US2683874A - Bearing-correlating system - Google Patents

Description

y 3, 1954 J. A. WAINRIGHT 2,683,874

BEARING-CORRELATING SYSTEM Filed Aug. 9, 1952 2 Sheets-Sheet l SOURCE OF ERASING POTENTIAL AMPLIFIER CLIPPER 50 D I 17-! 42 E I M 39) i I i 47 v- 46 I I I AMPLIFIER v- 58 '23? DIFFEREN I CLIPPER 29 mmm- *TIATOR VIBRATO C 57 R I I AMPLIFIER l I {B WW/WWI- 23 44, I? DIRECTION SWEEP TRANS- '''g gg GENERATOR MHTER OUPLEXER 25 I9 20 I l l POWER CONTROL CONTROL SUPPLY unn- H5Wa MA, UNIT Inventor: Joseph A.Wair1v-ight9 H is Attorn y 3, 1954 J. A. WAINRIGHT 2,683,874

BEARING-CORRELATING SYSTEM Filed Aug. 9, 1952 2 Sheets-Sheet 2 i W2 /7 3r Q I uhhh j" Inventor-z Joseph A Wainright,

His Attor-vwey Patented July 13, 1954 BEARING-CORRELATING SYSTEM Joseph A. Wainright, Baldwinsville, N. Y., assignor to General Electric Company, a corporation of New York Application August 9, 1952, Serial No. 303,459

6 Claims. 1

My invention relates to object locating apparatus and, more particularly, pertains to a novel bearing-correlating system for comparing the orientation of a pair of individually rotatable, directional, cnergy-receiving devices.

Although subject to a wide variety of applications, my invention is ideally suited for use in an installation including pulse-echo equipment of the radar-search type and directionfinding D.-F.) equipment and it is an object of the invention to provide a novel system for correlating the bearing information determined through the use of the rotatable, energy-receiving, directional antennas of these equipments. In that way, a remote object which originates wave energy intercepted by the D.F. antenna and which reflects wave energy radiated by the radar equipment may be identified from a group of other remote objects that reflect, but do not originate wave energy.

Another object of my invention is to provide a novel bearing-correlating system for a pair of directional antennas which may be rotated at different, possibly non-synchronous speeds.

Yet another object of my invention is to provide a novel bearing-correlating system for comparing the orientation of the rotatable, energyreceiving devices of individual equipments without reducing the normal operating efficiencies of these equipments.

The bearing-correlating in accordance with my invention usually is associated with a pair of rotatable, directional, energy-receiving devices and comprises an annular path of magnetizable material. Recording and pickup heads are dis posed in magnetic relation with respect to the magnetizable path. Means are provided for relatively displacing the path and the recording head in synchronism with rotation of one of the rotatable devices and for relatively displacing the path and the pickup head in synchronism with rotation of the other of the rotatable devices. The aforesaid one device is electrically coupled to the recording head for producing a change in magnetization on the magnetizable path at a position corresponding to the bearing of a remote energy-transmitting station. The system further includes means electrically coupled to the pickup head for producing an indication in response to the output of the pickup head derived at the aforesaid position of the magnetizable path thereby to denote the orientation of the other rotatable device at the bearing of the remote station.

The features or" my invention which are believed to be novel are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation, together with further objects and advantages, thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing in which Fig. 1 is a diagrammatic illustration of my invention, shown in association with radar and direction-finding equipments represented in block form;

ig. 2 is a detailed mechanical representation shown partly in cross section, of a portion of the apparatus illustrated in Fig. 1; and,

Fig. 3 is a modification of the arrangement shown in Fig. 2.

Fig. 4 is a modification, in diagrammatic form, of a portion of the apparatus shown in Fig. 1.

In Fig. 1 of the drawing, there is illustrated in the lower-right portion a complete radar equipment which includes a rotatable, directional antenna in to which pulses or bursts of radio frequency energy are supplied through a duplexer unit H by a transmitter [2 for radiation into space. These pulses travel through space and may impinge upon a reflecting surface of a remote object and. are returned toward the site of the radar apparatus for interception by antenna I8.

