US3307168A - Signalling system - Google Patents

Signalling system Download PDF

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Publication number
US3307168A
US3307168A US238407A US23840762A US3307168A US 3307168 A US3307168 A US 3307168A US 238407 A US238407 A US 238407A US 23840762 A US23840762 A US 23840762A US 3307168 A US3307168 A US 3307168A
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Prior art keywords
responder
magnetic field
signals
movable
oscillator
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Expired - Lifetime
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US238407A
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English (en)
Inventor
John F Zaleski
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General Precision Inc
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General Precision Inc
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Priority to US238407A priority Critical patent/US3307168A/en
Priority to DEG39180A priority patent/DE1230693B/de
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B61—RAILWAYS
    • B61L—GUIDING RAILWAY TRAFFIC; ENSURING THE SAFETY OF RAILWAY TRAFFIC
    • B61L25/00—Recording or indicating positions or identities of vehicles or trains or setting of track apparatus
    • B61L25/02—Indicating or recording positions or identities of vehicles or trains
    • B61L25/04—Indicating or recording train identities
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B61—RAILWAYS
    • B61L—GUIDING RAILWAY TRAFFIC; ENSURING THE SAFETY OF RAILWAY TRAFFIC
    • B61L25/00—Recording or indicating positions or identities of vehicles or trains or setting of track apparatus
    • B61L25/02—Indicating or recording positions or identities of vehicles or trains
    • B61L25/04—Indicating or recording train identities
    • B61L25/043—Indicating or recording train identities using inductive tags

