US1608546A - Distortion-measuring system - Google Patents

Description

Nov. 30 1926. 1,608,546

A. B. CLARK ET Al.

DIsToRTIoN MEASUMNQ SYSTEM v Filed May 10, 1923 I 'EN TORS ,x TTORNEY Patented Nov. 30, 1926.

ALVA B. CLARK, OF BROOKLYN,

AND ROY B. SHANCK, OF WOODSIDE, NEW YORK, AS-

SIGNORS TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION F N EW YORK.

DISTORTION-MEASURING SYSTEM.

Application filed nay 1c. 192s. serial No. 638,123.

This invention relates to electrical measuring systems and particularly to means for determining the existence and the magnitude ofdistortion of telegraph signaling impulses produced in the course of transmitting the said impulses between two stations upon the same line.

In the transmission of telegraph signals. each made up of a plurality of impulses, and each impulse having a` definite lengtl distortion of the impulses and therefore of the signals) may be produced by various causes inherent in the line or in the apparatus connected therewith or both. The distortion with which this invention is con- .cerned manifests itself in lengthening or shortening the duration of the impulses which constitute the. signal transmitted over the line. This lengthening or shortening of the duration of the impulse interferes with the proper recording of the signals atany station connected with the said line and consequently impairs the efficiency of transmission. y

Various systems for determining the existence and the magnitude of this form of distortion have been devised and used, but, due either to the .complexity of the apparatus required or to other causes, they have not been Widely used. VOne such method consists in the use of a l/Vheatstone tape recorder connected with the receiving end of a line. to which perfect signals are applied at the sending end for the purpose of recording the said signals at the receiving end. The tape records of these signals are then measured whereby any distortion and the magnitude thereof may be determined.` This method, however, is quite laborious and eX- pensive. Other ways employed heretofore indicate only average distortion.

. it is the object of this invention to provide simple means for indicating the existence of distortion of the signaling impulses and for measuring the magnitude of the same.

This invention will be clearly understood from the following description when read in connection withthe attached drawing, of which Figure l showsschematically an ar rangement embodying the invention and Fig. la shows graphical-ly two signal characters each comprising live impulses, which :ligure will assist inunderstanding the nature tue invention.

In Fig. "l, A represents a station from which signalling impulses may be applied to the line Ll extending between station A and station B, The transmitting device T1 is intended to represent symbolically any form of transmitting device such as a tape transmitter, a printing telegraph distributor or other device by means of which a plurality of impulses representing signal characters may be applied to the line L1. l), reprecents a differential polarized relay connected with the line L1 and with the artificial line ALl adapted to balance the real line. For the sake of brevity the details of the apparatus at station A need not be further described since they form no part of this invention.

The terminal apparatus at which preferably is similar to that at station A, includes a transmitter T2 and a differential polar relay P2 connected between the line Ll and the artificial line AL2. The armature of relay `P, may be connected through its upper contact with the negative pole ofthe battery B2, and the lower contact may remain disconnected. This armature is connected by conductor 16 with the brush 1l 4which is adapted to make contact with the segments of the receiving distributor ring D2. The ring, which is shown developedin a straight line in the drawing, comprises ten conductive segments of equal size and equally `spaced by insulating segments, but as will be apparent from the subsequent description of this invention, it may comprise any number of segments. Each segment is connected with its individual relay of the train of rclays designated R, to R1, inclusive. These relays, which asshown, are of the neutral type, will be Qperatedwhen a current impulse is impressed upon their respective seg-- ments by the brush 1l, and thus in effect store upq for the` purpose of further investi-- gation, the signal character received at sta tion B. Tt is customary in printirg tclcgraph systems to represent a signal characV ter by a combination of `live impulses, so the segments 1 to 5 and their associated relays are arranged tc receive one signal character and the segments 6 to l0 with their asso ciated relays toreceive another and preferably a different lsignal character. `Since the nature of the invention willbe clearly understood by 'the deecripticn of the inode station B, l

