The Thomas A. Edison Papers Digital Edition

Transcription

MEMORANDA OF AGREEMENT 
The invention by Edison of the curved edge recorder resulted in the formation of a record groove having curved sides and varying in width, depth  and length. The depth of these gouges necessarily bears a definite relation to their width, but the length of each gouge depends entirely upon the extent to which the recording surface has moved during its formation, i.e., upon the surface speed of the recording surface and the rapidity of the vibration. Edison’s suggestion of a spherical reproducer was, and must have been, made with the idea definitely in mind that such a reproducer would accurately track such a record, formed of waves or gouges having curved walls. Thus, in Edison’s United States patent No. 430,278, dated June 17, 1890, he said:-
“I employ also a reproducing point having a convex circular bearing surface that is to say a bearing surface which is the surface of a portion of a sphere. I prefer to employ as a reproducing point a ball or sphere at the end of a suitable stem. This is supported so that it has a slight movement laterally of the record, and when traveling in the circular depressions formed by the recording point it fits such depressions, and even if the lever which carries it is out of line with the record so that the ball does not stand vertically in the record, or if it bears against the curved sides of the depressions, it reproduced the vibrations with the same exactness.”
Any gouge or wave which is at least as long as it is wide can, therefore, obviously be tracked by a spherical reproducer, but if it is less in length than in width a spherical reproducer, but if it is less in length than in width a spherical reproducer will engage with the end walls of such a gouge and be prevented from engaging its bottom, i.e., the reproducer will not track to the full depth.
In this and subsequent analyses, it is assumed that , the diameter of the reproducer is very slightly less than that diameter, so that a gouge or wave which is correspondingly less in length than in width can theoretically be tracked by the reproducer.
The phonograph was originally designed primarily for office use, for dictation purposes etc., the records being formed by the operator in an ordinary conversational tone or sometimes even in a whisper, and being heard through listening tubes. Hence when so used, the amplitude of the sound waves would be relatively slight and their pitch comparatively low, and in consequence the record would not be characterized by very deep gouges. Even if the surface speed of the record were comparatively low, yet the limited amplitude and low pitch of vibration of the diaphragm would not result in the formation of gouges of less length and width.
Thus, referring to the attached drawings, the numerical 1 represents in cross-section an ordinary spherical reproducer having a diameter of about .75 mm (.03 inch) 2 portion of a cylindrical recording surface, and 3 a single wave or depression which the reproducer is tracking. The dotted lies 4, 4 represent the maximum width allowed on the recording surface for the formation of the record without overlapping on the adjacent waves or depressions at either side. The standard phonographs are made with a thread of .25 mm (.01 inch), so that the width of the path between the lines 4,4 is only .25 m. The wave or depression  3, therefore, has a width of only .125 mm  (.005 each), and a corresponding length, and can, therefore, be accurately tracked by the spheroid reproducer. Obviously the width of the wave or depression 3 depends entirely upon the amplitude of the vibration, or in other words, upon the intensity of the original sound, but its length depends upon the speed at which the recording surface is moving, as well as upon the pitch or rapidity of the vibration.
Since, as stated, the phonograph was originally designed for dictation purposes , and hence for the recording of comparatively low sounds, the surface speed of the record could be kept relatively low, to thereby permit the recording of a greater amount of matter on the recording surface. For this reason, in the original “Instructions for Using the Edison Phonograph, Style “M”,” which will be found printed in full in a magazine called “Phonogram”” (published by The National Phonograph Pub. Co., L’d., World Building, New York, copyrighted 1891 by V.H. McRae), Vol. II, Nos. 8—9, page 198, it was stated that:--
“The speed of the main shaft for dictating should not exceed seventy or eighty revolutions per minute, at which speed it will take about 4 ½ to five minutes to cover the entire surface.”
Although the original phonograph was designed principally for dictation purposes, the making of musical records was still contemplated, but it yet was the intention that such records should be heard through the listening tubes. Now if, in the making of musical records on the original phonograph, care was taken not to make them too loud, so that the maximum amplitude of vibration would not result in the making of gouges or waves wider than is shown in figure 1m and if the pitch or rapidity of the vibration was not too greatly increased, the shaft speed of seventy or eighty revolutions per minute above referred to could be used in the making of musical records, making of musical records, and such records, if made, could be just as accurately tracked as could the original conversation or dictation records. In the making of musical records, however, it would be almost certain that many of the vibrations would be of considerable amplitude and of great rapidity due to high pitch, and, therefore, if the surface speed of the record were not increased, the waves or depressions resulting from such vibrations would be comparatively wide and deep, while at the same time their length would not be increased.
Thus, in figure 2, the gouge or wave 5 is shown as occupying the entire width between the lines 4, 4 and hence it is of a maximum depth. A plan of such a gouge is shown in figure 2a, illustrating it as having only the same length as the gouge 3, since it is assumed to be formed at the same surface speed. In figure 2b is shown a cross-section of this gouge or wave, from which it is clearly apparent that the reproducer 1 cannot possibly accurately track it, but would in fact, engage only its front and rear edges. Since the gouges or waves which are shown in figures  1 and 2 are of the same length but of varying depth, it will be obvious that they are representative of the same pitch. If, in addition to being of greater amplitude, the gouge or wave of figure 2 were of a higher pitch, or, in other words, were formed in less time, it would be correspondingly shortened, and hence would be difficult to track. 
