Patent Description:
In railways industry, signalling system is one of the most critical system, as it is directly connected to the safety of the passengers and rail operators, both on-board and on-ground. A Signal Equipment Room (SER) may control a number of wayside devices in a station field area of a railway station using command signals. These wayside devices may include signal posts and point machines.

A typical station field area may include six signal posts and roughly eight-point machines. Each wayside device is hard wired using armored multi-core cable (for example, a <NUM>-core cable or a <NUM>-core cable) to the relay logic implemented in the SER. An average distance between the wayside device and the SER is approximately <NUM> meters. As such, the cost of laying these cables to setup communication between the SER and the wayside devices is high, as these armored multi-core cables are cost high. Moreover, large manual efforts are required to lay and maintain these cables.

Hence, there is a need to minimize the cost of the cables between the SER and wayside devices, and further reduce manual intervention required in laying and maintaining these cables.

In one embodiment, a system for setting up communication between a Signal Equipment Room (SER) and wayside devices is disclosed. The system includes a master controller configured to receive a first analog command signal from the SER over a first power line. This master controller is configured to generate a digital command signal based on the first analog command signal. The system further includes a plurality of slave controllers configured to receive the digital command signal from the master controller over a second power line. Each of the plurality of slave controllers is configured to generate a second analog command signal based on the digital command signal. Further, each of the plurality of slave controllers is configured to send the second analog command signal to a corresponding wayside device over a respective third power line. The second power line power line may include a lower core power cable than the first and the third power line.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, which is defined by the appended claims. Document <CIT> describes an intelligent terminal for a railway signal security device that is incorporated in or attached to a field device of the railway signal security device and performs electronic control thereof.

The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate exemplary embodiments and, together with the description, serve to explain the disclosed principles.

While examples and features of disclosed principles are described herein, modifications, adaptations, and other implementations are possible without departing from the scope of the invention as defined by the claims. It is intended that the following detailed description be considered as exemplary only.

Referring now to <FIG>, a block diagram of an environment <NUM> for setting up communication between a Signal Equipment Room (SER) and wayside devices is illustrated, in accordance with an embodiment. The environment <NUM> includes a SER <NUM> and a plurality of wayside devices 110A, 110B,. 110N (also, collectively referred to as plurality of wayside devices <NUM>).

As it will be appreciated by those skilled in the art, the SER <NUM> performs signaling control through a decentralized network of control points. These control points are implemented in the form of wayside devices. Further, these wayside devices may include signal posts or point machines. As such, the SER <NUM> may control train movements through railway signals, so as to ensure smooth running of railway operations, for example, by regulating safety, routes, and schedule. For example, the SER <NUM> may control train movements by transmitting command signals to the wayside devices <NUM>. Further, the SER <NUM> may provide for safe and reliable operations and maintenance of critical systems, such as signaling communication system and electrical distribution.

As mentioned above, each of the plurality of wayside devices <NUM> may be either a signal post or a point machine. It may be understood that signal post may be a visual display device that conveys instructions or provides advance warning of instructions regarding train driver's authority to proceed. The train driver interprets the signal's and acts accordingly. Further, the signal may inform the train driver of the speed at which the train may safely proceed, or the signal may even instruct the driver to stop. The point machine may be a device for operating railway turnouts. The point machine may also be known as a point motor, switch machine, or a switch motor.

The environment <NUM> implements a system <NUM> for setting up communication between the SER <NUM> and the plurality of wayside devices <NUM>. It may be noted that the system <NUM> may be implemented on a railway site, for example, a railway station. According to the invention, the system <NUM> includes one or more master controllers <NUM> which are configured to receive a first analog command signal from the SER over a first power line. Each of the one or more master controllers <NUM> is further configured to generate a digital command signal based on the first analog command signal. Further, the system <NUM> includes a plurality of slave controllers <NUM> which are configured to receive the digital command signal from a corresponding master controller <NUM> over a second power line. Each of the plurality of slave controllers <NUM> is configured to generate a second analog command signal based on the digital command signal, and send the second analog command signal to a corresponding wayside device of the plurality of wayside devices <NUM> over a third power line. The second power line is a lower core power cable than the first and the third power line.

It may be further noted that the one or more master controllers <NUM> may be positioned in proximity to the SER <NUM>. Further, the plurality of slave controllers <NUM> may be positioned in proximity to the corresponding wayside devices <NUM>.

