Projection engineering (Jan-Dec 1931)

Page 24 PROJECTION ENGINEERING New Developments and News of the Industry PHONOGRAPH PICKUP WITH AMPLIFIER FOR LARGE VOLUME The Sangamo Electric Company, Springfield, 111., manufactures a high-grade line of audio transformers for public address and auditorium sound systems. The outfit for use in public halls and auditoriums was designed to give large volume and high quality of tone. The company does not build the complete unit, but is in a position to furnish such parts as audio transformers, impedances and condensers. When equipped with an auditorium type of speaker which will handle the volume output, this amplifier and power supply will give exceptionally highgrade results. Volume sufficient for a large auditorium can be had with ease and without any 60-cycle hum. ▲ INTERNATIONAL PROJECTOR CORPORATION BUSY International Projector Corporation has placed its full factory staff on a 54-hour week basis in addition to running three nights a week overtime, according to an announcement made by Herbert Griffin, general sales manager of that corporation. The increased production and overtime work follows on the addition of three new items to the line, the Acme Portable Sound and Motion Picture Projector, the Pockette 16 mm. Camera, and the Casette 16 mm. Projector. International Projector Corporation has made no reductions in its factory staff since 1929 and the overtime was necessitated by advance orders for the new products. The corporation also manufactures the Simplex Projector equipment for use in motion picture theatres. ▲ BELL & HOWELL APPOINTS SALES MANAGER J. G. Llewellyn, for the past two and a half years assistant sales manager of the Bell & Howell Company, Chicago, has been advanced to the position of sales manager. Mr. Llewellyn has been acting sales manager for the past year. A SOLID GOLD CONTACTS NOW USED IN MODERN MICROPHONES The microphone, from the very nature of its use and construction, is a delicate piece of apparatus. It must be handled carefully and used only according to the manufacturers' directions. It has been found that ordinary microphones are subject to a certain type of deterioration, regardless of care, and, in fact, whether in use or on the dealer's shelf. This deterioration is caused by moisture in the atmosphere, which corrodes nearly all metals. In the case of the microphone, the surface of the metal diaphragm corrodes, ruining the contact with the carbon. To remedy this condition, gold plating was tried. It was then discovered that since the gold was porous, corrosion still took place. The Universal Microphone Co., Ltd., finally solved the problem through a patented process by which a 24-carat sheet of pure gold is stamped on to the surface of a duralumin diaphragm. Using this method, the gold is no longer porous and hence, moisture can no longer affect the diaphragm. Moreover, the gold does not flake nor come off the duralumin, even after extended use. ▲ INDOOR PHOTO LIGHT The amateur as well as the professional photographer can now obtain wonderful indoor photographs and movies with any camera, by using the new "Photo-Sun" Lamps manufactured by the Blue Seal Products Company, Incorporated, 264 Wyckoff Street, Brooklyn, New York. These lamps are miniature arc lamps, operating on either a-c. or d-c, and furnish brilliant light continuously from fifteen to twenty minutes, as required, and are being marketed in two sizes, model No. 395 at 8 amps, which lists at $3.95 complete and model No. 500, a slightly larger lamp, operating at 12 amps, which lists at $5.00 complete. The cost per picture with an ordinary camera amounts to 1/30 of a cent for carbon and current consumption. A COPPER OXIDE RECTIFIER INTRODUCED FOR MOTION PICTURE SERVICE The first copper-oxide rectifier to be introduced for the motion picture field, built to improve the growing use of full vision screens, wider films and colored motion pictures has been announced by the General Electric Company. The rapid strides made in the motion picture industry have required radical changes in theatre equipment. The socalled "low-intensity" projectors installed in most motion picture theatres are not entirely suitable for the present colored projection and greater screen areas. As a result, a rectifier of high intensity and capable of meeting these requirements was needed. One of the outstanding features of the new rectifier is that it may be used either for a high-intensity projector or for one or two low-intensity projectors. Used with a high-intensity projector, it supplies 60 to 70 amperes of arc current. Operated with one or two low-intensity projectors, each of the two sections supplies 30 to 35 amperes. The new rectifier makes use of the copper-oxide disc principle of rectification, which gives it durability, long life and freedom from maintenance expense. A system of forced ventilation, using radiating fans and two small electric blowers, forces a steady stream of cool air over the copper-oxide elements and maintains a temperature within eight degrees of the surrounding air temperature. Not until such a cooling system was perfected was it possible to develop a successful high output rectifier. No objectionable noise is made by the rectifier, which enables it to be placed in the projection room. Installation and operation of the unit are simple. One switch starts or stops the rectifier instantly, without the usual "starting" or "warming up" period. A NEW OPERADIO SPEAKER A new extremely small dynamic speaker for use with very small midget sets has just been added to the line of speakers built by the Operadio Manufacturing Company of St. Charles, Illinois. Though it is but 6 inches in diameter and 3i/i inches overall including the speaker transformer, it has an excellent response curve, high efficiency, and is capable of handling exceptional volume for a unit of these physical dimensions. Operadio patented inverted construction that places the field coil within the conical diaphragm allows excellent structure of the magnetic path and the use of a larger held coil than customary in small speakers of ordinary design. TYPE 2-AC X-CELLS The new type 2-AC X-Cell, manufactured by the Pacific Research Laboratories, 1907 4th Avenue, Los Angeles, Cal., is designed for the purpose of eliminating all batteries connected with the operation of motion picture sound-on-film apparatus. Owing to the nature of this type of cell it is possible to employ raw a. c. on the filament of the exciter lamp without the use of filters or additional apparatus of any kind. This means a great saving in the cost of equipment and maintenance and at the same time simplifies the operation to a remarkable degree.