In order that gouges of this objectionable kind might not be formed, it was obvious that the speed of the recording surface should be increased, so that the longitudinal dimension of such gouges should be at least equal to their transverse dimension. Thus, referring to figure 3 and 3a, we show a longitudinal and plan view, respectively, of a gouge or wave 6, which has the same width and depth as the gouge or wave 6, which has the same width and depth as the gouge 5 and hence which is graphically representative of a vibration having the same amplitude and pitch, yet which which is of double the length  i. o., formed at twice the surface speed. Such a wave could, therefore, since its length is at least equal to its width.  In consequence, the same “Instructions” from which we have above quoted said:- 
“Observe this carefully when reproducing when reproducing music, as a different speed from at that which the music was recorded will reproduce an entirely different pitch. The standard speed at which musical records are taken should be about 125 revolutions per minute.”
Here, then, we have a distinct recognition of the fact that an increase in speed was desirable in recording and reproducing music, and the only explanation which can be given for these instructions is that  by increasing the speed of the recording surface the formation of record waves or gouges or waves, then as the amplitude of vibration or pitch, or both, are increased, the surface speed should be correspondingly increased, in order that the correct trackable form of such gouges or waves may be preserved.
The development of the phonographic art became practically arrested along the lines of office work, but increased enormously along the line of musical reproduction. The public demand became stronger and stronger for louder records, which could be heard through a horn. The standards of size of record blanks, pitch of record groove, and shaft speed of mandrel, which had been adopted by Edison, made it difficult to depart from them, so that the public demand was attempted to be met by all manufacturers by simply making the records louder. These loud records were characterized by the formation of some gouges which actually overlapped the path of the record groove and which were very deep. Thus, such a wave or depression is shown at 7, in cross-section and plan respectively, figures 4 and 4a, Most, if not all of the gouges thus formed in the loud records were characterized by being shorter in length and width, and in consequence they could not be tracked by a spherical reproducer, which, in fact, was only allowed to enter the depressions to a comparatively limited extent, as shown as shown in figure 4b, illustrating a longitudinal section of the record.
As soon as the public demand such that the expense of new instruments could be afforded, it only became necessary to do with the present loud musical records what had been done originally with the first musical records, namely, to prevent the formation of the objectionable portions of such records, by increasing the speed of the recording surface. When this speed is sufficiently high, the very deep portions of the record, even when representative of sounds of high pitch, will never be less in depth than in width. Thus, in figures 5 and 5a, we show in longitudinal section and plan a wave or gouge 8, which has the same depth as the wave 7 but which is extended longitudinally by reason of an increase in surface speed, so that a spherical reproducer can accurately engage it. In other words, the same difference which existed between the very early musical records and the dictation records for hearing through listening tubes exists at the present time between the standard musical records and the loud “Concert” records, namely, that the latter record in each case is characterized by the formation of deep gouges; and the lengthening out of these gouges so as to make them of such a form that they could be accurately tracked by a spherical reproducer presented the same problem in the first instance as in the second instance and that problem was solved in the same way in both cases, i. o., by increasing the speed of the recording surface relatively to the recorder.
As further explanatory of the accompanying drawings, it will be assumed in each case that the parts are enlarged one hundred times, and that the record cylinder is of the usual diameter of 55.56 mm (2 3/16 inches). In figures 1, 1a, 2, 2a and 2b, if the record cylinder is turned at a shaft speed of 75 revolutions per minute, as specified in the Edison “Instructions” referred to, a gouge or depression of the length shown (.125 mm) will be formed in 1/1716 of a second. If, however, the record is turned at a speed of 125 revolutions per minute, a is also specified in the “Instructions”, for the recording of music, then the gouge or depression having the same depth width and formed in the same time, i. e., of same pitch, would be relatively elongated, and if the shaft speed were doubled to 150 revolutions per minute, the gouge or depression of figure 2a would be extended to the form shown in figure 3a. In figure 4, 4a and 4b, assuming the shaft to be turning at 125 revolutions per minute, resulting in the formation of a very deep but short gouge or wave, the length of time required to form such a gouge or depression is 1/2662 of a second. In order, therefore, that a wave of this depth may be elongated to the form shown in figures 5 and 5a, the surface speed of the record would have to be correspondingly increased. Therefore in order to form a gouge or depression of the size shown in figures 5 and 5a in the same time as in figures 4, 4a and 4b, or, in other words, to produce an elongated record of the same vibration, the record will be turned at 212 revolutions per minute, or to secure the same effect with a shaft speed of 125 revolutions per minute, the diameter of the record should be increased to 138.68 mm (5.46 inches).
