US1736814A - Electrical transposition system - Google Patents

Description

Nov. 26, 1929.

Lil/Le l H. A. AFFEI.

ELECTRICAL TRANSPOS ITION SYSTEM Original Filed Aug. 3l, 1922 ATTORN EY Patented Nov.` 26, 1929 l UNITED STATES,

PATENT o1-Fica HERMAN A. AFFEL, 0F MAPLEWOOD; NEW JERSEY, ASSIGNOR TO AMERICAN `PHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW LYORK' ELECTRICAL TRANSPOSITION SYSTEM Original application flied August 31, 1922, Serial No. 585,436, Patent No. 1,530,537, dated March 24, 1925.` Divided and this application led March 9, 1925.' Serial N'o. 14,312.

This invention relates to electrical transposition systems and particularly to an arrangement for transposing a line circuit adapted for the simultaneous transmission of a plurality of frequencies or bands of frequencies.

This application is a division of my copend- Aing application, Serial No. 585,436, filed August 31, 1922, which issued on March 24, 1925, as Patent No. 1,530,537.

Heretofore in the operation of systems in which signaling was carried on by means of a relatively low frequency current or range of low frequency currents such as required for voice transmission, where it has been necessary to transpose pairs of wires to prevent mutual interactions, due to inductive or. capacity effects between them, it has been customary to introduce the transpositions at intervals which were short relative to the wave lengths of the electric currents concerned. This has usually entailed no particular hardship, since, as noted-above, the

frequencies were relatively low and the wave len hs correspondingly long.

en transposing wires to prevent mutual interactions, or in other words crosstalk, be

` short and in order to carry out the general principle of providing transposition intervals which are a small fraction of the wave length, requires, in many cases, the insertion of transpositions at points extraordinarily close together. In fact the number of transpositions required and the physical difiiculty involved in obtaining the accurate frequency spacing, often renders it impracticable to employ such an arrangement, effective throughout a wide range of frequencies. A lesser number of transpositions may, however, be provided where it is desired to have the action eEective only atA a single frequency or over a relatively narrow range of frequencies because in this case the rapidphase changes act in a sense to transpose the currents automatically at frequent. intervals.

` between circuits throughout a wide range of frequencies, covering low frequencies as well as high frequencies, with a minimum number of transposition points. The particular feature by which this objective is achieved is the use of ywhat may be termed selective transpositions, namely, means whereby a line circuit may be effectively transposed at a given point for a particular frequency, or band of frequencies, and atY the same time rendered untransposed at the same point for other bands of frequencies than those for which it is desired to transpose the said line at that point. By this means a complete transposition system, effective throughout the desired wide range of frequencies, may be`provided by superposing the designs of a plurality of transposition systems, each of itself relatively simple, involving a minimum of transpositions and effective fora portion of the total frequency range involved. The points at which transpositions are required for one part of the range and not for another part of the range are effectively provided for by a selective transposition as above noted, the points at which both circuits are required to be transposed being served by a simple transposing of the Wires in the ordinary manner.

Other objects of this invention will be apparent from the following description when read in connection with the attached drawing, in which Figure 1 shows a simple form of embodiment of the invention, Fig. 2 shows the application to a line circuit of a plurality of units such as are shown in Fig. 1, and Fig. 3 shows the application of the invention to a directive radio antenna.

In Fig. l, 1 and 2 represent two sections of a line which is adapted to have transmitted thereover a plurality of frequencies, or bands of frequencies. Inserted between the sections 1 and 2 of the said line circuit, and in series therewith, is an electrical network which may be termed, for the purpose of description, a transposition group.

line into different bands,-thereby permittin the circuit carrying one or more of the ban s to be transposed, while maintaining in the circuit carrying the remainder of the frequencies, the normal disposition of the wires. This arrangement thus provides the selective transposition previously referred to.

