Projection engineering (Sept 1929-Nov 1930)

Page 26 Projection Engineering, November, 1930 New Developments and News of the Industry ELLIS DEMOUNTABLE MICROPHONES This invention is the latest achievement of the engineers of the Ellis Electrical Laboratory. This demountable feature is obtainable in the standard models of the Ellis Models No. 29N and 30N. The Ellis demountable microphone was designed tor convenience and safety — safety from theft and from exposure to the elements. These purposes are attained by making the microphone unit easily and quickly removable or "demountable" from the supporting fixtures and easily replaceable. The value of the improvement in the microphone field will be appreciated by those whose patience has been taxed by the clumsy and burdensome task of re moving a microphone, locating a screw driver to disconnect and reconnect the wires, unlacing and relacing a tight set of springs, and being careful to avoid mistakes in reconnecting the cable. There are many cases where it proves to advantage to use the very sensitive Model 29N for the speaking voice and then change to the Model 30N for music. This is an easy matter with the Ellis demountable and is especially important in the production of talking films, both in the studio and in the field. AMERTRAN SERIES SO AMPLIFIERS • AmerTran power amplifiers (type PA, series 80) exhibited by the American Transformer Company, 178 Emmet Street, Newark, N. J., operate directly from standard 115-volt, 50/60-cycle lighting circuits and have been designed to provide an economical means of obtaining high-quality reproduction of sound in large volumes. Although the larger sizes have sufficient power to flood a large auditorium with music or speech, models are also available for home use and smaller installations. These new amplifiers are mounted on a rugged metal chassis with all parts and wiring completely enclosed. Mounting holes are placed in flanges at the ends of the chassis to permit installation on standard 19 inch racks or in any other desired location. Controls are provided for adjusting the bias applied to the power tubes and for compensating line voltage variations. In addition, jacks are available for measuring the plate current of each power tube individually. The American Transformer Company bulletin No. 1079 describes these units in detail. LITTLE FUSES In the protection of delicate electrical equipment it is essential that the fuse be very sensitive or quick-acting. It must "blow" or burn out, before a heavy surge of current, due to a short-circuit or overload, has had time to burn out delicate wires, damage an instrument needle by slamming, or create other damage. To take a simple Illustration: Suppose a milliammeter has a resistance of 2 ohms. Neglecting the effect of inductance, according to Ohm's Law under a short-circuit across 110 volts, 55 amperes would flow through the meter (as long as it lasted) assuming that the source of supply could deliver that much current. It would nevertheless, take this surge of current some small time (a very small fraction of a second) to build up a magnetic field and start the armature moving, slam the needle and burn out the springs and windings. It is within this small split fraction of a second that the Little fuse does its work. Littlefuses are manufactured by the Littlefuse Laboratories, 1772 Wilson Ave., Chicago. ▲ RECTIFIERS A new series of Rectifiers and current supply packs has been released by the Forest Electric Company, 272 New Street, Newark, N. J. The rectifier delivers full wave, fully filtered direct current, humless and non-fluctuating, supplying current to the exciter lamp and tubes of the head amplifier. Forest Rectifiers will eliminate storage batteries or can be substituted during recharging. They are a permanent emergency power supply and are manufactured in several types, operating on 110 or 220 volts a-c, for use with sound apparatus. A .NEW LENS TURRET The Capitol Motion Picture Supply Company is manufacturing the Triplex lens Turret designed for Movietone, Vitaphone and Magnascope. The Triplex, mounted on the lens holder, revolves, bringing the proper wide image lens directly in position with the correct aperture. Stop positions assure centering of the lens. The Triplex turret is extremely steady and is furnished with a case enclosing the entire mechanism, yet allowing ample room for the projectionist to make the changeover. Further information and literature may be had by writing to the Capitol Motion Picture Supply Co., 630P Ninth Ave., New York City. A RESISTORS AND VOLTAGE CONTROLS FOR POWER SUPPLY REQUIREMENTS Electrad manufactures a complete line of resistors and voltage controls for all radio and power supply requirements, including television. Intelligently standardized production and mass purchasing of raw materials effect large savings in Electrad's original manufacturing costs — savings which are passed on to the user