EP0116293B1 - Modulation system for railway circuits - Google Patents

Modulation system for railway circuits Download PDF

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Publication number
EP0116293B1
EP0116293B1 EP84100273A EP84100273A EP0116293B1 EP 0116293 B1 EP0116293 B1 EP 0116293B1 EP 84100273 A EP84100273 A EP 84100273A EP 84100273 A EP84100273 A EP 84100273A EP 0116293 B1 EP0116293 B1 EP 0116293B1
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Prior art keywords
carrier frequency
output
modulation
modulator
shift register
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EP84100273A
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German (de)
French (fr)
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EP0116293A1 (en
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Claude Pontier
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Alstom SA
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Alstom SA
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B61—RAILWAYS
    • B61L—GUIDING RAILWAY TRAFFIC; ENSURING THE SAFETY OF RAILWAY TRAFFIC
    • B61L1/00—Devices along the route controlled by interaction with the vehicle or train
    • B61L1/18—Railway track circuits
    • B61L1/181—Details
    • B61L1/188—Use of coded current

Definitions

  • the present invention relates to modulation systems for rail track circuits, making it possible to make as low as desired their probability of disturbance by parasitic currents, to which the devices used are subjected in operation.
  • Track circuits are devices very old and widely used in railway technology to ensure the absence of trains in a specific portion of track.
  • the principle of track circuits is based on the division of a railroad into successive cantons isolated from each other by pairs of joints or electrical separation devices creating an electrical discontinuity in each of the rails.
  • An electrical signal transmitter is arranged to be connected to the two rails at one end of the block and a receiver of the same signals having passed through the rails is arranged at the other end of the same block between the two rails also.
  • a train entering the canton entrance on the receiver side causes a short circuit of the signals by the electric rail-axle link of the train and this short circuit of the signals detected by the receiver causes a change in signaling state, lights, for example, turning red at the entrance to the train in the block and thus preventing the next train from entering the block as long as the block is occupied by the train preceding it.
  • the modulation systems of the track circuits used up to now can be, for example, either of the type of pulse modulation (see for example the document FR-A-1 007 492), or of the type of sinusoidal carrier frequency modulated in amplitude or frequency (see for example document FR-A-2 118 946).
  • pulse modulation these are generated by the channel transmitter of a block with a certain polarity, the pulses having a particular recurrence frequency, while the transmitter of the adjacent block generates pulses of 'reverse polarity, the pulses having a slightly different frequency of recurrence.
  • the carrier frequency is different from one canton to another as well as the modulation frequency.
  • pulse modulation or modulation of the sinusoidal carrier the information to be transmitted which leads to state one or zero state of the signaling depends either on the pulse polarity and its amplitude or on the torque carrier frequency-modulation frequency and its amplitude.
  • the receiver detects an absence of pulse, a reverse pulse polarity or an insufficient amplitude, in the case of pulse modulation, the receiver changes the signal to red.
  • the receiver detects an absence of carrier or an insufficient amplitude of carrier or an incorrect modulation frequency in the case of amplitude or frequency modulations, the receiver changes the signal to red also.
  • the modulation systems of conventional track circuits have the disadvantage of not being reliable enough from the safety point of view. Indeed, the ever increasing power of modern traction motors and ancillary electrotechnical bodies such as converters of all types (current, voltage, frequency) leads to the production of parasitic currents of increasingly high level and forms of increasing complexity. .
  • the modulation signals used in conventional systems are fixed and have immutable characteristics. It is obvious that a parasitic signal in the frequency band used by the track circuit and similar to the signals used, can cause in the receiver the transition to a state reverse of the state commanding the stop of the trains which can lead to disasters.
  • the modulation system of the present invention overcomes this drawback. This in fact provides very high security due to the insignificant probability of identification error which is obtained.
  • Figure 1 shows an electrical block diagram of a channel circuit transmitter modulated by a pseudo-random binary series generator.
  • FIG. 2 represents a block diagram of a channel circuit receiver modulated by signals coded by the pseudo-random binary series having crossed the channel.