This network consists in a plurality of filters connected in parallel electrically with each other, thereby affording a plurality of paths between the sections 1 and 2 of the'said line circuit, through which the plurality of frequencies, or bands of frequencies traversing the said line must pass. While only two filters have been shown in the group in Fig. 1, it is to be understood that 'the invention is not limited to this particular number, but may be varied without changing the scope of the invention. The filter designated A is of the type known in the art as a band-suppression filter and is disclosed in the patent to G. A. Campbell, No. 1,493,600, dated May 13, 1924. This filter, the transmission frequency characteristic of which is represented by the dotted curve a in Fig. 1", is adapted to suppress a particular band of frequencies such, for example, as that represented by f1-f2 and to transmit readily, or substantially so, all frequencies lying without that band. This is clear from a consideration of Fig. 1, which shows the variation of loss of the network A for various frequencies impressed upon the said network. Thus, it will be seen that for frequencies below f1 and above f2, the transmission loss is fairly low, whereas it is very high for the band lying between f1 and f2. The filter B, whose characteristic curve is designated b in Fig. 1, is of the type known as band-pass filters. This filter, with the exception of the transposition of the conductors designated 3, is disclosed in the patent to G. A. Campbell, 1,227,113, dated May 22, 1917. A consideration of the characteristic curve shown in Fig. 1"l shows that the transmissin loss to currents below f1 and above f2 is very great, whereas the transmission loss lylng between these limiting frequencies is relatively small.` This means, of course, that the band f1--f2 will be readily transmitted through a filter of the type rep resented by B, but that frequencies or bands of frequencies lying without those limits will be substantially sup ressed. Since filter A sup resses the same and of frequencies which 1s readily transmitted by filter B, these filters are termed complementary and are hereinafter referred to by that term. By reversing the conductors of the filter B at the point 3, the line is electrically transposed with respect to the currents that are transmitted through the filter B, but the line is not transposed with respect to currents of the frequencies transmitted through the filter A. It will be clear, therefore, that if, for example, a band of frequencies f1-f2 and another band of frequencies lying without the range of the s aid first band, arrive over the section 1 ofthe line circuit, the band f1-f2 will be transmitted through the filter B and, due to the transposition 3, will be impressed in an opposite sense across the section 2 of the said line circuit. The other frequencies will not pass through the filter B, but will be transmitted through the filter A, and since the conductors thereof are not reversed, the said other band of frequencies will be impressed across the section 2 of the line in the same sense in which they were impressed across the line 1.

The application of a plurality of transposition groups, such as shown in Fig. 1, is illustrated in Fig. 2. In this figure, 1, 2, 3, 4 and .5 represent five sections of a line circuit which 'are connected together by means of a plurality of transposition groups, the object of which is to transpose the said line for a particular frequency, or band of frequencies in order to prevent cross talk into some adjacent pair of wires. Let it be assumed that the points X and X1 represent points at which it is desired to .transpose to prevent cross talk for frequencies lying within the band f1-fz and Y and Y1 represent desired transposition points for preventing cross talk for frequencies lying within the band fs-. ThereV should accordingly be inserted at X and X1 a transposition group comprising a -filter`B adapted to transmit the band of frequencies )t1-f2 and to suppress all other frequencies, and a filter A which will transmit all of the said other frequencies and will suppress the band f1-f2. The transposition group shown at Y and Y1 comprises a filter D, which is adapted to transmit the band of frequencies f1-f4 (viz. the said other frequencies transmitted by the filter A at points X and X1) but to suppress the band )f1-f2, and a filter C, which is adapted to transmit the band )c1-f2, but to suppress the band fS-f1. Each of the filters B and D has its conductors reversed as represented by 3 in Fig. 1. Accordingly, it will be seen that if two hands of frequencies, for example, )i1-f1 and f3-f4 arrive over the section 1 of the said line, the band f1-f2 will 'be transmitted through the filter lB and will be impressed across the line 2 in an opposite sense. The band )cf-f1 will be transmitted through the filter A and impressed across the section 2 in the same sense'in which it was impressed across the section 1. These two bands will then be impressed across the transposition group at Y. The band 7f3-f1 will be transmitted through the filter D and. due to the transposition therein, the band will be impressed across the section 3 in an opposite sense to that in which it was impressed across section 2. The band )f1-f2 will be transmitted through the filter C and impressed across section 3 in the same sense in which ,10 to 15 inclusive.

it was impressed across section 2. Accordingly, it will be seen that the line, which iS made up of a plurality of sections designated, for example, 1 to 5 inclusive, is transposed at the points X and X1 for currents of the band fl-fg. but is not transposed for all other frequencies. At points Y and Y1 the said line is transposed for currents of the frequencies 7f3-f, but is not transposed for currents of other frequencies. L

It will he apparent that any number of transposition groups may be used in aline such as shown in Fig. 2. depending upon the number of bands of frequencies for which it is desired to transpose the said line.