By way of an example, as shown in <FIG>, the environment <NUM> may include the SER <NUM>, the plurality of wayside devices <NUM>, and the system <NUM> for setting up communication between the SER <NUM> and the plurality of wayside devices <NUM>. The system <NUM> includes one or more master controllers 106A, 106B,. 106D (also, collectively and individually referred to as one or more master controllers <NUM> and master controller <NUM>). The one or more master controllers <NUM> are communicatively coupled to the SER <NUM> over the first power line. Each of the one or more master controllers <NUM> is configured to receive a first analog command signal from the SER <NUM> over the first power line. In some embodiments, the first power line may include one of a <NUM>-core power cable or a <NUM>-core power cable.

The system <NUM> further includes a plurality of slave controllers 108A, 108B. 108N (also, collectively and individually referred to as plurality of slave controllers <NUM> and slave controller <NUM>). Each of these plurality of slave controllers <NUM> is communicatively coupled to a corresponding master controller <NUM>. Each of the plurality of slave controllers <NUM> receives the digital command signal from the master controller <NUM> over the second power line. The second power line includes a lower core power cable than the first power line. For example, the second power line may include a <NUM>-core power cable. In some embodiments, the second power line may include two redundant power cables, for redundant 2x2-core power line.

It may be noted that the each of the plurality of slave controllers <NUM> generates a second analog command signal based on the digital command signal. Further, each of the plurality of slave controllers <NUM> sends the second analog command signal to a corresponding wayside device of the plurality of wayside devices <NUM>. To this end, each of the plurality of slave controllers <NUM> is communicatively coupled to a corresponding wayside device from a plurality of wayside devices <NUM> over a third power line. The third power line includes a higher core power cable than the second power line. For example, the third power line may include one of a <NUM>-core power cable and a <NUM>-core power cable.

In particular, as shown in <FIG>, a first set of slave controllers including slave controllers 108A, 108B, and 108C may be communicatively coupled to the first master controller 106A. Similarly, a second set of slave controllers including slave controllers 108D, 108E, 108F, and <NUM> may be communicatively coupled to the second master controller 106B. A third set of slave controllers including slave controllers <NUM>, 108I, 108J, and <NUM> may be communicatively coupled to the third master controller 106C. A fourth set of slave controllers including slave controllers <NUM>, <NUM>, and 108N may be communicatively coupled to the fourth master controller 106D.

Further, the slave controller 108A may be communicatively coupled to a wayside device 110A, the slave controller 108B may be communicatively coupled to a wayside device 110B, and the slave controller 108C may be communicatively coupled to a wayside device 110C. Further, the slave controller 108D may be communicatively coupled to a wayside device 110D, the slave controller 108E may be communicatively coupled to a wayside device 110E, the slave controller 108F may be communicatively coupled to a wayside device 110F, and the slave controller <NUM> may be communicatively coupled to a wayside device <NUM>. Further, the slave controller <NUM> may be communicatively coupled to a wayside device <NUM>, the slave controller 108I may be communicatively coupled to a wayside device 110I, and the slave controller 108J may be communicatively coupled to a wayside device 110J. Further, the slave controller <NUM> may be communicatively coupled to a wayside device <NUM>, the slave controller <NUM> may be communicatively coupled to a wayside device <NUM>, the slave controller <NUM> may be communicatively coupled to a wayside device <NUM>, and the slave controller 108N may be communicatively coupled to a wayside device 108N.

By way of an example, the wayside devices 110A, 110B, 110C, 110D, 110E, 110F, and <NUM> may be signal posts, and these wayside devices (i.e. signal posts) may be communicatively coupled to the corresponding slave controller via <NUM>-core power cables. Further, the wayside devices <NUM>, 110I, 110J, <NUM>, <NUM>, <NUM>, and 110N may be point machines and may be communicatively coupled to the corresponding slave controller via <NUM>-core power cables.

In some embodiments, each master controller <NUM> may receive, from the SER <NUM>, a first analog command signal over a first power line for controlling a wayside device from a plurality of wayside devices <NUM>. Further, each master controller <NUM> may generate a digital command signal based on the first analog command signal, and transmit the digital command signal to each of the plurality of slave controllers <NUM> over a second power line. As mentioned above, each of the plurality of slave controllers <NUM> may generate a second analog command signal based on the digital command signal, and send the second analog command signal to a corresponding wayside device <NUM> over the third power line.