Received echo-pulses of radio-frequency energy from the antenna are applied through duplexer i i to a receiver l3 for demodulation. Duplexer l i may be of any suitable construction for preventing damage and/or blocking of the receiver !3 during the occurrence of radio-fre quency pulses at transmitter l2 and for translating intercepted echo pulses from antenna iii to the receiver with substantially no attenuation which might otherwise occur because of the connection between antenna It and transmitter 12.

Receiver i3 derives from the received radiofrequency energy an undulating potential including pulses representing the reflected pulses and this potential is supplied to the cathode circuit of a cathode-ray type indicator it. The indicator displays echo pulses in such a manner that both bearing and range information of refleeting objects are presented.

As is generally well-known, the velocity of propagation of radio-frequency energy is substantially constant; hence, the range of the reflecting object may be determined by measuring the total travel time of a reflected pulse. In the radar equipment of Fig. 1 this is performed through the use of an accurate time-base sweep for cathode-ray device E4 provided by a sweep generator 5%. Generator it may comprise any well-known form of circuit for deriving a highly linear sawtooth wave having each of its undulations initiated with the transmission of a pulse of radiofrequency energy. One such sawtooth undulation is represented in Fig. 1 and is identified by the letter A. The pulser portion (not shown) of transmitter i2 is coupled to generator l5 so that the necessary synchronism is maintained.

Generator 55 supplies the sweep wave to the deflection coils (not shown) of a deflection yoke it encompassing the neck portion of cathode-ray device The sweep wave causes the beam of device i i to be deflected along a linear path originating at the center of the viewing screen and termihating at the edge thereof.

Deflection yoke 56 is rotatable relative to the neck of device I4- and is mechanically coupled by a suitable gearing, shown for convenience by a dash line ii, to antenna id for rotation therewith. Yoke it rotates once for each revolution of antenna ill.

The sweep wave applied to yoke IE deflects the electron beam radially in a direction corresponding to the orientation of antenna ill and the intensity of the electron beam projected towards the viewing screen is increased in response to each echo pulse. Accordingly, received echoes from one or more remote objects produce intensified spots on the viewing screen at respective distances from the center of the screen proportional to the range of the corresponding object. The angle subtended by a reference radial line and a radial line intercepting an object indication represents the bearing of the object. Therefore, the radar equipment may be utilized to determine both range and bearing of remote objects.

Antenna i8 usually is continuously rotated about a vertical axis by a driving motor 18 which is powered from a source of alternating potential 5 A control unit 23 is provided so that the rotational speed of motor 18 may be adjustably fixed. The motor speed may be such that antenna ii? rotates, for example, at a speed of 30 revolutions per minute. Since the Viewing screen of indicator i i has a persistence comparable to the time of several revolutions of antenna 56, a maplike or plan-position presentation of remote objects in the area surrounding the radar equipment is displayed on the screen.

The arrangement of Fig. 1 also includes direction-finding (ll-F.) equipment, shown in the lower-left portion of the figure. This equipment comprises an antenna system including a directional, rotatable loop antenna 2| and a sense antenna 22 for intercepting radio-frequency energy radiated from remote stations. The antennas 2i and 22 are coupled to a receiver 23 in such a manner that the overall space pattern of the antenna system is essentially unidirectional, having an axis of maximum directivity.

Antenna 2i is continuously rotated about a vertical axis by a synchronous constant-speed driving motor 24 which is powered from source z..-

i9. Another control unit 25 permits an individual speed adjustment for antenna 2| and, for example, this antenna is rotated at a speed of 1860 revolutions per minute.

Although direction-finding equipment 2 l-23 has been illustrated as of the type including a loop antenna, it may alternatively comprise a goniometer arrangement in which a group of fixed antenna are electrically coupled to a commutating system operable in a well-known manner to provide a rotatable axis of maximum directivity for the antenna system.

In operation, receiver 23 is tuned to the transmitting frequency of a remote station, which usually is different from the operating frequency of radar transmitter I2, and as antenna 2! 1'0- tates, the amplitude of the radio-frequency energy supplied to the receiver varies from a low value, to a maximum and to the low value as the axis of maximum antenna directivity is altered from one side, to the exact bearing of the remote transmitter and then to the other side. More specifi cally, if the remote transmitter is tone modulated, the output tone derived by receiver 23 at an output lead 25 is amplitude modulated at a frequency of 30 cycles per second, or a frequency corresponding to the speed of rotation of antenna 24. This output wave is represented at B in Fig. 1. Since motor 24 is synchronous with the frequency of power supply [9, the phase of the modulation of wave B, with respect to that of source I 9, or of the rotational phase of motor 24, is dependent upon the bearing of the remote transmitter.

