIONAL PROJECTIONIST October 1936 recording. Its advantages are: indication of peak values of voltage; full indication for sounds of short duration; adjustment for slow restoring action for greater ease of reading; the device may be given the same sensitivity-frequency characteristic as that of the light-valve; use of a well damped longscale indicating type of meter. A NEON-TYPE VOLUME INDICATOR S. Read, Jr. RCA A number of gaseous discharge lamps of the neon type have been used to indicate instantaneous peak amplitude of audio-frequency voltages. When the instantaneous value of the signal voltage increases to the value at which the first lamp is adjusted to discharge, the lamp starts to glow. When the voltage is still further increased, additional lamps begin to glow as their discharge values are reached. As the instantaneous voltage decreases the lamps are extinguished in the reverse order. Such a device provides a definite indication of the peak value, even though of extremely short duration. Due to the persistence of vision, such extremely short peaks are not lost, although voltages sustained over longer periods produce brighter glows. Only one-half of the voltage wave actuates the neon lamps; therefore, either positive or negative peaks may be noted. Any portion of the scale may be expanded or compressed as desired. Radiotrons of the Acorn type are used so as to achieve a compact unit. The device is compared with volume indicators of other types, and some of its unique circuits are discussed. Diagrams and performance curves are included. A NEON TUBE OSCILLOSCOPE FOR THE PROJECTION ROOM T. D. Hover Ohio Theatre, Lima, Ohio A neon type of rotating mirror oscilloscope is described intended for routine use by projectionists to aid in eliminating noise due to microphone tubes, improperly meshed gears, etc. The parts may be either purchased or built by the projectionist. NEW RECORDING EQUIPMENT D. Canady and V. A. Wellman Canady Sound Appliance Co. A new sound-film recorder for studio or portable use is described. Three flywheels in addition to a non-resonant drive sprocket filter enable the machine to operate satisfactorily on power lines of poor regulation. Tests have proved that violet surges on the power supply line have no noticeable effect upon the linear film speed. The recorder is unusually quiet in operation. It can be used on the set if need arises. Mention is made of recording lamp improvements, and a noise-reduction unit for operation in connection with glow lamps is described. A self-contained semi-portable recording amplifier is also discussed. AN IMPROVED REEL-END ALARM D. Canady and V. A. Wellman Canady Sound Appliance Co. Scratching and mutilation of release prints by mechanical reel-end alarms in projectors are touched upon, and a description of an improved indicating device is given. Use is made of a light-source and a photoelectric .cell. The light-rays from the light-source pass at a tangent to, or across, the him. When the point of tangency has been reached, the film that previously obstructed the light-ray allows the ray to reach the photoelectric cell, which, in turn, actuates the signalling device. The device is positive in action and automatic in operation. Nothing mechanical touches the film. RECENT DEVELOPMENTS OF H.-I. ARC SPOTLAMPS FOR MOTION PICTURE PRODUCTION E. C. Richardson Mole-Richardson, Inc. In order to utilize high-intensity carbon arcs more effectively as sources of illumination for photographic purposes, two newly designed spotlamps have been developed. Improvements have been incorporated in the design which particularly adapt the lamps for use under modern photographic conditions, particularly in the production of colored motion pictures, where uniformity of special distribution and intensity are vital factors. In the design of the arc mechanism used in these lamps, vital improvements are: (1) increased rotational speed of the positive carbon; (2) continuous non-intermittent feeding of both positive and negative electrodes; (3) rapid-action positive and negative manual adjustments. The paper describes in detail the application of "Morinc" flat corrugated lenses to the new equipment, and illustrates, by means of graphs, the light distribution attained for various beam divergencies. The new equipment has had sufficient practical application in motion pcture production to have proved its worth in photographing under both normal and Technicolor production. THREE-WIRE D-C. SUPPLY FOR PROJECTION ARCS C. C. Dash Hertner Electric Co. The introduction of the non-rotating, highintensity, low-voltage, d-c. arc has made it desirable to use a d-c. supply of as low voltage as practically possible. The auxiliary projection equipment, such as the spotlamp, dissolver lamps, and effect machines, are still equipped with arc lamps requiring 55 to 65 volts across the arc. In order to obtain the benefits of the new lamps using the Suprex type of carbon, it is desirable to have a d-c. source of the proper voltage