second signal character, which will be applied to the segments 6 to 10 inclusive, comprises `a spacing impulse followed by two marking impulses, which are in turn followed by two spacing impulses. For the salre o'l' brevity we will describe the operation oit the system for the first signal character. The application of the first marl;- ing impulse, viz, anegative impulse, will continue as long as the brush 11 remains in contact with the segment 1 and until the brush is about to enter upon segment 2. Similarly, the application of the second marking impulse will continue throughout the time that the brush 11 remains in contact with segment 2 and until it is about to move onto segment 3. And, in like manner, the succeeding impulses will continue as long as the brush 11 remains in Contact with the respective segments, assuming, of course, that the said source ot distortionless naling impulses is not only in synchronism but also in phase with the ring D2. As the brush 11 moves over segment 1, current will flow through the winding of the relay R1 to ground, thereby effecting the operation ci the said relay, which will be locked-up by eurrentthat flows through a circuit embracing battery B2, the back contact of relay R12, conductor 14.-, upper contact of relay R1 and the winding of the said latter relay. y, In similar manner, relay R2 will be operated when the brush 11 moves over segment 2 and the said relay will be locked-up by current from battery B2.V As the brush 11 moves over segment 3, relay R3 will not be energized since the armature of relay P2 will be on its lower contact with which no source of potential is connected. It is desirable to point out that if sources of opposite polarity were connected with the upper and lower contacts respectively of relay P2, it would necessitate the use ot polar' relays in the re-` lay train represented by R1 to Rlo inclusive. F or the sake of simplicity, neutral relays have been used for this purpose and therefore a space is represented by the absence of current rather than by a current impulse et polarity opposite to a marking impuls Accordingly, relay R3 remains unoperated and consequently its armature is held against its lower Contact by the action of the retractile spring. In like manner, relay R4 remains unouerated durine the assafe of the 1 C CJ brush 11 over the segment t and its armature is similarly held against its lower contact. Relay will respond to the llowof current representing a marking impulse during the passage o the brush 11 over segment 5 and `its armature will be drawn against its upper contact, and the relay will be locked-up by current from the source B2.

Upon the operation of relay R5, current will flow from the battery B2 over a circuit embracing conductor 14:, upper contacts of relays Rl and R2, lower R2 and' R2, upper contact of relay R5 and winding ot' relay R11 to ground, thereby energizing the last relay and causing its armature to be held away from its grounded contact. It will, therefore, be seen that relay Ru will not operate unless the circuit through the said contacts is closed, which in turn depends upon the operation oit relays Rl to 2 "Whether relay R11 has operated is determined as follows: l/Vhile the brush 11 is traveling over contacts 6 to 10 inclusive and is thereby storing up the second signal character of Fig. 1, the brush 12, associated with the ring D2, is likewise traveling over segments 6 to 10 of ring D2. Vhen the brush 12 makes contact with segment 7', the grounded source of potential B3 will be applied to the indicating device 13. This. however, will not operate it' the armature ot relay R21, with which the device 13 is. connected, is held away from its grounded contact due to the energization of the said relay Rn. The failure of this device to operate indicates, of course, that the ring is so oriented while the distortionless signals are being applied to it during the process ot' calibration that the relays of the relay train have been properly operated to close the circuit ot the alarm control relay R12. Then the brush 12 makes contact with segment 9 the release relay R22 will be energized and its armature will be drawn to its right-hand contact, thereby disconnecting the grounded battery B2 from the train ot' relays Rl to R5 inclusive and also from the alarm relay R thus restoring the system to normal.

In Calibrating the system, it is desired to determine'how tar in either direction oit ro tation, the ring D2 may be oriented betere it fails to properly transmit to the r '.'s R1 to R5 inclusive the signaling impulses impressed by the source of distortionlcss signaling impulses upon the brush 1l, l" the ring D2 is oriented, for example` in the lett-hand direction a point will be reaclmd where, ttor example, a iiegative impulse will be applied to the relay This is denced by the tact that relay R2, which would normally not be energized it lthe signaling impulses were properly centered. will now be energized by the How of current therethrough. Accordingly, its armature will contacts ot relays be attracted to its upper Contact and loclred in that position, `and consequently the circuit embracing battery B2 conductor lland the contacts ol relays R, to R, will be cut olf from relay R2. Accordingly the alarm control relay R11 will not be energized and its armature will remain upon its grounded contact. Vfhen the brush 12mm-.fes onto segment 7 the alarm device 13 will be operated by current flowing therethrough :trom battery B2 to ground. The operation of this device serves to apprisef the person who is making the test that the ring D2 has been oriented so far in a left-hand direi-tion that the receiving apparatus fails'to receive the Ndistortionless signals being applied to the Vhand direction until the apparatus fails to properly receive signals, which would he indicated yin the manner just described. rilhis latter point is also noted upon the said ring and the distance between the tivo points is known Vas the range of orientation Without failure. @ne-half of this distance is commonly known as the niargin for distortiollless signals.