In some embodiments, the master controller <NUM> may digitize the analog command signals received from the SER <NUM> and package them in multiple digital messages. The master controller <NUM> may then transmit the packaged digital command signals to the corresponding slave controllers <NUM> over the second power line, using appropriate modulation. It may be noted that the digital command signal transmitted by the master controller <NUM> may include multiple digital command signals. Further, each of these multiple digital command signals may correspond to each slave controller of the first plurality of slave controllers <NUM>.

In some embodiments, each of the plurality of slave controllers <NUM> may have a unique slave controller ID assigned to it. Upon receiving the multiple digital command signals from the master controller <NUM>, each slave controller <NUM> may map the unique ID assigned to it with the ID associated with each of the multiple digital command signals. Based on the mapping, each slave controller <NUM> may identify a digital command signal corresponding to that slave controller.

Once the slave controller <NUM> has identified the corresponding digital command signal, the slave controller <NUM> may decode that digital command signal. Upon decoding, the slave controller <NUM> may trigger a control action for controlling a corresponding wayside device <NUM> (i.e. control output ports), based on the decoded digital command signal. For example, the control action may include generating a signal on the signal post, or causing to align the railway track with one of two or more connecting tracks.

In some embodiments, the master controller <NUM> may validate integrity of received analog signal. To this end, the master controller <NUM> may embed a cyclic redundancy check (CRC) and/or a life counter in the digital command signal. Further, in some embodiments, the master controller <NUM> may transmit the digital command signal at a predefined interval to ensure that required safety is achieved. Further, each slave controller <NUM> may validate the received message against the received CRC and state of the life counter value of the message. Further, the slave controller <NUM> may act on the decoded message to accordingly control the wayside device.

In some embodiments, the slave controller <NUM> may receive a feedback signal from the corresponding wayside device in the form of load current or limit switches. The slave controller <NUM> may further digitize the feedback signal and transmit the feedback signal to the master controller <NUM> as a response message. The response message may include the slave controller ID, feedback values, CRC and life counter information. Further, the slave controller <NUM> may transmit the response message on dual power lines. Based on the response received, the master controller <NUM> may control feedback lines connected to the SER.

Referring now to <FIG>, a block diagram of a master controller <NUM> is illustrated, in accordance with an embodiment of the present disclosure. As shown in <FIG>, in some embodiments, the master controller <NUM> may include one or more first processors <NUM>, a first memory (computer-readable medium) <NUM>, and first input/output devices <NUM>. The first memory <NUM> may store instructions that, when executed by the one or more first processors <NUM>, cause the one or more first processors <NUM> to receive, from the SER, an analog command signal for controlling the second plurality of wayside devices, generate a digital command signal corresponding to the analog command signal, and cause to transmit the digital command signal to a slave controller from the first plurality of slave controllers to control an associated wayside device from the second plurality of wayside devices. The first memory <NUM> may also store various data that may be captured, processed, and/or required by the master controller <NUM>. In some embodiments, the master controller <NUM> may interact with a user via the first input/output devices <NUM>.

Referring now to <FIG>, a functional block diagram of the first memory <NUM> of the master controller <NUM> is illustrated, in accordance with an embodiment of the present disclosure. The first memory <NUM> may include an input module <NUM>, a data dictionary module <NUM>, a data repository <NUM>, a device driver module <NUM>, a communication module <NUM>, a diagnostics module <NUM>, a configuration module <NUM>, a business logic module <NUM>, and an output module <NUM>.

In some embodiments, the input module <NUM> of the master controller <NUM> may receive analog command signals from SER <NUM>. The input module <NUM> may further digitize the analog command signals and update corresponding one or more variables in the data dictionary module <NUM>. By way of an example, the one or more variables may include a green light command, a dual yellow command, a feedback for dual yellow, and a feedback for green light. The input module <NUM> may further receive feedback signal from the slave controller <NUM>, and update corresponding variables in the data dictionary module <NUM>. In some embodiments, the data dictionary module <NUM> of the master controller <NUM> may be coupled to the data repository <NUM> where the data dictionary module <NUM> may maintain and validate the one or more variables required for functioning of the system <NUM>. In some embodiments, the data dictionary module <NUM> may store and maintain block CRC and life timer for data structure of the one or more variables.