for each type of lamp to be used. Two flat-compounded generators may be connected in series so as to have the voltage of each generator available or the combined voltage of the two in series. There has been developed a double-voltage motor-generator arranged so that low voltage is available for the non-rotating highintensity projection lamps, and also double the voltage of the single generator for the auxiliary equipment. The design of this type ef motor-generator may be such that changing the load on either generator does not affect the output voltage of the other generator. Performance curves of this twounit motor-generator set demonstrate the steadiness of the output voltage with changes of load. A DEMONSTRATION TRIODE FOR VISUALIZING ELECTRONIC PHENOMENA F. E. Eldridge and H. F. Dart Westinghouse Lamp Co. To augment theoretical discussion with a practical demonstration, a new type WL-787 triode has been developed for visualizing the electronic effect when changes are made in the grid and plate voltages of a vacuum tube. The filament consists of several parallel oxide-coated wires, all of which are located in one plane so that the plate current will be uniformly distributed. The anode is the fundamental flat plate mounted parallel to the plane of the filament. The grid is a fairly open and conventional structure, mounted between the filament and the plate. The side of the anode facing the grid and the filament is coated with willemite, which shows a bright greenish fluorescence when bombarded by electrons of the plate current. A pronounced and clearly visible glow occurs at all points where the electrons strike, resulting in a definite pattern of the grid upon the plate. Plate size is such that the action can be observed by everyone in a room of reasonable size. Either alternating or direct current may be used to heat the filament and to supply the voltages for the grid and plate. The demonstration triode, therefore, becomes a tool that can be used in the classrooms of universities, colleges, and technical schools to supplement the theoretical discussions. It is useful also for demonstrating visually any vacuum tube phenomena depending upon the fluctuation of the grid voltage to vary the plate current. STATEMENT OF THE OWNERSHIP. MANAGEMENT. CIRCULATION, ETC., REQUIRED BY THE ACTS OF CONGRESS OF AUGUST 24, 1912, AND MARCH 3, 1933, Of International Projectionist, published monthly at New York, N. Y., for October 1, 1936. County of New York 1 State of New York J Before me, a Notary Public in and for the State and county aforesaid, personally appeared James J. Finn, who, having been duly sworn according to law, deposes and says that he is the Editor of International Projectionist and that the following is, to the best of his knowledge and belief, a true statement of the ownership, management (and if a daily paper, the circulation), etc., of the aforesaid publication for the date shown in the above caption, required by the Act of August 24, 1912, ' as amended by the Act of March 3, 1933, embodied in section 537, Postal Laws and Regulations, printed on the reverse of this form, to wit: 1. That the names and addresses of the publisher, editor, managing editor, and business managers are: Publisher, James J. Finn Publishing Corp., 580 Fifth Avenue, New York, N. Y. Editor, James J. Finn, 580 Fifth Avenue, New York, N. Y. Managing Editor, None. Business Manager, Ruth Entracht, 580 Fifth Avenue, New York, N. Y. 2. That the owner is: James J. Finn Publishing Corp., 580 Fifth Avenue, New York, N. Y. James J. Finn, 580 Fifth Avenue, New York, N. Y. Ruth Entracht, 580 Fifth Avenue, New York, N. Y. 3. . That the known bondholders, mortgagees, and other security holders owning or holding 1 per cent or more of total amount of bonds, mortgages, or other securities are: None. 4. That the two paragraphs next above, giving the names of the owners, stockholders, and security holders, if any, contain not only the list of stockholders and security holders as they appear upon the books of the company but also, in cases where the stockholder or security holder appears upon the books of the company as trustee or in any other fiduciary relation, the name of the person or corporation for whom such trustee is acting, is given; also that the said two paragraphs contain statements embracing affiant's full knowledge and belief as to the circumstances and conditions under which stockholders and security holders who do not appear upon the books of the company as trustees, hold stock and securities in a capacity other than that of a bona fide owner; and this affiant has no reason to believe that any other person, association, or corporation has any interest direct or indirect in the said stock, bonds, or other securities than as so stated by him. James J. Finn, Editor Sworn to and subscribed before me this 2nd day of October, ly36. (Seal) JOSEPH HOPF Notary Public Queen's County No. 718; Queen's County Register's No. 4309. (My commission expires March 30, 1937.)