The arrangement shown in Fig. 3 represents the application of this invention to a directive loop antenna, the object of which is to make the antenna better responsive to waves received from a particular direction. 1H my Patent No. 1,615,896, that issued on February 1, 1927, I showed the use of a transposed loop antenna, which, by the proper locating of the transposition points, was better adapted to receive waves of a particular fre uency, or band of frequencies, and to exclu e or suppress currents of other frequencies. Such an arrangement, as was therein disclosed, tended to minimize the effects of static and also of interference from stations other than that from which it was desired to receive signals. The arrangement shown in Fig. 3 is an application of the present invention to the antenna broadly shown and claimed in the said copending application. In Fig. 3, the antenna per se is represented by a plurality of sections designated Across the one end of section 1() is a terminating resistance 16, which simulates the characteristic impedance of the antenna. The other end of section 10 is connected with the filters A and B, the filter B being designed to transmit. for example. the band f1 f2 and filter A being designed to suppress that frequency but to transmit all other frequencies. By the proper location ot' the transposition groups at the points X. X,. X2 and X3 the antenna is made highly selective for frequencies lying within the desired band and is made non-selective for other frequencies.

vhile l have shown tivo uses to which my invention may be applied, its scope is notv so limited. since many other and varied uses will occur to those familiar with the art. Furthermore. while 1 have shown the use of band fillers of various types -in the drawing in which the invention is embodied, and have described these particular types of filters in the specification." it must be understood that the invention is not limited to these particular types of filters. Nor is it limited to the transmission of hands of frequencies since the invention is applicable to the transposition of a transmission circuit for a plurality of single frequencies as well as `for bands of frequencies.

Although this invention has been disclosed in a particular form it is capable of einbodiment in other and different forms Within the spirit and scope of the appended claimsl What is claimed isz' 1. An antenna having a plurality of groups of frequency selecting devices connected at predetermined intervals therein. the devices of each group being in parallel and so designed and adjusted that the frequency selected by one will be that suppressed by the other.

2. A loop antenna having inserted therein at predetermined intervals a plurality of groups of frequency selecting devices, the devices of each group being in parallel and complementary in nature whereby the frequencies selected by one device will be those suppressed by the other, the conductors of the said antenna being transposed for the selected frequenciesat each point of connection of the said groups with the said antenna, and

transposed at its midpoint for the nonselected frequencies.

3. In a radio signaling system, the combination with an antenna adapted to transmit a plurality of bands of frequencies, of a group of filters inserted between sections of the said antenna, the said filters being connected in parallel and being of the complementary band-pass and band-suppression types, the band-pass lter having its conductors transposed whereby the said antenna will be transposed at that point for the frequencies transmitted through the said band-pass filter.

4. In a radio signaling system` the combination with an antenna adapted to transmit a plurality of frequencies. of a group of filters arranged in parallel with each other. the said group being inserted between sections of the said antenna. one of said filters being adapted to transmit readily one of the said frequencies and to suppress other frequencies. and the other of the said filters being adapted totransrnit said other frequencies and to suppress the said first-mentioned frequency, the said antenna being transposed through the said first-mentioned filter.

5. In a radio signaling system. the combination `with a. loopy antenna, of groups of filters connected therewith. each group comprising a band-pass and a band-suppression filter of complementary types. the said bandpass filter of each group having its conductors transposed. thereby effecting a transposition of the antenna at that point for the frequencies passed bv the said filter. the said groups being spaced along the said antenna at intervals representing a transposition section for the frequencies passed b v the said band-pass filter of each group,

6. An antenna effectively transposed at certain points for predetermined frequencies but eiectively non-transposed at those points for other frequencies.

7. An antenna, transposed at its midpoint 5 to neutralize interfering frequencies, and effectively transposed at'other points for certain of said frequencies but effectively nontransposed at lthe said other points for other frequencies. lo 8. An antenna rendered selective for a certain group of frequencies by being transposed at certain points along its length and at the same time non-transposed at the said certain points for other frequencies than those of the said certain roup.

In testimony Whereo I have signed my name to this specification this 6th day of March, 1925.

A HERMAN A. AFFEL.

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