US1548059A - Electrical testing system - Google Patents

Description

Patented Aug. 4, i925.

Y BARRY efr-FICE.: j

NYQUIST, orY EIMHURST, NnwyonxynssIeN'oR yiro AMERieAN TELEPHONE AND'TELEGRAPH-CQMPANY, A CORPORATION 0F' NEW YORK."

' 'nLEcTnacAn TESTINGLSYSTEM.

application fued :my V1e, 192i. seriai No'. $5,308.

all 'wheat t ma/ z/ concern.' r Be it'kn'ownl that I, HARRY siding at Elmhurst, in the county of Queens mination of the degree-ofunbalance by apand' State of NewYork, have `invented certain Vimprovements vin Electrical Testing Systems, of which the following is a specification. fi! f This invention relates to electrical testing' y upon the amount of -unbalance existing between the line circuit and its balancing net systems and particularly to anv arrangement for determining thedegree of vunbalance ybetween two networks, such-as a signaling circuit and -thenetwork designed 'to vbalance the said circuit. l

f In order to operate most efficiently certain types of signaling circuits, as, for example telephonerepeater circuits andrduplex telegraphv circuitsyit. is necessary to maintain a high degreeof balance'between the line circuit andthe network which is intended to A balance the said'circ'uit.- Y To attain thisresult, itis necessary to determinefthe degree of unbalance'between a line circuit and its balancing network.v An

arrangement for determining the unbalance between a line and its network in af-telephonel repeater circuit is shown in -thepatent yof Clark and Crisson, No. 1,407,983,granted Feb. 28, 1922'. Thisprovides for the deterplying sinusoidalwaves of different frequen cies, preferably throughout the voice range,

and determining the unbalance at each frev quency. Such a method of measuring'is'de- `sirable in telephony because we are there Vconcerned with [the steady-state condition,

but, in telegraphy the transient phenomena are of greater concern'.`

A telegraph signaling impulse'is slopedwave comprising a pluralityl ofdiier- Aent frequencies which are simultaneously im pressed 'upon the line4 circuit wheneverv the key ofthe transmitting device'is closed. vIt

will accordinglyl be seen-tliatin telegraphy the transient Vphlinomena'arejof vprime inip'ortance, land consequently, a measurement made by a's'inusoidal wave of' a definite fre-Y quency does notgive correct results. j

It is well known'to those familiar with the art'of duplex telegraphy that if unbalance exists betweenV a liney circuit and a network NYQisT, re-

a steep,

' whi'ciivig designed@ 'simulate eicaieauyrthe i said, circuit, the application of signaling impulses yto the line circuit by the 'transmitter` connected with" the 'terminal' circuit at one' end yof the said line. circuit .will cause the receivingrelay connected with. the ,samefterminal circuit to respond 'to the transmitted signals, the degree of response dependingl ,ment .of-the network .so that the receiving relay willbeaii'ectedito the minimum extent bythe transmission of signals from'that endv of the circuit at whichtherelay is located.

Although this linvention will be described` in connection with a "metallic duplex tele? graph circuit, `it is to be understood that it is not limited to ithis particular. type of cir-r cuit,`but is capable of measuring unbalances Y existing between any two types 'of networks. VThis invention will be better understood from' the'following description when read in connection with the attached drawing of which Figurelshows one form of embodiment of `the* invention andfF ig. 2 shows the currentcurves 2, 2", 2, 'and 2d, which serve to'make V'clear` the principle upon" which the invention'.,IIefsts.A

In Fig-i1 a line circuit extends between two stations X and Y. 'Connected with the line IJ at the station X is a balancing network N1 the` function of whichis to balance" the's'aidline with respect to the transmission ofgsign'aling impulses by the 'transmitter T1. Connected between the? line L 7and its' net-l work N, is a receiving relay R1, having a plurality of windings designated 1, 2, 3, 4, 5 and G. Windings 1, 2, 3 and 4 are of the same magnitude and are connected serially in the line. Vindings 5 and 6 are connected in series with what is commonly known as the vibratory circuit. All of these windings are arranged upon the same core, the magneto motive force of which is adapted to control the action of armature 7 of the receiving rela f.

