EP1409324B1 - Method of detecting the presence of a vehicle travelling on a railway-type track and the equipment therefor - Google Patents

Abstract

The central block has a circuit (42) which couples with right or left blocks (48,47) at first and second frequencies (F1,F2) and coupling circuits (43,45) linked to the transmitter and receiver (44,46). At the first frequency the right block is short circuited and the left block open circuited and at the second frequency the converse applies such that the joint is respectively a receiver and transmitter at the two frequencies. <??>An Independent claim is also included for a method for detecting the passage of a train using a three block joint and frequencies between 20 and 100KHz.

Description

Object of the invention

The present invention relates to a presence detection method or more particularly of the non-presence of a moving vehicle on a railway type track comprising two rails.

The present invention also relates to associated equipment for the implementation of the said device.

Technological background

The tracks of the railway network for which train detection is provided by circuit of track are currently equipped with either insulating joints, either of electrical joints, in both cases arranged to regular intervals along the track sections (also called "cantonments"), as described in GB 2 213 972A.

Electrical seals have the advantage, compared to insulating joints, maintain a path galvanically without interruption, that is to say continuous, while limiting energy transmission in a portion of way. This considerably reduces the costs of laying, maintenance and track monitoring while allowing higher speeds. This is of interest particularly important for track equipment high speed trains.

From an electrical point of view, the "joint" is consists of two successive "plug circuits" which are separated by a section of track. An electric joint is therefore consisting of two rails of a certain length and each electrically represented by a self, of a first and a second chord block also called "Tuning Unit" in English (TU) allowing the realization a tuning to the frequency of the track circuit.

Usually, a first block of agreement perform the short circuit at a given first frequency while the second chord block assures the tuning of the joint electrical and coupling at this same frequency. To the second frequency, these functions are reciprocal for the two track circuits that each seal separates.

• empêcher la propagation du signal d'un circuit de voie vers le circuit de voie adjacent. Ceci est réalisé par le bloc d'accord extérieur qui présente à la fréquence du circuit de voie une impédance suffisamment faible;
• présenter à l'extrémité du circuit de voie une impédance suffisante à la fréquence utilisée, au moyen d'un accord parallèle au bloc d'accord intérieur et à la portion de voie du joint électrique;
• réaliser le couplage entre le circuit d'émission ou de réception et la voie. Cette fonction est assurée par les blocs d'accord.

The functions of the electrical joint are multiple:

• to prevent signal propagation from one channel circuit to the adjacent channel circuit. This is achieved by the external tuning block which has at the frequency of the track circuit a sufficiently low impedance;
• presenting at the end of the track circuit a sufficient impedance at the frequency used, by means of a tuning parallel to the inner tuning block and the track portion of the electrical joint;
• coupling between the transmitting or receiving circuit and the channel. This function is provided by the chord blocks.

It is known to use this type of circuit electrical joint track to detect presence or more precisely the non-presence of a train in the section of track considered. Indeed, when passing an axle train, a short circuit between the two rails will be created via the axle. This makes it possible to detect the presence of said train according to the evolution of the voltage received by the receiver associated with the same frequency.

It is usual to use, depending on the state of the technique, electrical joints as described previously for important sections of track, that is to say between 100 meters and 2 kilometers, then that usually the distance between two blocks successive agreements (TU) is between 15 and 30 meters within the same "plug" circuit.

Usually, the implementation of such processes are carried out for sections in full frequencies used are therefore low type frequency, that is to say less than 5 kHz.

The problem of detecting the presence of a train or more precisely its non-presence is all more critical in high concentration areas switches such as railway stations where the distances between two successive switches decrease drastically.

In this case, it is particularly important to be able to determine with accuracy, and this in the sense of railway safety of the term, the presence or rather the non-presence of a train under a adequate track section.

Currently, the devices proposed for determine said presence or non-presence are essentially consisting of mechanical devices such axle counters.

Goals of the invention

The present invention aims to propose a new configuration of electrical equipment that does not does not have the disadvantages of the state of the art.

The present invention aims to propose a solution that helps reduce the distances used to placement of electrical joints and thereby reduce uncertainty about the position of the point of occupancy or release of the section in the electrical joint.

