Patent Description:
The European Train Control System (ETCS) in level <NUM> involves a cable connection between an electrical unit, called a LEU for Lineside Electrical Unit, and a balise. This connection is used to transmit from track to train the status of the lateral signals like the traffic lights. This is part of an automatic track-to-train information transmission which is received by the on-board vital computer (EVC).

The electrical unit is connected to the traffic light. Each active light is detected by the electrical unit which sends to the balise thru a cable a telegram signal. This telegram is retransmitted by the balise to the train using an inductive coupling RF channel, called the interface 'A1'.

The cable interface between the LEU and the balise is generally called the interface 'C' and denoted by I/F C. The electrical signal transmitted by the C interface comprises two additively mixed signals called signal C6 and signal C1. Signal C6 is a sinusoidal signal at f=<NUM>. Signal C1 is a telegram signal. More specifically, signal C1 is a Manchester-like encoded differential data signal. Signal C1 comprises digital information. Signal C1 typically conveys <NUM> or <NUM> bits that repeat cyclically without interruption at a data rate of <NUM> kbits/s. The signal C(t) in the cable is the additive mixing of both C1(t) and C6(t): C(t) = C1(t) + C6(t).

Document <CIT> relates to a device and a method for monitoring the operability of a signal connection between the LEU and the balise. A problem of this known method is that it requires to inject a monitoring signal in the cable.

Document <CIT> describes a monitoring board signal extracting circuit of an LEU. The extraction circuit is composed of a C-interface voltage interface, a C-interface current interface, a C-interface voltage processing circuit, and a C-interface current processing circuit.

Document <CIT> describes a method of locating defect position in conductor circuits. The method involves introducing first and second electrical test signals into each end of the conducting circuit. The signals are picked up at two different points in the circuit with two signal detectors. A measurement signal is produced corresponding to the difference between the signals detected by the two detectors. The pick-up points for either or both detector are extended, so that the length of the section of conducting circuit between the two pick-up points is varied. Document <CIT> discloses a method for monitoring an electrical signal in a cable between an electric unit and a balise in a railway installation.

An object of the present invention is to monitor and help for the maintenance of a railway installation.

Accordingly, the invention relates to a process for monitoring an electrical signal in a cable between an electric unit and a balise in a railway installation; the electrical signal comprising a first part and a second part, the first part comprising a first telegram signal and a first sinusoidal signal, the second part comprising a second telegram signal and a second sinusoidal signal; the process comprising the following steps:.

The invention copies of the telegram signal (C1) and the sinusoidal signal (C6) of the first and second parts of the electrical signal and uses any of them, or a combination of several of them, to generate a process output, which relates to the railway installation and thus indicates a possible problem in the railway installation. An alarm can be triggered if the process output is above a threshold or is different from reference data. There is thus no need of injecting any signal in the cable.

In order to extract the copies of the first and second parts of the electrical signal, the bidirectional coupler uses voltage measurements. It does not measure any current. Its outputs, at the third and fourth ports, are voltages as function of time.

Using information from both the telegram signal (from the first and/or second part of the electrical signal) and the sinusoidal signal (from the first and/or second part of the electrical signal) is not necessary within the frame of the invention, but it is preferred since it improves the monitoring.

Using information from both the first part (telegram and/or sinusoidal) and the second part (telegram and/or sinusoidal) is not necessary within the frame of the invention, but it is preferred since it improves the monitoring.

The relationship between the first part and the second part of the electrical signal reflects the condition of the circuit between the bidirectional coupler and the balise.

The process according to the invention is made to be run continuously. It can for example run continuously during one week.

One bidirectional coupler at a fixed location along the cable is sufficient to obtain the copies. There is no need of multiple probes on a cable. The bidirectional coupler is preferably not powered.

The electrical signal has a forward direction from the electric unit to the balise, and a reverse direction from the balise to the electric unit. The first part of the electrical signal may be considered as the power wave travelling from the electric unit to the balise. It may be called "forward signal" or "incident power wave". The second part of the electrical signal may be considered as the power wave travelling from the balise to the electric unit. It may be called "reverse signal" or "reflected power wave". The skilled person is familiar with the concept of power waves for example because of the article "<NPL>.