Bi'idged across the junction point of windings 1 and 2, and the junction point of windings 3 and 4 is the transmitting circuit 8, by means of which signaling impulses from the transmitter T1 are effectively applied to the line L for transmission to the receiving circuit at the distant station Y. This transmitting circuit comprises in addition to the transmitter T1 a transmitter-branch filter F, which is adapted to modify the impulses generated by the transmitter T1 so that they will have a wave shape which is best adapted to produce an arrival wave of the most desirable form at station Y, and at the same time to prevent interference with the telephone signaling currents which vmight be transmitted simultaneously over the cir'- cuit L.

It will be clearlyseen that the current impressed by the transmitting circuit 8 will flow in opposite directions in windings 1 and 2, and also oppositely in windings 3 and 4, and if the network N1 exactly balances the line L, the current will likewise be of the same magnitude in the respective windings so that no resultant flux will be set up on the core and consequently no effeet will be produced upon the armature 7. If, however, there exists an unbalance between the network N1 and its line L, the.

magnitude of the currents in the network and' the line will be different, thereby affectingthe armature 7. The object of this invention is to determine the degree of unbalance that exists between the network and its line and to eliminate or reduce the unbalance by proper adjustment.

The vibratory circuit, in which the windings 5 and 6 are located, also contains a condenser 9 and a resistance 10, the Jfunction of which will later be made clear inl the description of the operation of the circuit. Bridged symmetrically across the vibratory circuit, between the junction point of windings 5 and 6, and the junction point between condenser 9 and resistance 10 is a circuit containing the armature 7 and its .associated apparatus. The `armature 7 whichV is con'- nected by conductor 30 with the midpoint of windings 5-6, is adapted to move between contacts 11 and 12, with which are connected batteries 13 and 14 of opposite polarity. Connected between the batteries 13 and 14 are the resistances15 and 16, the

junction point of which is connected by conductor 31 with the polar sounder 17 and tl'irough the resistance 18 to the vibratory circuit at the junction point between condenser 9 and resistance 10.

The terminal circuit at station Y is similar to the circuit at station X'as described above and needs no further explanation.

Bridged across the conductors 30 and 31 is the winding 19, which is adapted to control the movement of the arma-ture 20 connected to one of the corners of the distortion bridge, which is of the type shown and described in the patent to Nyquist 1,435,323, dated Novemberl 14, 1922. Connected with the correspondingly opposite corner of the said bridge is another armature 21, the

movements of which are controlled bythe flow of' current in the winding 22 which is connected with a transmitting device 23, designed to be operated in synchronism with the transmitter T2 at station Y except 4that it operates with a lag which is made'substantially vequal to the lag produced by the telegraph system. This bridge is so designed that when the armatures 20 and 21 are in the position lshown in the drawing, or when the armatures are upon corresponding contacts, that is to say, when armatures 20 and 21 are upon contacts of A and B respectively, or upon contacts of C and D respectively, the bridge remains balanced and no current will flow through the path containing the galvanometer G. If, however, one of the armatures is in its neutral position and the other armature has closed either one of its contacts, or if the said armatures are upon oppositely disposed contacts the bridge will be unbalanced and the magnitude of the unbalancing currentV will be indicated by the galvanometer.

Having in mind the foregoing description of the apparatus shown in the drawing, the invention will be clearly understood from the following description of the mode of operation of the circuit in which it. is embodied. Y

This invention is based upon the principle of beating together two waves, each comprising a series of reversals of two different frequencies and detecting the variations in the operation of the armature of thereceiving relay resulting from the effect of unbalance between the line circuit and its balancing network. Let it be assumed that rel OO versals ofva frequency f are being transmitted by the ytransmitter T2 over the line L soV as to operate the armature 7 Y of the receiving relay and that nosignals are being transmitted by T1. When the current from the transmitter T2v flows through the windings 1-2 and 3 4 in a definite direction, it will move the armature 7 to one of its contacts, as for example, 12. Current will then flow from batteryf14 through contact the opposite side ofthe battery.v Thiswill chargek thelcondenser 9,LA located infthe vif Furthermore, thel flow of fdirecti'onsv Vfrom their respective junctionpoints therewill be no resulting magnetiza`-- bratory circuit. current through the; winding` will be in such direction'as to create a magneto-motive force .whichwill have v.such effect upon `the armature-.7 as to tendto-pull it away from:

the contact 12,-'although it will not affect the l.actual opening of this contact Solong as theline current from thetransmitter T21 tends to flow in lthe vpreviously assumed direction through the line Vwindings of the,

relay R1. fWhenftheline current through the windings 1-2 and. 3 4, falls below a certain minimum value the condenser 9 willA discharge through av circuit comprising'the windings 5 and' 6 Yin` series with Vthe resistance V10, andthe resultant discharge of our# rent through these windings'will be in such direction ask to move, the armature 7 quickly from contact 12. Since it has been assumedv that .the wave being transmitted by the transmitter,T2 constitute aseries of reversals otfrequency f, such as 'shown by` curve 2a, the reversal of the current on the line L and in the windings 1-2 and -ftwill move thearmature tocontact y11 andwill cause current of positive-.polarity to flow throughr the vibratory circuit, charging the condenser Qin an oppositesense.- The fiow of currentthroughthe winding 6 will ybe in' a Vdirec-V tion as will tend; to i lcause the armature y 7 to move away from contact 11 Vand this will be affected by theaction ofthe discharge otrcondenser -9 Athrough the windings 5 and 6, as 'soon as the current inthe line windings falls kbe'low,a deiinite yminimum amount. Thepurpose of this vvibratory circuit is'to overcome the sluggish action ofthearmature T'fwhen thecurrentjin v.the line circuit reverses, as in the sending of marking and spacingfsignals, and provides therefor a means for obtaining quick positive action1 of the receiving relay. Therefore thel receipt of a series of reversals of frequency flvas represented by'curve' 27 will cause uniform operation of the receiving relay.

Now, assumethat whilefthe transmitter Tf2 at station Y'is beingoperated to send overthe line L vreversals of frequency f, the transmitter T1 is simultaneouslyoper-A ated for fthefpurpose, of transmitting from stationXto sta-tion Y, a series of current ref versals of frequency f. which may be `either slightlyrgreater or less thantwice @the i're.- quency f of the signals sent over the lineL by the transmitter T2. The `current from the transmitter ',Tl, is impressed by the transmitting circuit 8 across the lineL at the junction points between the windings 1-2 and the windingsv 3-4. This current divides, `part of it flowingy throughthe winding llover the line L and back through the winding 4, and the other part -tlowing through the winding 2 through the. line bal- `ancing ,network N1 andl thev vwinding 3.

Since theselwindings are uponthe Sameicore,

and sincerthe How of currentis yiii-opposite Y tion'fofthecore if the currents| are equal, which means if the line balancing network exactlybalances the line L. If, however,`

there. exists anV unbalance between the line balancing network and the line circuit, the.y

the unbalance current that tends -to magnetize the core of the relay R1 and there fore to operate the armature Y2' and has, for example, been assumed` to be slightlyless than 2f. It is ythe difference in the current that flows from the midpoint of thewind-V ings Ri through theline and and through the'line balancing network N1. This re-A wise produces irregularityof operation `of f the armature 7. .The armature will not remain upon itscontacts for equalperiods of,

time since the time that it will'remain upon any one conta-ctvwill depend upon`thedura tion of the magnetizing current.

