The motion picture projectionist (Nov 1931-Jan 1933)

November, 1931 Motion Picture Projectionist 37 New P. E. Cell C*OR many years photoelectric cells *■ have been serving an extremely useful mission in experimental and industrial work in controlling the operation of apparatus and equipment, in controlling various processes and in many counting operations. A number of different type cells have been available for experimental, commercial and scientific applications, each type, however, had its own inherent limitations in operating performance or had to be used in conjunction with expensive auxiliary equipment. The discovery of an ideal type of photoelectric cell has been the subject of continual scientific research. To be of the most practical value the cell sought after should combine all the good qualities of existing cells with none of their shortcomings or limitations. Such a cell would be truly ideal but its successful attainment has been a baffling scientific problem. The development of the Weston Photronic Cell, with its amazing performance characteristics and its utter simplicity of design marks a sensational advance and fulfills the need for an ideal type of photoelectric cell. Notwithstanding the superiority of this photronic cell, it is exceptionally low in cost as is also its auxiliary apparatus. Its discovery now places photo cell equipment well within reach of every amateur experimenter. Electronic in its character, the Weston Photronic Cell employs a highly light sensitive disc which transforms light energy directly into electrical energy without the use of any auxiliary voltage whatsoever. Its response to light variations is instantaneous and sufficient current is developed to operate directly Weston relays without the use of auxiliary apparatus or any battery. It delivers about one microampere per footcandle of light intensity. When exposed to direct sunlight the output is approximately 5 milliamperes. The cell resistance varies from about 1,500 ohms for 10 foot-candles light intensity to about 300 ohms for 240 foot-candles intensity. As far as is known, the life of the cell is practically unlimited and a continuous current flow does not harm it in any way. Since it does not contain any liquid nor require vacuum or gas, there is nothing to get out of order as it is not subject to physical or chemical change and it has a constant output. It can be exposed to direct sunlight without deterioration, has no dark current since its energy is derived directly and only from light; no drifting, hence no circuit adjustments are necessary; no fatigue and it is non-microphonic. The photronic cell is enclosed in a handsome moulded black bakelite case fitted at the bottom with two connection prongs which fit into the standard UX radio tube socket. It is rugged in construction and is so simple in design that there is nothing to get out of order. The case is 2*4 inches in diameter and 1 inch in thickness. New Changeover Signal A new product just being introduced by the GoldE Mfg. Co., Chicago, 111., after seven months' operation in many theatres, is the GoldE Three Alarm — a great help for projectionists— a boon to theatre owners and of immediate interest to every movie-goer. The GoldE Three Alarm was developed for a great need. With the GoldE Three Alarm in the upper magazine of all projectors, and with the Standard Release Print, the projectionist is aided in making exact changeovers. Without going into technical discussion— The GoldE Three Alarm affords the projectionist three separate and distinct warnings — each at an exactly predetermined spot and at exactly the right spot for (1) general warnings, (2) start motor, (3) changeover. This is accomplished by a novel mechanical device, simple in installation and simpler in operation. Positions may be set off according to each projector's pickup speed. Micrometers once set need never be varied. Shows run off smoothly because there is never any doubt as to Start Motor Time or Changeover Time. Marking, punching, cutting, scratching of film, is absolutely done away with. The projectionist need never fear that the wink of an eye will lose the motor or changeover cue. The GoldE Three Alarm takes the place of the regular reel end alarm — is easily and quickly installed and is of nominal cost. Novel Advertising Projector A NEW sound-on-film advertising ■*"*■ projector has just been placed on the market by the Auto Cinema Sales Company of New York. The equipment is designed for use with 35 mm. film and is housed in an attractive cabinet which stands ab$ft 5 feet 6 inches high and is approximately 3 feet square. The apparatus comprises RCA Photophone sound equipment and a projector supplied with an endless, frictionless re-winding device, invented in Germany, by means of which continuous projection is secured. So simple is the operation that once the projector is started, it will perform and repeat without interruption and without further attendance. The projector, sound pickup, amplifier, motor and 6 inch loudspeaker forming the outfit operate as a single unit from power supplied from a lamp socket. The picture is projected upon a transparent daylight screen 18 by 22 inches, located "top front" of the cabinet. Among the features claimed for the apparatus, in addition to those al ready mentioned, are: no wear on film, absence of tension eliminating the possibility of film breakage, and maximum advertising return for minimum cost.