The international photographer (Jan-Dec 1936)

January, 1936 7 /; INTERNATIONAL P H 0 TOGRA P H E R Seven S «3SS£5«S«S SHa SBftna^ -;-:„. as «s as jk- arws ara Torsional viurii of scanner showjng suspension of scanning frame. television on several vital points: "First, it must be fool-proof; that is, it must not exceed the present simplicity of operation of the standard radio set. "Second, it must have clear definition and be capable of being witnessed by at least a roomful of people, or on a par with the latest 16 mm. film projection. "Third, it must be within reach of the average pocketbook, and with no more upkeep cost than the present set." Having outlined these requirements, Doctor De Forest then drew attention tc the actual machine which was to qualify under these rather unmistakable counts, and prefaced his explanation by highly complimenting the inventor who is responsible for this ephocal invention. This is William H. Priess, of New York City, who is a brilliant scientist and well known in the U. S. Patent Office for his important inventions. He is also renowned in the electrical fraternity for his valued contributions and, if Dr. De Forest is correct in his estimate, Mr. Priess will, with the public introduction of his invention, be added to the world's immortals. The scanning unit is completely disarming in its simplicity of construction and one immediately recognizes in it these earmarks of all genuine solutions, which invariably invoke the remark: "Why didn't someone thing of that before?" Doctor De Forest stated: "It makes use of the torsional properties of a steel wire, somewhat after the old and well known principle of the galvanometer, except in this case two wires of unequal length are employed and crossed at right angles." He indicated where a small lA by Va inch metal mirror was welded at the center of the shorter wire and had a small iron vane or arm projecting from the back side of the mirror and extending into an air-gap between the poles of an electro magnet. The Doctor interrupted the inspection at this point to explain what occurs here in practical operation. "This electro magnet," he explained, "produces an alternating magnet field of 1500 cycles per second, which moves this arm to and fro as many times, producing an oscillating motion to the mirror around the axis of the wire. This alternate rocking of the mirror is sufficient to completely sweep a bright spot of reflected light upon a screen measuring from two to six feet in an optional size area. The wire, of course, only sweeps the mirrored spot on the horizontal, or in other words is to form just the lines." The Doctor then continued his explanation of each part by pointing out that this wire upon which the mirror and vane are welded, is anchored at each extremity upon an oval shaped channel framework of aluminum, measuring about two by four inches in area, and one-half inch thick, and weighing but a few ounces. This wire is aligned in the direction of the length of the framework and the framework, in turn, is suspended at its exact mid-section by a wire extending out at ach side, not unlike a pair of oars in a small boat. These wires are fastened at their outer extremity at the top of a pair of upright metal standards mounted upon the final base. This arrangement of mounting produces a balanced unit or framework which may be rocked like a walking beam or like a simple see-saw. Doctor De Forest paused here to explain that when the device is in operation this framework assembly is alternately rocked by the larger electro-magnet underneath at the rate of 24 vibrations per second, giving a verticle displacement to the reflected spot after each horizontal sweep. He laid particular stress upon the fact that neither (Turn to Page 27) Please mention The International Photographer when corresponding with advertisers.