Having determined the margin through which the receiving ring D2 may be oriented before failure when receivingdistortionless signals, the receiving; apparatus should then be connected effectively to the line L1. After the yreceiving apparatus has thus been connected it should be adjusted to compensate for the time lag resulting from the transmission of signals over the said line. This adjustment consists in orienting the ring D2 in such direction and to such extent that the brush llrivill begin to make contact with the segment l When the first impulse of the signal transmitted over the line L1 from the distant station A is ar-` riving at station B. Since the rings at station B are operated in synchronism Tvith the transmitting apparatus at station A and since there is a timelag inthe transmission of a signal from A to B, the brush il will normally `have travelled some distance along the segment l heforeth-e signal transmitted from station A begins to arrive at station B if the brush l1. began to make Contact with segment l of ring D,2 at the same time that the armature of the transmitter T1 at station A touched the. contact point connected with one of the poles of the trans mitting battery. The adjustment for time lag consists simply in orienting the ring D2 so that the brush .ll moves over the segment l While the signal transmitted from SMOH A arrives at station B.

Having calibrated the distortion measure ing apparatus, that is, having determined its margin for distortionless signals, and furthermore, having adjusted the receiving apparatus for time lag, the nent step consists in determining the change in themargin diie to distortion of signals received at station liet-.it be assumed that the transmitting apparatus at station A is sending the first signal character shoivn in Fig` la, consisting of tivo marking impulses followed by tivo spacing impulses, which in turn are `followed hy a Vsinglemarking impulse. Y As ing Will be manifested by the operation of the indicating device 13 when the ring D2 is oriented. lf the third impulse, which is an open circuit spacing impulse, is appreciahly lengthened, the preceding marking impulse, which is closed circuit' impulse, will he correspondingly shortened. To determine the magnitude of this distortion the ring D2 should be oriented .in both directions. Since the duration of the marking impulse, which would normally be applied' to the vsegment 2 While the brush 6 is in contact therewith, is shortened by the corresponding lengthening of the succeeding spacing impulse, it Will be apparentl that the ring D2 cannot be oriented as far in onegdirection as when distortionless signals are being received before failure occurs, which would be indicated by the alarm bell 13.

rlhe difference between the margin With noV distortion and the margin With distortion is the measure of he distortion of the signal.

'lher manner of testing the existence of excessive distortation in the signal character set up hy the relays BG to R10 inclusive by the passage of the brush l1 over t-he segments 6 to 10 is identical with that for testing the firstr signalcharacter and need not be described in detail. Furthermore, for the sake of simplicity, the indicating device and the release relay and other equipment asso;- ciated with the relay train BG to B10 have not been shoivn since such apparatus and its mode of connection would he similar to that shown and 'described in connection With relays R1 to inclusive. Y

lt is desired to point out that the mode of connection of the armatures of relays R1 to with the contact points or the armatures of their adjacent relays depends upon the. arrangement ofthe marking and spacing impulses constituting the particular signal character intended to be received by the train of relays R1 to Thus, for example,

if, instead of the signal character repre-Kv sented by Fig. la, it is desired to receive'a character in which the first, third and fifth impulses are of the marking type andthe second and fourth of the spacing'type, the armature of relayfB.1 should be connected With the armature of relay R2 and the lovver contact of relay R, with the upper contact of relay B3, the armature of relay R3 With the armature of relay B4, the lower contact of which should be Vconnected with the upper contact of relay B5. n practice, it is den sii-able to provide a vplurality of simple switches whereby the armatures of each relay oli' a train may readily be connected With the adjacent higher numbered relay in any desired manner. i

In the drawing the length ot the conductive segment of ring D2 is shown as approximately one-half the total length of a conductive and an insulating' combined. ln practice better results will be obtained if the length of the conductive segment is small, that is, one-fourth or even less of the said total length of the conductive and insulating segments.