Output wave B at lead 26 is supplied to an amplifier 21, in turn, coupled to a rectifier 28 and a wave C, representing the modulation component of wave B, is applied to an amplifier-clipper 29. Thus, there is derived at output lead 3? of stage 29 a wave D comprised of narrow pulses each of which is timed with one of the maxima of wave B.

Pulse-wave D is applied over lead 33 and a brush-slip ring arrangement to a magnetic recording head 32 fixed to a carriage 33. Recording head 32 is disposed in magnetic relation with respect to an annular, preferably circular, tape of magnetizable material 34. The tape defines a circular path which is supported for rotation about a concentric axis 35, extending transversely to the plane of the sheet of Fig. l. Carriage 33 also is supported for rotation about axis 35.

Circular tape 34 is rotatably coupled with antenna ill by an extension of linkage 5?; hence, the tape rotates in the direction of arrow W synchronously with antenna l0, or revolves once for each revolution of the antenna. Antenna 2i is rotatably coupled via a linkage 33 to one input shaft 31 of a mechanical differential device 38 having another, coaxial input shaft 39 rotatably connected by a linkage 40 with tape 3 In other words, input shafts 31 and 39 are effectively mechanically coupled with antennas 2i and i3 and are arranged to rotate in the same direction, in an installation in which these antennas rotate in the same direction, so that frame 4! of dif ferential 38 rotates at a speed equal to the di.f-- ference in antenna speeds. Frame 41 rotates carriage 33 via a linkage 42; thus, recording head 32 rotates about axis 35 in the direction of arrow X at a speed equal to the aforesaid difference. Since tape 34 rotates at the speed of and in synchronism with antenna H], it is apparent that the system includes means for relatively displacing path 34 and recording head 32 in synchronism with rotation of D.-F. antenna 2 l.

A pickup head 43 is disposed in magnetic relation with respect to magnetic tape 34 and is mechanically fixed relative to axis 35. Thus, the aforesaid means also operates relatively to dis place path 34 and pickup head 43 in synchronism with rotation of radar antenna it.

Because antenna 2! rotates in synchronism with motor 24, the relative rotation between recording head 32 and tape 34 provides a reference against Which the phasing of the output wave of receiver 26 may be compared. In other words, each pulse of wave D, for a remote transmitter having a fixed bearing, occurs when a particular portion P, and only that portion, of tape 3 3 passes recording head 32. Since D.-F. antenna is effectively coupled via receiver 23, amplifier 2i, rectifier 23, amplifier-clipper 29, lead 39 and brush-slip ring arrangement 3! to recording head 32, a change in magnetization in response to each pulse of Wave D is produced on path 34 at position P corresponding to the bearing of the remote-energy transmitting station. For a remote station having a different bearing, of course, other portion of tape 3' 3 is similarly affected. Thus, the 360 degrees of perimeter of tape 3 define equivalent degrees of rotation for antenna Since antenna ill rotates at 30 revolutions per minute and antenna 2! rotates at 1800 revolutions per minute, recording head 32 passes point P a plurality of times before point P reaches the vicinity of pickup head d3. As a consequence, wave energy received from the remote transmitting station is effectively integrated with respect to time by reason of the storage properties of magnetic tape 3 and the signal-to-noise ratio of the direction finding equipment thereby is materially improved as compared with a system in which the output of receiver 25 is supplied directly to an indicator.

As point P of tape 3 passes pickup head it a pulse is derived therein, as a result of the discontinuity in magnetization along the tape, and applied over a lead ed to an amplifier-clipper stage 45. The resulting sharpened pulse, represented at E, is applied to a diiTerentia-tor 86. The output of differentiator 36 is a Wave F which includes a positive pulse corresponding to the leading edge of pulse E and a negative pulse corresponding to the trailing edge of pulse E. The positive output pulse of stage 48 is employed to trigger a single-shot multivibrator i! which produces a rectangularly-shaped wave G that is applied over a lead 48 to the control electrode of cathode ray indicator 54. Each rectangular pulse of wave G is of positive polarity and a duration corresponding to the occurrence of approximately two successive undulations in sawtooth wave A.