The bidirectional coupler is plugged on the cable in such a way that the cable coming from the electric unit is connected to its first port and the cable coming from the balise is connected to its second port. The bidirectional coupler is characterized by a coupling factor. It may be called "bidirectional RF coupler". The first port may also be called input port, and the second port may also be called output port. The third port (which may also be called coupled port, or forward coupled port) provides a copy of the first part of the electrical signal. It is the product of the multiplication of the incident power wave by the coupling factor of the bidirectional coupler. The fourth port (which may also be called isolated port, or reverse coupled port) provides a copy of the second part of the electrical signal. It is the product of the multiplication of the reflected power wave by the coupling factor of the bidirectional coupler. This is due to the intrinsic nature of the bidirectional coupler.

The copy of the first part of the electrical signal, as provided on the third port, is a voltage as function of time. It may be called "first extracted signal" or "first voltage". The copy of the second part of the electrical signal, as provided on the fourth port, is a voltage as function of time, different from the copy of the first part of the electrical signal. It may be called "second extracted signal" or "second voltage".

The electric unit may be called a "Lineside Electronic Unit" or LEU. It is generally part of the European Train Control System (ETCS).

The cable may be called an "Interface C". It preferably comprises a pair of conductors (for example copper) for the transmission of a differential electrical signal. The cable may have a constant characteristic impedance and behaves like a transmission line.

In some embodiments, the computer unit may include logic carry out by a processor, a central processing unit (CPU), a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or the like, or any combinations thereof, and can include discrete digital or analog circuit elements or electronics, or combinations thereof.

A bidirectional coupler is an electronic device known by the skilled person. It has four ports: the input port, the output port, the forward coupled port, and the reverse coupled port. The signal passing from the input port to the output port is copied, as a voltage as function of time, at the forward coupled port. The signal passing from the output port to the input port is copied, as a voltage as function of time, at the reverse coupled port.

In an embodiment of the invention, the process output is based on a detection of an absence of at least one of:.

In practice, if the telegram signal is absent in the first part of the electrical signal, it is also absent in the second part (and the same for the sinusoidal signal). Anyway, the absence of any of these four signals in the cable indicates a problem in the railway installation. The process output preferably indicates said absence(s).

In an embodiment of the invention, the process output is based on a phase difference between the second telegram signal and the first telegram signal, and/or a phase difference between the second sinusoidal signal and the first sinusoidal signal. The phase difference of telegram signal or the sinusoidal signal provides information about the state of the cable, the electric unit and/or the balise.

In an embodiment of the invention, the process output is based on at least one of:.

The amplitude provides information about the state of the cable, the electric unit and/or the balise. For example, an amplitude in the first part of the electrical signal at least ten times higher the amplitude in the second part of the electrical signal for the telegram and/or the sinusoidal signal typically indicates a normal state of the railway installation. An amplitude in the second part of the electrical signal higher than a tenth of the amplitude in the first part of the electrical signal for the telegram and/or the sinusoidal signal is an indication of a possible problem in the railway installation (an open or short for example). An increase in the amplitude for the second telegram and/or the second sinusoidal signal is an indication of a possible problem in the railway installation.

The reference value the data rate of the telegram signal of both the first and the second parts is <NUM> kbits/s. The reference value the frequency of the sinusoidal signal of both the first and the second parts is <NUM>. A deviation of more than a threshold (for example <NUM>%) with respect to the reference value is an indication of a possible problem in the railway installation.

In an embodiment of the invention, the process output is based on a digital content of the first telegram signal, and/or a digital content of the second telegram signal. The digital content means the sequence of bits (<NUM> or <NUM>) in the telegram signal in the first and/or the second part.

In an embodiment of the invention, the process output is based on a comparison with reference data to identify a problem in the railway installation.

In an embodiment of the invention, the process comprises a timestamping of the process output and a storage of the process output in a memory.

In an embodiment of the invention, the process comprises a transmission of the process output from an equipment located along the railway installation, and comprising the bidirectional coupler, and the signal processing unit to a remote receiver. The transmission can be done through Internet and/or can be wireless. The receiver can for example be in a portable device of a security operator, in a server, and/or in a facility of a railway company.

The invention also relates to a system according to claim <NUM> for monitoring for monitoring an electrical signal in a cable between an electric unit and a balise in a railway installation; the electrical signal comprising a first part and a second part, the first part comprising a first telegram signal and a first sinusoidal signal, the second part comprising a second telegram signal and a second sinusoidal signal; the system comprising:.

The bidirectional coupler is such that a copy of the first part of the electrical signal is provided at the third port and a copy of the second part of the electrical signal is provided at the fourth port.