The device driver module <NUM> of the master controller <NUM> may encapsulate functions to communicate with hardware and provide data to other modules. The communication module <NUM> of the master controller <NUM> may periodically receive data from the data dictionary module <NUM>. The communication module <NUM> may further create packets with a device ID, CRC and life counter, and send to a physical layer. The communication module <NUM> may further periodically check received data, validate CRC, decode message, and update corresponding variables in the data dictionary module <NUM>. The diagnostics module <NUM> of the master controller <NUM> may monitor life counter of data packets to check if communication is lost. The diagnostics module <NUM>, on detecting any fault that hinders safety of the overall system, may overwrite output variables in the data dictionary module <NUM>.

The configuration module <NUM> of the master controller <NUM> may load system configuration of the master controller <NUM>, for example, during power up. The business logic module <NUM> of the master controller <NUM> may include logic to operate the system <NUM>. The output module <NUM> may provide outputs as per the variables updated by the business logic module <NUM> and diagnostics module <NUM>, in the data dictionary module <NUM>.

Referring now to <FIG>, a block diagram of the slave controller <NUM> is illustrated, in accordance with an embodiment of the present disclosure. As shown in <FIG>, in some embodiments, the slave controller <NUM> may include one or more second processors <NUM>, a second memory (computer-readable medium) <NUM>, and second input/output devices <NUM>. The second memory <NUM> may store instructions that, when executed by the one or more second processors <NUM>, cause the one or more second processors <NUM> to receive the digital command signal from the master controller, decode the digital command signal, and trigger a control action for controlling the associated wayside device based on the decoded digital command signal. The second memory <NUM> may also store various data that may be captured, processed, and/or required by the slave controller <NUM>. In some embodiments, the slave controller <NUM> may interact with a user via the second input/output devices <NUM>.

Referring now to <FIG>, a functional block diagram of the second memory <NUM> of the slave controller <NUM> is illustrated, in accordance with an embodiment of the present disclosure. The second memory <NUM> may include an input module <NUM>, a data dictionary module <NUM>, a data repository <NUM>, a device driver module <NUM>, a communication module <NUM>, a diagnostics module <NUM>, a configuration module <NUM>, a business logic module <NUM>, and an output module <NUM>.

The input module <NUM> may receive feedback signals from the corresponding wayside device <NUM>. The data dictionary module <NUM> may communicate with the data repository <NUM> to maintain and validate the one or more variables required for functioning of the system. In some embodiments, the data dictionary module <NUM> may maintain CRC and life counter for data structure of the variables. The device driver module <NUM> may encapsulate functions to communicate with hardware and provide data to other modules. The communication module <NUM> may periodically check received data, validate CRC, decode digital command signal, and update corresponding data dictionary variables. Further, the communication module <NUM>, in response to received command message from the master controller <NUM>, may pick data from the data dictionary module <NUM>, and create data packets using the slave controller unique ID, feedback information, CRC and life counter information. The communication module <NUM> may further send these data packets to the physical layer.

The diagnostics module <NUM> may monitor life counter of data packets to check if communication is lost. Upon detecting any fault, the diagnostics module <NUM> may overwrite output variables in the data dictionary module <NUM>. The configuration module <NUM> may load system configuration of the slave controller <NUM> at power up. The business logic module <NUM> may include logic to operate the system. The output module <NUM> may provide outputs as per the variables updated by the business logic module <NUM> and diagnostics module <NUM>, in the data dictionary module <NUM>.

In some embodiments, the master controller <NUM> and the slave controller <NUM> may implement a fail-safe mechanism, as explained in detail in conjunction with <FIG>.

Referring now to <FIG>, a block diagram of the master controller <NUM> is illustrated, in accordance with another embodiment of the present disclosure. In some embodiments, the master controller <NUM> may include dual master sub-controllers, i.e. a first master sub-controller <NUM> and a second master sub-controller <NUM>. It may be noted that the first master sub-controller <NUM> and the second master sub-controller <NUM> may operate independently of each other. Further, in some embodiment, the master controller <NUM> may include an arbitrator <NUM>. The first master sub-controller <NUM> and the second master sub-controller <NUM> may have the same hardware components, and together they may provide redundancy and increases availability.