Definitions

  • a train of railroad cars arriving at a switching terminal are first individually identified and then uncoupled and sorted in a predetermined manner, with selected cars being directed to various tracks and storage locations. Further, when an outgoing train is to be assembled, it is often necessary that a search be made among a large number of railroad cars in order to locate a particular car.
  • various data processing systems have been deviced which are readily adaptable to sort, classify, and store data associated with any desired number of cars, yet the deviation of suitable input data relating to the characteristics of the individual cars has proven to be relatively expensive, so that full use of the available data processing machinery has not been extensive.
  • Photoelectric sensing means have been proposed for reading binary stripes on railroad cars, wherein the binary data is encoded in either dark or light stripes.
  • microwave power has been beamed at passive responder units which include fractional wave length apertures to provide a predetermined and unique reflected signal pattern.
  • radioactive sensing means have been proposed to detect radioactive elements carried in otherwise passive responders.
  • most of the systems of the prior art have, as yet, not enjoyed extensive commercial success. This results from the fact that in many of the systems, the accuracy and reliability of the derived input data is critically affected by the distance between the interrogating element and the responder element, which, of course, is movable over relatively wide limits.
  • Patent No. 3,125,753 assigned to the assignee of the present invention.
  • the system utilizes completely passive responder elements which are inductively energized as they intercept an interrogation station, and each responder element provides a uniquely coded response signal, when interrogated by the interrogation station, which response signal is thereafter decoded by the interrogation station to provide the desired input data relating to the char- 3,307,168 Patented Feb. 28, 1967 acteristics of the moving vehicle upon which the responder is mounted.
  • Apparatus of this general type exhibits several advantages over systems of the prior .art, including an improved signal-to-noise ratio which is uneffected by environmental conditions, as well as readily adaptability to large scale installations wherein many thousands of different objects must be individually identified.
  • the apparatus of the invention includes one or more interrogation stations and one or more responder elements.
  • the interrogation station first provides a constant magnetic field which is effective to energize a responder element.
  • Each responder element upon being energized by this magnetic field, thereupon provides a number of signals at predetermined radio frequencies, selected in accordance with the input data to be derived therefrom, which :are thereafter accepted by the interrogating station.
  • the interrogating station decodes the signals received from each energized passive responder element in a novel manner, which includes an electronic counter operating with a fixed time base, and provides the input data relating to the characteristic of the movable vehicle upon which the responder elements :are mounted in a form determined by the overall data handling system.
  • Another object of the invention is to provide an improved apparatus for signalling between one or more movable devices and one or more fixed locations.
  • a further object of the invention is to provide a signalling system including improved passive responder elements for deriving input data relating to the identities of or characteristics of movable vehicles.
  • Still another object of the invention is to provide a more economical signalling system for transmitting predetermined information between fixed and movable locations.
  • Another object of the invention is to provide an improved signalling system for transmitting information between fixed and movable locations wherein the order of information is insensitive to the direction of relative motion between the locations.
  • Yet another object of the invention is to provide a signalling system including improved means for interrogating one or more passive responder elements.
  • a still further object of the invention is to provide an improved signalling system for identifying and classifying the movable vehicles of a transportation system.
  • a related object of the invention is to provide an improved signalling system for identifying and classifying the movable items on a conveyor line in a material handling system.
  • FIG. 1 is a schematic diagram of a preferred embodiment of the invention.
  • FIG. 2 is a further schematic of a portion of the apparatus of FIG. 1.
  • FIG. 3A illustrates the magnetic field provided by a bar magnet.
  • FIG. 3B is an enlarged view of portions of FIG. 3A.
  • FIG. 4 indicates the location of a responder element and an interrogation station as installed in one embodiment of the invention.
  • FIG. 5 illustrates the output signals provided by a responder element of the invention.
  • FIG. 1 illustrates a preferred embodiment of the invention, which includes a single responder element and an interrogation station 12, it being understood that a plurality of such responder elements and one or more interrogation stations are employed in any large scale system.
  • the responder unit is mounted upon the movable device to he identified and includes a pair of passive oscillator units, each operable at a predetermined frequency.
  • each of the passive oscillators is sequentially automatically operated in a novel manner, which is independent of the relative direction of motion between a responder element and an interrogation station, as more particularly hereinafter described.
  • responder element 10 includes a pair of pickup inductors 13 and 14, each of which is coupled to a simple yet reliable crystal-controlled transistor oscillator.
  • a voltage is induced in each inductor in the conventional manner, and this voltage is sufficient to provide the necessary power for the oscillator associated therewith.
  • the oscillators are oppositely connected to their respective inductors, and for this reason, only one oscillator is operable at any instant of time.
  • a current flows through the collector-emitter circuit of transistor 15 and a resonant feedback tank circuit which includes a coil 17 and a variable capacitor 18.
  • coil 17 additionally functions as a loop antenna to radiate the generated signal at a frequency determined by a crystal 19, and the loop is distributed over as wide an area as is possible in order to obtain maximum radiation.
  • a capacitor 20 contributes significantly to oscillator stability and greatly increased efiiciency at the lower crystal frequencies. However, as will be understood by those skilled in the art, it must be maintained at a minimum value in order to avoid excessive crystal ringing.
  • the distributed capacitance of inductor 13 is effective to by-pass the RF. signal around the inductor impedance.
  • the oscillator associated with transistor 16 is identical to that described above, and, since the oscillators per se form no part of the invention, various other types and circuits may be substituted therefor, provided only that they supply the necessary stable predetermined output frequencies. Finally, a wide choice is available with respect to the inductor design other than that as illustrated in FIG. 1, including, but not limited to, a bifilarly wound inductor, or even a single inductor with the pair of oscillators coupled thereto by means of a pair of oppositely-poled diodes.
  • interrogation station 12 of FIG. 1 it is seen first that a pair of permanent magnets 36 and 38 are associated therewith. Alternatively, an electromagnet could also be employed. Either of these magnets individually provides the necessary energizing power for each of the oscillators of a moving responder unit, as will be better understood in conjunction with the hereinafter detailed description of the operation of the system.