These facts have been recognized by Mr. Edison since the inception of the art, and they must be obvious to persons intimately familiar with phonographic work. Possibly, however, the microscopically small character of these records has prevented the usual observer from nothing the peculiarities in the waves of depressions above referred to. If, however, a phonograph record of sounds of high pitch or of great amplitude, or both, taken at relatively low speed, be examined through the microscope, it will be found that many of the waves or depressions, perhaps all of them, will be greater in width than in length, and it will be readily seen that they could not be tracked by a spherical reproducer. If, on the other hand, a record of the same sounds made at a higher surface speed be examined through the microscope, it will be found that the waves or depressions are relatively elongated, so that they can be tracked by such a reproducer. These facts have been so obvious to Mr. Edison and his associates since the very foundation of the art that he has not considered tit necessary to make a public explanation of them, as they were capable of verification by anyone scientifically examining into the question. The references to the “Phonogram” before referred to constitute; therefore, the only direct public record we can find pointing out the desirability of a relatively high speed in the recording and reproduction of music in comparison with that of dictation. 
A public document which, however, has some bearing on the question, is Edison’s U.S. patent No. 610,708, dated September 13, 1898, patented in England September 8, 1891m No. 15,108. In this patent, provision is made for recording either upon a blank 4’ or upon a larger blank 4. The former is shown as being less than one-third the diameter of the latter. The intention was that records made on the smaller blanks could be transported through the mails in the place of letters, while the larger blanks were used for dictation purposes, for transcription by a typewriter. In recording on the larger blanks the record would have to be loud enough  to be heard by a typewriter operator above the noises of an office or commercial establishment. Hence, the records made on the smaller blanks were of low amplitude and pitch, and consequently of short width, while the records made on the larger blanks were of greater amplitude and pitch, and consequently of greater width. With the former records, the formation of waves or gouges which would be of less length than width could be avoided by operating the blanks at a relatively low surface speed, while with the latter records that result could only be obtained by operating the blanks at a higher surface speed. In consequence, with the machine in question, the mailing blanks were, as stated, made of small diameter, and the dictation blanks were made of large diameter, so that the necessary surface speed could be secured in either case by maintaining a constant shaft speed in all cases.
It thus appears from Edison’s work that he has appreciated the necessity of increasing the surface speed of a recording surface when records of considerable amplitude or high pitch are to be made, and that he has suggested that this increase can be effected either by increasing the shaft speed or by increasing the diameter of this record.
We submit, therefore, that a claim covering broadly the operation of a recording surface at a surface speed of at least forty-four meters per minute, or any other abnormally high speed, does not present a patentable invention in the sense of Section I of the German patent law. On the contrary, it seems to us to be merely the exercise of the ordinary skill of a phonograph operator, who, seeking to make a very loud record prevents the formation of waves or gouges which are greater width than length by merely increasing the surface speed of the record surfaces
II.
If there is any explanation of the improved reproduction which is secured by operating the recording surface at a high surface speed, we believe it is that which we have above given, namely, that the increase in the surface speed results in the lengthening  out of the record, so that it can be accurately tracked by the spherical reproducer even when the vibrations which produce it are of great amplitude or high pitch. It is possible, however, that the Columbia Company, in their application for German patent, may have given the same theoretical explanation of the improved result which was given by them in support of the corresponding United States application. That theory may be briefly stated to be:- First, that in recording, the high speed causes the recording surface to be withdrawn always out of line with the heel of the cutting tool, so that a resistance due to that fact will not be imposed on the recorder; and second, that by operating the record at a high speed the velocity of movement of the reproducer will be correspondingly increased.
(a). Of course, there is a minimum speed which effectively used in the making of any kind of records with a cutting or gouging tool, and particularly with a tool which is placed at an angle to the blank. If the speed of the record is too low compared to the vibrations of the cutting tool, there would be danger of the portion of the cutting tool immediately behind its cutting edge engaging with the crest and posterior wall of the gouge, whereby a greater resistance would be imposed upon the cutting tool than that due strictly to the cutting action. This would tend to dampen the vibrations and prevent the record from being cut to a depth graphically representative of the original sound. Edison has, however, very clearly recognized this point in his United States patents numbered 393,967 and 393,968, from the latter of which patents the following quotation is made:-
“It is supposed that a cutting tool would be unsuitable for the recording point and that the heel of the tool would strike the bottom of the groove and prevent the formation of a perfect record, or obliterate the record as made by smoothing or pressing out the indentations more or less; but I have found that the movement of the recording surface is sufficient to keep the heel of the tool clear of the indentations.”
(b) The assumption that a high speed results in more rapid movements of the diaphragm is, of course, without any basis in fact. If a wave or gouge of a certain depth is made at one speed and another wave of the same depth is made at another speed, the reproduction from either gouge or wave will move the diaphragm to exactly the same extend and in exactly the same time as was required to produce the depression, so as to give a reproduction thereof. If the diaphragm did not move responsively to the wave, the reproduction would not correspond to the original sound.
We submit, therefore, that so far as the first hypothesis is concerned, the reeling of the recording device takes place only when the record surface is moving at a very slow speed, and that Edison, in the patents referred to, distinctly recognize the possibility and suggests that in every instance the speed of the recording surface should be high enough to prevent such an operation from taking place; and that so far as the second hypothesis is concerned, it is entirely without foundation.