Antennas it and 2! are so aligned that point P arrives at recording head 42% at the same time antenna IE! rotates to the bearing of the remote transmitting station. Inasmuch as the radial sweep caused by wave A is oriented in accordance with the position of antenna it], it is evident that the rectangular pulse of Wave G- increases the intensity of the electron beam within cathode ray indicator i at the time antenna it rotates to the station bearing. Hence, the system of Fig. 1 comprises means electrically coupled to pick up head 53 for producing an indication, in the form of an intensified, radial line on the screen of tube It, in response to the output of the pic:- up head, derived at position P of path 3A. This denotes the orientation of radar antenna ii at the bearing of the remote transmitting station.

If, for example, the remote transmitting station is carried by a vehicle such as an aircraft, in addition to the bearing indication derived through the use of the system embodying my invention, the radar apparatus itself produces intensified area of the viewing screen of tube it at a position defining the range bearing of the craft. The spot so produced is intersected by the radial line due to the D.-F. equipment; consequently the craft may be positively identified from others in the vicinity that cause echo-produced indications on indicator Hi but which do not originate radio-frequency energy for interception by D.-F. antenna 2! To permit the system of Fig. l to follow a remote object which is continually changing its bearing, there is provided an erasing head 59 disposed in magnetic relation with respect to tape 3 and fixed relative to pickup head 33. A source Ell supplies an alternating, erasing poten tial to head 49 and it is positioned to one side of the pickup head it so that point P, for example,

passes the pickup head before arriving at the erasing head. Thus, subsequent to the production of a radial line on indicator i i in response to the output of pickup head is, the magnetization at point P is altered or reduced to a quiescent value corresponding to that of the remainder of the tape and the bearing information is there= by erased. Of course, if the remote station remains at the same bearing, information by way of a change in magnetization is again recorded and stored as point P and recording head 32 one another. The cycle of operation thereupon continues in the manner described hercinbeiore with an indication produced upon indicator followed by the erasing operation of head it.

It is, therefore, apparent that each time 11-1 antenna 2! rotates through the bearing of a remote transmitting station, a record is made on tape 36. The record is utilized so that when antenna it) rotates to the remote stations bearing a trace-brightening pulse produces a corresponding radial indication on the viewing screen of cathode ray device id. Although the system has been shown in association with a driving motor supply effecting synchronous operation, it erfectively measures absolute angles and there is no requirement as to relative speeds and/or synchronism in rotation of antennas it El. This is advantageous because each of the radar and D."F. equipments may be operated in the manner best suited to its needs. Therefore, the bearing correlating system in accordance with my invention does not impose any operating limitations or reductions in efiicienoy on either of these equipments, yet it functions to correlate direction information derived by these equip-- ments.

Although the trace-brightening pulse G which is applied to indicator i l by multivibrator t? has not been defined as having any particular synchronous relationship with sweep wave A generator IE, it is to be understood that ssynchronism may be suitably employed. For ample, multivibrator i? may be arranged so that the positive pulse of wave F transfers it from a non-operative to an incipiently-operative con dition. into operation with the inception of the nearfollowing undulation of the sawtooth wave. this case, it is preferable that the duration of the rectangular pulse in wave G be equal to that of one sawtooth undulation and a single trace along the viewing screen of indicator i4 is tensified.

In Fig. 2 the mechanical details or r ing and reproduction system of Fig. l are she Corresponding elements are represented same reference characters.

Linkage H is coupled with a shaft 55 that is supported for rotation by journals 52, 53, A cylindrical, drum-like carriage 54 is disposed coaxially with respect to shaft i and is provided with an end wall 55 having a coaxial opening which receives shaft 5 I Shaft 5| is threaded and nut 56 is tightened against wall 55 driving it into engagement with a flange 5'? of the shaft thereby fixing drum 54 to the shaft. Thus, car riage 54 is supported for rotation about concentric axis 35 and is mechanically coupled to radar antenna H2 for synchronous rotation therewith.