in Electrad's moderate prices for exceptionally high grade products. EXHIBITORS' PROBLEMS It is unfair on the part of the reproducer equipment builders to place the responsibility of making their product perform correctly, upon the exhibitor's shoulders. He (the exhibitor) is fitted for this task by neither technical training, environment nor inclination and is therefore subjected to a legion of high pressure artists who have everything imaginable by the way of acoustical "cure-alls" to sell him. He is confronted with "padding" and plaster for his walls and ceilings, echo wires, new types of seating, carpets, draperies and whatnot, all of which run into an • aggregate sum that fairly staggers him. Does the exhibitor— who is supposed to be a smart business man — ever stop to consider that his faithful old pipe organ never cried for acoustical treatment? He does not! Smart fellows, these organ builders and their installation men. Yes, indeed! Contrary to popular belief, organs were never custom built. However, their component parts were placed and installed in such a manner so that the completed unit would give the best possible performance under all conditions. That is what must be done with present-day reproducer equipment installations. Unfortunately, due to the electrodynamic intricacies of this modern equipment, mechanical, electrical and absorption engineers are unable to adequately cope with the exhibitor's problems and it therefore remains for specialists to be called in. Such an organization has now made its debut. A folder describing this new and unique engineering service has been prepared and will be mailed to interested exhibitors who will address the firm of Kendell & Dasseville, Inc., 67 West 44th Street, New York City. A RHEOSTATS Hoffmann & Soons contracting electrical engineers who manufacture Perfection Rheostats have compiled a flier of theatres, recording and research laboratories and auditoriums where Perfection Rheostats have been installed. Tins impressive list of Perfection users is now available. You may have a copy for the asking. RECORDED BROADCASTS Hollywood continues to be the center for electrical transcription activity because of its strategic location in talkie, song and music circles. So many song writers, big-timers in vaudeville, stage and screen stars, to say nothing of broadcast personalties, are now around Los Angeles that the electrical transcription business is flourishing. Continental Broadcasting Corporation, one of the earliest groups in the field, has announced its winter catalogue of features and through their distribution to various radio stations all over the country the serials will be heard by hundreds of thousands. Continental now has contracts with 275 stations in all parts of the United States, Canada, the Hawaiian Islands. New Zealand and Australia and is negotiating with the British Post Office System to supply stations in the British Isle with electrical transcriptions from Hollywood. A AMPLIFIER ACCESSORIES Jenkins and Adair, Inc., Chicago, HI., manufacture Type GL-35 gain control. Many of these units have been in service for two years and are giving entire satisfaction. A NEW SYNCHRONOUS MOTORS The Electric Specialty Company, Stamford. Conn., have a new type of a-c synchronous, commutator motor, operating with unusually high efficiency, and power factor, and low starting current. The performance of the motor is in compliance with the recommendations of the joint committee on fractional h.p. motors. The motors are made in sizes of from % to 3 h.p. The saving in power in one year, resulting from the use of these motors, as compared with the old type induction synchronous motor, may more than compensate for the initial cost of the motor. REFLECTOR LAMP HOUSE Mr. Frank H. Bliss, office manager and engineer of Kliegl Bros., stage and light effects manufacturers, announces that within a short time important developments concerning an improved reflector lamphouse will be made. Kliegl Bros, have a complete line of spot, flood, reflector and arc lamps for sound picture recording. Color and scenic effect lighting apparatus of latest designs together with dimmer banks are fully described in the newest catalogue. Write to Kliegl Bros., 321 W. 50th Street, New York City. A GUIDE TO HOME RADIOVISION The remarkable progress scored during the past few months in practical home radiovision, is summed up in an attractive folder just issued by the Jenkins Television Corporation, 370 Claremont Avenue, Jersey City, N. J. Two models of living room radiovisors in attractive cabinets, two special forms of radiovision receivers for use with self-synchronizing and power line synchronizing radiovisors, the stripped or laboratory form of radiovisor, the radiovisor kit for home assembly, the self-synchronizing motor attachment, photoelectric cells and television lamp are described in this unusual folder, which will be sent to anyone on request.