The present invention is all particularly to propose a solution that can be applicable in the field of railway stations, where the distances between switches (and therefore the lengths available for placement of electrical seals) are lower than in the open and where the detection of presence of a train must be carried out with more than precision.

The present invention also aims to propose a solution that allows embedding joints provided according to the present invention to equipment such as as proposed according to the state of the art to be able to monitor any section of track while avoiding the presence of insulating seal.

The present invention also aims to allow the superposition of track circuits.

Main characteristic elements of the invention

The present invention relates to a method of detecting the presence or non-presence of a vehicle, such as a train, traveling on a railway with two rails under the form of a series of track circuits called cantonments and separated by electrical joints, each seal forming a separation between a first track circuit which operates at a first frequency and a second circuit track that operates at a second frequency.

According to the invention, at least one of said frequencies is greater than 5 kHz, preferably 10 kHz and still preferably at 20 kHz. Preferably both frequencies of use are greater than 5, 10 or even 20 kHz.

According to a first embodiment, at least one of the two electrical joints is a three-block joint, which is arranged between the rails, a first block playing the role of a short circuit at said first frequency and being transparent to said second frequency, a second block acting as a short circuit to said second frequency and being transparent to said first frequency, and the central block playing the role of a capacity at each two frequencies.

• un premier bloc et un deuxième bloc qui forment un circuit bouchon à la première fréquence, ladite fréquence étant inférieure à 5 kHz, le premier bloc jouant le rôle d'un court-circuit, le deuxième bloc jouant le rôle d'une capacité, lesdits blocs étant disposés dans un ordre prédéterminé,
• un troisième bloc et un quatrième bloc qui forment un circuit bouchon à la deuxième fréquence, ladite fréquence étant supérieure à 5 kHz, le troisième bloc jouant le rôle d'une capacité et le quatrième bloc jouant le rôle d'un court-circuit,

lesdits troisième et quatrième blocs étant disposés entre lesdits premier et deuxième blocs et dans l'ordre inverse que celui desdits deux premier et deuxième blocs.According to another embodiment, at least one of the two electrical joints is a four-block joint, which is disposed between the rails, comprising:

• a first block and a second block which form a plug circuit at the first frequency, said frequency being less than 5 kHz, the first block acting as a short-circuit, the second block acting as a capacitor, said blocks being arranged in a predetermined order,
• a third block and a fourth block which form a stop circuit at the second frequency, said frequency being greater than 5 kHz, the third block acting as a capacity and the fourth block acting as a short circuit,

said third and fourth blocks being disposed between said first and second blocks and in reverse order as that of said first and second blocks.

According to another object of this invention, it is proposed to superimpose track circuits low frequency with high frequency track circuits while using the methods described above.

A final object of the present invention resides in a device for the implementation of processes described above.

• un bloc central, comprenant deux branches parallèles, la première branche comprenant un circuit RLC et un premier circuit de couplage, la deuxième branche comprenant un deuxième circuit de couplage,
• un bloc comprenant un circuit RLC, ce bloc jouant le rôle d'un court-circuit à l'une des deux fréquences et étant transparent à la deuxième fréquence,
• un bloc comprenant un circuit RLC, ce bloc jouant le rôle d'un court-circuit à la deuxième des deux fréquences et étant transparent à la première fréquence.

According to a first exemplary embodiment, such a device comprises:

• a central block comprising two parallel branches, the first branch comprising an RLC circuit and a first coupling circuit, the second branch comprising a second coupling circuit,
• a block comprising an RLC circuit, this block acting as a short-circuit at one of the two frequencies and being transparent at the second frequency,
• a block comprising an RLC circuit, this block acting as a short circuit at the second of the two frequencies and being transparent to the first frequency.

