[0001] The invention relates to a system for detecting trains on railway lines and communicating
with said trains, which system comprises:
- a) a railway line having at least one track, which track is divided into a plurality
of successive track segments, known as track blocks,
- b) means for generating signals for detection of or communication with the train being
provided for each of said track segments;
- c) and means for receiving from the track block said detection and communication signals
produced by a train by active signal generation or change of the detection and communication
signals transmitted to the track block;
- d) means for processing the detection signals or the communication signals received
from the track block to determine the operating or working conditions of the train
and/or the track block based on the changes found in the received signals with respect
to the transmitted signals and/or on the information contained in the communication
signals transmitted by the train,
- e) means for generating signals indicative of the operating or working conditions
of the train and/or the track block and for transmitting said status signals to a
central railway network control unit, known as central Interlocking System, which
is connected to said detection and communication unit and receives signals therefrom,
indicative of the conditions of the train and/or the track block,
- f) means for receiving control signals for detection of or communication with the
train from said central control unit.
[0002] Train detection systems are known in the art, as disclosed for example in a prior
patent application by the applicant hereof, with publication number
EP 1338492. This train detection system is known as track circuit. The track of a railway line
is divided into a plurality of segments. Each segment, known as block, has a unit
associated therewith, with a transmitter and a receiver designed for alternate connection
to each other and to one of the two opposite ends of a corresponding track segment.
One signal is injected by the transmitter to one end of the track segment and is received
at the opposite end thereof. The transmitted signal has predetermined and appropriately
defined frequency, amplitude and coding characteristics wherefore, when a train is
present on the track segment, the short circuit between the rails of the track segment
caused by the train axles causes a change, particularly a reduction of the signal
and allows train detection.
[0003] Further prior art systems are the so-called axle counters, which include sensors
for detecting the axles of a train passing a block.
[0004] In yet other systems the track and the segments are used for communication of messages
between the train and the wayside unit and vice versa.
[0005] All the above prior art systems include electronic operating units, which are basically
of hardware type and have a dedicated, special-purpose construction designed for the
specific function thereof. For example, concerning the track circuits and as disclosed
in the above document with publication number
EP 1338492, whose information content is integrated herein by reference, the operating units
of the track circuit located at the track, i.e. the trackside or wayside units, include
all the sections required for their operation. Particularly, these operating units
include track segment interface sections and diagnostic sections, as well as sections
for generating the signals to be transmitted and for processing the receive signals
and sections for communicating with the central railway traffic management unit, i.e.
for transmitting train presence data to said central management unit and for receiving
controls from said central management unit.
[0006] Also, still concerning the track circuits, various construction types are known,
which are used in different systems, each involving specific advantages and drawbacks.
[0007] Thus, for example, in certain track circuits, the joint that connects the receiver
and the transmitter to the track segment is controlled by a switch that, depending
on the expected train direction, selects the transmitter end of the track segment,
and consequently the receiver end, thereby actually defining a signal propagation
direction within the track segment. These joints, known as directional joints, allow
the use of acoustic or pulse signal coding techniques. The units, that are specially
designed to operate in one of the above mentioned modes, cannot operate in other modes
wherefore specific dedicated operating units have to be provided for each track circuit
type, that have track interfacing heads with a construction specially dedicated to
the particular signal coding and transmission mode and especially include the sections
for generating the signal to be transmitted and for processing the received signal,
which sections are constructed in accordance with the techniques used for coding and
decoding or processing said signals for retrieval of train presence information. As
a result, any technological modification to a railway line requires either the maintenance
of the existing track circuit technology to avoid replacement of the operating units
or the replacement of the operating units for adaptation to the new track circuit
technologies, the latter option involving the replacement of parts of these operating
units that might be used even in combination with the new track circuit technologies.
[0008] Furthermore, each of the various track circuit types have particular characteristics
that make it more or less suitable to use in different operating, wear or degradation
conditions of the track segments. In prior art, once a track circuit type has been
selected and the operating units dedicated to the selected track circuit type have
been installed, the operating mode of the track circuit cannot be changed unless the
operating units are also replaced. Such replacement would involve cost drawbacks,
and be unfeasible due to time constraints. Nevertheless, in certain cases, for instance
in case of oxidative rail degradation, impulsive track circuits should be used, which
ensure lower signal attenuation.
[0009] The operating conditions of the track can also depend on weather. Whole short weather
variations might be neglected as transient events, there are climatic zones in which
weather effects, such as rain, snow and ice are of seasonal nature and remain for
a relatively long period of time, while being still of short duration when considering
the time and costs required for shifting to train detection technologies other than
those in use and particularly suitable for those weather conditions. It shall be further
noted that, at the end of one season, a new season follows, with weather conditions
changing again.
[0010] Yet another drawback of prior art track circuits is that each operating unit is connected
independently of the others to the track and the central railway traffic management
unit, i.e. the interlocking computers. This requires considerable costs in terms of
both materials and installation.
