Projection engineering (Jan 1932-Mar 1933)

Page 28 PROJECTION ENGINEERING CAPACITORS AND RESISTORS The Federal Telegraph Company, 200 Mount Pleasant Avenue, Newark, N. J., announces a new line of wire wound vitreous enamelled resistors, and a line of paper-wax and paper-oil capacitors. Harry C. Gawler, is sales manager of the company. Mr. Gawler was formerly with the De Forest Radio Company at Passaic, N. J. ▲ MALLORY PURCHASES YAXLEY On October 15, 1931, P. R. Mallory & Co. Inc., Indianapolis, pioneers in the development of dry electrolytic condensers sold under the trade name "Elkon," purchased the Yaxley Manufacturing Company of Chicago. The "Yaxley" name has been for twenty-five years identified with a line of quality electrical parts known throughout the world. The Yaxley company will receive full benefit of the Mallory company's engineering, chemical and metallurgical facilities. Ray F. Sparrow will remain in his executive capacity as sales manager, in full charge of service in all its aspects to the many Yaxley customers. RCA-RADIOTRON COMPANY, INC., AND E. T. CUNNINGHAM, INC., ANNOUNCE PHOTOTUBE RCA-Radiotron Company, Inc., and E. T. Cunningham, Inc. have recently made available to experimenters a phototube designated as Radiotron RCA-868 and Cunningham CX-868. This tube is of particular interest because of its use for sound movies in the home and because of its adaptability to many novel experimental uses with light. This phototube is an electronic device and consists of two electrodes enclosed in a glass bulb. One electrode, the cathode, has a sensitized surface which emits electrons when the surface is exposed to light. The other electrode, the anode, acts as a collector for these electrons when a battery is connected across the cathode and View, showing arrangement of cathode and anode, of RCA868 and CX-868 phototubes. anode terminals. The anode or collector, is, of course, connected to the positive terminal of the battery so as to assist the flow of electrodes from the cathode to the anode. This circuit is not unlike that of the usual vacuum tube except that the electrons are emitted from a light sensitive surface instead of from an incandescent cathode. The current flowing in the phototube circuit is dependent on the amount of light received by the sensitized surface. The phototube, like a vacuum tube, has prac tically no time lag, so that variations in light intensity instantaneously affect the amount of current passing through the tube. The cathode of the 868 is a semi-cylindrical sheet of metal and is coated with a thin film of caesium. The anode or collector consists of a small wire placed in the axis of the cathode surface. A small amount of gas is used in this tube to produce high sensitivity. The 868 is sensitive to light over the entire visible spectrum and also to radiation in the near infra-red zone. The large response in the red and infra-red region makes this tube very well adapted to sound reproduction and television work where incandescent lamps are used for light sources. Ordinarily, the output of an 868 requires further amplification. This may be accomplished by a suitable tube amplifier resistance coupled to the phototube circuit. CONDENSER MICROPHONES Three new models of condenser microphones for every requirement of broadcasting, recording and public address operation are announced by the Gates Radio and Supply Co., Quincy, Illinois. Bulletin No. 6 describes these new units. RESISTORS Ohmite Manufacturing Company, 636 N. Albany Avenue, Chicago, announces the publication of a new stock list, Bulletin No. 10, which illustrates and describes Carbohm and Wirohm resistors. The bulletin lists 75 different values of carbon resistors in both 1 watt and H watt sizes, as well as 42 different values of wirewound resistors. These wire-wound resistors, called Wirohms, are of special interest because of their high wattage rating and very small size. A NEW PHOTO-TUBE An announcement from the Cable Radio and Tube Corpn., 84 N. 9th Street, Brooklyn, N. Y., reads : "Speed Fotoelectric tubes are the culmination of years of experimental research work conducted both in this country and abroad. "They have two zones of maximum sensitivity. The first extends into the near ultra-violet, peaking at approximately 3500 Angstroms but falling off rapidly below this point due to glass absorption. "The second zone has a much broader peak extending into the red and infra-red region and peaking from 7500 to 8500 Angstroms. The great sensitivity at this point taken in conjunction with the fact that radiation from an incandescent lamp source is largely in this region gives a large overall sensitivity. . "Because of trie uniformly high sensitivity brought about by a special cathode treatment, it has been found practical to supply Speed Fotoelectric tubes with a somewhat higher ionizing voltage than that generally obtainable. This allows increased latitude in pickup adjustment, in addition to minimizing tube damage from accidental ionization during adjustment, while still retaining gain equivalent to that obtainable from other photoelectric tubes at similar operating voltages. "These photoelectric tubes have an ionization voltage of 108 ± 8 volts and are designed for operation at 90 volts. However, tubes having other operating voltages are regularly stocked and may be obtained without delay. "No photoelectric tube should be oper ated at voltages above ionization for more than a few seconds, although speed Fotoelectric tubes will safely handle hundreds of microamperes for short periods without serious damage. "It is recommended that these tubes be protected against intense illumination or excessive heat, to avoid shortening of life, under light of moderate intensity they will retain their sensitivity for long periods of time. "While the gas-filled Fotoelectric tube is supplied as standard equipment, vacuum Fotoelectric tubes may be obtained to special order. Their sensitivity, however, is only a fraction of that obtained from gasfilled tubes and thus their use is restricted to applications where extreme constancy is of prime importance, such as quantitative measuring, etc. "Particular attention has been given in the design of these tubes to a sturdy anchored construction, insuring noiseless nonmicrophonic operation, free from transient disturbances. "Speed Fotoelectric tubes, without appreciable loss of sensitivity, have an expected life in excess of one year, provided they are not subjected to abuse. They are guaranteed against defects in workmanship or material for a period of six months from date of purchase." NEW BALL-BEARING MOTOR WITH BUILT-IN SPEED REDUCER A new line of fractional-horse-power motors with worm-gear speed reducers has been developed by the Bodine Electric Company, 2264 W. Ohio St., Chicago, 111. These motors are built into the new Bodine Type N-5 frame, which is of three-piece construction with pleasing contour lines. The ventilating ducts and fan have been enlarged and the ratings increased. Gear reductions of 10-1, 20-1, and 40-1 are available, which afford slow shaft speeds of 28, 43, 56, 86, 112, and 172 r.p.m. at standard motor speeds of 1125 and 1725 r.p.m. The speed reducer consists of a separable nitralloy steel worm and an oversize bakelite gear, mounted in a grease tight housing forming an integral part of the end shield of the motor. Double ball bearings absorb the end thrust on the rotor shaft and preserve alignment of the gears after long service. The ball bearings are packed in grease before the motor is shipped and require no further attention for several years. The slow-speed shaft runs in leaded bronze bearings with wool-packed lubrication. These motors are rated from 1/20 to Y% h. p., and they are available in two types : Type NSIR for alternating current, and Type NSHR for direct current. FELT FEET DON'T SCRATCH The T. R Brawley Felt Company, Inc., 279 20th St., Brooklyn, N. Y., manufacture felt feet for four types of chassis, cabinet, loudspeaker, amplifier and other assemblies. Samples will be sent upon request.