The cylindrical wall of carriage 56 is provided with a section of section 58 of reduced thickness formed by providing coaxial, channe1-1ike grooves in the inner and outer surfaces of the wall. A ring or band of magnetizable material 3-4 is fixed to and extends about the outer surface of wall portion 58 of carriage 54.

Another carriage, in the form of a disk 59, is disposed at the open end of carriage 5t and is supported in a bearing 66 for rotation about the axis of rotation 35 of shaft 5!. Recording head 32 is fixed to carriage 59 and extends within carriage 54 to a position just adjacent wal portion 53 and is thereby disposed interiorly of cylindrical carriage 54 in magnetic relation with respect to magnetic ring 3 3. Since recording head 32 is movable, brush-slip ring arrangement 35 is provided in order to maintain electrical connections therewith.

To dynamically balance this portion of the mechanical system, a counterweight iii is to carriage 59 in a position diametrically opposite recording head 32.

Pickup head 43 is disposed exteriorly of cy1indrical carriage 54 and extends toward wall section 58 so that it is disposed in magnetic relation with respect to ring 34. Head 43 is secured to a stationary support 62 and thus is mechanically fixed relative to the rotational axis 35 of carriage 5d. The erasing head 49 (not shown) is fixed to support 62, behind head As pointed out in connection with Fig. l, in order to cause recording head 32 and path 35 to rotate relative to one another at a speed equal to the difference in rotational speeds of antennas it and 2 l, the mechanical system includes differential device 38. Linkage 36 connects antenna with input shaft 37 of differential 38 and its other coaxial input shaft is formed by an extension of shaft 5|. Thus, the input shafts of differential 38 are driven in synchronism with antennas it and 2|.

A gear 31, having a coaxial opening (not shown) through which input shaft 39 passes, is mechanically connected with frame ll of the difierential device and rotatable therewith. Gear t? may be defined as an output shaft for deriving the difference in rotational speeds between the input shafts and is mechanically coupled to recording head 32 by a gear system. In this gear system, a driven gear 63 is in mesh with gear 67 and fixed to a shaft 64. A driving gear 55, also fixed to shaft 65, and is in mesh with a gear 66 formed at one end of journal 68, so that carriage 59 is driven in synchronism with rotation of output gear 61. With the foregoing arrangement, recording head 32 and path 34 are rotated relat ve to one another at a speed corresponding to the rotational speed of D.-F. antenna 23.

In the modified form of the carriage 54 shown in. Fig. 3, instead of using a band of magnetic material for path 3A, a circular wire 3 is embedded in wall section 58 of the carriage.

If it is desired to eliminate diiferential device 33 from the system, certain modifications may be made in the arrangements of Figs. 1 and 2 as shown in Fig. 4. In the first place, magnetic tape 34 is fixed relative to axis 35 and carriage 33 is directly coupled with linkage 36 so that recording head 32 rotates in synchronism with D.-F. antenna 2!. In addition, pickup head 33 and erasing head 48 are supported for rotation, by another carriage in synchronism with rotation of radar antenna it. A suitable brush-slip ring arrangement is provided in order to make electrical connections with heads 13 and 59. The operation of this modification follows that presented in connection with the arrangement of Fig. 1.

While particular embodiments of my invention have been shown and described, it is apparent that changes and modifications may be made Without departing from the invention in its broader aspects and therefore the aim of the ap pended claims is to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A bearing-correlating system for a pair of rotatable, directional energy-receiving devices comprising an annular path of magnetizable material, recording and pickup heads disposed in magnetic relation with respect to said path, means for relatively displacing said path and said recording head in synchronism with rotation of one of said devices and for relatively displacing said path and said pickup head in synchronism with rotation of the other of said devices, means electrically coupling said one device to said rccording head for producing a change in magnetization on said path at a position corresponding to the bearing of a remote energy-transmitting station, and means electrically coupled to said pickup head for producing an indication in response to the output of said pickup head dcrived at said position of said path thereby to denote the orientation of said other device at said bearing.

