International projectionist (Jan-Dec 1947)

SOUND SYSTEM DEFINITIONS {Continued from page 19) does not flow during any part of the input cycle, the suffix "1" may be added to the letter or letters of the class identification. The suffix "2" may be used to denote that grid current flows during some part of the cycle. Control-GridPlate Transconductance : See definition of "Transconductance." Conversion Transconductance: The ratio of the magnitude of a single beat-frequency component (ft + fa) or (fi — f2) of the output current to the magnitude of the input voltage of frequency fi under the conditions that all direct voltages and the magnitude of the second input alternating voltage f» must remain constant. As most precisely used, it refers to an infinitesimal magnitude of the voltage of frequency fi. Converter (generally, in superheterodyne receivers): A converter is a vacuum-tube which performs simultaneously the functions of oscillation and mixing (first detection) in a radio receiver. Cross Modulation: A type of intermodulation due to modulation of the carrier of the desired signal in a radio apparatus by an undesired signal. Current Amplification: The ratio of the alternating current produced in the output circuit of an amplifier to the alternating current supplied to the input circuit for specific circuit conditions. Cathode Ray Data Deflection Factor of a cathode-ray oscillograph tube is the reciprocal of the deflection sensitivity. Deflection Sensitivity of a cathoderay oscillograph tube is the quotient of the displacement of the electron beam at the place of impact by the change in the deflecting field. It may be expressed in millimeters or inches per volt applied between the deflecting electrodes, or in millimeters or inches per gauss of the deflecting magnetic field. Detection is any process of operation on a modulated signal wave to obtain the signal imparted to it in the modulation process. Detector: A device used for operation on a signal wave to obtain the signal imparted to it in the modulation process. Diode: A type of thermionic tube containing two electrodes which passes current wholly or predominantly in one direction. Direct Capacitance (C) (between two conductors): The ratio of the charge produced on one conductor by the voltage between it and the other conductor, divided by this voltage, all other conductors in the neighborhood being at the potential of the first conductor. Dynamic Sensitivity of a Phototube: The alternating-current response of a phototube to a pulsating light flux at specified values of mean light flux, frequency of pulsation, degree of pulsation, and steady tube voltage. (To be Continued) WAA OFFERS 45 CINEFLEX CAMERAS Forty-five unused 35-ttim A-5 Cineflex silent motion picture cameras and kits which originally cost $1,950 each are being offered for $1,450 each by the War Assets Administration at 37 Broadway, N. Y. City. Cameras are motor-driven, complete with following items: 4 separate lens assemblies of 35-, 50-, and 75-mm size, all of F: 2.3 speed, and a 130-mm assembly with a speed of F: 4.5; 1 combination carrying case; 1 carrying case for six 200-feet magazines; 1 adaptor assembly, tripod mount; 1 rain cover; 6 holder filters; 1 driving motor, 24 volts, and 1 200-feet magazine. { WENZEL "Smooth-Running' I We are actively represented in every part of the world. Now you can be assured of "smooth running" performance with this time-proven projector. Too, your present equipment will do a "smoothrunning" job with Wenzel precision replacement parts. New ROLL TICKET HOLDER TH-2 Instantly adjustable to hold your roll at the correct tension. Can be used in any position. Write for our catalog. Mention dealer serving you. THE COMPLETELY NEW jfl !) n 0 s a a p ij "A A" PROJECTOR by America's oldest manufacturer of projectors IT SETS A NEW STANDARD IN SCREEN PERFORMANCE Its design and construction assures long life and minimum upkeep. See the projector you've been waiting for now at your Motiograph dealers. MOTIOGRAPH, INC. 4431 W. Lake St., Chicago 24, lit. EXPORT DEPARTMENT: J. E. Robin, Inc., 330 W. 42nd St., New York, N.Y. INTERNATIONAL PROJECTIONIST February 1947 29