• un premier bloc et un deuxième bloc qui forment un circuit bouchon à la première fréquence, ladite fréquence étant inférieure à 5 kHz, le premier bloc jouant le rôle de court-circuit, le deuxième bloc jouant le rôle de capacité, lesdits blocs étant disposés dans un ordre prédéterminé,
• un troisième bloc et un quatrième bloc qui forment un circuit bouchon à la deuxième fréquence, ladite fréquence étant supérieure à 5 kHz, le troisième bloc jouant le rôle de capacité et le quatrième bloc jouant le rôle de court-circuit,

lesdits troisième et quatrième blocs étant disposés entre lesdits premier et deuxième blocs et dans l'ordre inverse que celui desdits deux premier et deuxième blocs.According to another embodiment, such a device comprises:

• a first block and a second block which form a plug circuit at the first frequency, said frequency being less than 5 kHz, the first block acting as a short-circuit, the second block acting as a capacitor, said blocks being arranged in a predetermined order,
• a third block and a fourth block which form a stop circuit at the second frequency, said frequency being greater than 5 kHz, the third block acting as a capacitor and the fourth block acting as a short-circuit,

said third and fourth blocks being disposed between said first and second blocks and in reverse order as that of said first and second blocks.

Finally, the present invention also aims to allow detection of presence or non-presence of a railway vehicle in track configurations including a large number of referrals such as stations.

Brief description of the drawings

Figure 1 shows a track provided with 2-block electric seals (in a 2 + 2 configuration blocks).

• la figure 2a représente une voie comprenant deux cantonnements séparés par des joints électriques à deux blocs,
• les figures 2b et 2c représentent les circuits de voie correspondant aux deux cantonnements séparés par un joint électrique à deux blocs,
• la figure 2d représente les potentiels des signaux dans les deux circuits de voie, ceci en utilisant ce joint à deux blocs,
• la figure 2e représente les courbes de shunt pour un joint à deux blocs.

FIG. 2 represents an embodiment according to FIG. 1 and its mode of operation, in which:

• FIG. 2a shows a channel comprising two boxes separated by two-block electrical joints,
• FIGS. 2b and 2c show the track circuits corresponding to the two boxes separated by a two-block electric joint,
• FIG. 2d represents the signal potentials in the two channel circuits, this using this two-block joint,
• Figure 2e shows the shunt curves for a two-block joint.

• la figure 3a représente une voie comprenant deux cantonnements séparés par un joint électrique à trois blocs,
• les figures 3b et 3c représentent les circuits de voie correspondant aux deux cantonnements séparés par un joint électrique à trois blocs,
• la figure 3d représente les potentiels des signaux dans les deux circuits de voie, pour un joint électrique à trois blocs, et
• la figure 3e représente les courbes de shunt pour un joint électrique à trois blocs.

FIGS. 3 and 3 show an embodiment in which an electrical joint with 3 blocks is used and its mode of operation, in which:

• FIG. 3a shows a channel comprising two compartments separated by a three-block electric joint,
• FIGS. 3b and 3c show the track circuits corresponding to the two boxes separated by a three-block electric joint,
• FIG. 3d represents the signal potentials in the two channel circuits, for a three-block electrical joint, and
• Fig. 3e shows the shunt curves for a three-block electrical joint.

Figures 4 and 5 represent schematic the shunt curves (corresponding to the figures 2nd and 3rd) for electrical seals respectively at two blocks and three blocks, using low frequencies (BF - BF).

Figures 6 and 7 show two shapes preferred embodiment of a high frequency electrical seal, according to one embodiment of the invention.

Figure 8 shows the elements of an electric joint 3 high frequency blocks according to one embodiment of the invention.

Figure 9 shows an example of seals 3 blocks, able to receive or send two signals at the same time time.

Figures 10 and 11 show two shapes execution for a 4-block configuration where are used, on the one hand, a low frequency joint and other on the other hand, a high frequency seal.

Fig. 12 shows an embodiment particular of the present invention where a superposition of a high-frequency channel circuit is performed in a low frequency track circuit.

Detailed description of several forms of execution preferred embodiment of the invention

To better understand the solutions proposed according to the present invention, an analysis detailed implementation for electrical joints respectively two blocks and three blocks will be resumed below.