2. A bearing-correlating system for a pair of rotatable, directional energy-receiving devices comprising an annular path of magnetizable material, recording and pickup heads disposed in magnetic relation With respect to said path, means for relatively displacing said path and said recording head in synchronism with rotation of one of said devices and for relatively displacing said path and said pickup head in synchronism with rotation of the other of said devices, means electrically coupling said one device to said recording head for producing a change in magnetization on said path at a position corresponding to the bearing of a remote energy-transmitting station, means electrically coupled to said pickup head for producing an indication. in response to the output of said pickup head derived at said position of said path thereby to denote the orientation. of said other device at said bearing, and an erasing head disposed in magnetic relation with respect to said path and in fixed physical relation relative to said pickup head for altering the magnetization of said path subsequent to the production of said indication.

3. A bearing-correlating system for first and second rotatable, directional energy-receiving devices comprising a circular path of magnetizable material supported for rotation about a concentric axis and mechanically coupled to said second device for synchronous rotation there-- with, a recording head disposed in magnetic relation with respect to said path and supported for rotation about said axis, a pickup head disposed in magnetic relation with respect to said path and mechanically fixed relative to said axis, differential means including one input shaft mechanically coupled to said first device, another input shaft mechanically coupled to said second device and a difference, output shaft mechanically coupled to said recording head for producing relative displacement between said path and said recording head in synchronism with rotation of said first device, means electrically coupling said first device to said recording head for pro ducing a change in magnetization on said path at a position corresponding to the bearing of a remote-energy-trans1nitting station, and means electrically coupled to said pickup head for producing an indication in response to the output of said pickup head derived at said position of said path thereby to denote the orientation of said second device at said bearing.

4. A bearing-correlating system for first and second rotatable, directional energy-receiving devices comprising a cylindrical carriage supported for rotation about a concentric axis and mechanically coupled to said second device for synchronous rotation therewith, a ring of magnetizable material fixed to said carriage in coaxial relation therewith, another carriage supported for rotation about said axis in proximity to said first-mentioned carriage, a recording head fixed to said other carriage and disposed in magnetic relation with respect to said ring, a pickup head disposed in magnetic relation with respect to said ring and mechanically fixed relative to said axis, differential means including one input shaft mechanically coupled to said first device, another input shaft mechanically coupled to said second device and a difiference, output shaft mechanically coupled to said other carriage for producing relative displacement between said ring and said recording head in synchronism with rotation of said first device, means electrically coupling said first device to said recording head for producing a change in magnetization on said ring at a position corresponding to the bearing of a remote energy-transmitting station, and means electrically coupled to said pickup head for producing an indication in response to the output of said pickup head derived at said position or" said ring thereby to denote F to said first-mentioned carriage, a recording head fixed to said other carriage and disposed interiorly of said cylindrical carriage in magnetic relation with respect to said ring, a pickup head disposed exteriorly of said cylindrical carriage in magnetic relation with respect to said ring and mechanically fixed relative to said axis, difierential means including one input shaft mechanically coupled to said first device, another input shaft mechanically coupled to said second device and a difference, output shaft mechanically coupled to said other carriage for producing relative displacement between said ring and said recording head in synchronism with rotation of said first device, means electrically coupling said first device to said recording head for producing a change in magnetization on said ring at a position corresponding to the bearing of a remote energy-transmitting station, and means electrically coupled to said pickup head for producing an indication in response to the output of said pickup head derived at said position of said ring thereby to denote the orientation of said second device at said bearing.

6. In combination with a direction-finding antenna having a field pattern including an axis of maximum receptivity and rotatable at a first speed and a radar antenna having a field pattern including an axis of maximum receptivity and rotatable at a second speed, lower than said first speed, an annular path of magnetizable material, recording and pickup heads disposed in magnetic relation with respect to said path, means for relatively displacing said path and said recording head in synchronism with rotation of direction-finding antenna at said first speed and for relatively displacing said path and said pickup head in synchronism with rotation of said radar antenna at said second speed, means electrically coupling said direction-finding antenna to said recording head for producing a change in magnetization on said path at a position corresponding to the bearing of a remote wave-energy-transmitting station each time said axis of said direction-finding antenna attains said bearing, and a plan-position type indicator mechanically and electrically coupled with said radar antenna and electrically coupled to said pickup head for producing an indication in response to the output of said pickup head derived at said position of said path thereby to denote the orientation of said axis of said radar antenna at said bearing.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,551,589 Everhart May 8, 1951 2,582,962 Burroughs Jan. 22, 1952 2,597,895 Novy May 27, 1952

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