The impulses resulting from the action of the armature will be impressedupon the winding 19 which controls thearmature 20 connected with one of the corners of the distortion bridge. application of current to the winding 19 there will be impressed upon the Winding 22a current wave of thesame magnitude and phase as shown in curve 21, which is the curve of the current set up by the transmitter T2 as corrected for the lag due toy transmission over the line. -The currents inthe windings l19 and 22 will causetheir corresponding armatures to 'touch their right-hand or yleft-hand contact points, depending upon the direction of flow of current `through the windings. If the currents in the two windings were identical in phase and magnitude, the positions ofthe Aarmatures20` and 21 would at all times Vcorrespond, that is to say, that at any instant ofk time both armatures would be on their right-hand contacts or their left-hand contacts, or in the neutral position between the contacts. Since, however, thecurrent arriving over the line L from the transmitter T2 has superimposed thereon the unbalance current of the transmitter T1, which exists by virtue of the imbalance between the line and its balancing network, the current flowing inthe winding 19 will not be in the same phase as the current flowing-through the winding 22 and consequently the movement of the armature 2() will not be in synchronisin with the movement of the armature 21. rlhe movement of the armature 2O into contact with either of its contact points in advance of the time when the armature 21 comes into contact with the corresponding contact point will produce on imbalance in the bridge network, which imbalance will be indicated by the movement of the needle of the galvanoineter G. Adjustments are then made on the artificial line while observing the periodic change in the reading given by thev distortion bridge galvanometer needle. This adjustment is continued until the needle indicates the minimum variation throughout a definite period of time which indicates the minimum imbalance between the lines and its balancing network.

VIt will be seen that the method of detei'- mining the degree of imbalance between two networks comprises the simultaneous impression of two periodic signaling waves upon a relay, the frequency of one of the signaling waves being slightly greater or less than double the frequency of the other signaling wave, and allowing the resultant magnetizing current to control the operation of the armature of the relay, the freqiiencyV of operation of which closely follows the frequency of the combined waves.

Byvimpressing the impulses resulting from the action of the armature upon one of the windings of the distortion bridge, as shown in my application, Serial No. 353,- L16 filed January 23, 1920, and simultane- Y oiisly impressing upon another winding of the distortion bridge a wave having the same frequency and shape as the lower frequency signaling wave, the extent of the imbalance between the line network and the line circuit may be determined, and the line network may be adjusted until the point of minimum imbalance is obtained.

'Although this invention has been disclosed as having a. definite form and arrangement of parts it is to be understood that it is capable of embodiment in other and different forms without departing from the spirit and scope of the appended claims.

What is claimed is:

1. InV an electrical testing system, the method for determining the degree of unbalancev between two networks, which consists in simultaneously transmitting and receiving telegraph signals of different frequencies, and 'indicating the distortion ofV the received signals byl the transmitted signals. i

2. In an electrical testing system, the method forv determining the degree of unbalance between a line circuit and its balancing circuit, which consists inA simultaneously receiving and transmittingtelegraph signals, the respective signals. being of different frequencies, allowing the said signals to actuate a signal receiving device, and indicating the distortion of the received signals by the transmitted signals'due to unbalance between the line circuit and its balancing circuit.

V3. In an electrical testing system, the method for determining the degree of unbalance between two electrical networks, which consists in impressing signaling impulses of different frequencies from separate sources upon the said networks, allowing the impulses from one of said sources to interfere with the impulses from the other of the said sources in proportion to the degree of unbalance between the two networks, and determining the degree of imbalance byvirtue of the degree of distortion produced in the impulses from the other of said sources.

4L. In an electrical testing system, the method for determining the degree of unbalance between two electrical networks, which consists in creating signaling imp-ulses of different frequencies, impressing said impulses of different frequencies simultaneously upon the said networks, beating together the said frequencies, and determining the degree of unbalance betweenthe said networks by virtue of the beat frequency produced.

5. In an electrical testing system, the method for determining the degree of unbalance between two electrical networks, which consists in creating signaling impulses of different frequencies impressing said impulses simultaneously upon the said networks, beating together the said frequencies, and allowing the resultant frequency to control an indicating device whereby the degree of distortion resulting from unbalance between the said networks may be determined.

6. In a duplex telegraph signaling system characterized by a plurality of transmit-- ting circuits, a line circuit connecting said transmitting circuits, a balancing circuit, a receiving circuit having distortion indicating means associated therewith, and means for electrically relating the said balancing circuit and receiving circuit with the said line circuit and one of said transmitting circuits, the method for determining the degree of unbalance between the line circuit and its balllt) anoing circuit', which; consists''ioff'inlipre'ssingl simultaneously acrossv the saidl linefcircuity "at opposite ends thereof telegraph signalsfof different fre'opiiencies,`v beating .together;v the signals of the' saidffrequencies 'and comparingntliev resultant frequency with? that im'-l pressed uponfthe said line circuit at the dist-ant end thereof whereby the degree of unbalance between the line circuit and lthe balancing circuit may be determined. n