  • the bit introduced at entry 12 of register 10 for each period of the clock is obtained by adding modulo 2 by means of three EXCLUSIVE OR 13, 14, 15 in this example connected to stages 1, 3, 5 and 6 of the register 10. It should be noted that in another transmitter the EXCLUSIVE OUs 13, 14, 15 would be connected to other stages of register 10 with the exception of stage 6 which is still used.
  • the bit present at the output 16 of the register 10 at each period of the clock 11 constitutes the continuation of the binary pseudo-random series being generated.
  • Such a device generates for a length n of the shift register 10 and certain combinations of the modules OR EXCLUSIVE a linear periodic binary series of length 2 "- 'bits.
  • the theory of polynomials indeed shows that if we consider the binary numbers of n bits contained at each instant in the shift register 10 all the possible numbers except 0 ... 0 appear successively once and only once in each period of the series in an order which depends on the number and location of the modules. Therefore if we know the length n of the shift register 10, the number and location of the modules and the number it contains at a given time, it is possible to predict its successive future contents and therefore the series issued.
  • the output 16 of the register 10 communicates with a modulator or a pulse generator 17 delivering a signal to a power amplifier 18 in order to amplify it.
  • a modulator 17 the signal consists of a carrier frequency of value 1000 Hz for example, modulated in amplitude or in frequency by a modulating frequency FI of value 12 Hz for example when a bit "one" is present at the output 16 of the register 10 and by a modulating frequency F2 of value 17 Hz for example when a "zero" bit is present at the output 16 of the register 10.
  • the signal consists of pulses, for example rectangular, with positive polarity, for example when a bit "one" is present at output 16 of register 10 and with negative polarity, for example, when a "zero" bit is present at output 16 of register 10.
  • the modulated signal amplified by the amplifier 18 at the power level required for the operation of the track circuit, is injected into the track, at one end of the portion of track in which it is desired to ensure the absence of the train , by the output 19 of the amplifier 18.
  • FIG. 2 shows the track circuit receiver corresponding to the transmitter which has just been described.
  • the receiver is connected to the track by its input 20 at the end opposite the transmitter of the track portion in which it is desired to ensure the absence of the train.
  • the signal present at the input 20 of the receiver is first filtered in a filter 21.
  • the filter 21 is adapted to the width of the pulses and to their frequency of recurrence.
  • the filter 21 is a bandpass filter centered on the carrier frequency.
  • the signal is then demodulated in the demodulator 22.
  • the latter consists of active elements such as diodes for example.
  • the register 100 comprises the same number of modules OR EXCLUSIVE 130,140 and 150 connected to the same stages 1, 3, 5 and 6 of the register 100 as modules 13, 14 and 15 of register 10 of the transmitter.
  • the polynomial theory shows that after a synchronization period of duration at most equal to n bits (n being the length of the registers), the bit existing at the output 24 of the modules 130, 140 and 150 is the same as that which will be received at the output 23 of the demodulator 22 at the following period of the clock 11 of the transmitter. This equality is controlled by the comparator 25.
  • the bits present at the inputs 23 and 24 of this comparator are 1 and 1 or O and O its output 26 delivers the state 1 which means that the comparison is correct.
  • the bits present at inputs 23 and 24 of comparator 25 are 1 and 0 or 0 and 1, output 26 of comparator is in logic state 0, which means that the comparison is incorrect.
  • the output 26 of the comparator 25 is applied to an attraction timer 27 which controls the relay 28 for outputting the receiver of the track circuit, the contacts 29 of which control the lighting of the lamps of the input signal in the track circuit.
  • the delay time delay of the timer 27 is fixed so that the relay 28 is only energized after a certain number m of successive exact comparisons. It is chosen so as to obtain the desired probability of error in identifying the pseudo-random binary series provided for the channel circuit considered.
  • the applications of the present invention are in the field of rail transport and in particular rail control and safety.

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  • Engineering & Computer Science (AREA)
  • Automation & Control Theory (AREA)
  • Mechanical Engineering (AREA)
  • Train Traffic Observation, Control, And Security (AREA)

Description

La présente invention concerne les systèmes de modulation pour circuits de voie ferroviaires, permettant de rendre aussi faible qu'on le désire leur probabilité de perturbation par les courants parasites, auxquels les appareils utilisés sont soumis en fonctionnement.The present invention relates to modulation systems for rail track circuits, making it possible to make as low as desired their probability of disturbance by parasitic currents, to which the devices used are subjected in operation.

