US1063396A - Means for increasing the speed of transmission of signals over telegraph and cable lines. - Google Patents

Description

G. SEIBT.

MEANS FOR INCREASING THE SPEED OF TRANSMISSION OF SIGNALS OVER TELEGRAPH AND CABLE LINES.

APPLICATION FILED OUT. 12, 1909.

1 0 3 396 Patented June 3, 1913.

F791. Z V 6 5 i6 2 I E 15' 1. i I I f/ H H .H J

1 9 i 1 i i I H 25' wmm s a! v Q UNITED STA as rrnir ononen SEIBT, or new YORK, n. Y.

MEANS FOR INCREASING THE SPEED OF TRANSMISSION OF SIGNALS OVER. TELEGRAPH AND CABLE LINES.

Specification of Letters Patent.

Patented June 3, its.

Application filed October 12, 1909. Serial No. 522,225.

To all whom it may concern.-

Be it known that I, GEORGE SEIB'r, a subject of the Emperor of Germany, residing in the city, county, and State of New York, have made a certain new and useful Invention in Means for Increasing the Speed of Transmission of Signals Over Telegraph and Cable Lines, specification.

This invention relates to means for increasing the speed of transmission of mes sages or signals over deep sea, long distance, or other cables or conductors, telegraphically or otherwise. i

The invention consists substantially in the construction and arrangement hereinafter set forth, as illustrated in the accompanying drawings and finally pointed out in the appended claims.

It is a well-known fact that the speed of transmission of telegraphic messages or signals over longrcables or very long land lines depends more upon the quality of the cable or conductor itself than upon the receiving or transmitting apparatus or instrument employed. In the practical operation of cable and long land telegraphic lines it is a common practice to consider as a measuring unit for the retardation of signals or messages in transmission, the product of the capacity and resistance of the conductor. As bot-h quantities are proportional to the length of the conductor, the speed oftransmission decreases according to the square of the length of the conductor. Consequently, a limit is reached in the length of conductors beyond which it is diflicult to maintain a profitable operation of the line for the transmission of messages or signals. By reason of this difiiculty, it is common practice to employ relay stations at some convenient point along the cable or line in which the messages or signals transmitted are received from one or the other transmitof which the following is atice in some instances to employ automatic relays for receiving at such intermediate or relay station the transmitted messages or signals and automatically to repeat or relay the same on toward the other end of the line. The use of a relay station, whether automatic or otherwise, is objectionablefor the reason that it involves additional operating cost and expense. Moreover, it is evident that such relays cannot always be conveniently used, as, for instance, in deep sea cables, available relay stations are not obtainable. Moreover, in receiving and relaying messages, the danger of error in the transmit-ted message is multiplied.

It is among the special urposes of the present invention to provid d means whereby the speed of transmission of 'messages may be greatly increased without the necessity of establishing or employing automatic or other relay stations or apparatus, without the necessity of employing extra labor or extra operating expense, and to avoid the danger, annoyance and objection of errors in transmission due to the double reception and transmission of the messages.

In arriving at the discovery embodying the present invention, I have been influenced by the following theoretical considerationsi The difl'erential equations for calculating the potential and current in telegraphic conductors, the self-induction of which may be neglected, but the leakage from which must not be neglected, are as follows:

wherein C is capacity,"W is resistance, g the leakage per unit of length, V is potent al, I is current and w the location of the point in the length of the cable at which the calculation is to be made. If the conductor at the receiving end is connected to ground and at the other end is connected to one pole of a battery, the second pole of the battery being connected to ground, the solution for equation 1 is the following, by integration: a n: 00 Jae: Vact=V +e 2 Ae sin in which n runs through all non-fractional members. If, however, the connection of the conductor with the battery is broken, as, for instance, by raising the key, the solution from the moment of opening the circuit of the conductor is as follows:

m n t it m 00 z wo tion 1, indicates a damping four-fold that of the first member, and the second member in the solution of equation 2, indicates a damping of nine-fold the first member thereof. Therefore, it will be suflicient for the theoretical computation to consider only the first members of the equations, as all of the subsequent members thereof may be neg- 1 lected. The damping coeflicients of the solutions of the equations, that is, the factors which determine the damping rate, may be expressed as follows:

=2 i fiz wo and 9 6! f. 2 Jaz wo J During the transmission of messages or signals over the conductor, said conductor,

at the transmitting end, is being repeatedly opened and closed or grounded through the battery; that is, during the operation of transmission of the message, the manipulation of the key first grounds the conductor through the battery and then opens the con-' ductor, and this operation 1s successively repeated, while, at the receiving end, the receiving apparatus offers a resistance to the flow of current through the conductor, which resistance slightly delays the outlet of the current to the ground at the receiving end of the line and, consequently, in our theoretical calculations, we will have to take into consideration a damping eifect of medium roeaaee strength and which can be estimated to be represented by the following equation:

where Zis the length of the conductor. From a consideration of these theoretical calculations it will be seen that an increased leakage is desirable in order to attain the best theoretical results. It is not desirable, however, to decrease the resistance of the insulating material in order to secure the desired increase of leakage, as to do so would result in increasing the danger of short circuits. With deep sea cables in which gutta percha is used as the insulating material, the first member of the above stated equations and their solutions may be'neglected as compared with the second members of said solutions. In other words, it is desirable in the use of deep sea cables to increase the leakage without decreasing the insulation in order to avoid the danger of short circuits. Therefore, in accordance with the principles of my present invention, I propose to attain these desirable results, and, as one form of means for accomplishing the desired object, I propose to employ'what may be termed an artificial leakage, as, for instance, by inserting resistances between the conductor and the ground or return circuit, and this forms an important part of my present invention. 1 shall designate this characteristic of my invention as an artificial leakage, but I desire it to be understood that this term is used in a broad and generic sense, and that one specific form or embodiment thereof is the insertion of a suitable resistance in the long distance line or cable or a series of such resistances at various points throughout the length of the cable or line.

In the drawing I have indicated various arrangements for carrying my invention into practical operation, as illustrative of the method set forth.

Figure 1 designates diagrammatically a long distance line or cable for the transmission of messages or signals, and showing at a point intermediate the length of the cable.

the application of an artificial leakage embodying the principles of my invention. Fig. 2 is a similar view showing the application of a series of artificial resistances connected to the cable or line at uniform distances apart. Fig. 3 is a similar view showing the application of artificial leakages to the cable at various points throughout its length, the distance apart of the artificial leakages increasing from about the midlength of the cable or line toward the ends thereof. Fig. 4 is an enlarged broken view in section of a cable showing the application of an artificial leakage embodying the principles of my invention. Fig. 5 is a view similar to Fig. 4, showing a modified coni goeseee struction and connection of the artificial leakage.

In Fig. 1 the cable A is grounded at one end as B, which may be considered, for example, as the receiving end of the cable, the grounding being effected in the ordinary manner through the receiving apparatus. A source of current C is placed in the circuit of the cable at its other end which, for example, may be considered the transmitting end, D'representing the key, the source of current C being grounded as at E. The artificial leakage is indicated at G and may be represented diagrammatically as a resistance connected to the cable at, say, for instance, a point midway its length and grounded or connected to the return as at H. If this artificial leakage G is small'in comparison to the resistance of the cable or conductor'A, the insertion of this artificial leakage orresistance G at a point at the mid-length of the conductorwill have the same efiect upon the damping of the conductor as if the length of the conductor were decreased by one-half. By an examination of the equation last above given, which I have designated as equation 3, it will be seen that, with the length of the cable reduced by onehalf, the damping is increased four-fold. If the resistance or artificial leakage is increased the damping is naturally increased correspondingly. In case the diverting resistance or artificial leakage is distributed throughout the length of the cable at not too lengthy intervals apart and the resistances of the diverting leakages are large in comparison to the resistances of the sections of the cable between them, the cable should then act similarly to a defective insulation and consequently the equation 3 may be used for calculating the damping effect.

In Fig. 2 I have shown a plurality of diverting resistances or artificial leakages G connected to a cable A at equal distances apart throughout the length of the cable. In this arrangement, however, it is usual to employ equal diverting resistances or artificial leakages. I do not desirefhowever, to be limited or restricted in this respect, since the same results may be attained by employing diverting resistances or artificial leakages of difi'erent degrees but spaced at unequal distances apart throughout the length of the cable or line and preferably the diverting resistances are placed closer together as the mid-length of the cable or conductor is approached. A specific example with figures will show to what a high degree the damping effect can be increased by employing the diverting resistances or artificial leakages.

the capacity of the conductor per sea mile is 0.32 micro-farad, and the resistance of the conductor 10 ohms. With an efficient insu- Suppose the length of the cable is 1,000 sea miles; and suppose lation for the conductor it will be found,

according to equation 3, above given, that am: 1.5a

g= 10* then 1. An aeroplane including a-gliding strucand the entire damping is, as will be'seen, thereby increased to 4.67 that'is, the damping is increased three-fold.