The form of embodiment of the invention shown in Fig. l is purely schematic and is not intended to constitute a limitation of the scope of the invention. it is desired to point out that While We have shoivn the receivingapparatus, viz, the. distortion measuring apparatus located at a ditllerent station from that trom which the signals are transmitted, it is to be understood that such distortion measuring apparatus may be located at the transmitting station, sucli being the custom in making so-called loop measure-- ments wherein both terminals ot the line are available at the. same station. in such case, a printing telegraph distributor might be used as a transmitter of the signal characters, which distributor would be operated by the same shaft that drives the brushes ot rings D2 and D.S so that exact synchronism of the transmitting and receiving apparatus could readily be maintained.

While this invention has been as embodied in a particular rangement of parts it is to that it is not so limited but is capable of embodiment in other and diil'erent forms Without departing from the spirit and scope of the appended claims.

What is claimed is:

l. In a distortion measuring system in which a signal comprising a plurality oit electrical impulses is transmitted over a line, the combination With a. source of current impulses of a line and a receiving device comprising means to automatically indicate the magnitude by which the distortion of any of said impulses exceeds a predetermined magnitude.

2. In a distortion measuring system in which a signal comprising Aa plurality of electrical impulses is transmitted over a line, the combination with a source of current impulses of a line and a receiving device comprising means to indicate automatically the distortion of any impulses exceeding a predetermined magnitude and to measure the degree of the said. distortion.

3. In a distortion measuring system the combination with a line ot a transmitting device adapted to impress upon said line signaling characters, each comprising a pluraldisclosed form and arbe understood `ctmnected with said line, and

'of the lengthening or ity ot impulses, and a distortion measuring device comprising a train oi" relays connected Witli a segmental distributing ring whereby cach relay ot said train may be effectively an indicating system connected with said relays to show Whether distortion ot said signal characters exceeds a predetermined limit. Y

4. ln a distortion measuring' system, the combination with a line or' a source of current impulses, a receiving relay responsive to said impulses, a segmental distributor having it-s brush connected with the armature ot said relay whereby open or closed impulses may be applied to said distributor depending upon the position of said armature of the receiving relay, a relay train comprising a plurality of relays, each individual to and connected with a segment of said distributor, the armatures of which relays are connected with certain contacts of the succeeding relays, the mode of connection depending upon the signal character to be received, a second distributor having a sou ce oi potential connected with the brush thereof and an alarm device connected with a predetermined segment thereof, and a relay connected with the armatures of said relay train to prevent the operation olsaid alarm device When the distortion oi the received signal does not exceed a predetermined limit.

5. The method for determining the degree shortening of signal impulses transmitted by a printing telegraph transmitter over a line to a printing telegraph receiver, which consists in applying undistorted impulses to the said receiver and measuring the range through which the receiving segments may be oriented Without failure, applying undistorted impulses to the sending end or the said line for transmission thereover, adjusting the receiving segments to compensate for the time lag between the transmission and reception of signal impulses transmitted over the said line, measuring the range through which the said receiving segments may be oriented Without failure and determining the magnitude or' distortion by the diiierence between the said second measurement and the said tirst measurement.

6. The. method for determining the degree of the lengthening or shortening of signal impulses transmitted by a printing telegraph transmitter over a line to a printing telegraph receiver, Which consists in measuring the range of the receiving segments for undistorted signals, measuring the range of said segments for signals distorted by transmission over the said line and the magnitude of distortionby the difference between the second range and the first range.

7. The method for determining the degree of the lengthening or shortening of signal determiningl lli',

impllllesA transmitted* by a printing telegraph transmitter over 2L iinevte printing teiegraph receiver, which consists in adjust-y ing'the receiving segments Yjor the receptionV iivuridistorted signals, adjusting-for the time lag between transmission and reception of thesaidvsigrials orlenting the receiving segments in each direction rmtil failure occurs Y May, '1923.

in the reception olf theseid segments, and

producing an alarmV Whenever'the receiver 10 AWA' B. @LAR EL. ROY B. SHANGK.

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