Les circuits de voie sont des dispositifs très anciennement et très largement répandus en technique ferroviaire pour s'assurer de l'absence des trains dans une portion de voie déterminée. Le principe des circuits de voie est fondé sur la division d'une voie ferrée en cantons successifs isolés les uns des autres par des paires de joints ou des dispositifs électriques de séparation créant une discontinuité électrique dans chacun des rails. Un émetteur de signaux électriques est disposé pour être relié aux deux rails à l'une des extrémités du canton et un récepteur des mêmes signaux ayant parcouru les rails est disposé à l'autre extrémité du même canton entre les deux rails également. Un train pénétrant à l'entrée du canton du côté du récepteur provoque un court-circuit des signaux par la liaison électrique rails- essieux du train et ce court-circuit des signaux détecté par le récepteur engendre un changement d'état de la signalisation, les feux passant par exemple au rouge à l'entrée du train dans le canton et empêchant ainsi le train suivant de pénétrer dans le canton tant que le canton est occupé par le train qui le précède.Track circuits are devices very old and widely used in railway technology to ensure the absence of trains in a specific portion of track. The principle of track circuits is based on the division of a railroad into successive cantons isolated from each other by pairs of joints or electrical separation devices creating an electrical discontinuity in each of the rails. An electrical signal transmitter is arranged to be connected to the two rails at one end of the block and a receiver of the same signals having passed through the rails is arranged at the other end of the same block between the two rails also. A train entering the canton entrance on the receiver side causes a short circuit of the signals by the electric rail-axle link of the train and this short circuit of the signals detected by the receiver causes a change in signaling state, lights, for example, turning red at the entrance to the train in the block and thus preventing the next train from entering the block as long as the block is occupied by the train preceding it.

Les systèmes de modulation des circuits de voie utilisés jusqu'à présent peuvent être, par exemple, soit du type de modulation à impulsions (voir par exemple le document FR-A-1 007 492), soit du type de fréquence porteuse sinusoidale modulée en amplitude ou en fréquence (voir par exemple le document FR-A-2 118 946). Dans le cas de la modulation par impulsions, celles-ci sont générées par l'émetteur de voie d'un canton avec une certaine polarité, les impulsions ayant une fréquence de récurrence particulière, alors que l'émetteur du canton adjacent génère des impulsions d'une polarité inverse, les impulsions ayant une fréquence de récurrence légèrement différente. Dans le cas de la modulation en amplitude ou en fréquence d'une fréquence porteuse, la fréquence porteuse est différente d'un canton à l'autre ainsi que la fréquence de modulation. Dans tous les cas, modulation par impulsions ou modulation de la porteuse sinusoïdale, l'information à transmettre qui conduit à l'état un ou l'état zéro de la signalisation dépend soit de la polarité d'impulsion et de son amplitude soit du couple fréquence porteuse-fréquence de modulation et de son amplitude. Lorsque le récepteur détecte une absence d'impulsion, une polarité d'impulsion inverse ou une amplitude insuffisante, dans le cas de modulation par impulsions, le récepteur fait passer le signal au rouge. Lorsque le récepteur détecte une absence de porteuse ou une amplitude insuffisante de porteuse ou une fréquence de modulation incorrecte dans le cas de modulations d'amplitude ou de fréquence, le récepteur fait passer le signal au rouge également.The modulation systems of the track circuits used up to now can be, for example, either of the type of pulse modulation (see for example the document FR-A-1 007 492), or of the type of sinusoidal carrier frequency modulated in amplitude or frequency (see for example document FR-A-2 118 946). In the case of pulse modulation, these are generated by the channel transmitter of a block with a certain polarity, the pulses having a particular recurrence frequency, while the transmitter of the adjacent block generates pulses of 'reverse polarity, the pulses having a slightly different frequency of recurrence. In the case of amplitude or frequency modulation of a carrier frequency, the carrier frequency is different from one canton to another as well as the modulation frequency. In all cases, pulse modulation or modulation of the sinusoidal carrier, the information to be transmitted which leads to state one or zero state of the signaling depends either on the pulse polarity and its amplitude or on the torque carrier frequency-modulation frequency and its amplitude. When the receiver detects an absence of pulse, a reverse pulse polarity or an insufficient amplitude, in the case of pulse modulation, the receiver changes the signal to red. When the receiver detects an absence of carrier or an insufficient amplitude of carrier or an incorrect modulation frequency in the case of amplitude or frequency modulations, the receiver changes the signal to red also.