The arbitrator <NUM> may decide which of the first master sub-controller <NUM> and the second master sub-controller <NUM> may drive output. For example, condition of each of the first master sub-controller <NUM> and the second master sub-controller <NUM> may be monitored. Based on the monitored condition, the arbitrator <NUM> may cause one of the first master sub-controller <NUM> and the second master sub-controller <NUM> to perform one or more operations. These one or more operations may include receiving the digital command signal from the master controller over the second power line, generating the second analog command signal based on the digital command signal, and sending the second analog command signal to the corresponding wayside device over the third power line. In other words, one of the first master sub-controller <NUM> and the second master sub-controller <NUM> may be selected to perform the above one or more operations, based on their conditions. The arbitrator <NUM> may decide which among the two master sub-controllers may drive the final output, based on the health of each master sub-controller. These outputs may be finally fed to the SER logic. In case both the master sub-controllers fail to operate, the arbitrator <NUM> may fall back to a fail-safe state. This will trigger the SER logic to take the necessary action to keep the overall signaling system safe.

For example, analog command signals of 24V DC or 110V AC may be fed to from the SER <NUM> the master controller <NUM>. These analog command signals may be received by front end circuits 408A, 408B of the first master sub-controller <NUM> and the second master sub-controller <NUM>, respectively. Thereafter, the first master sub-controller <NUM> and the second master sub-controller <NUM> may digitize these analog command signals, and then package them in multiple digital messages addressed to corresponding wayside devices. The first master sub-controller <NUM> and the second master sub-controller <NUM> may then transmit the multiple digital messages over two power lines (belonging to the second power line) using appropriate modulation. Both the first master sub-controller <NUM> and the second master sub-controller <NUM> may transmit these multiple digital messages independently to the plurality of slave controllers <NUM>.

The first master sub-controller <NUM> may include an isolated front-end circuit 408A, a general-purpose input/output (GPIO) controller 410A, an isolated output drivers module 412A, a configuration memory 414A, a diagnostics memory 416A, and a PLC controller 418A.

For example, the isolated front-end circuit 408A may convert the analog signals into low level signals compatible with the GPIO controller 410A, and may provide optical isolation and noise filtering. The GPIO controller 410A may translate the analog commands into digital messages and vice-versa. The isolated output drivers module 412A may translate the GPIO controller level signals to the SER level analog commands while maintaining optical isolation between the two systems. The configuration memory 414A may be a non-volatile memory, and may hold the communication baud rate and device ID. The diagnostics memory 416A may log in diagnostic messages. It may be noted that an application may perform background scans to monitor the communication quality and may log diagnostics messages in the diagnostics memory 416A, which may be retrieved by maintenance engineers, if required. The PLC controller 418A may modulate/demodulate the digital messages from/to the GPIO controller 410A over the power line using power line carrier communication technique. The arbitrator <NUM>, which may be a pure hardware component, may be wired to compare the individual output of the GPIO controller 410A and decide the final output of the SER.

It may be noted that the second master sub-controller <NUM> may also include various components corresponding to the first master sub-controller <NUM>. These various components may include an isolated front-end circuit 408B, a GPIO controller 410B, an isolated output driver module 412B, a configuration memory 414B, a diagnostics memory 416B, and a PLC controller 418B. The functionality of these is already explained above.

It may be noted that, in response to receiving the multiple digital messages, the slave controllers <NUM> may send feedback signal associated with the corresponding wayside device, on two power lines. The feedback signal may be independently received by the first master sub-controller <NUM> and the second master sub-controller <NUM> of the master controller <NUM>.

In some embodiments, the number of master controllers <NUM> required to be implemented in the system <NUM> may be calculated based on the information that can be exchanged between the SER <NUM> and the wayside devices <NUM> by either of the master sub-controllers. This is explained by way of an example with respect to wayside device of a <NUM>-aspect signal post. One or more parameters with respect to the system may be obtained. For example, the one or more parameters may be as follows:.

From (<NUM>), (<NUM>), (<NUM>), (<NUM>), (<NUM>), <MAT> From (<NUM>), (<NUM>), and (<NUM>), <MAT>.

