Projection engineering (Jan-Dec 1931)

Page 26 PROJECTION ENGINEERING New Developments and News of the Industry RCA PHOTOPHONE For the third time within the past few months, RCA Photophone portable sound reproducing equipment has been installed in the American Embassy, London, Eng., at the request of Ambassador Dawes, who entertained a party with a program of sound motion pictures. As upon the two previous occasions, Paramount cooperated with RCA Photophone in the presentation of the program. NEW VISITRON PHOTOELECTRIC CELL A new size of Visitron photoelectric cell is announced by G-M Laboratories, Inc., Chicago, to meet the demand for a Visitron cell of medium size with a globular bulb. This new cell measures 2 13/16 inches from the bottom of the bakelite base to the top of the bulb, the bulb itself being 1 15/16 inches in diameter. Except in the matter of size, the Visitron 73-A is the same as other Visitrons having the same high sensitivity and long life for which Visitrons are noted. THE PAM-O-GRAPH The Samson Pam-O-Graph will be found particularly useful in broadcasting studios for recording auditions or parts of radio programs. Schools and colleges can use it effectively in recording the lectures of prominent educators and members of the faculty for future reproduction. In the teaching of languages, dramatics, and elocution it is very helpful in correcting faulty pronunciation and enunciation. The large corporation can use it for sales promotion and advertising purposes, at conventions, in demonstration booths, etc. Police officials will now be able to record accurately and comprehensively the confessions and statements of criminals and witnesses. The Pam-O-Graph comes complete, with tubes, microphone, microphone stand, 15 feet of microphone cable, recording needle, and a package of special bamboo playback needles. It is designed for operation from the ordinary 110-volt, 60-cycle, a-c. lamp socket. It is manufactured by the Samson Electric Co., Canton, Mass. VACUUM TUBES FOR INDUSTRIAL PURPOSES The Vas Corporation, 125 No. 3rd St., Newark, N. J., was incorporated for the purpose of conducting development work on industrial tubes and to produce on a commercial scale types for which there is a demand at present. So far the efforts of the company have been devoted largely to several types of hot cathode vapor tubes. Rectifiers up to 75 amperes and up to 50,000 volts are being produced or are in preparation. A grid controlled rectifier which can be operated on d-c. similar to a power amplifier tube for high plate currents has been produced. A grid modulated hot cathode television lamp is in preparation. SELENIUM CELL The Pacific Research Laboratories, 1907 Fourth Ave., Los Angeles, are marketing Type Z-A-C X-cell, a highly developed selenium light sensitive device for a-c. operation of sound equipment without the use of filters. KNOWLES BRINGS OUT NEW POWERS REAR SHUTTER A new rear shutter for Powers projectors that is said to afford nearly 78 per cent cooling at the aperture, an almost complete absence of film buckling and a light increase of 20 to 35 per cent at the screen, has been developed and is being marketed by the Knowles Rear Shutter Co. of Los Angeles, Cal. This device, the company claims, modernizes the Powers projector to where it is no longer necessary to discard the Powers now in use for a heavier and more expensive make of projector because of the excessive heat generated by the high intensity arc. A smooth and novel framing device replaces the old jerky form of framing bar that invariably overshot the mark. A quick means of setting the shutter while running is also had with a new type of collapsible glare shield. The device is built as an integral part of the projector head mechanism and will last as long as the projector itself, besides sharpening the focus to a truly remarkable degree, the company states. A IN FAIRNESS TO THE SCREEN In line with the great improvements which the past few seasons have found in projection screens is the increasing appreciation by projectionists of the fact that in order to give the new and better screens an opportunity to do their best, modern projector lamps are required. This is plainly indicated by the increasing popularity of the equipment built by Hall & Connolly, Inc., who report recent sales of its FR-10 projection lamps to the RKO Plaza of Schenectady, N. Y., the Palace Theatre, of Milwaukee and to the export department of the National Theatre Supply Company, for shipment to Manila, P. I. Other recent Hall & Connolly shipments include nine EF-4 Spots. Six of these were to the Earl Carroll Theatre, New York, two to the RKO Palace, Columbus, Ohio and one to another RKO house, the Plaza, of Schenectady, N. Y. NEWEST LINE RESISTORS FOR D-C. SETS ELIMINATE HEATING TROUBLES A brand new plug-in type line resistor has been developed by the Clarostat Mfg. Company, of Brooklyn, N. Y., especially for use in d-c. radio receivers. Set manufacturers who have changed over their 110-volt d-c. sets to use the new 6-volt, 0.3 ampere tubes, will find this resistor particularly applicable to their needs. The new line resistor follows the same general construction which has proved so efficient in the Clarostat line ballast. It is wound on a sturdy mica frame, and is protected by its perforated metal housing which acts as a ventilating stack, thus rapidly dissipating heat. The unique method of construction tends to keep the line resistor from heating up. This prevents possible injury to nearby components and also precludes disturbing capacity or inductance changes due to overheating. Hence, maximum efficiency of operation is definitely assured. The Clarostat line resistor may be plugged into a regular two hole tube-type socket, or it may be obtained with flat prongs, for use in any standard electrical outlet. Line resistors of various values are available to supply the voltage drop required in reducing the standard line potential (110-115 volts, etc.) to the value needed by the tubes, which are all connected in series. The cost of the new Clarostat line resistor, compares favorably with the ordinary enamelled resistor and cover, which it now renders obsolete.