Classically, an electrical seal (called electrical joint RX / TX) as shown in Figure 1 comprises, arranged between two rails 1 and 2, two blocks OK, respectively TU.RX ("Tuning Unit - Receiver") and TU.TX ("Tuning Unit - Transmitter"), which connect two rails, and which are arranged at a distance between 15 and 30 m apart. The distance between two joints 3 and 4 can vary between a few hundred meters and one or even two kilometers. This seal then separates the way in two parts 5 and 6, called "cantonments", with a recovery zone 7, corresponding to the distance between the two blocks. Presence detection of a train is carried out via signals electrical devices present in the circuits corresponding to so-called cantonments at typical frequencies for each cantonment, which allows an electrical separation of two adjacent circuits.

In the case of Figure 1, block 10 of seal 3 includes RLC circuits, which make this block equivalent to a capacitor tuning to a first F1 frequency. At the same time, this block 10 is linked to a issuer (not shown), which is essentially equivalent to a series AC voltage source with said capacity and transmitting a signal at a frequency F1. In the same way, the block 11 of the joint 4 is equivalent to a tuning capacitor at frequency F1 and this block 11 is linked to a receiver (not shown), which is basically equivalent to a selective AC voltmeter arranged in parallel on the block 11 and which is capable of detect a potential difference at the frequency F1. The block 12 of the gasket 4 includes RLC circuits which make said block is equivalent to a short circuit at the frequency F1. Thus, the signal at frequency F1 can not go from circuit from Box 5 to the adjacent circuit of cantonment 6.

In turn, block 12 behaves like a capacitor tuning to a second frequency F2 and this block 12 is linked to a transmitter at this frequency F2, which sends a signal to the ring circuit. same, the block 11 of the seal 4 is equivalent to a short circuit at frequency F2. Short circuits, respectively at the frequency F1 and at the frequency F2, thus ensure the effective separation of the two circuits adjacent quarters 5 and 6.

The detection of a train on the quarter 5 for example is due to the fact that the axle of this train forms in itself a short circuit between the rails. In reality, the axle has a low impedance which can be equated with a short circuit and that will cause a fall current in the receiver linked to block 11, which off. This deactivation then corresponds to the detection of a train between blocks 10 and 11.

Figures 2a, 2b and 2c show the equivalent circuits for a two-block electric joint. Figure 2d shows the potential curves of the two signals 15 and 16, near and in the electrical joint.

Figure 2e shows the curves of "shunt" for the seal as shown in Figure 2a. These curves give the resistance that is recognized as being the maximum impedance that causes the deactivation of a receiver (voltage drop detected) and so allows the detection of a train. This value is dependent on the position along the track, and at each position, this value must be greater than the effective resistance of the axle, which is represented by the value 17. As long as this value is below the shunt curves, the train will be detected without problem.

There is, however, uncertainty about the value of this impedance, which depends on the circumstances (ambient humidity, ballast condition, etc.). Thereby are defined curves 19 and 19 ', which correspond to the optimal circumstances, ie for insulation minimum ballast and a minimum voltage of transmission, and the corresponding curves 18 and 18 ' under the worst circumstances, that is, for a maximum insulation of the ballast and a maximum voltage of transmission.

The position of these curves is particularly important for the detection of train as it passes through zone 7 of recovery of a electric joint. As shunt resistors decrease very quickly in this area, there comes a time when the axle resistance becomes greater than these curves. AT this moment, the train is no longer detected.

Suppose a train moves from left to right on the horizontal axis. Taking into account the definition of the curves 18,18 'and 19,19', we can observe that the train (more precisely its first shunting axle) will be detected by circuit 6 (frequency F2) at the latest in point 20. Similarly, the train (more precisely its last shunting axle) will no longer be detected by the circuit 5 (frequency F1), at the earliest at point 21. It is clear that, to ensure detection at all times, either by circuit 5 or by circuit 6, point 20 shall precede point 21 on the horizontal axis.

The same detailed analysis can be done for another embodiment, according to which a seal electrical device comprising three chord blocks is shown as in Figure 3a. Of course, this seal forms the separation between two adjacent track circuits 5 and 6 and called cantonments, for which the signals used are at frequencies F1 and F2.