Cependant les systèmes de modulation de circuits de voie classiques ont l'inconvénient de ne pas être assez fiables au point de vue sécurité. En effet, la puissance toujours croissante des moteurs de traction modernes et des organes électrotechniques annexes tels que les convertisseurs de tous type (courant, tension, fréquence) entraîne la production de courants parasites de niveau de plus en plus élevé et de formes de complexité croissante. D'autre part, les signaux de modulation employés dans les systèmes classiques 'sont fixes et ont des caractéristiques immuables. Il est évident qu'un signal parasite dans la bande de fréquences utilisée par le circuit de voie et semblable aux signaux utilisés, peut provoquer dans le récepteur le passage à un état inverse de l'état commandant l'arrêt des trains ce qui peut conduire à des catastrophes.However, the modulation systems of conventional track circuits have the disadvantage of not being reliable enough from the safety point of view. Indeed, the ever increasing power of modern traction motors and ancillary electrotechnical bodies such as converters of all types (current, voltage, frequency) leads to the production of parasitic currents of increasingly high level and forms of increasing complexity. . On the other hand, the modulation signals used in conventional systems are fixed and have immutable characteristics. It is obvious that a parasitic signal in the frequency band used by the track circuit and similar to the signals used, can cause in the receiver the transition to a state reverse of the state commanding the stop of the trains which can lead to disasters.

Le système de modulation de la présente invention remédie à cet inconvénient. Celui-ci assure en effet une très grande sécurité par suite de la probabilité d'erreur d'identification insignifiante qui est obtenue.The modulation system of the present invention overcomes this drawback. This in fact provides very high security due to the insignificant probability of identification error which is obtained.

Ce but est atteint selon l'invention par le système tel qu'il est défini par. chacune des revendications indépendantes. En ce qui concerne des exemples de mises en oeuvre préférées, référence est faite aux sous-revendications.This object is achieved according to the invention by the system as defined by. each of the independent claims. With reference to examples of preferred embodiments, reference is made to the subclaims.

En se référant aux figures schématiques 1 et 2 ci-jointes on va décrire ci-après un exemple de mise en oeuvre de la présente invention, exemple donné à titre purement illustratif et nullement limitatif.With reference to the attached diagrammatic figures 1 and 2, an example of implementation of the present invention will be described below, an example given purely by way of illustration and in no way limiting.

La figure 1 représente un schéma de principe électrique d'un émetteur du circuit de voie modulé par un générateur de série binaire pseudo-aléatoire.Figure 1 shows an electrical block diagram of a channel circuit transmitter modulated by a pseudo-random binary series generator.

la figure 2 représente un schéma de principe d'un récepteur de circuit de voie modulé par des signaux codés par la série binaire pseudo-aléatoire ayant traversé la voie.FIG. 2 represents a block diagram of a channel circuit receiver modulated by signals coded by the pseudo-random binary series having crossed the channel.

On voit sur la figure 1 un émetteur de circuit de voie constitué d'un registre à décalage 10 comprenant n = 6 cellules à titre d'exemple les étages 1, 2, 3....6 du registre 10 sont incrémentés par une horloge 11 dont la période commande l'avance du registre. Le bit introduit à l'entrée 12 du registre 10 pour chaque période de l'horloge est obtenu par addition modulo 2 au moyen de trois OU EXCLUSIF 13, 14, 15 dans cet exemple branchés sur les étages 1, 3, 5 et 6 du registre 10. Il est à noter que dans un autre émetteur les OU EXCLUSIFS 13, 14, 15 seraient branchés sur d'autres étages du registre 10 à l'exception de l'étage 6 toujours utilisé.We see in Figure 1 a channel circuit transmitter consisting of a shift register 10 comprising n = 6 cells by way of example stages 1, 2, 3 .... 6 of register 10 are incremented by a clock 11 whose period commands the advance of the register. The bit introduced at entry 12 of register 10 for each period of the clock is obtained by adding modulo 2 by means of three EXCLUSIVE OR 13, 14, 15 in this example connected to stages 1, 3, 5 and 6 of the register 10. It should be noted that in another transmitter the EXCLUSIVE OUs 13, 14, 15 would be connected to other stages of register 10 with the exception of stage 6 which is still used.