The signal processing unit is configured to analyze the copy of the first part of the electrical signal and the copy of the second part of the electrical signal to determine a process output related to the railway installation, using at least one of : the first telegram signal, the first sinusoidal signal, the second telegram signal, or the second sinusoidal signal.

The system is preferably installed at a fixed location.

In an embodiment of the invention, the bidirectional coupler provides a galvanic isolation between the cable and the analyzer.

In an embodiment of the invention, the bidirectional coupler is unable to inject any signal in the cable.

In an embodiment of the invention, all the components of the bidirectional coupler are passive. The bidirectional coupler may comprise capacitors, resistors, inductors, transformers. The bidirectional coupler does not comprise any transistor or active device for example.

In an embodiment of the invention, the signal processing unit comprises at least one of the following:.

Each filter selects the desired part of the electrical signal and the subsequent slicer cleans it.

The invention also relates to an equipment located along a railway, comprising a system according to any embodiment, and the electric unit, the equipment being configured to be located along the railway installation.

For a better understanding of the present invention, reference will now be made, by way of example, to the accompanying drawings in which:.

The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto. The described functions are not limited by the described structures.

On the figures, identical or analogous elements may be referred by a same number.

<FIG> illustrates a railway installation <NUM> comprising a railway <NUM>, a lineside signaling device <NUM>, a cable <NUM>, an electric unit <NUM>, and a balise <NUM>. The cable <NUM> is located along the railway <NUM> and connects the electric unit <NUM> and the balise <NUM>. The cable <NUM> is intended to be used, for example, in a European Train Control System (ETCS) level <NUM>. The electric unit <NUM> is connected to the lineside signaling device <NUM>, for example a traffic light. The balise <NUM> is able to transmit information to a train computer <NUM> (usually called EVC for European Vital Computer) in a train <NUM> on the railway <NUM>.

A system <NUM> according to the invention is preferably located in an equipment <NUM> located along the railway installation <NUM>, in a same housing as the electric unit <NUM>.

<FIG> illustrates a system <NUM> according to an embodiment of the invention. The system <NUM> comprises at least one bidirectional coupler <NUM>, each bidirectional coupler <NUM> being electrically and mechanically coupled one cable <NUM>. In the embodiment of <FIG>, each bidirectional coupler <NUM> is part of a probe <NUM> electrically and mechanically coupled to two cables <NUM>. The bidirectional coupler <NUM> may be called "Passive and Isolated Probe". The bidirectional coupler <NUM> is a pass thru device, and is intended not to disturb the transmission of the signal in the cable <NUM>.

The system <NUM> also comprises a signal processing unit <NUM> comprising at least one analyzer <NUM>, preferably connected to at least one bidirectional coupler <NUM> through a connection <NUM>. In the embodiment of <FIG>, each analyzer <NUM> is connected to two probes <NUM>. If the analyzer <NUM> is connected to several bidirectional couplers <NUM>, the analysis performed by the analyzer <NUM> may be done using a cyclic multiplexing method.

The data transfer between the bidirectional coupler <NUM> and the analyzer <NUM> is preferably unidirectional: there is no data transferred from the analyzer <NUM> to the bidirectional coupler <NUM>. The analyzer <NUM> is preferably an analog and digital electronic device.

The signal processing unit <NUM> also comprises at least one processing unit <NUM>, preferably connected to at least one analyzer <NUM> through a connection (USB, serial connection or LAN/Ethernet). The processing unit <NUM> preferably comprises a computing unit <NUM> and a memory <NUM>.

The system <NUM> may also comprise a transmission device <NUM>, like a modem, connecting wirelessly the processing unit <NUM> to the Internet <NUM>.

<FIG> illustrates, very schematically, a bidirectional coupler <NUM>. It comprises four ports. The third port <NUM> outputs a copy of the power wave entering the first port <NUM>, i.e. a copy <NUM> of a first part <NUM> of the electrical signal <NUM>. The fourth port <NUM> outputs a copy of the power wave entering the second port <NUM>, i.e. a copy <NUM> of a second part <NUM> of the electrical signal <NUM>. The signal processing unit <NUM> is connected to the third port <NUM> and the fourth port <NUM>.