The central block 25, called TX.RX ("Transmitter and Receiver"), serves as a capability for both F1 and F2 frequencies. Block 26 (on the left) serves as short circuit at frequency F2 and has an impedance raised to the frequency F1. Block 26 is therefore a open circuit at F1; we also say that it is "transparent" at frequency F1. Similarly, block 27 (on the right) serves of short circuit at frequency F1 and this block 27 is transparent at frequency F2. The central block 25 is linked at the same time to a transmitter at frequency F2 and a receiver at the frequency F1. This implies that in a adjacent joint, these functions will be reversed and we will have a transmitter at frequency F1 and a receiver at the frequency F2.

Figures 3b and 3c show the equivalent circuits, highlighting the separation effective of the two circuits. Figure 3d shows the potential in both circuits.

The main advantage of a three-block joint can be perceived by analyzing the shunt curves represented in Figure 3e. The point from which curves start their fall towards zero resistance to the height of the short circuit, is now located in the middle of the attached, that is, where the voltage source is. This means that the overlapping area of the two curves shunting 28 and 29, for the same axle resistance (line 17), becomes more important. The minimum recovery area is between points 30 and 31. By comparing figures 2e and 3e, observes that the recovery zone is more important for the three-block version. This in fact leads to a better detection in the electrical joint, which allows to reduce the minimum length and therefore increase the maximum length of the track circuit.

According to the state of the art, it is proposed to use electrical joints for circuits of full channel with frequencies of use included between 1.5 and 4 kHz. We call them low frequencies because they require distances between chord blocks successively relatively high so as to achieve a sufficient seal impedance. It has been represented schematic in Figures 4 and 5 the behavior of the curves shunt for configurations according to the state of the technique of an electrical joint respectively two blocks and three blocks using low frequencies.

According to the invention, it is suggested to use for train detection of high frequency signals, i.e. signals having a frequency greater than 5 kHz and preferably greater than 10 kHz and still preferably greater than 20 kHz.

This makes it possible to bring the blocks closer together (and so to reduce the length of the electrical joint), which becomes particularly advantageous in areas of strong concentrations of switches such as railway stations.

According to a preferred embodiment shown in Figure 6, the chord blocks are no longer located in different places, such as those represented in Figure 3, but they are in a common unit of agreement 35, called "TU.HF" ("Tuning unit - High Frequency ", which is connected by cables 36 to the three adequate positions along the track. Cables 37 connect the unit 35 to the transmitter and receiver.

The present invention provides a version where the distance between the central block and the two blocks outside is of the order of three meters, that is to say that the length of the complete joint is about six meters. A such seal is especially useful in referral areas where we need greater precision in the measurement of the position and therefore the space available for the placement of the electrical seal is lower.

In another embodiment, the unit common is located next to the track, as shown in Figure 7. Equivalent circuits and curves of shunt are quite similar to the circuits and curves shown in Figure 3, although the distance between the outer terminals of the seal is reduced.

Figure 8 shows the components of the unit agree TU.HF for a version installed between the rails. The two functions of the tuning unit 35, namely the transmission function and the reception function, are therefore grouped within the same entity. Two circuits are connected to this entity on both sides of the connections transmission / reception. Each of these circuits can work as a short circuit or with a high impedance depending the frequency considered.

The resistance and the self of the rails are modeled by elements 40 and 41. The central block of joint includes two parallel branches, the first branch comprising an RLC circuit 42 and a circuit 43 of coupling connected to the transmitter 44, the second branch comprising a coupling circuit 45 connected to the receiver 46. The two outer blocks each include a circuit RLC, respectively 47 and 48. the resistance 49 is present between the tuning unit and the transmitter 44. This is a precaution to avoid the appearance of waves stationary in the cable.

• le circuit RLC 42 est conçu de manière à ce que l'unité d'accord soit équivalente à une capacité qui permet le couplage avec l'impédance constituée par le demi-joint du côté droit de la voie à une fréquence F1,
• le circuit RLC 48 de l'unité d'accord (côté droit) agit alors comme un court-circuit à la fréquence F1,
• le circuit RLC 47 de l'unité d'accord (côté gauche) est équivalent à une haute impédance le rendant transparent à cette fréquence F1,
• à la fréquence F1, le joint HF est donc équivalent à un joint RX classique.