  • a typical receiver unit which is broadly tuned to accept any frequency generated by any of the plurality of responder elements. This receiver is coupled to loop antenna 39 and is represented by amplifier block 40.
  • Block 40 provides the necessary gain to amplify the minimum signal from a responder unit to a level sulficient for use with the output circuitry employed.
  • Gate 42 isolates the output of block 40 from further decoding circuitry until the level of the output exceeds a predetermined level at which time detector 44 is effective to open gate 42, and to maintain the gate open until the output signal fails to exceed the predetermined level.
  • the decoder comprises an Events-Per-Unit-Iime Meter (or commonly an E-put meter), indicated as block 44 in FIG. 1, which is coupled to the output of gate 42 by a line 46 and to detector 44 by a line 48.
  • E-put meter or commonly an E-put meter
  • a typical E-put meter comprises an electronic pulse counter effective to count all input pulses occurring during a predetermined time period, the length of which is controlled by an accurate and highly precise time base.
  • a simplified E-put meter, corresponding to block 44 of FIG. 1, is shown in somewhat more detail in FIG. 2.
  • a crystal-controlled clock pulse oscillator 50 provides a continuous and precisely timed train of pulses. Since the accuracy of the frequency measurement is directly determined by the pulse timing, this timing accuracy is generally held to 1 part per million or less. In order to attain this precise timing, however, it is usually necessary to operate at crystal frequencies in the order of 10 me., a frequency which does not provide for sufficient counting time. For this reason, frequency division is accomplished in FIG. 2 by a binary counter 52 and a gate circuit 54.
  • Gate circuit 54 is connected to the stages of binary counter 52 in order to determine the presence of a predetermined count therein, at which time an output signal is provided along a line 56. Upon the next occurrence of the predetermined count in counter 52, another output signal is provided along line 56.
  • the signals along line 56 are coupled to flip-flop 58, a first output of which is applied to the reset and readout inputs of a decimal counter 60 and the second output of which is fed to an input of a differentiator 62.
  • diiferentiator 62 which consists of a sequence of alternate positive and negative accurately timed pulses, is coupled to one input of a gate 64, the operation of which is controlled by level detector 44 (see FIG. 1) along line 48.
  • the output of gate 64 comprising a series of pulses, timed by flip-flop 58 when a signal above a predetermined level is being received by interrogation station 12, is then fed to a further flipflop 66 which controls the operation of yet another gate 68.
  • signals appearing along line 46 are coupled to counter 60 only during the predetermined time periods.
  • the readout data from counter 60 is coupled to a printer or output data converter, the latter being effective to link the counter to a strip chart recorder, a card punch, a paper, a punch, or the like, in accordance with the overall system requirements.
  • a responder element is secured at a common loca tion of each car, with the frequencies of the crystals therein selected in accordance with the input data to be derived from the individual car, as more particularly hereinafter explained.
  • An interrogation station is then installed at a desired location with the magnets associated therewith positioned to ensure that a magnetic field, of at least a predetermined magnitude, is present in the area to be traversed by the responder elements.
  • the interrogation station may be located in the movable car, with the responder elements installed in the railroad roadbed.
  • the magnetic field provided by the interrogation station must be parallel to the directions of motion of the railroad cars; i.e., parallel to the tracks, and the major axes of inductors 13 and 14 of the responder element (see FIG. 1) must also be parallel to the tracks.
  • the responder inductors link the flux of the magnetic field and the change in flux resulting from the moving inductors, and the stationary magnetic field induces a voltage in the inductors of first one polarity, for example that shown in FIG.
  • FIG. 3A illustrates the conventional flux lines which indicate the magnetic field produced by a standard bar magnet.
  • FIG. 3B is an enlargement of the dashed portions of FIG. 3A.
  • the sequence of frequencies generated by the responder element that is, f -f is independent of the direction of motion between the responder element and the interrogation station
  • the frequency sequence is not independent of the orientation of the responder element with respect to the magnetic field, and it is for this reason that a pair of separated magnets are employed in the apparatus of the invention.
  • FIG. 4 there is illustrated a typical installation of the apparatus as applied in a railroad car identification system. As shown, loop antenna 39 is positioned along the center line between the tracks, while magnets 36 and 38 are offset therefrom.
  • each magnet is aligned eighteen inches inwardly from the adjacent flange, resulting in a two foot separation between the magnets to thereby prevent the magnetic fields generated by the magnets from interacting one to another.
  • a responder element 10 is secured to the lower surface of a railroad car and offset one foot from the center line thereof as shown.
  • the movable device or railroad car is movable only back and forth between a pair of fixed locations only a single magnet is required. In the general case, however, wherein the probability of the movable device being rotated exists, it is necessary that the double magnet installation illustrated in FIG. 4 be employed.
  • poles of the magnets are oppositely positioned as indicated in FIG. 4 in order to counteract the 180 rotation of inductors 13 and 14.
  • a single magnet could be employed in a general installation provided that f never exceeds a predeterminer frequency and that f never be selected to fall below the predetermined frequency. Such restrictions, of course, materially reduce the maximum number of individually identifiable responder elements.
  • An exemplary system uses response frequencies ranging from 2.5 me. to 7.5 mc. spaced at uniform 10 kc. intervals, providing 500 different response frequencies. Since two crystal-controlled oscillators are used in each responder element, approximately 250,000 different responders may be provided, each of which produces a unique set of two response signals. By way of example, employing fre quencies of 4,020 kc. and 6,170 kc. in a responder, and a time base of 1 millisecond in the E-put meter, the resulting output identification would be 4020 and 6170, identifying, for example, Car Number 402617.
  • time base should not be less than three times the time of the shortest response signal to ensure obtaining a positive count, that is, to ensure that gate 68 (see FIG. 2) is open dur ing a counting interval, and, in general, the time base is made longer than this.
  • Resistor 21 50,000 ohms.
  • Inductor 13 35,000 turns, No. 37 heavy Form- Coil 18 8 rogation station in the range of l to 60 miles per hour, the peak power level induced into coils l3 and 14 is at least 4 milliwatts and ensures a signal-to-noise ratio of about 30 db. Further, the operation of the responder element is unaffected by ferrous or non-ferrous structures in the vicinity thereof provided the structures are separated from the responder element by at least 3 inches and do not themselves generate a magnetic field.