Le bit présent à la sortie 16 du registre 10 à chaque période de l'horloge 11 constitue la suite de la série binaire pseudo-aléatoire en cours de génération. Un tel dispositif engendre pour une longueur n du registre à décalage 10 et certaines combinaisons des modules OU EXCLUSIF une série binaire périodique linéaire de longueur 2"-' bits. La théorie des polynômes montre en effet que si l'on considère les nombres binaires de n bits contenus à chaque instant dans le registre à décalage 10 tous les nombres possibles à l'exception de 0...0 apparaissent successivement une fois et une seule à chaque période de la série dans une ordre qui est fonction d' nombre et de l'emplacement des modules. De ce fait si l'on connaît la longueur n du registre à décalage 10, le nombre et l'emplacement des modules et le nombre qu'il contient a un instant donné, il est possible de prévoir ses contenus successifs futurs et donc la série émise.The bit present at the output 16 of the register 10 at each period of the clock 11 constitutes the continuation of the binary pseudo-random series being generated. Such a device generates for a length n of the shift register 10 and certain combinations of the modules OR EXCLUSIVE a linear periodic binary series of length 2 "- 'bits. The theory of polynomials indeed shows that if we consider the binary numbers of n bits contained at each instant in the shift register 10 all the possible numbers except 0 ... 0 appear successively once and only once in each period of the series in an order which depends on the number and location of the modules. Therefore if we know the length n of the shift register 10, the number and location of the modules and the number it contains at a given time, it is possible to predict its successive future contents and therefore the series issued.

La sortie 16 du registre 10 communique avec un modulateur ou un générateur d'impulsions 17 délivrant un signal à un amplificateur de puissance 18 afin de l'amplifier. Dans le cas d'un modulateur 17 le signal est constitué d'une fréquence porteuse de valeur 1000 Hz par exemple, modulée en amplitude ou en fréquence par une fréquence modulante FI de valeur 12 Hz par exemple quand un bit "un" est présent à la sortie 16 du registre 10 et par une fréquence modulante F2 de valeur 17 Hz par exemple quand un bit "zéro" est présent à la sortie 16 du registre 10.The output 16 of the register 10 communicates with a modulator or a pulse generator 17 delivering a signal to a power amplifier 18 in order to amplify it. In the case of a modulator 17 the signal consists of a carrier frequency of value 1000 Hz for example, modulated in amplitude or in frequency by a modulating frequency FI of value 12 Hz for example when a bit "one" is present at the output 16 of the register 10 and by a modulating frequency F2 of value 17 Hz for example when a "zero" bit is present at the output 16 of the register 10.

Dans le cas d'un générateur impulsions 17, le signal est constitué d'impulsions par exemple rectangulaires, à polarité positive, par exemple quand un bit "un" est présent à la sortie 16 du registre 10 et à polarité négative, par exemple, quand un bit "zéro" est présent à la sortie 16 du registre 10.In the case of a pulse generator 17, the signal consists of pulses, for example rectangular, with positive polarity, for example when a bit "one" is present at output 16 of register 10 and with negative polarity, for example, when a "zero" bit is present at output 16 of register 10.

Le signal modulé, amplifié par l'amplificateur 18 au niveau de puissance requis pour le fonctionnement du circuit de voie, est injecté dans la voie, à une extrémité de la portion de voie dans laquelle on désire s'assurer de l'absence de train, par la sortie 19 de l'amplificateur 18.The modulated signal, amplified by the amplifier 18 at the power level required for the operation of the track circuit, is injected into the track, at one end of the portion of track in which it is desired to ensure the absence of the train , by the output 19 of the amplifier 18.

La figuré 2 montre le récepteur de circuit de voie correspondant à l'émetteur qui vient d'être décrit.FIG. 2 shows the track circuit receiver corresponding to the transmitter which has just been described.

Le récepteur est relié à la voie par son entrée 20 à l'extrémité opposée à l'émetteur de la portion de voie dans laquelle on désire s'assurer de l'absence de train. Le signal présent à l'entrée 20 du récepteur est d'abord filtré dans un filtre 21. Dans le cas de la modulation par impulsions le filtre 21 est adapté à la largeur des impulsions et à leur fréquence de récurrence. Dans le cas de la modulation de la porteuse le filtre 21 est un filtre passe-bande centré sur la fréquence porteuse.The receiver is connected to the track by its input 20 at the end opposite the transmitter of the track portion in which it is desired to ensure the absence of the train. The signal present at the input 20 of the receiver is first filtered in a filter 21. In the case of pulse modulation the filter 21 is adapted to the width of the pulses and to their frequency of recurrence. In the case of carrier modulation, the filter 21 is a bandpass filter centered on the carrier frequency.