The behavior of the high frequency electrical joint for the first channel (frequency F1) of channel can be summarized as follows:

• the RLC circuit 42 is designed in such a way that the tuning unit is equivalent to a capacitor which allows coupling with the impedance formed by the half-joint on the right side of the channel at a frequency F1,
• the RLC circuit 48 of the tuning unit (right side) then acts as a short circuit at the frequency F1,
• the RLC circuit 47 of the tuning unit (left side) is equivalent to a high impedance making it transparent at this frequency F1,
• at frequency F1, the HF seal is equivalent to a conventional RX seal.

• le circuit RLC 42 est conçu de manière à ce que l'unité d'accord soit équivalente à une capacité qui permet le couplage avec l'impédance constituée par le demi-joint du côté gauche de la voie à une fréquence F2,
• le circuit RLC 47 de l'unité d'accord (côté gauche) agit alors comme court-circuit à la fréquence F2,
• le circuit RLC 48 de l'unité d'accord (côté droit) est équivalent à une haute impédance le rendant transparent à cette fréquence F2,
• à la fréquence F2, le joint HF est donc équivalent à un joint TX classique.

The behavior of the high frequency electrical joint for the second track circuit can be summarized as follows:

• the RLC circuit 42 is designed in such a way that the tuning unit is equivalent to a capacitance which allows coupling with the impedance constituted by the half-joint on the left side of the channel at a frequency F2,
• the RLC circuit 47 of the tuning unit (left side) then acts as a short-circuit at the frequency F2,
• the RLC circuit 48 of the tuning unit (right side) is equivalent to a high impedance making it transparent at this frequency F2,
• at frequency F2, the HF seal is equivalent to a conventional TX seal.

The invention also relates to devices similar to the version of Figure 9, which receive two signals at the same time or that send two signals at the same time (Tx / Tx seals, Rx / Rx seals). This is for example the case for the joints 50 and 51 shown in Figure 11. The tuning unit of the seal 50 is linked to two receivers 52, and the tuning unit of the seal 51 is linked to two transmitters 53. The function of the circuits of coupling 43 and 45 will naturally be adapted to these different embodiments of the seal according to the invention.

For example, a receiver / receiver joint (as the seal 50 shown in Figure 9) would need two identical coupling circuits instead of the two different circuits 43 and 45 as shown in FIG. 10, which couple the central block to two receivers.

According to another embodiment, the The present invention proposes to superpose circuits of low frequency and high frequency path.

According to the form of execution shown in Figures 10 and 11, a low four block configuration frequency - high frequency is described.

The seal shown is a four-block joint 100 to 103. Blocks 100 and 103 form a plug circuit for the right lane circuit, which works at the F1 frequency. F1 is a 'low' frequency, that is, in below 5 kHz. For this reason, blocks 100 and 103 are separated by a considerable distance, for example 30m.

Blocks 101 and 102 form a circuit plug for the left lane circuit, which works at the frequency F5. F5 is a 'high' frequency: it is at less than 5 kHz, and preferably greater than 20 kHz. The blocks 101 and 102 are therefore positioned at a low distance, for example 3m.

What is important is the positioning of the 'high frequency' plug circuit (blocks 101 and 102) opposite of the 'low frequency' plug circuit (blocks 100 and 104). The example in Figure 10 shows a positioning inadequate, as shown by the shunt curves 105 and 106. In the worst situation (curves 105), it occurs a lack of recovery curves, resulting in a zone 107 of uncertainty of the location.

In FIG. 11, the HF plug circuit (101, 102) is well positioned. An overlap of the curves of shunt is guaranteed even in the most disadvantageous (curves 105).

• un circuit bouchon basse fréquence (BF), comprenant deux blocs : un court-circuit et une capacité, disposés dans un ordre prédéterminé,
• un circuit bouchon haute fréquence (HF) superposé sur le circuit bouchon BF, c'est-à-dire entre les blocs du circuit BF, le circuit bouchon HF comprenant également deux blocs : un court-circuit et une capacité, disposés dans l'ordre inverse que celui du circuit BF.