  • the oscillator has a varying impulse of voltage applied to it. Since the impedance of the transistor is a function of this varying voltage, the crystal controlled voltage should also be expected to vary. However, in the circuit shown and described, this variation is only 0.02% or less of the selected frequency. Further, over a temperature range of 50 C. to +85 C. the maximum oscillator frequency deviation is about 0.002%. This is a cumulative deviation due to crystal and transistor changes. Amplitude change over this same temperature range is less than 1 /2 decibels. A typical response provided by a responder element is illustrated in FIG. 5.
  • the preferred embodiment of the invention as above described provides an automatic vehicle identification system relating to moving vehicles, wherein the vehicle is provided with a coded responding identification unit which is not dependent upon any conventional built-in power supply subject to statistical failure or require replacement or servicing of the supply elements.
  • the responder element comprises a pair of radio frequency oscillators powered by internally connected inductors which are energized as the vehicle carrying the responder element passes over a permanent bar magnet located in the roadbed. The nature of the connections of the oscillators to the inductors is such that, regardless of the direction of travel of the vehicle along the roadbed the radio frequency signal combinations are always emitted in an h-f sequence.
  • a signalling system comprising,
  • At least one responder element At least one responder element
  • At least one interrogation station At least one interrogation station
  • said responder element including a pair of inductors, a pair of normally passive oscillators, and means coupling each of said oscillators to one of said inductors;
  • said interrogation station including means to provide a time-invariant magnetic field and means responsive to response signals from said pair of normally passive oscillators of said responder element to determine the frequencies of said oscillators;
  • said signal being effective to sequentially energize said oscillators.
  • a signalling system comprising,
  • a responder element including first and second normally passive oscillators, said first oscillator being operable in response to a signal of one polarity and said second oscillator being operable in response to a signal of the other polarity, each of said oscillators being compi ed to a pickup inductor;
  • an interrogation station including means for providing a time-invariant magnetic field
  • said interrogation station includes measuring means to measure the frequencies of said first and second oscillators, said measuring means including means for counting each of said oscillator signals for predetermined times.
  • a signalling system comprising,
  • an interrogation station including means for receiving and identifying radio signals within a predetermined frequency range and means for providing a time-invariant magnetic field;
  • a responder element including a pair of normally passive crystal oscillators, each of said oscillators including a resonant circuit consisting of a coil and a capacitor wherein said coil additionally operates as a radiation antenna, and an inductor coupled to each of said oscillators, each of said inductors being oppositely coupled to its associated oscillator;
  • a signalling system comprising,
  • a movable station including means selectively operable to transmit information signals at a plurality of discrete frequencies lying within a predetermined frequency range;
  • (0) means for operating said selectively operable means of said movable station including means positioned adjacent said fixed station for providing a predetermined time-invariant magnetic field in the path of said movable station.
  • a signalling system in which said means for transmitting said information signals comprises a plurality of successively operated oscillators.
  • a signalling system in which said time-invariant magnetic field in the path of said movable station includes a plurality of components of mutually-opposite sense whereby inductor means traversing said components successively will provide successive operating signals of opposite sense, and in which said means selectively operable to transmit said information signals comprises a plurality of oscillators connected to be selectively operated by said successive operating signals.
  • said means for receiving said information signals includes amplifier means, level detector means for providing a first control signal, timing means for providing a second control signal, a pulse counter, and gate means responsive to said control signals for applying signals from said' amplifier means to said pulse counter.
  • timing means comprises a further oscillator, a counter connected to be advanced by signals from said further oscillator, and gating means connected to be operated by said couter to provide said second control signal.
  • a signalling system comprising, in combination:
  • said devices being relatively movable with respect to each other along a line in first and second opposite directions
  • said interrogator device including means for providing a unidirectional magnetic field having a component extending in a third direction normal to said line and means for receiving and decoding a response signal
  • said responder device including an inductor operable to generate current upon traversal of said responder device through said magnetic field, and oscillator means connected to be powered by said current to generate said response signal.
  • said means for receiving and decoding said response signal comprises a pulse counter and means for applying said response signal to said pulse counter for a predetermined length of time.
  • said unidirectional magnetic field includes a first portion having a component extending in said third direction and a second portion having a component extending in a fourth direction opposite to said third direction, said first and second portions being spaced apart from each other along said line
  • said oscillator means comprises a first oscillator connected to provide response signal at a first selected frequency upon generation of said current with a first polarity and a second oscillator connected to provide response signal at a second selected frequency upon generation of said current with an opposite polarity.
  • a railroad car identification system comprising;
  • an interrogation station including means stationed at a railroad trackway for providing a time-invariant magnetic field and means to measure the frequency of received response signals within a predetermined frequency range;
  • each of said cars being movable along said trackway and each including a responder element
  • each of said responder elements including normally passive oscillator means for transmitting to said interrogation station first and second response signals when said responder elements enter into and leave from said magnetic field,
  • said means for providing said magnetic field consists of a pair of spaced apart bar magnets.
  • a railroad car identification system comprising;
  • an interrogation station including means for providing a magnetic field having first and second spaced apart mutually-parallel components extending in first and second mutually-opposite directions, means for receiving signals within a selected band of frequencies, and means for determining and indicating the frequency of any signal received within said band; a plurality of railroad cars to be identified, each of said cars including a responder element secured thereon and positioned to intercept said magnetic field when said cars pass said interrogation station thereby to produce first and second successive operating signals of mutually-opposite sense, the sequence in which said operating signals are produced being independent of the direction of travel of said car with respect to said station; each of said responder elements including normally passive oscillator means for transmitting to said interrogation station first and second response signals upon generation of said sequence of operating signals when said movable responder elements traverse said first and second magnetic field components,