Further, based on the number of signal posts present in the station field area and the above calculate maximum number of (<NUM>-Aspect) signal posts that can be handled by one master controller, the required number of master controllers may be determined. Referring now to <FIG>, a block diagram of a slave controller <NUM> is illustrated, in accordance with another embodiment of the present disclosure. The slave controller <NUM> may include a first slave sub-controller <NUM> and a second slave sub-controller <NUM> (redundant sub-controllers). Further, in some embodiment, the slave controller <NUM> may include an arbitrator <NUM>. The arbitrator <NUM> may control the final outputs, based on the health of each of the first slave sub-controller <NUM> and the second slave sub-controller <NUM>.

Similar to the master controller <NUM> as explained above, the arbitrator <NUM> may decide which of the first slave sub-controller <NUM> and the second slave sub-controller <NUM> may drive output of the slave controller <NUM>. For example, condition of each of the first slave sub-controller <NUM> and the second slave sub-controller <NUM> may be monitored. Based on the monitored condition, the arbitrator <NUM> may cause one of the first slave sub-controller <NUM> and the second slave sub-controller <NUM> to perform one or more operations. These one or more operations may include receiving a digital command signal from a master controller over a second power line, generating a second analog command signal based on the digital command signal, and sending the second analog command signal to a corresponding wayside device over a third power line. In other words, one of the first slave sub-controller <NUM> and the second slave sub-controller <NUM> may be selected to perform the above one or more operations, based on their respective health conditions. To this end, the master controller <NUM> and the slave controller may be connected via two redundant power lines. For example, the first master sub-controller <NUM> may connected to the first slave sub-controller <NUM> via a redundant power line, and similarly the second master sub-controller <NUM> may be connected to the second slave sub-controller <NUM> via a redundant power line.

The first slave sub-controller <NUM> may include various components similar to the first master sub-controller <NUM>. These components may include an isolated front-end circuit 508A, a GPIO controller 510A, an isolated output driver module 512A, a configuration memory 514A, a diagnostics memory 516A, and a PLC controller 518A. Further, the second slave sub-controller <NUM> may include various components corresponding to the first slave sub-controller <NUM>, and may include an isolated front-end circuit 508B, a GPIO controller 510B, an isolated output driver module 512B, a configuration memory 514B, a diagnostics memory 516B, and a PLC controller 518B. The functionalities of these have already been explained above with respect to the first master sub-controller <NUM>.

It may be noted that by way of incorporating two master sub-controllers (<NUM> and <NUM>) and two slave sub-controllers (<NUM> and <NUM>), and by way of selecting one from each of these two master sub-controllers and two slave sub-controllers to perform the above operations, high availability and reliability of the system <NUM> is ensured. Moreover, any fatal failure may cause the system <NUM> to push the SER <NUM> into a fail-safe state.

The specification has described method and system for setting up communication between a SER and wayside devices. Such alternatives fall within the scope and spirit of the disclosed embodiments.

Examples include random access memory (RAM), read-only memory (ROM), read-write memory, volatile memory, nonvolatile memory, hard drives, CD ROMs, DVDs, flash drives, disks, and any other known physical storage media.

As will be appreciated by those skilled in the art, the techniques described in the various embodiments discussed above relate to setting up communication between a SER and wayside devices. The techniques described above provide a convenient solution for substantially replacing the higher core power cables (for example, <NUM>-core or <NUM>-core) connecting the SER to the wayside devices with lower core power cables (for example, <NUM>-core). By way of this, overall cable cost is significantly reduced (as much as by approximately sixty percent in some cases). Further, time and effort required for setting up the communication is reduced. Furthermore, by implementing dual controllers (two master sub-controllers and two slave sub-controllers), high availability and reliability of the overall system is ensured.

Claim 1:
A system (<NUM>) for setting up communication between a Signal Equipment Room (SER, <NUM>) and wayside devices (<NUM>), the system (<NUM>) comprising:
a master controller (<NUM>) configured to receive a first analog command signal from the Signal Equipment Room (SER,<NUM>) over a first power line, wherein the master controller (<NUM>) is configured to generate a digital command signal based on the first analog command signal; and
a plurality of slave controllers (<NUM>) configured to receive the digital command signal from the master controller (<NUM>) over a second power line, wherein each of the plurality of slave controllers (<NUM>) is configured to generate a second analog command signal based on the digital command signal, wherein each of the plurality of slave controllers (<NUM>) is further configured to send the second analog command signal to a corresponding wayside device (<NUM>) over a respective third power line, and characterised in that the second power line comprises a lower core power cable than the first and the third power line.