[0011] The structural rigidity of the modes of the operating units associated with the track
circuits is a constraint especially when adapting and maintaining existing lines,
but also when making new lines having devices or systems from different manufacturers
to be combined together, in which the selection of operation and construction technologies
depends on tradition.
[0012] Track circuit types are also known in which the joints for connection of the transmitter
and the receiver of the operating units are of non-directional type and the signal
injected into the track circuits propagates in both directions.
[0013] Here again the operating units are constructed with a structure and an architecture
dedicated to their intended tasks and namely to the track interfacing modes.
[0014] Concerning the track circuits, there exist a number of variants thereof, mostly including:
Jointless Audio Frequency ,
Mechanical Joint Low Frequency;
Mechanical Joint Impulsive.
[0015] A further drawback concerning all track circuits is that the controlled track sections
cannot be longer than about 2 km. Even at such length, track sections require the
provision of capacitors arranged along the track segment with the purpose of compensating
for signal energy loss.
[0016] Furthermore, any failure or malfunctioning of an operating unit or a track circuit
requires the track circuit and/or the corresponding operating unit to be restored,
because the malfunctioning or damage condition triggers a restrictive signal for the
corresponding track circuit, i.e. a train presence condition, which signal is transmitted
to the traffic management unit. Here, if no replacement operating unit is available,
then the corresponding track circuit will be idle, wherefore either it will be forced
into a permissive condition or it will always indicate a malfunctioning condition.
[0017] Concerning the other units, such as the axle-counters and the track to train communication
sections, these have substantially the same problems as the track circuits. Furthermore,
if several different train detection systems are required to be simultaneously present
on the same railway line, i.e. on the same track, e.g. particularly at least one track
circuit, at least one axle counter and/or at least one system for exchanging messages
from and to the train, a full operating unit is required in prior art for each of
these systems, as many operating units being required as there are track segments
or blocks.
[0018] Therefore, considering for example the above mentioned systems, hardware requirements
will be three times as great, and this will generate problems both in terms of implementation
times and costs and in terms of space requirements for the installation of operating
units.
[0019] Thus, the object of the invention is to improve a train detection system in view
of overcoming the above drawbacks without requiring any cost increase, while further
simplifying and enhancing the efficiency of the general system architecture, towards
a more flecible configuration of the detection methods being used.
[0020] The invention achieves the above purposes by providing a system as described hereinbefore,
which includes the following additional characteristics:
g) one or more local heads are associated with each track block for interfacing with
a corresponding track block, which include:
means for generating and transmitting signals for detection of or communication with
the train to the corresponding track block
and means for receiving from the track block said detection and communication signals
produced by a train by active signal generation or change of the detection and communication
signals transmitted to the track block;
h) said local interface heads further include an interface for digital message communication,
according to a predetermined communication protocol, with a separate central processing
and control unit;
i) said central processing and control unit includes a digital message communication
interface which operates with the same communication protocol as the local track block
interface heads;
j) and said processing and control unit includes hardware in whose memories a processing
and control program is stored, to be executed by said hardware and whereby said processing
and control unit generates and transmits the control signals to the local track block
interface heads for triggering said local interface heads to generate and transmit
predetermined detection and/or communication signals and for receiving detection and/or
communication signals;
k) and whereby the processing and control unit processes the detection and communication
signals received from the local interface heads to determine the operating or working
conditions of the train and/or the track block based on the changes found in the received
signals with respect to the transmitted signals and/or on the information contained
in the communication signals transmitted by the train, and generates signals indicative
of the operating or working conditions of the train and/or the track block;
1) whereas said central processing and control unit communicates with the railway
traffic management unit for transmitting thereto said status signals or messages transmitted
by the train and for receiving therefrom control signals and/or messages to be transmitted
to the train.
[0021] As used in the present disclosure and claims, the term train detection system is
not only intended to mean the track circuit that is used to detect the presence or
absence of a train on a track block, but also any type of device or system adapted
to receive feedback from a train on a track, which train passes the successive track
segments that form the track. Particularly, the term train detection also includes
axle counting devices and devices for communication with the train and transmission
of messages to the train.
[0022] Therefore, according to the present invention, traditional operating units include,
on the one hand, units designed for direct connection to the track and allowing interfacing
with the track and transmission and reception of signals having a well determined
structure and organization. On the other hand, central processing and control units
are provided which also carry out the tasks of prior art operating units, i.e. define
the structure of the signals to be transmitted, the detection result by processing
the received signals, such as the presence/absence of the train on a given track block
and/or the number of axles or even define the content of the messages to be transmitted
to the train.
[0023] While the block interface units, interfacing with the individual track segments,
substantially include controllable transmitter and receiver units and are hardware-based,
the processing and control units are formed of a combination of hardware and software,
including a computer with at least one program stored in its memory, to be executed
by such computer, thereby forming a hardware/software operating unit adapted to accomplish
the tasks of the processing and control units, required for determining the structure
of the signals to be transmitted and the content of any messages to be transmitted,
controlling the block interface units to transmit and receive and decode or extract
information from the received signals.
