Showmen's Trade Review (Oct-Dec 1943)

38 SHOWMEN'S TRADE REVIEW October 9, 1943 No More Loose Chairs! Permanently anchors loose chairs to concrete floors in ten minutes. COMPLETE KIT AND INSTRUCTIONS ... $5. f.o.b. Chicago. PATCH-A-SEAT Quickly repairs cuts and rips on leatherette seats. Colors: brown, green, black, maroon, blue. Specily color when ordering. COMPLETE KIT . . . $6. l.o.b. Chicago. CHAIRS • PARTS Complete line of used We carry a comand rebuilt theatre chairs — veneer back plete line 01 new and box spring seat. ^ged parts lor Also insert panel back , • ■ and spring edge seats. all makes ol chairs. GENERAL CHAIR CO Z035 ChcuUilon St. CHICAGO, ILL. New • Used • Rebuilt Proiectors, Screens, Chairs, Soundheads, Amplifiers, Arc Lamps, Rectifiers, Generators, etc. Write for bargain booklet. ^Equipment bought at highest prices S. 0. S. CINEMA SUPPLY CORP, 449 W 42nd si , N Y C WE MAKE OLD THEATRE CHAIRS LIKE NEW — LAST EIGHT TO TEN YEARS ASK PARAMOUNT ABOUT OUR WORK PRICES REASONABLE REPUBLIC SEATING CO. 45 W. 45th Street BR. 9-4245 New York City Mote $$$inPop(6mi Reduce Supply Costs Vte the world's finest guaranteed pop com. COSTS LESS! Sells faster, produces greater profit! Complete line of pop corn, salt, seasoning, cartons, sacks. Prompt delivery. WRITE today for full details and Low Prices! World's Largest Pop Corn Producers AMERICAN POP CORN CO., SIOUX ClTf. IOWA Make those improvements now! • Now Is the time to make those much needed improvements to your theatre. Allow us to offer our suggestions and estimate. NOVELTY SCENIC STUDIOS, INC. Murals New York Draperies . Tnterior Decoration 318 320 W 48th Street ADV. What Are Your Needs? Joe Hornstein Has It KEEP ON BUYING MORE WAR BONDS Know Your Sound Projection Terms First installinciit of A Practical Glossary of descriptive terms relating to sound. (Note (*) appearing after terms indicate such definitions are reprinted zvith permision front A Selected Glossary for the Motion Picture Technician, Compiled by the Academy Technicial Bureau of the Academy of Motion Picture Arts and Sciences.) A.C. : Alternating current. A.C.C.W. : Alternating current continuous waves. * ACOUSTICS: (1) Science of sound. (2) Acoustics of an enclosure : refers to hearing conditions within the enclosure, due to reflections and absorptions of sound. A.F. : Audio frequency. AMPLIFICATION FACTOR: Measure of the grid voltage effectiveness in relation to the plate voltage in affecting plate current. * AMPLIFIER: A device for increasing the amplitude of electric current, voltage, and/or power, through the control by the input power of a larger amount of power supplied by a local source to the output circuit. Specifically, (1) a vacuum tube used for this purpose; (2) the whole circuit of which such a tube is the essential element. * AMPLITUDE: The maximum height, or maximum depth, of a wave, measured from its base line or middle position. One-half the distance through which each part of the medium carrying the wave will vibrate from the time a crest passes to the time the next trough passes. The energy contained in a wave varies as the square of the amplitude of the wave. * ANODE: Positive terminal of an electric device (cell or tube), at which the current (in the conventional direction) enters the device. * ATTENUATION: Weakening of intensity. * AUDIO FREQUENCY : Frequency of vibration with the limits of good hearing, 20 to about 10,000 cycles per second. Abbreviated A.F. * AUDIO FREQUENCY AMPLIFIER: Magnifies currents whose frequency of alternation lies in the audio-frequency range. *AUDION: Three-electrode vacuum tube. "B" POWER SUPPLY: Device for current supply in the plate circuit of a vacuum tube. * BAFFLE : A portable wall or block for the absorption of reinforcement of sound. BEAT FREQUENCY: Number of beats per second. * BEATS : Vibrations produced by interference between two or more wave-lengths. * BLOOP, noun : Dull thud emitted in sound reproduction, due to a poorly made Blooping Patch. * BLOOPING PATCH: Triangular or oval black section introduced over a splice in the positive sound track, to prevent the noise which the splice would otherwise