<FIG> is a flowchart of a process <NUM> according to an embodiment of the invention. An electrical signal <NUM> is present in the cable <NUM> between the electric unit <NUM> and the balise <NUM>. The electrical signal <NUM> comprises a first part <NUM> and a second part <NUM>, the first part <NUM> comprising a first telegram signal <NUM> and a first sinusoidal signal <NUM>, the second part <NUM> comprising a second telegram signal <NUM> and a second sinusoidal signal <NUM>.

The bidirectional coupler <NUM> connected to the cable <NUM> extracts a copy <NUM> of the first part <NUM> and a copy <NUM> of the second part <NUM> and transfers them, as a bidirectional coupler output <NUM>, to the analyzer <NUM>.

<FIG> illustrates an exemplary embodiment of the bidirectional coupler <NUM> coupled to a cable <NUM> comprising two conductors 90a, 90b. The signal electrical <NUM> flows in the two conductors 90a, 90b between the electrical unit <NUM> and the balise <NUM>, through the bidirectional coupler <NUM>. The exemplary embodiment of the bidirectional coupler <NUM> comprises four transformers and two resistors:.

For the bidirectional coupler <NUM> illustrated at <FIG>, which is called a Tandem Match RF Coupler, the coupling factor in dB is given by: <MAT> For N large enough, for example for N≥ <NUM>, the coupling factor is roughly given by: <MAT> For N=<NUM>, the coupling factor is roughly <NUM> dB.

N may be equal to <NUM> for example. Tr3 and Tr4 provide galvanic isolation between the cable <NUM> and the analyzer <NUM>. Preferably, the bidirectional coupler <NUM> only comprises passive electric components. Preferably, the bidirectional coupler <NUM> is not powered, except through the cable <NUM>.

The connection <NUM> between the bidirectional coupler <NUM> and the analyzer <NUM> preferably comprises four conductors: two conductors 29a, 29b for the copy <NUM> of the first part <NUM> of the electrical signal <NUM>, and two conductors 29c, 29d for the copy <NUM> of the second part <NUM> of the electrical signal <NUM>. The bidirectional coupler <NUM> sends to the analyzer <NUM> the copy <NUM> of the first part <NUM> of the electrical signal 10CFWD(t) and the copy <NUM> of the second part <NUM> of the electrical signal <NUM> CREV(t), which are voltages as a function of the time.

Many other embodiments of the bidirectional coupler <NUM> are possible within the frame of the invention.

Referring back to the process of <FIG>, the signal processing unit <NUM> receives the copy <NUM> of the first part <NUM> and the copy <NUM> of the second part <NUM> and the analyzer <NUM> analyzes them to determine a measurement output <NUM>. The analysis by the analyzer <NUM> preferably comprises the determination of at least one of:.

The measurement output <NUM> is based on one or several of these signals <NUM>, <NUM>, <NUM>, <NUM>. Preferably, one or several of these signals <NUM>, <NUM>, <NUM>, <NUM> may be included or may form the measurement output <NUM>.

<FIG> shows a possible architecture of the analyzer <NUM>. If the analyzer <NUM> is connected to several bidirectional couplers <NUM>, the blocks (except blocks <NUM>, <NUM>) can be replicated. The analysis may comprise data analog filtering, signal reconditioning, analog envelope detection, digital decoding and data recording.

To determine the signals <NUM>, <NUM>, <NUM>, <NUM>:.

The low-pass filter <NUM> extracts the first sinusoidal signal <NUM> which is expected to be a pure sine wave at <NUM>. The same holds for the second sinusoidal signal <NUM>. The low-pass filters <NUM>, <NUM> can be of any type. Their purpose is to reject the C1 signal which starts at <NUM>. An example is a Butterworth low pass filter of order n=<NUM> with 3dB cut-off frequency at <NUM>.

The high-pass filter <NUM> removes the C6 and just extracts the first telegram signal <NUM>. The same holds for the second telegram signal <NUM>. Preferably the C6 rejection is more than <NUM> dB. An example is a Butterworth of order n=<NUM> with 3dB cut-off frequency of <NUM>.

The analyzer <NUM> may comprise four envelop detectors <NUM>, <NUM>, <NUM>, <NUM>. The envelop detectors <NUM>, <NUM> are AC signal envelop detector configured to determine the amplitude of the C6 extracted component, i.e., the amplitude |Vfwd6| of the first sinusoidal signal <NUM> for <NUM> and the amplitude |Vrev6| the second sinusoidal signal <NUM> for <NUM>. The envelop detectors <NUM>, <NUM> are AC signal envelop detector configured to determine the amplitude of the C1 extracted component, i.e., the amplitude |Vfwd1| of the first telegram signal <NUM> for <NUM> and the amplitude |Vrev1| of the second telegram signal <NUM> for <NUM>. The envelop detectors <NUM>, <NUM>, <NUM>, <NUM> are preferably linear with respect to the input signal amplitude.

