US1654890A - Loading system - Google Patents

Description

" Jan. 3; 1928. 1,654,890

R. C. MATHES LOADING SYSTEM Filed Oct. 19. 1922 lnvenfar; I

Robe/*7 GMaf/zes Affq.

Patented Jan. 3,

UNITED ATES PAr E T-oFFic ROBERT c. MATHES, or NEW YORK, 'N.V,Y., ASSIGNOR To w'nsrnnnnLnormccon- PANY, INCORPORATED, F NEWVYORK, N. Y., A com-cannon ornnw'yonx, I

- LOADING SYSTEM.

' 'Applica'tion filed October'19, 1922.: Serial No. 595,519.

' This invention relates togloading systems;

and particularly to, a loading system for multiplex signaling circuits. r

The loading of a transmission line according to the Pupin system'of loadinglto improve the characteristics of the line for one range of frequencies may sometimes fail to graph frequencies it probably would have 1 an objectionable attenuation at voice frequencies. 7

An object of this invention is to provide meansfor loading. a line which will be equally effective for a plurality of bands or ranges oflfrequency in improving the trans mission and impedance characteristic of the line, such as, for example, could be employed in a line containing telegraph, telephone and carrieror ultra-audiov currents.

This invention in one form comprises of loading into the line, eachof which functions for a particular range of frequencies frequencies below those'of importance in speech, for'eirample, low frequency telegraph "signals, this invention providesa plurality'of' without introducing any. appreciable distortion in the transmission of'currents not designed to be loaded by the loading arrangement in question.

currents may beQindependently loaded for two types of signals by inserting theusual spaced loading coilsfor loading the line for telephone currents and at other points in the line inserting loading coils' particularly designed to improve the transmission for telegraph frequencies. In order to pr'event distortion of theftelephone currents due to the presence of the inductances which load the circuit for the telegraph currents, a'condenser maybe shunted acrossthe terminals of each telegraph loading inductance of such a value that the inductance and the con denser form an anti-resonant circuit for a frequency intermediate the important telegraph frequency band and the important telephone frequencyband; With such an armeans for introducing independent systems Thus, a signaling line containing both telephone and telegraph ra'ngement v the anti-resonant circuit would be substantially a'capacity reactance for the telephone frequencies, while the anti-reed nant circuit would present a substantially inductive reactance for the telegraph fre- I quencies. 'This capacity need not be connected directly in shunt to the terminals of the loadingv coil but may, for example, be included in series with a winding of a transformer-which is capable of repeating the telephone currents, the telegraph loading coil being connected between the pri-'' mary and secondary windings of said coil.

Referring tothe drawings, Fig. 1 represents this invention embodied in a combined telephone and telegraph signaling system; v o

Fig. 2 is a modification ofth'e multiplex system of Fig. 1 in which the signaling line is 'divided' into a plurality of sections by transforinerswhich' repeat only telephone currents. 4

In Fig. 1, a signaling line 7 is disclosed on which, it is-to be understood, are impressed both telephone frequency signals and signals of another frequency range, such'as low frequency telegraph signals. A plurality -of loading coils 8 are uniformly distributed along the line 7 whereby the line is loaded for telephone currents according to the 'Pupmsystem. Y

In order to simultaneously loadlin'e for to beloaded It has beenfound that'no' detrimental effect is produced by having the low frequency telegraph current pass through the various speech frequency-loading coils since they do not possess sufiicient induc tance to cause'appreciable distorting effects. The reverse, however, is true with respect to the passage of speech frequency currents through'the telegraph loading coils 9, since co1ls9 will be'of sufiicient inductance to se-- rioiisly distort and attenuate the speech frequency signals, thereby rendering ineffective the beneficial results obtained from the insertion of the telephone; loading coils 8. In

order'to prevent this distorting efiect, the

quency of 5500 cycles.

9 are to load the line for telegraph currents of frequenciesv less than l cycles, and load ing coils 8 are to load-Ythc line for: speech frequencies. of 300 cycles or greater. f'lhe most desirable frequencies to choose in any particular case for this anti-resonant condition dependsnpon the telegraph and telephone requirements and upon the type of signaling'system employed. Suppose that for an extra light loadedtelephone cable wvith a capacity of .065 m. f. per mile we space'the coils 9 fifty miles apart and give them an inductance of about 40 henrys. The telephone coils may have values of. .044.- henrys-spaced about 6000 feet apart. Above about 100 cycles the system would function asan ordinary extra light loaded cable of 700 ohms impedance and with a cut-off fre- In the lower frequency range it will act like a loaded line of about 3000 ohms impedance and a cut-off frequency of 30 cycles, assuming, that the -anti-resonant frequency is from 10 to 00 7 cycles.