7 The method for detecting unbalance between two electrical networks, which consists in impressing across the said networks telegraph signaling impulses of different frequencies, and detecting the unbalance between the said networks by the effect produced in a receiving circuit. f

8. The method for detecting unbalance between two electrical networks, which consists in impressing across the said networks telegraph signaling impulses of different frequencies, and detecting the imbalance be-y tween said networks by an indicating device in a receiving circuit coupled to the said networks.`

9. In a duplex telegraph signaling system, the combination with a line circuit of a plurality of terminal circuits, each comprisingI a transmitting circuit adjusted tol transmit signals of different frequencies, a receiving circuit, a network adapted to balance the said line circuit, and a'relay having a. plurality of windings for electrically connecting the said circuits, and a distortion bridge circuit connected with a receiving circuit of one of the said terminal circuits for determining the magnitude of the unbalance between the line circuit and the balancing network associated with the said latter terminal circuit.

10. In a duplex telegraph signaling -K system, the combination with a line circuit of a plurality of terminal-circuits each comprising a transmit-ting circuit, a receiving cirrcuit, a network adapted to balance the saidline circuit and means for electrically connecting the said circuits so arranged as to respond normally only to signals from the transmitting circuit of the other of said terminal circuits, and means connected with the receiving circuit of either terminal circuit to indicate the magnitude of the interference set up in that receiving circuit by impulses from the transmitting circuit of the said terminal circuit due to imbalance between the line circuit and the network associated with the same terminal circuit.

1l. In 'an electrical testing system, the combination with a transmitting circuit having a source of current connected therewith, a plurality of networks-connected in parallel with the said transmitting circuit, the said networks being also connected serially with a second source of signaling current, a receiving circuitconnected with the sai'd'ffline circuit; :means Vfor impressing thereoii4 currentsffrom both offsaidfsources,V

and nieansrfconn'ected V.with the said receiving circuit tofldetectftlie imbalance existing between-the said-networks arising from the interference between'f Ythe Vcurrent fromV7 the said source-'and from the vsaidtransmitting circuit.

12. In an electrical testing system, the

networks, arising from the interference betweenY the` current from the said source and from the said transmitting circuit.

13. In a duplex telegraph signaling sys- Y ,tem "comprising a transmitting circuit, av vreceiving circuit, a line circuit having a source of signaling current connected therewith, a network intended to balance the said line circuit and a,receiving relay having a pluralityof v,windings for electrically connecting the said circuits, the method for determining the magnitude of the unbalance between' theline circuit and its network,

which consists in simultaneously impressing signaling impulses of a definite frequency from said source upon said line circuit, and also impressing signaling impulses of a different frequency from* said transmitting circuit upon said line circuit and said network in parallel, and allowing the resultant current to control the operation of a relay, to impress upon a distortion bridge circuit-the impulses from said relay and also from a source having the same frequency as the said first-mentioned source, and to compare the relative strengths of the said impulses by4 a suitable current indicating device. f y

14. In a duplex telegraph signaling system, the combination with a line circuit, of a distant transmitting circuit, a lioine terminal circuit comprising a transmitter adjusted to transmit at a dierent frequency from the said distant transmitting circuit, a balancing circuit, a receiving circuit, means for electrically connecting the said circuits, and a measuring device associated with the said receiving circuit to measure the inagniture of distortion produced upon signals received from the said line circuit by sigiials from the said home transmitter due to unbalance between the line circuit and the balancing circuit. Y

15. In a duplex telegraph signalingA system, the combination with a line circuit, of

a distant transmitter, a home terminal circuit vcomprising a transmitter adiusted to transmit signals of a different frequency llU :from the said distant transmitter, a receiviing circuit, a balancing circuit for the said line circuit, a receiving relay having a plurality 'of windings for electrically cnne-cting the said circuits, and means connected With the said receiving relay for measuring distortion of the received signals by the transmitted signals, duef'to unbalance between the said line circuit and its balancing circuit. f v A Y 10 In testimony whereof, I have signed my name to this specification this 15th day of a July, 1921. Y

HARRY NYQUIST.

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