As above indicated, it is preferable to insert the diverting resistances at irregular distances apart, such distances apart decreasing toward the mid-length of the cable. The reason for this arrangement lies in the fact that the dissipation of the current at the ends of the cable where the conductor is grounded is large anyway, and therefore there is less need for the diverting resistance than atthe' mid-length of the cable where there is no natural grounding. The same result may-be obtained by equally spacing the diverting resistances or artificial leakages, as indicated in Fig. 2, but varying the amounts of such diverting resistances. A merely cursory consideration of the foregoing mightlead to the view that with any considerable increase'in the damping of the cable the current for signaling or messagetransmitting purposes would be reduced and the inertia ofthe receiving apparatus would assert itself and not permit of any increase in the speed of transmission. According to experiments which I have made, I have found that the ordinary siphon such as are commonly employed in cable recorders,

telegraph oflices to receive the transmitted messages, have damping coefficients at 15 to' 20, so that the mechanical inertia of such devices can be practicallyneglected in comparison wi h the electrical inertia of the cable. One consequence of the insert-ion of the diverting resistance or artificial leakage which at first glance would seem to make its use a matter of questionable value, may be here pointed out. It would seem that by the use of such artificial leakages or diverting resistances considerable loss of current and strength is entailed, so that the current arriving at the receivin end of the cable is considerably weakene If, however, the

artificial leakages or diverting resistances are-inserted in the cable and distributed in short intervals, the departing current for any signal, that is, departing from the transmitting end, to the arriving current, that is, the current at the receiving end, will be equal, after the full load of the cable has been attained, to

m= /Wg Applying this last given equation to the speclfic example above noted, we find that With the three-fold damping of the cable the tendency of the current is to approach when - its maximum very quickly, that is, the current, after it has reached the stage where it is governed by the ohmic law or its maximum value, has a tendency to try to quickly adjust itself, and in practical operation'the time within which this maximum is reached is very short, the rate of flow of the current through the receiving apparatus with the artificial leakage being considerably more ratus should be used, such, for instance, as

the optical printer set forth in my pending application Serial No. 487557 filed April 2, 1900, in which the deflections of a wire ,galvanometer are microscopically enlarged and photographically registered upon a strip of sensitive paper. Obviously, other forms of sensitive receiving apparatus or devices'might be used. ll do not desire, therefore, in the broadest scope of my invention as defined in the claims, to be limited or restricted in respect to the particular structure or arrangement of the recording apparatus employed. I have found, however, the optical printer above mentioned most efficient, and comparative tests with an optical printer as embodied in my said application, employing a gold thread of 0.0035. millimeters cros's-section and 10 centimeters length arranged in a magnetic field of 1,000 lines of force per square centimeter and a microscope of two-hundredfold magnifying power and an ordinary siphon recorder such as is employed for commercial'cable telegraphy, shows the sensibility. of the optical printer to be sixty times higher than that of the siphon recorder with the tension of the threads employed in the apparatus so applying the regulated that the damping coefiicients of the instrument were in each case 25. With the optical printer however, the sensitiveness can be still further increased by increasing the strength of the magnetic field in which the old thread operates and consequently suc apparatus answers to a very high degree the purpose and requirements to be met by a receiving apparatus in commercial cable use with strong artificial leakage or diverting resistance. In other words, any loss of current strength due to the use of the diverting resistance may be more than compensated by increasing the sensitiveness of the receiving apparatus or by employing apparatus of increased sensitiveness. Consequently, any desired type of construction or arrangement of receiving apparatus may be employed, so long as it ossesses the required sensibility and sel 'damping, and still attain the benefits and advantages of the increased rate of transmission contemplated by the practice of my invention.

With referenceto the location of the diverting resistances in accordance with my invention, it may be pointed out that with deep sea cables having stations located in the ocean, such resistances may be inserted at "such stations. In many cases the insertion at one point only of a diverting resistance or artificial leakage is sufiicient to greatly improve and simplify the service, and consequently, by the use of the method of my invention, the relay apparatus at such island station, for instance, as m the case of the trans-Atlantic cable station on the Azores, may be dispensed with by merely inserting at that point the desired or required diverting resistance, thereby avoiding the necessity for maintaining such relay station and its operation of receiving and retrans" mitting the received messages.' Of course the insertion of the diverting resistance in long. distance conductors over land does not ofier these difficulties, since they may be inserted conveniently at any desired point. With cables which do not touch the land at all or at insuflicient points, it is necessary to insert the diverting resistance into the interior of the cable itself. In such case the diverting resist-ance may be applied to the' cable in such manner as not to enlarge the cross-sectional area of the cable itself or at least to a very small extent only. sistance may be easily inserted in the proximity of'the core of the cable or may be placed upon the core.

