US1702309A

US1702309A - Composite set

Info

Publication number: US1702309A
Authority: US
Priority date: 1927-10-19
Publication date: 1929-02-19
Anticipated expiration: 1946-02-19
Also published as: CH137893A

Description

Feb. 19, 1929. 1,702,309 H. NYQUIST COMPOSITE SET Filed Dec. 18, 1926 .Balawwing/Wtwork 5 INVENTOR. lzn ma A TTORNEYS.

Patented Feb. 19, 1929.

UNITED STATES PATENT OFFICE.

HARRY NYQUIST, OF MILLBURN, NEVT JERSEY, ASSIGNOR TO AMERICAN TELEPHOIJE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

COMPOSITE SET.

Application filed December 18, 1928.

known as a composite set whereby the incoming telegraph and telephone currents may be separated and diverted to their respective circuits without interference with each other. The composite set, furthermore, functions to prevent the outgoing telegraph currents from entering the telephone path at the terminal facilities and vice versa. Heretofore, composite sets have separated the telephone and telegraph channels by means of frequency selectivity. The improved composite set of this invention not only makes use of frequency discrimination or selectivity to separate the incoming telephone and telegraph channels, but embodies certain novel features and principles with respect to the prevention of interference between the different types of currents originating in the different telephone and telegraph branches at the terminal facilities. By satisfying certain impedance relations in the composite set of this invention,

it is possible to obtain a conjugate relationship between the telephone and telegraph branch so that interfering currents from either of these cannot enter the other regardness of frequency discrimination. Furthermore, by making the impedance of both the telegraph and telephone terminal apparatus substantially equal to a common pure resistance, the impedance of the two, as seen through the composite set, to the line, also is substantially equal to a pure resistance at all frequencies, Also the impedance of the line to the telephone and telegraph, as seen through the composite set, may be made pure resistance, line impedance, or other desired impedance. This will tend to improve the transmission characteristics of the systems by obviating echoes, reflections, and reflection losses. Further features or objects of the invention will appear more fully from the detailed description hereinafter given.

Serial No. 155,728.

The invention may be more fully understood from the following description, together wlth the accompanying drawing in the F igures 1 to 8 of which the invention is illus trated. Figs. 1, 2, 4 and 5 illustrate schematically, certain principles involved in the invention. In Figs. 3 and 6, the invention is shown inschematic form. Fig. 7 shows a practical embodiment of the invention, and Fig. 8 a modification thereof.

One of the principles utilized in the com posite set of this invention is illustrated in Fig. l, in which the telegraph and telephone branches are shown tentatively as connected to the opposite sides of a Wheatstone bridge composed of the equal resistances 7",, 1' 7' and 1",. According to the well known prin ciples of the Wheatstone bridge current bommg in over the telegraph branch will not be transmitted out over the telephone branch as the points P and P are of equal potential. Likewise, current from the telephone branch will not be transmitted out over the telegraph branch as the latter would be connected to the equi-potential points P and P In other words, a conjugate relationship is established between the telephone and telegraph branch so that interfering currents from either of these branches cannot enter the other, even without frequency discrimination. The line circuit is shown schematically as as sociated with one of the arms of the bridge.

In Fig. 2, a capacity C is substituted for the resistance arm 1, of Fig. 1 and the resistance arm 1*, is changed into an inductance L. By proper adjustments of the constants of the arms of the Nheatstonebridge, a conjugate relationship may still be established between the telegraph and telephone branches so that interfering currents from either of these cannot enter the other regardless of frequency discrimination. Because of the capacity C, the low frequency currents coming in from the telegraph branch will not take the path C73, but will take the path 03L. On the other hand, the high frequency currents from the telephone branch, due to the inductance L, will not take the path In", but will follow the path 13C. Accordingly, by utilizing an inductance and a capacity as arms of the VVheatstone bridge and connecting the telephone and telegraph branches thereto, as shown, we find that currents from both branches will be transmitted through the cal arm 1 Accordingly, the line circuit will be associated with this arm 1, in the manner to be pointed out hereinafter.

The composite set of the invention is shown in schematic form in the arrangements 0t Fig. 3. The arrangement and proportionment of the elements of Fig. 3 will be more apparent from a discussion of Figs. l and 5.