The analyzer <NUM> may comprise four signal slicers <NUM>, <NUM>, <NUM>, <NUM>. They are analog comparator-based signal reshaper. They are configured to convert an analog AC signal to a square signal at TTL/CMOS levels with rising/falling edges corresponding to the negative-to-positive and positive-to-negative transitions of the signal respectively. The signal slicers <NUM>, <NUM>, <NUM>, <NUM> make possible to remove a possible DC offset and/or possible deformation of the signal. The output of the signal slicers <NUM>, <NUM> (i.e. for C1) is Differential Bi-Phase Level (DBPL) coding.

The analyzer <NUM> may comprise four analog-to-digital converters <NUM>, <NUM>, <NUM>, <NUM>, which convert the analog signal between <NUM> and Vmax provided by the envelop detectors into a digital quantized representation to be processed by the FPGA <NUM> and the CPU <NUM>. The four analog-to-digital converters <NUM>, <NUM>, <NUM>, <NUM> have preferably a vertical resolution of at least <NUM> bits.

The analyzer <NUM> may comprise an FPGA <NUM>.

The FPGA <NUM> may determine the frequency of the first sinusoidal signal <NUM> by measuring the frequency of the signal provided by the signal slicer <NUM>. The FPGA <NUM> may determine the frequency of the second sinusoidal signal <NUM> by measuring the frequency of the signal provided by the signal slicer <NUM>.

The FPGA <NUM> may determine, from the output of the signal slicers <NUM>, <NUM> a phase difference ϕ6 between the second sinusoidal signal <NUM> and the first sinusoidal signal <NUM>. The FPGA <NUM> may determine, from the output of the signal slicers <NUM>, <NUM> a phase difference ϕ1 between the second telegram signal <NUM> and the first telegram signal <NUM>.

The FPGA <NUM> may decode the output of the signal slicer <NUM> to extract the digital content of the telegram signal <NUM> of the first part <NUM>. The FPGA <NUM> may decode the output of the signal slicer <NUM> to extract the digital content of the telegram signal <NUM> of the second part <NUM>.

The FPGA <NUM> may determine, from the output of the signal slicers <NUM>, the data rate of bits of the first telegram signal <NUM>. The FPGA <NUM> may determine, from the output of the signal slicers <NUM>, the data rate of bits of the second telegram signal <NUM>.

The FPGA <NUM> may determine the analog level of any of the four signals <NUM>, <NUM>, <NUM>, <NUM> after analog-to-digital conversion.

The analyzer <NUM> may comprise a central processing unit (CPU) <NUM>, which collects the data outputted by the FPGA <NUM> and prepare them for recording and transmission.

The analyzer <NUM> sends, preferably continuously, the measurement output <NUM> (both analog and digital) to the processing unit <NUM>. A process output <NUM> may be determined by the processing unit <NUM> or may be formed by at least part of the measurement output <NUM>.

The processing unit <NUM> may store in its memory <NUM> the measurement output <NUM> and/or process it further to determine the process output <NUM>. The processing unit <NUM> may provide the process output <NUM> to the transmission device <NUM> (<FIG>) for a transmission outside the equipment <NUM> (figure <NUM>), to a remote receiver, for example to a server including a database.

The analyzer <NUM> and/or the processing unit <NUM> may also assess the actual presence, and thus the absence of at least one of the four signals <NUM>, <NUM>, <NUM>, <NUM>.

The signal processing unit <NUM> may determine phasor quantities for the four signals <NUM>, <NUM>, <NUM>, <NUM> as follows: <MAT>.

The input voltages of the bidirectional coupler <NUM> illustrated at <FIG> (between 90a and 90b on the side towards the electric unit <NUM>, i.e. on the first port <NUM>) may be determined as: <MAT> <MAT>.

The relationship between the phasors Vfwd6,<NUM> and Vrev6,<NUM> reflects the condition of the circuit between the bidirectional coupler <NUM> and the balise <NUM>:.