cause during reproduction. The patch effects a relatively gradual diminution in the transmitted light, followed by gradual restoration to the original value. The sound frequency due to a properly blooped patch is too low to be heard; but see BLOOP. * BRIDGING AMPLIFIER: Any amplifier or relatively high input impedance, so that a number of such units may be connected in multiple across a relatively low impedance circuit without materially affecting its electrical condition and without reaction on one another. Abbreviated B.A. "C" POWER SUPPLY : Device for supplying current to apply a grid bias ; connected between the cathode and grid of a vacuum tube. * CAPACITANCE: The measure of the quantity of electricity a condenser can hold. It equals the quantity stored divided by the voltage (pressure) storing it. CAPACITATIVE COUPLING: Coupling of one circuit with another by means of a capacity common to both. * CAPACITY, CARRYING: Current a conductor can carry without becoming overheated. * CATHODE: Negative terminal of an electric device (cell or tube), from which the current (in the conventional direction) leaves the device. * CHOKE, CHOKE COIL : Coil of wire wound on an iron core and thus possessing high inductance. CLASS A AMPLIFIER: Amplifier whose grid bias and alternating grid voltages produce a plate current that flows at all times in a specific tube. CLASS AB AMPLIFIER: Amplifier whose grid bias and alternating grid voltages produce a plate current that flows less than the full, but more than half the electrical cycle. CLASS B AMPLIFIER: Amplifier in which the plate current in a specific tube flows for about one-half of each cycle with grid voltage applied but in which plate current is zero without grid voltage applied. CLASS C AMPLIFIER: Amplifier in which plate current in each tube is zero when alternating grid voltage is not applied. COUPLING : Interconnection of two circuits in a way that permits transfer of energy from one to the other. * COEFFICIENT OF SOUND ABSORPTION. When sound energy strikes any substance, it is partly reflected, partly transmitted, and partly absorbed (converted into heat). The percentage of energy absorbed by a given object is the object's absorption coefficient. * CONDENSER: (1) A device for the temporary storage of electric energy, consisting of two conductors (or else one conductor and ground) separated y an insulator, or of a number of such elements combined to act as a unit. (2) A lens or set of lenses used to focus light upon the aperture of a motion picture projector or into an intense spot of light for use in a motion picture studio. * CONDENSER LOUDSPEAKER: Loudspeaker in which the mechanical forces producing the sound are obtained by varying the voltage between two electrodes of a condenser forming a part of an electrical circuit. CURRENT AMPLIFICATION: Ratio of the A.C. produced by the output circuit to the A.C. supplied to the input circuit of an amplifier. * CYCLE : One complete set of the changes of a wave (or other periodic phenomenon), as from crest to trough and back to crest again. May refer to waves of sound, or alternating current, or any other waves or vibrations. Always relative to a second of time ; thus "cycles" means 60 cycles per second. * DECIBEL : Unit of gain and loss of energy, intensity, loudness. Equal to ten times the logarithm to the base 10) of the ratio l/L where 1 is final intensity and lo is initial intensity in a transmitting system, or (when the decibel is used as an absolute unit) L is a standard intensity. Other names and abbreviations are db. DU, sensation unit, TU, transmission unit. Note : the logarithm of 2 is 0.3 very nearly, therefore intensity is doubled for each gain of 3db. * DYNAMIC CONE: Type of LOUDSPEAKER in which the modulated electric current passes through a coil placed in a magnetic field. The coil and an attached paper cone vibrate and thus generate sound in accordance with the modulations of the current. * ELECTRODE : Terminal of an electric de,vice such as a cell or vacuum tube. * ELECTRON: Unit of negative electricity, and smallest particle of matter, next to the proton. (To Be Continued)