US1733063A - Telephone cable - Google Patents

Description

Oct; 22, 1929. H. JORDAN TELEPHONE CABLE Filed Nov. 19, 1.926

\ Inventor HansJordar-a, by MW H i s Attorney Patented Oct. 22, 1929 v UNITED STATES PATENT OFFICE COMPANY, A CORPORATION OF NEW YORK TELEPHONE CABLE Application filed November 19, 1926, Serial No. 149,525, and in Germany December 2, 1925.

With cable installations, which serve for I the transmission of intelligence, it is necessary for economical reasons to combine as large a number of lines in one cable as possible. From this the necessity arises of bringing into one and the same cable, lines which have to satisfy very different requirements and only a relatively small number of lines is provided for line paths on which the highest requirements are placed. Such line paths are, for example, the lines which serve for traffic to the greatest distances and lines which are to make a particularly good transmission of. speech or music possible, even though to relatively short distances. For these purposes, as is well known, cable lines which are equipped with loading coils and amplifiers are used, and it is further well known that the natural frequency obtained is the determining factor for the value of the lines. As is well known the natural or cut ofl frequency (n is determined by the expression MLO in which L, C indicate the kilometric values of the inductance and capacity, ,8 the distance apart of the coils in kilometers.

The difficulty of the problem of obtaining high value properties for special lines in an installation consist in the fact that in the selection of the means for carrying out this purpose, consideration must be given to the fact that by far the greater proportion of the costs of the installation falls on the other lines on whose properties the same high requirements are not placed. For these lines, for example, only a moderately high value of natural frequency, about 17000 is necessary, this value corresponding to an impressed frequency of 2700 cycles per second. If, therefore, the high natural frequency with the high value lines is to be obtained by going over to considerably smaller distances apart of the coils than the other conductors require, then at the same time the main proportion of the costs of the coils, namely, the costs of the coils of all the other lines is excessively increased without any advantage being ob tained. It appears from this that the main difficulty in imparting to the lines preferred properties for particular purposes arises from the fact that in the interest of economy of the whole plant, certain rules must be laid down simultaneously for all lines. To this belongs, in addition to the spacing apart of the coils, also the spacing apart of the amplifying points. Further, the economy of the cable design necessitates that the lines be built into the cable according to definite uniform points of view. For the production of lines with specially high natural frequency in view of the previously mentioned limitations, the procedure previously has been as follows Of a large number of similar lines in the cable, the required small number, which is intended for special purposes, has been brought to the higher natural frequency by loading them less. By this means the specific damping of the line is increased, and therefore a higher number of amplifiers is necessary. This method is only possible in any case when kinds of line are provided in the construction of the cable which require two different amplifier spacings. For example, a kind of line which requires the amplifier spacing of 75 kilometers and a kind of line which requires the amplifier spacing of 150 kilometers. Thus it is possible to load the kind of line to a little extent, which with normal load has an amplifier spacing of 150 kilometers, Thus a correspondingly higher damping will result and the damping must then be brought to the double value so that when the amplifiers at 75 km. distance apart give exactly the required perfect removal of damping. Asis well known this is obtained by reducing the inductance to the fourth part and the natural frequency then increases to double the value which is obtained for the normal loading. When using this auxiliary means for inoreasing the natural frequency, it is necessary owing to the fixed amplifying points to double,

the expenditure for amplifiers.

The subject of the invention is the introduction of a further auxiliary means for increasing the natural frequency of individual lines. It consists in providing in the cable, lndividual lines with specially low capacity.

For reasons of economy cables are always so manufactured that the capacities of all lines almost agree with one another. If in a cable lines are provided which have considerably lower capacity, a lower inductance is also necessary in order again to come to the amount of the damping of an amplifier field. If therefore, for example, the capacity is reduced to one-half in comparison to similar lines of the cable, the inductance will also have to be reduced to one-half in order again tohave the same damping and then at the same time the natural frequency is brought to double value without a diminution of the amplifier s acing being required. The expenditure or the amplifiers is not therefore increased. If, for example, a cable contains lines with 1.4 and 0.9 mm. conductors, be-. tween the lines with 1.4 mm. conductors, lines with 0.9 mm. conductors can be arranged, which take up the same space as the lines with 1.4 mm. conductors. They will then have a considerably lower capacity than the other lines with 0.9 mm. conductors. Accordingly these lines may be loaded lower than the other 0.9 mm. conductors and thus give also a higher natural frequency. At the same time there again results a uniform design of the cable since the cable is only composed of groups with two different diameters.

Referring to the accompanying drawing which illustrates a cable constructed in accordance with my invention, it will be seen that the conductors indicated in the groups 1 are of small diameter. These groups have interposed therebetween conductors 0 larger size arranged in groups 2. All of these conductors are so arranged within their respec- .tive groups, how ver, that they occupy the same amount of pace within the cable.

Lines according to th invention with a considerably lower capacity than corresponds to the normal cable design, can in given cases also be obtained by connecting together into double lines, cores of different pairs or groups, which lie in the same or in different positions of the cable arrangement, the couplings between such connected lines being sys-, tematically removed by a crossing method, as a is known for overhead lines arranged in parallel. Lines with small capacity may ac cordingly also be used for the purpose .of bringing already low loaded lines to a higher natural fre uency.

In genera in a cable, operating ca acities of lines of the same kind (main or qua ruple) w-illfluctuate by at the most 10 per cent. lowering of the capacity inth'e sense of the invention amounts to considerably more than 10 .per cent.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. A multi-line cable adapted feethe electrical transmission of intelligence comprising certain lines which have a materially higher natural frequency than the other lines in the cable, said higher natural frequency lines being constructed to have a materially lower natural capacity than the other lines.

2. A multi-line cable adapted for the electrical transmission of intelligence comprising certain lines which have a materially higher fr uenc than the other lines in the cable, sai big or natural frequency lines being inade up of smaller conductors than the other mes.

3. A multi-line cable adapted for the electrical transmission of intelligence comprising certain lines which have a materially higher fre uency than the other lines in the cable, sai higher natural frequency lines being made up of smaller conductors than the other lines, and having a materially lower natural capacity than the other lines.

4. A multi-line cable adapted for the electrical transmission of intelligence comprising certain lines which have a materially higher frequency than the other lines in the cable, said higher natural frequency lines being made up of smaller conductors than the other '"lines but occupying the same amount of space in the cable as the other lines.

In witness whereof, I have hereunto set my hand this 5th day of November, 1926.

HANS JORDAN.

Images