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Train Traffic Observation, Control, And Security (AREA)
  • Near-Field Transmission Systems (AREA)
US238407A 1962-11-19 1962-11-19 Signalling system Expired - Lifetime US3307168A (en)

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US238407A US3307168A (en) 1962-11-19 1962-11-19 Signalling system
DEG39180A DE1230693B (de) 1962-11-19 1963-11-15 Elektrische Einrichtung zur Identifizierung von entlang einer vorbestimmten Bahn bewegbaren Gegenstaenden

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3543261A (en) * 1968-06-14 1970-11-24 Us Air Force Upper threshold circuit
US3662167A (en) * 1970-04-09 1972-05-09 Westinghouse Air Brake Co Train identity control system
US3713102A (en) * 1970-04-23 1973-01-23 S Martin Pulse interrogation article-sorting system
US3717864A (en) * 1971-11-02 1973-02-20 Teledyne Ind Periodic event detector system
US3859652A (en) * 1972-06-26 1975-01-07 North American Systems Corp Method and apparatus for detecting the theft of articles

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DK145277C (da) * 1977-04-26 1983-05-02 Foss Electric As Identifikationssystem med flere kodemaerkninger

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3040247A (en) * 1958-01-21 1962-06-19 Roland L Van Allen Magnetic field detector
US3205352A (en) * 1961-08-04 1965-09-07 Gen Precision Inc Presence detector

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE362032C (de) * 1919-07-06 1922-10-21 Robert R A Hoffmann Verfahren zum Anzeigen der Bewegung von Koerpern
DE969289C (de) * 1951-06-27 1958-05-14 Interessengemeinschaft Fuer Ru Anordnung zur UEbertragung von Signalen

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3040247A (en) * 1958-01-21 1962-06-19 Roland L Van Allen Magnetic field detector
US3205352A (en) * 1961-08-04 1965-09-07 Gen Precision Inc Presence detector

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3543261A (en) * 1968-06-14 1970-11-24 Us Air Force Upper threshold circuit
US3662167A (en) * 1970-04-09 1972-05-09 Westinghouse Air Brake Co Train identity control system
US3713102A (en) * 1970-04-23 1973-01-23 S Martin Pulse interrogation article-sorting system
US3717864A (en) * 1971-11-02 1973-02-20 Teledyne Ind Periodic event detector system
US3859652A (en) * 1972-06-26 1975-01-07 North American Systems Corp Method and apparatus for detecting the theft of articles

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DE1230693C2 (en:Method) 1967-07-06
DE1230693B (de) 1966-12-15

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