In Fig. lis shown an arrangement oi i111 pedances which has the following properties:

( 1) Opposite resistances are conjugate.

(2) The impedance connected to any one oi. the tour resistances is a pure resii-itance equal. to B. These facts are made more obvious it' the figure is redrawn to an equivalent form, as shown in Fig. 5, in which the same impedauccs are shown in the term of a balanced lVhcatstone bridge, which is reaiflily tami liar and is known to have the two properties above stated. This figure also permits us to state by inspection what the necessary relations must be in order that the network, as shown in Fig. l, should have these properties. The equation expresses the necessary and suflicient condition.

Accordingly, if we now substitute the telc phone and telegraph terminal circuits and apparatus for the right and left resistance elements R of Fig. 4: and connect the line circuit in place of the lower resistance and make the upper resistance a balancing; network, it will be apparent that we will have the composite set shown schei'natically in Fig. 3 and this composite set will have the above referred to properties. Accordingly, by thus satisfying certain impedance relations and by connecting the telegraph and telephone branches, as shown, a conjugate relationship is established between these branches so that interfering currents from either of these branches cannot enter the other regardless of frequency discrimination. It is point ed out that energy from the member marked Linc circuit in Fig. 3 is not equally divided between the telephone and telegraph branches but that the ratio of division is a tuinctimi. of frequency. At a frequency determined by the relation tween the line and network or in other words, conjugacy between the telephone and telegraph branches.

It is pointed out that it is also desirable to make the impedance of both the telegraph and telephone terminal apparatus substanti ally equal to a common pure resistance. Under such conditions, the impedance of the two as seen through the composite from the line equals a pure resistance at all he quencics. This will tend to obviate echoes, reflections and reflection loss and. materially improve transmission. it may be preferable, however, to make the impedance facing the telephone or telegraph branches, or both, an inqiedancc easy to simulate by means of simple network,-perhaps pure resistance 01' line in'ipedance. It may, therefore, be desirable to make the 7 and r members of the bridge impedance diti'erent from pure inductance and capacity, remoectively, and r, member different tron: pure resistance or line impedance. This, obviously, may be done it the condition tor conjugacy is maintained such as r ap 1t Frequency discrimination will be obtained if r, be an impedance high at telegraph frequencies and low at telephone frequencies and r, the reverse.

In carrying the design from the schematic l orm shown in Fin. 3 to a form, which practically applicable, certain facts have to be considered. in the first place, the line met with in practice is balanced to ground. In the second place, it is not permissible to establish this balance by means of a transt'ornr er liiecauw-r it is necessary to transm t direct current. dome "areinust also be taken so that the number of connections between the composite set and the circuits which it connects should not be greater than necessary.

In Fig. 6 is shown an arrangement which applies one balancing network llN to each of the two line wires. This gives two sets of places for the telephone and telegraph to be connected. The telegraph case can be reduced to a single one immediately by making the connection indicated in the dotted line. The two telephone branches can be combined in a similar manner by the use of a transformer. The corresponding arrangement is shown in F 1 which is arranged in a more usual manner and includes connections for a phantom circuit.

The arran 'emcnt shown in Fig. 7 is not as good or desiraliile in re pect to toe matter of deriving the phantom circuit, shown as the connection Ph. because the phantom telenot derive the benefit of balance disc initiation. The arrangeshown in Fig". i5 is more at actory in phone circuit (i( the not in that the plat-atom circuit is put on ruc lmsie-r :rhe de circuits. The

apparat showi'! above the dotted line in iii and is external to the composite set proper, but should be grouped with the apparatus below the dotted line for the sake of simplifying the wiring. The apparatus above the dotted line is made up of three transformers which have been designated I, II and III. I and II are the side circuit transformers and III is the phantom circuit transformer. The poling of the various windings is indicated by the numerals which are so arranged that current flowing from an odd to an even terminal produces magnetism of a given sign. The cross-fire among the various telegraph circuits seems to be taken care of, particularly if the neutral point is grounded, as indicated by the dotted connection in Fig. 8.