In Figs. 4 and 5 I have shown methods of diverting resistance to the cable.

Referring particularly to Fig. 4:, reference sign 6 designates the core of the cable, 7 its insulation and 8 the inclosing armor. At a convenient point the core of the cable is reduced in thickness or cross-sectional The reoeaeee area, as indicated at 9. Upon this reduced portion of the core coils indicated at 10 may be placed. A convenient arrangement is to employ spools of insulating material such for instance as micanite and upon each spool a coil of suitable resistance material such, for instance, as constantan wire, is wound, so that the diameter of the coil Wound upon the spool will be approximately the same as the diameter of the unreduced portion of the cable core. I have found that a serviceable construction may be formed of the following proportions: Suppose the thickness of the core of the cable conductor is 5 millimeters and it is reduced at the desired point to about, say,.3 millimeters. A. number of the micanite spools of say 0.25 millimeters of Wall thickness are then strung upon the reduced portion of the cable core and then constantan wire is Wound upon the spools, such wire being attached at one end to the cable-core and wound in series upon the spools until the thickness at the point of reduced portion of the cable is again o'millimeters. If the contantan wire is of 0.05

millimeters thickness the total length of the spools employed to attain the resistance of 10,000 ohms will be about 3.5 centimeters. As above indicated, one end of the resistance wire is connected to the core of the cable. The other should be led through the insulation surrounding the core of the cable and attached to the armor. It is advisable to lead the end of the resistance wire through I the insulation at an angle as indicated at 12 Fig. 4:, thereby avoidingthe danger of in uring the insulation. If desired, and in order to increase the mechanical strength of the core at a weakened point of the cable, the copper wires of the core may be replaced by steel wires soldered outside of the copper coil. Of course it will be obvious that where a return wire is employed the resistanceshould be connected to such return wire instead of being connected to the ground.

In Fig. 5 Ihave shown another formof connection of the resistance which might well answer the purpose. In .this arrangement the cable A is led through an iron box 13, a portion 14 of the cable core beingexposed within said box.- A diverting resistance 15 of the desired strength isthen connected at one end to the exposed portion 14 of. the core and at the other end to the iron box or casing 13. .-The interior of the iron box or casing is then" filled with a suitable .-i nsu1atingcomp0l1nd indicated at 16. In I this arrangement it is important to emciently solder or otherwise secure the ends of the casing upon the cable so as to hermetically seal the ends of the casing.

In order to calculate the resistance to b inserted in accordance with the principles of my invention, and in order to determine ac-' curately the proper spacing apart of the resistance where a plurality are employed for any given case, it may be difiicult to make the calculations upon the cables themselves as they may be in service and inaccessible. I therefore propose to make the desired calculations upon an artificial cable, that is, a cable loaded to approximately the capacity, length and resistance of the particular cable to be equipped, thereby enabling me to ascertain the correct resistance to .be employed for that particular cable and the correct distances apart to place the resistances.

Having now set forth the object and nature of my invention and a form of means for carrying the same into practical operation, what I claim as new and useful and of my own invention, and desire to secure by Letters-Patent is.

1. As a means for increasing the speed of transmission of telegraphic signals over a conductor, artificial leakages connected to the conductor at'points 'in the length thereof of increasing distances apart from the midpoint of the length of such conductor toward the ends thereof.

2. In a means for increasing the speed of transmission of telegraphic signals over a conductor, the combination with the conductor having a portion of its core reduced in diameter and a resistance coil connected-to the reduced portion of the conductor core and to ground or return.

-3. In a means for increasing the speed of transmission of telegraphic signals over a conductor, the combination with a conductor having a core reduced in size for a portion of its length, and insulating spools carryin resistance coils connected in series, one en of the resistance coils being connected to the reduced portion of the cable core, and the other end connected to ground or return.

In testimony whereof Ihave hereunto setmy hand in the presence of the subscribing witnesses, onthis 11th day of October A. D., 1909. v

i GEORGE SEIBT.

, Witnesses:

S. E. DARBY, G. C. HUNIQKE.

Images