When circuit is matched, REV voltage is very small and almost zero (since N is considered as large usually greater than <NUM>). In the terminology of bi-directional coupler, this corresponds to a circuit where all energy is transmitted to the load with no reflection (REV voltage is zero). When the circuit is open, the REV voltage is high and almost equal in magnitude, but reversed in phase (since N is usually larger than <NUM>). When the circuit is shorted, the REV voltage is high and equal in magnitude and in phase with the FWD voltage. In other word, high REV voltages correspond to energy reflection and to open/short circuit conditions. Low and almost zero REV voltages correspond to well-matched circuits.

It is clear from these formulas how the amplitudes and/or phases can be used to measure voltages and currents at the output on the side of the electric unit <NUM>, to detect open/short cable failures, and use this information to generate the process output <NUM> related to the railway installation <NUM>.

The processing unit <NUM> may compare measured data (preferably the measurement output <NUM> or data extracted from it) with reference data <NUM> to detect deviation with expected nominal range or value and thus identify a problem in the railway installation <NUM>. The reference data <NUM> comprise an expected value or an expected sequence, and for example if the comparison indicates a difference above a threshold, the process output <NUM> indicates which measured data may be problematic, preferably with the measured data and its expected value. For example, if the measured data is a sequence of bits provided by the digital content of the first telegram signal <NUM>, it may be compared with an expected sequence (the reference data), and the process output <NUM> may indicate that the sequence is as expected or may indicate the measured sequence and the expected sequence.

The processing unit <NUM> may also determine a drift in at least one of the measured data of the measurement output <NUM>.

The processing unit <NUM> may analyze the digital content of the first telegram signal <NUM> and/or the digital content of the second telegram signal <NUM> to detect, for example, the following problems:.

The process output <NUM> relates to the railway installation <NUM>. The process output <NUM> may comprise a timestamp corresponding to the time when it was determined. The process output <NUM> may be a message, displayed on the equipment <NUM> and/or send by the transmission device <NUM> and/or stored in the memory <NUM>. It can be an alarm message and/or a warning message for example. It may be sent only if the comparison with the reference data <NUM> indicates a deviation with respect to a nominal range.

The process output <NUM> contain information, for example explicit information, about at least one of the following:.

In other words, the invention relates to the monitoring an electrical signal <NUM> in a cable <NUM> between an electric unit <NUM> and a balise <NUM> in a railway installation <NUM>. The first part <NUM> and the second part <NUM> of the electrical signal <NUM> are copied, and their copies <NUM>, <NUM> are analyzed to determine a process output <NUM> based on the telegram signal <NUM> of the first part <NUM>, and/or the sinusoidal signal <NUM> of the first part <NUM>, and/or, the telegram signal <NUM> of the second part <NUM>, and/or the sinusoidal signal <NUM> of the second part <NUM>.

Claim 1:
Process (<NUM>) for monitoring an electrical signal (<NUM>) in a cable (<NUM>) between an electric unit (<NUM>) and a balise (<NUM>) in a railway installation (<NUM>); the electrical signal (<NUM>) comprising a first part (<NUM>) and a second part (<NUM>), the first part (<NUM>) comprising a first telegram signal (<NUM>) and a first sinusoidal signal (<NUM>), the second part (<NUM>) comprising a second telegram signal (<NUM>) and a second sinusoidal signal (<NUM>); the process (<NUM>) comprising the following steps:
• a bidirectional coupler (<NUM>), comprising a first port (<NUM>) connected to the electric unit (<NUM>) through the cable (<NUM>) and a second port (<NUM>) connected to the balise (<NUM>) through the cable (<NUM>), extracts a copy (<NUM>) of the first part (<NUM>) of the electrical signal (<NUM>), which is a voltage as function of time and is obtained on a third port (<NUM>) of the bidirectional coupler (<NUM>), and a copy (<NUM>) of the second part (<NUM>) of the electrical signal (<NUM>), which is another voltage as function of time and is obtained on a fourth port (<NUM>) of the bidirectional coupler (<NUM>);
• a signal processing unit (<NUM>), connected to the third port (<NUM>) and the fourth port (<NUM>) of the bidirectional coupler (<NUM>), analyzes the copy (<NUM>) of the first part (<NUM>) and the copy (<NUM>) of the second part (<NUM>) to determine a process output (<NUM>) related to the railway installation (<NUM>), based on at least one of :
∘ the first telegram signal (<NUM>),
∘ the first sinusoidal signal (<NUM>),
∘ the second telegram signal (<NUM>), or
∘ the second sinusoidal signal (<NUM>).