As a rule, the four-block seal as just described consists of:

• a low frequency plug circuit (BF), comprising two blocks: a short circuit and a capacitance, arranged in a predetermined order,
• a high-frequency plug circuit (HF) superimposed on the plug circuit BF, that is to say between the blocks of the circuit BF, the plug circuit HF also comprising two blocks: a short-circuit and a capacitor, arranged in the reverse order than that of the BF circuit.

Preferably, the HF plug circuit is positioned closer to the capacity of the BF circuit than the short circuit of the BF circuit.

It is also possible according to the invention superimpose an HF seal comprising three blocks, at a joint to two blocks at low frequency or high frequency.

Figure 12 shows another combination HF-BF. An HF channel circuit 110 is superimposed on a BF track circuit 120. The HF circuit is between two HF electric seals 111 and 112, each comprising a first block 113 which is a capacity at the frequency F5 of the HF circuit, and a second block 114, which is a short circuit at F5. HF circuit 110 allows monitoring additional part of the track that corresponds to the said circuit, for example to increase the level of security in a referral area.

Claims (7)

1. Method of detecting the presence or the absence of a vehicle, such as a train, travelling on a railway-type track comprising two rails, said method taking the form of a series of track circuits, called block systems and separated by electric joints, each joint forming a separation between a first track circuit operating ac a first frequency and a second track circuit operating at a second frequency, characterised in that at least one of said frequencies is greater than 10 kHz and characterised in that at least one of said electric joints is a three-block joint which is disposed between the rails, a first block playing the part of a short-circuit at said first frequency and being transparent to said second frequency, a second block playing the part of a short-circuit at said second frequency and being transparent to said first frequency, and the central block playing the part of a capacitor at each of the two frequencies.
2. Method according to claim 1, characterised in that at least one of the utilisation frequencies is a frequency greater than 20 kHz.
3. Method according to claims 1 or 2, characterised in that she two utilisation frequencies are frequencies greater than 10 kHz and preferably greater chan 20 kHz.
4. Method of detecting the presence or the absence of a vehicle, such as a train, travelling on a railway-type track comprising two rails, said method taking the form or a series of track circuits, called block systems and separated by electric joints, each joint forming a separation between a first track circuit operating at a first frequency and a second track circuit operating at a second frequency, characterised in that at least one of said electric joints is a four-block joint which is disposed between the rails, comprising:

   a first block (100) and a second block (103) which form a trap circuit at the first frequency, said frequency being lower than 5 kHz, the first block (100) playing the part of a short-circuit, the second block (103) playing the part of a capacitor, said blocks being disposed in a predetermined order,

   a third block (101) and a fourth block (102) which form a crap circuit at the second frequency, said frequency being greater than 5 kHz, the third block (101) playing the part of a capacitor and the fourth block (102) playing the part of a short-circuit, said third and fourth blocks (101, 102) being disposed between said first (100) and second (103) blocks and in the reverse order from that of said two first and second blocks (100 , 103).
5. Device for implementing the method according to any one of claims 2 to 3, comprising:

   a central block, comprising two parallel branches, the first branch comprising an RLC circuit (42) and a first coupling circuit (43), the second branch comprising a second coupling circuit (45),

   a block (47) comprising an RLC circuit, this block playing the part of a Short-circuit at one of the two frequencies and being transparent to the second frequency.

   a block (48) comprising an RLC circuit, this block playing the part of a short-circuit at the second of the two frequencies and being transparent to the first frequency.
6. Device for implementing the method according to claim 4, comprising:

   a first block (100) and a second block (103) which form a trap circuit at the first frequency, said frequency being lower than 5 kHz, the first block (100) playing the part of a short-circuit, the second block (103) playing the part of a capacitor, said blocks being disposed in a predetermined order,

   a third block (101) and a fourth block (102) which form a trap circuit at the second frequency, said frequency being greater than 5 kHz, the third block (101) playing the part of a capacitor and the fourth block (102) playing the part of a short-circuit,

   said third and fourth blocks being disposed between said first (100) and second (103) blocks and in the reverse order from that of said two first and second blocks (100, 103).
7. Utilisation of the method according to any one of the preceding claims for detecting the presence or the absence of a railway vehicle in track configurations comprising a large number of junction points, such as railway stations.

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