Le signal est ensuite démodulé dans le démodulateur 22. Celui-ci est constitué d'éléments actifs tels que des diodes par exemple.The signal is then demodulated in the demodulator 22. The latter consists of active elements such as diodes for example.

A la sortie 23 du démodulateur 22 apparait la série binaire engendrée par l'émetteur à la sortie 16 du registre 10. Cette série binaire est appliquée à un registre 100 de même longueur que le registre 10 de l'émetteur. L'avance du registre est commandée par une horloge 110 synchronisée par les signaux présents à la sortie 23 du démodulateur 22. Le registre 100 comporte le même nombre de modules OU EXCLUSIF 130,140 et 150 reliés aux mêmes étages 1, 3, 5 et 6 du registre 100 que les modules 13,14 et 15 du registre 10 de l'émetteur.At the output 23 of the demodulator 22 appears the binary series generated by the transmitter at the output 16 of the register 10. This binary series is applied to a register 100 of the same length as the register 10 of the transmitter. The advance of the register is controlled by a clock 110 synchronized by the signals present at the output 23 of the demodulator 22. The register 100 comprises the same number of modules OR EXCLUSIVE 130,140 and 150 connected to the same stages 1, 3, 5 and 6 of the register 100 as modules 13, 14 and 15 of register 10 of the transmitter.

La théorie des polynômes montre qu'après une période de synchronisation de durée au plus égale à n bits (n étant la longeur des registres), le bit existant à la sortie 24 des modules 130, 140 et 150 est le même que celui qui sera reçu à la sortie 23 du démodulateur 22 à la période suivante de l'horloge 11 de l'émetteur. Cette égalité est contrôlée par le comparateur 25. Lorsque les bits présents aux entrées 23 et 24 de ce comparateur sont 1 et 1 ou O et O sa sortie 26 délivre l'état 1 ce qui signifie que la comparaison est correcte. Lorsque les bits présents aux entrées 23 et 24 du comparateur 25 sont 1 et 0 ou 0 et 1 la sortie 26 du comparateur est à l'état logique 0 ce qui signifie que la comparaison est incorrecte.The polynomial theory shows that after a synchronization period of duration at most equal to n bits (n being the length of the registers), the bit existing at the output 24 of the modules 130, 140 and 150 is the same as that which will be received at the output 23 of the demodulator 22 at the following period of the clock 11 of the transmitter. This equality is controlled by the comparator 25. When the bits present at the inputs 23 and 24 of this comparator are 1 and 1 or O and O its output 26 delivers the state 1 which means that the comparison is correct. When the bits present at inputs 23 and 24 of comparator 25 are 1 and 0 or 0 and 1, output 26 of comparator is in logic state 0, which means that the comparison is incorrect.

La sortie 26 du comparateur 25 est appliquée à un temporisateur à l'attraction 27 qui commande le relais 28 de sortie du récepteur du circuit de voie dont des contacts 29 commandent l'allumage des lampes du signal d'entrée dans le circuit de voie. Le retard de temporisation du temporisateur 27 est fixé de telle sorte que le relais 28 ne soit excité qu'après un certain nombre m de comparaisons exactes successives. Il est choisi de manière à obtenir la probabilité désirée d'erreur d'identification de la série binaire pseudo-aléatoire prévue pour le circuit de voie considéré. Un exemple de réalisation prévoit ainsi par exemple un nombre de m = 32 comparaisons exactes successives pour un registre à n = 6 étages.The output 26 of the comparator 25 is applied to an attraction timer 27 which controls the relay 28 for outputting the receiver of the track circuit, the contacts 29 of which control the lighting of the lamps of the input signal in the track circuit. The delay time delay of the timer 27 is fixed so that the relay 28 is only energized after a certain number m of successive exact comparisons. It is chosen so as to obtain the desired probability of error in identifying the pseudo-random binary series provided for the channel circuit considered. An exemplary embodiment thus provides for example a number of m = 32 successive exact comparisons for a register with n = 6 stages.

Les applications de la présente invention sont du domaine des transports ferroviaires et notamment du contrôle et de la sécurité ferroviaires.The applications of the present invention are in the field of rail transport and in particular rail control and safety.