While the invention has been disclosed as embodied in certain specific arrangements which are deemed desirable, it is understood that it is capable of embodiment in many other and widely varied forms without departing from the spirit of the invention as defined by the appended claims.

What is claimed is:

1. A V'Jheatstone bridge substantially balanced for all frequencies having one set of opposite arms comprising a line circuit and a balancing network and another set of opposite arms comprising an inductance and a capacity, respectively, a telegraph circuit connected to the junction point of said line circuit and said capacity and to the junction point of said inductance and said balancing network, and a telephone circuit connected to the junction point of said line circuit and said inductance and the junction point of said balancing network and said capacity.

2. A line circuit, a balancing network, an inductance, a capacity, the impedances of said elements being so adjusted and said elements being so arranged as to form a Wheatstone bridge substantially balanced for all frequencies, and a telephone circuit and a tele graph circuit so associated with said elements as to be in conjugate relationship with each other. I

3. A /Vheatstone bridge substantially balanced at all frequencies having one set of opposite arms comprising a line circuit and a balancing network and another set of opposite arms comprising an inductance and a capa ,ity, and signaling circuits of different types connected to the opposite junction points of the arms of said bridge.

4. A transmission line and a composite set associated therewith, said composite set comprising a telephone circuit and a telegraph circuit so arranged as to be in conjugate relatio-nshlp to each other and having the constants of said circuits so adjusted that the impedances presented to said circuits will each be substantially equal to a common pure resistance.

5. A balanced VVheatstone bridge having one set of opposite arms comprising a line circuit and a balancing network and another set of opposite arms comprising an inductance and a capacity, a telegraph circuit connected to the junction point of said line circuit and said capacity and to the unction point of said inductance and said balancing network, and a telephone circuit connected to thejunction point of said line circuit and said inductance and the junction point of said balancing net work and said capacity, the constants of said telephone and telegraph circuits being so adjusted that the impedances of said circuits will each be substantially equal to a common pure resistance.

6. A. balanced Nheatstone bridge having one set of opposite arms comprising a line circuit and a balancing network and another set of opposite arms, one of which comprises an impedance much larger for telephone than for telegraph currents, and the other of which comprises an impedance much larger for telegraph than for telephone currents, a telegraph circuit connected to the junction point of said line circuit and the last mentioned one of said second set of opposite arms, and to the junction point of said network and the first mentioned one of said second set of opposite arms, and a telephone circuit connected to the junction point of said line circuit and the first mentioned one of said second set of opposite arms and to the junction point of said network and the second mentioned one of said second set of opposite arms.

7. A balanced Wheatstone bridge having one set of opposite arms comprising a line circuit and a balancing network and another set of opposite arms one of which comprises an impedance much larger for telephone than for telegraph currents and the other of which comprises an impedance much larger for telegraph than for telephone currents, a telegraph circuit connected to the junction point of said line circuit and the last mentioned one of said second set oi opposite arms and to the junction point of said network and the first mentioned one of said second set of opposite arms, and a telephone circuit connected to the junction, point of said line circuit and the first mentioned one of said second set of opposite arms and to the junction point of said network and the second mentioned one of said second set of opposite arms, the constants ofthe arms of said bridge being so adjusted that as seen from either said telephone circuit or said telegraph circuit the impedance of the bridgewill be substantially a pure resistance within a working frequency range.

8. A balanced VVheatstone bridge having one set of opposite arms comprising a line circuit and a balancing network and another set of opposite arms one of which comprises an impedance much larger for telephone than for telegraph currents and the other of which comprises an impedance much larger for telegraph than for telephone currents, a telegraph circuit connected to the junction point of said line circuit and the last mentioned one of said second set of opposite arms and to the junction point of said network and the first mentioned one of said second set of opposite arms, and a telephone circuit connected to the junction, point of said line circuit and the first mentioned one of said second set of op posite arms and to the junction point of said network and the second mentioned one of said second set of opposite arms, the constants of the arms of said bridge being so adjusted that as seen from either of said telephone circuit or said telegraph circuit the impedance of the bridge will be substantially equal to the line impedance within the Work ing frequency range.

In testimony whereof, I have signed my name to this specification, this 17th day of December, 1926.

HARRY NYQU 1ST.