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Eighteen
The INTERNATIONAL PHOTOGRAPHER
November, 1929
out. Bone, No. 1,580,112 shows a film sound record in which the record part is of constant density but varying width and the record proper comprises some conducting substance like a metallic ink, instead of the usual photographic silver. The reproduction is carried out by making the entire film with its conducting record one pole of a condenser while a small metal plate right over the surface of the film and past which the film is rolled, forms the other pole. As various parts of the record come opposite the small metal plate, a condenser of various capacities is formed. The changes in capacity act on a vacuum tube amplifier and the record is reproduced. The record part of the film has also been made of an insulating substance and forms the dielectric element of a condenser of two plates, one on each side of the film in about the same manner as above. A very curious way of reproducing ordinary film records is to have the film run past a spark gap. On the other side of the film is a source of ionizing rays like X-Rays, ultra-violet rays or the like. As the film goes by, the band of ionizing rays goes through the film and is altered by the sound record, much like a beam of light. This beam of ionizing rays has the property of changing the sparking potential of a spark gap. The result is that sparks of varying intensity and potential will jump the gap, due to the changes in the ionizing rays. These varying potentials across the spark gap are supposed to operate a telephone receiver. Another equally curious method of reproduction of the same kind of a record is to allow the record to be run between the poles of adjacent electro-magnets. One electromagnet forms part of an oscillating circuit, that is a circuit where alternating currents surge back and forth. The record alters the mutual induction of the two electro-magnets and the sound is reproduced in the second electro-magnet. Since the record is formed of metallic silver, this is possible.
There are several other curious methods of recording and reproducing in which the record body is different than the common ones described above. The French patent 607,156 shows a strip of paper rolled between two wires. Talking currents cause sparks of various strengths to jump through the paper strip, from one wire to the other. The record is formed of a series of different sized holes burned in the paper. To reproduce, the paper is rolled between two wires which press on each side of the paper. When there is a hole in the paper, the wires touch and a contact through a
Merritt B. Gerstad
SAYS
"This is just the form of investment that I have always wanted."
ALBERT ESCHNER
PACIFIC COAST BX»DG.-L,OAN ASSN.
310 Taft Building, Hollywood, Calif. GRanite 1721
telephone receiver is established. The patent to Reynolds No. 287,166 shows a record cut on the sharp edge of a triangularly or rectangularly shaped wire. The reproduction is affected by having a finger ride on the edge and operate a microphone. Patent 1,350,246 shows a thread used in about the same manner, the thread being compressed variably. Probably the two most extraordinary methods of recording and reproducing sound are shown by Fuller 934,600 and British patent 145,804. Both use wires. Fuller passes his wire through an electroplating solution. The wire is protected from the solution by two insulated tubes except at one point. Talking currents are caused to actuate a mirror which changes the resistance of a selenium cell in accordance with sound waves. The direct but varying currents through the selenium cell are led to the electroplating cell. The wire forms one pole and a metal electrode forms another pole. A variable deposit of iron is produced on the wire which is supposed to correspond to the original sound waves. The wire record, as finished, has an irregular cylindrical surface of a varying diameter. To reproduce this record, it is passed between the poles of an electromagnet. The British patent uses even a more remarkable method of obtaining a wire record which probably resembles Fuller's record in shape. In the British patent, the wire is drawn through two separated and insulated chambers filled with a liquid low melting metal. Between the two chambers a draw plate exerts a tension on the wire. A current of electricity goes from one metal bath to the other via the wire and heats the wire to incandescence at the draw plate. Where the wire comes out from the top metal bath, a roller guides the wire to the receiving spool. This roller is acoustically vibrated and tends to exert a varying tension on the wire. The wire being mechanically weakest at the draw plate where it is incandescent, yields there and is elongated to varying degrees depending upon the position of the vibrating roller. The wire is cooled in the metal bath right after passing the draw plate so that the yielding of the wire is localized at the draw plate. The methods of reproduction of this extraordinarily made record are fit companions for the recording method. In one method, the wire is drawn through the same apparatus. The differences in electrical resistance of the wire between the two liquid metal baths varies a current which actuates a telephone receiver. Another method of reproduction is purely mechanical but is interesting. The wire is drawn through a draw plate — the inventor appears to have a decided penchant for draw plates — but this draw plate is made of ebonite or some substance having a slight degree of elasticity. This draw plate serves as a flexible valve for a container of compressed air. As the wire is drawn through, the varying diameters cause a varying amount of leakage of the compressed air and thus the sound is supposed to be reproduced. Whatever else the patent lacks, there is no doubt but that there is considerable novelty in it.
Some Practical Applications Apparatus for recording and reproducing sound are used for more than
merely making records and reproducing them for pleasure. Thus many patents show a recording and reproducing system in conjunction with the telephone set. In case a person is away from his office, the machine will answer the telephone and merely state that the person is out and ask that the caller state his message so that the machine will record. Later when the person comes in again, he can reproduce the recorded message. The telegraphone is peculiarly fitted for such work, inasmuch as both the recording and reproducing operations are very simply carried out and under conditions that are not unusual. There is also a patent in which a record is made of the hours and minutes of the day and a subscriber calling the telephone exchange and asking for correct time, will be switched to this machine which reproduces the correct time for that instant. In certain secret systems for the transmission of speech over telephone systems or by radio, the telegraphone is used to record part of a syllable and reproduce it an instant later while some other syllable is being enunciated, thus making the message unintelligible without special apparatus. Sound recording systems have been developed for the purpose of orienting the location of some sound source. Thus it may be desirable to locate where a certain gun is being fired. Several transmitters are scattered over an area, each transmitter feeding into a sound recorder. By noting the difference in time of arrival of identical sounds at the various transmitters by means of the sound records or graphs, the source of the firing may be determined with more or less accuracy. There is also a curious device disclosed by patent No. 766,225. It is like a typewriter, having keys, each keycontrolling a sound reproducer which will reproduce some particular speech unit. By pressing one key after another, the machine may be made to say various things.
Within the last few years, sound recording and reproduction has turned a very sharp corner in the direction toward the better. Radio has been a great help in this art and the advance of one will bring the other to a higher plane. There are no revolutionary improvements in recording or reproducing wax records in sight but there is a healthy activity which bodes very well for that branch of the art. A tremendous amount of work is being done in film recording and reproducing in connection with talking movies and while the practical stage of the art needs considerable improvement, these improvements will eventually come, and come soon.
John Arnold says
"I am looking forward to the time when this money that I am now 'salting away' will pay me a good living income."
ALBERT ESCHNER
PACIFIC COAST BLDG.-LOAN ASSN.
310 Taft Building, Hollvwood, Calif. GRanite 1721