Claims (9)

1. A modulation system for railway track circuits, comprising
- a transmitter equipped with a pulse modulator (10-17) for generating a pulse sequence having a positive or negative polarity and adapted for being applied to the input of a railway track circuit, and
- a receiver comprising detection means for detecting the pulses appearing at the output of the railway track circuit, characterized in that the modulator (10-17) comprises a generator (10, 15) for delivering at least one pseudorandom binary sequence, of which the "1" bits cause pulses having one of the two polarities to be generated, and of which the "0" bits cause pulses having the other polarity to be generated.
2. A modulation system for railway track circuits, comprising
- a transmitter equipped with a carrier frequency generator, and with a modulator (17) for modulating the carrier frequency with a first and a second modulation frequency, wherein the modulated carrier frequency signal is applicable to the input of a railway track circuit, and
- a receiver comprising detection means (20-22) for detecting the modulated carrier frequency signal delivered at the output of the railway track circuit,
- characterized in that the modulator (10-17) comprises a generator (10-15) for delivering at least one pseudorandom binary sequence, of the which the "1" bits cause the carrier frequency to be modulated by the first modulation frequency, and of which the "0" bits cause the carrier frequency to be modulated by the second modulation frequency.
3. A modulation system according to one of the claims 1 or 2, characterized in that the pseudorandom binary sequences for the railway track circuits formed by the successive track sections are different from each other, and that the pseudorandom binary sequence generator is constituted of a shift register (10) incremented by a clock (11) and of Exclusive OR modules supplying the input of the shift register with a binary value resulting from the combination of bit values of certain register stages, the choice of the stages (1, 2, 3, 4, 5, 6) being distinct for each pseudorandom binary series.
4. A modulation system according to claims 1 and 3, characterized in that the modulator comprises, at the output of the last stage of said shift register (10), a generator (17) for pulses having a variable polarity, followed by a power amplifier (18) which delivers amplified pulses to the track circuit, said pulse generator (17) delivering a positive pulse,, when the bit at the output of the shift register amounts to "1", and a negative pulse, when the bit at the output of the shift register (10) amounts to "0".
5. A modulation system according to claims 2 and 3, characterized in that the modulator (17) is connected to the output of the last stage (6) of said shift register and is followed by a power amplifier (18) supplying the modulated carrier frequency signals to the track circuit, said modulator (17) supplying the carrier frequency signals modulated by the first modulation frequency, when a bit at the output of the shift register amounts to "1", and modulated by the second modulation frequency, when the bit at the output of the shift register amounts to "0".
6. A modulation system according to claim 5, characterized in that the modulator (17) for the carrier frequency signals operates in the amplitude modulation mode for generating said modulated carrier frequency signals.
7. A modulation system according to claim 5, characterized in that the modulator (17) for the carrier frequency signals operates in the frequency modulation mode for generating the modulated carrier frequency signals.
8. A modulation system according to one of claims 1 or 2, characterized in that the receiver comprises a cyclic code generator constituted of a shift register (100) identical with the one of the corresponding transmitter, the Exclusive OR modules (130, 140, 150) of which are connected to the same register stages, adopting the same disposition, and the output of which is connected to a comparator (25) for comparison with the pseudorandom binary sequence issuing from said detector means.
9. A modulation system according to claim 8, characterized in that the comparator (25) is followed by a pick-up delay device (27) acting upon an output relay (28) of the receiver, said delay device (27) having a time delay which allows to obtain the desired identification error probability of the pseudorandom binary sequence allocated to the considered track circuit.
EP84100273A 1983-01-13 1984-01-12 Modulation system for railway circuits Expired EP0116293B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8300429A FR2539372A1 (en) 1983-01-13 1983-01-13 MODULATION SYSTEMS FOR RAILWAY CIRCUITS
FR8300429 1983-01-13

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EP0116293A1 EP0116293A1 (en) 1984-08-22
EP0116293B1 true EP0116293B1 (en) 1988-07-20

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EP84100273A Expired EP0116293B1 (en) 1983-01-13 1984-01-12 Modulation system for railway circuits

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US (1) US4582279A (en)
EP (1) EP0116293B1 (en)
DE (1) DE3472779D1 (en)
ES (1) ES8504582A1 (en)
FR (1) FR2539372A1 (en)

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Also Published As

Publication number Publication date
ES528870A0 (en) 1985-04-16
FR2539372A1 (en) 1984-07-20
EP0116293A1 (en) 1984-08-22
FR2539372B1 (en) 1985-03-15
ES8504582A1 (en) 1985-04-16
US4582279A (en) 1986-04-15
DE3472779D1 (en) 1988-08-25

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