' Fig. 2 shows an alternative arrangement; in which loading coils are distributed along the line- 16, as in Fig.1, for loading the line 16 for speech frequencycurrents. At every point where .it is desired to load line 16 for low frequency telegraph signals a repeating coil 18 is inserted each compris' ing a primary and a secondary winding. Shunted around the terminals of these wind ings are the telegraph frequency loadii'ig coils 20so that :lortelegraph frequencies the various sections of line 16 are direetly connected. while for speech frequencics'they are inductively connected by the repeating coils l8. \Vith this arrangement. the speech frequenc currents areLnot required to traverse the telegraph frequency loading coils and y the telegraph frequency currents may be pre- I vented from. passing through the windings of the repeating coils 18 by including a condenser 22 in circuit with each winding of each repeating coil between the points of connection of the telegraph loading coils.

.-;plicable .to either 'metallic telegraph on These condensers as in Fig.1 are effectively in shunt to the'telegraph loading coils.

It is to be understood, of course, that the system of loading, describedabove, is apgrounded telegraph systems, since the'signal-v 1 g n in Q' Fisnw .1 and 2 is sh w to be balanced telegraph loading coils being included in each side. It is also to be understood that tlns invention is applicable'to the loading of a plurality of frequency bands employed in signals of any desired character and the invention is not limited to the particular combination shown of a line loaded for telephone conversations and telegraph signals For example. the systememployed in Fig. 1, without modification, exceptas to.

changes .in the values of the capacities and inductances. and the relative distances between loading points could be employed for simultaneously loading the line for both carrier current signals of a frequency of 10,000 cycles for, example, and speech frequency currents. V

The blocks marked X, in shunt to each of the windings of the transformers of Fi -2,

are for the purpose of indicating at what point in the circuit it may be found preferable to introduce nnpedance compensators to overcome any impedance irregularities 1ntroduced in the line at the lower range of the speech frequencies due to thepresenceof the telegraph frequency loadlng ce ls. These compensators may range of frequencies, and a condenser connected effectively in shunt to each of said loading coils andhaving a value sufficient to make said condenser substantially opaque tothc frequencies to be loadedby said coils each suchparallel combinationof condenser be of any desired type, i such; as the networks described and disclosed in the Hoyt U. S. PatentNo. 1,333,111Qot and loading coilv bein'g connccted in series with said means for loading saidline' for said one range of frequencies.

2'. ln combination a line, Y distributed along said line for loading said line fol-one Tango of frequencies, other load ing coils distributed along said; line at greater intervals thansaid first coils for loading said line for a lower range of frequencies. and a, condenser connected effectively in shunt to each of said secondmentioncd coils and having a value sufficient to make said condensers substantially opaque to the frequencies to be loaded by said second coils, each such parallel combination of condenser and loading coil being connected in series with saidfirst mentioned loading coils.

3. In combination a line, means for loading said line for one frequency-range; loading coils distributed'along said linefor load; ing said line for another frequency range, a condenser connected effectively in shunt to each of said loading coils. said-condenser lia ns a valu forming wit ae l dins loading coils coil a circuit anti-resonant for a frequency intermediate the two mentioned frequency ranges. I

I. In combination a line, means for loading said line for one frequency range, loading coils distributedalong said line for loading said line for another frequency range, a condenser in shunt to each of said coils, said condenser liaving'such a value that for one frequencyrange the combined coil and condenser presents a substantially inductive reactance, and for another range presents a substantially capacitative reactance.

5. In combination a line, loading coils for loading said line for one frequency range, other loading coils for loading said line for another frequency range, a condenser in shunt to each of said other loading coils, said condenser having such a value, that the combined coil andcondenser presents a substantially inductive reactance for the frequencies to be loaded by the shunted coils and' a sub stantially capacitative reactance for the frequencies to be loaded by the remaining coils.

6. In combinationa line loading coils distributed along said line for loading said line for telephone frequencies loading coilsdistributed along said line at greater intervals for loading said line for low frequency telegraph, and a condenser in shunt to each of said second loading coils, said condenser having such a value that the condenser and the shunted loading coil form a closed circuit anti-resonant at a frequency intermediate the telephone frequency band and the low frequency telegraph band.

7. In combination a line, means for loading said line for one range of frequencies, loading coils uniformly distributed along said line in series with said loading'means for loading theline for another range of frequencies, and a condenser connected effectively in shunt to each of said loading coils and having a value suflicient to make said 1 frequencies, and a condenser connected effectively in shunt to each of said second men tioned coils and having a value sulficient to make said condensers substantially opaque to the frequencies to be loaded by said second coils.

9. In combination a line, means for load ing said line for one frequency range, loading coils connected in series with said load ing means distributed along said line for loading said line for another range of frequencies, a condenser connected effectively in shunt to each of said loading coils, said condensers having a value forming with each loading coil a circuit anti-resonant forv a" frequency intermediate oftthe two mentioned frequency ranges.

10. In combination a line, loading coils of two kinds in said line for respectively loading said line for two ranges of frequencies, the loading coils of one kind being connected in series in said line with the loading coils of the other kind and being connected so" that the currents of the lower frequency range pass through the coils of bothkinds,

and means for by-passing the currents of the higher range of frequenclesaround the coils which load the line for the lower frequency range. v In witness whereof, I hereunto subscribe my name this 18th 1922.

ROBEItT C. MATHES] iii day of October, A. D. I

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