[0024] Therefore, concerning the various train detection methods, the operating tasks involved
in these methods are introduced in the processing and control units by the software
which changes according to the method being used, whereas the hardware part for software
processing and execution is substantially the same and the track interface units are
substantially the same and are dedicated to the pitch of signal injection and extraction
from and into the track.
[0025] Communication between the interface heads, i.e. the track interface units and the
processing and control units advantageously relies on a communication network, with
the interface heads and the processing and control units being connected thereto,
each of them being identifiable by a unique ID code.
[0026] Therefore, thanks to the invention, one processing and control unit hardware configuration
and a few specific interface hardware units will allow construction of several different
train detection devices, such as a track circuit, an axle counter and/or a track to
train communication unit, by simply providing different software programs to be executed
by the processing and control unit, each of which software programs causing the processing
and control unit to perform the typical tasks of one of the various train detection
devices.
[0027] Particularly, considering the above train detection devices, one hardware configuration
may be also provided for the track segment interface units, particularly in the form
of signal transmitting and/or receiving units.
[0028] However, concerning the various track circuit variants, for example, here again the
processing and control unit can perform the tasks of said different track circuit
variants by executing a corresponding software program.
[0029] The flexibility of the present system, owing to the implementation of the tasks of
train detection devices at software level, the device consisting of the combination
of hardware and executable software, and also considering the combination with track
interface units, whose tasks are limited to communication with the track and whose
configuration is reduced to a minimized number of parts, provides further advantages.
[0030] An traditional train detection device construction may be provided, for example,
in which each track segment comprises at least one interface unit and at least one
processing and control unit for each interface unit with a track segment associated
therewith.
[0031] Otherwise, one processing and control unit may be arranged to cooperate with multiple
interface units, each associated with one or more blocks, i.e. track segments.
[0032] In both cases, the processing and control units may execute several different processing
and control software programs, each being designed to cause the operation of the processing
and control unit according to a different type of detection device and particularly
a different type of track circuit.
[0033] In one practical example, for instance, a track segment has a track circuit associated
therewith with pulse signal operation and, in the variant in which each interface
unit has its own dedicated processing and control unit, a processing and control program
for performing the tasks of an operating unit of a track circuit with pulse signal
operation is stored in this processing and control unit. However, the track circuit
for another track segment, e.g. an adjacent track segment, may be for example of the
low frequency or jointless audio frequency operation type, wherefore a corresponding
processing and control program is stored in the processing and control unit, whereby
such processing and control unit performs the tasks of a track circuit of the low
frequency or jointless audio frequency type.
[0034] Likewise, the above also applies to the case in which certain track circuits have
an additional interface unit which is designed to form, in combination with the processing
and control unit and a corresponding software program executed by such unit, an axle
counting device or a track to train communication device. When this is possible, instead
of providing two or more different track interface units for two or more different
detection devices or track circuits, a common interface unit is provided. For injection
of signals into a track segment and reception of signals existing on the track segment
irrespective of the information to be transmitted or extracted from the signals, identical
interface units can be used, the different tasks associated with the type of signal
being transmitted, such as a particular coding or modulation of the signal transmitted
to the track or a particular processing of the signal received for extracting the
requested information being implemented in the processing and control software program
executed by the processing and control unit.
[0035] The above described practical configuration example, in which each interface unit
associated with a track segment has a dedicated processing and control unit associated
therewith also applies to the variant in which a processing and control unit is associated
with or serves multiple interface units, each associated with one of multiple track
segments.
[0036] The above mentioned possibility of switching among several variant track circuit
types by simply providing a different processing and control software program to be
executed by the processing and control unit, which causes said unit to perform the
typical tasks of the selected track circuit type, allows the track circuit to be adapted
to the changing conditions of the track segments and possibly to the various conditions
of operation of the track circuits, namely to weather conditions.
[0037] By simply using a different processing and control program, which implements the
tasks of a different track circuit type or a different detection device type, a track
circuit type and/or a detection device type may be set for each track segment and
each weather condition to best suit the specific conditions of the track segments
and/or the weather conditions.
[0038] Thus, for example, track circuits with pulse signal coding should be used in case
of highly oxidized tracks, whereas other track circuit types that use different signal
coding techniques and different signal frequencies can be more advantageous in case
of heavy rains.
[0039] Advantages especially derive from an implementation of the different types of track
circuit or train detection device that essentially consists in the storage and execution
of a different processing and control software program, wherefore the system can be
realistically and simply adapted to weather conditions, i.e. to short-duration changes
of the operating conditions.
[0040] Particularly, if one processing and control unit is associated with multiple interface
units of multiple track segments, then ascertained malfunctioning conditions of certain
track circuits may be corrected. With common control of multiple track circuits, an
operating fault of a damaged track circuit can be hidden and corrected at the processing
and control unit. Hazards are obviously associated with the above arrangement, wherefore
a parallel diagnostics system has to be provided to particularly make sure that a
false train detection on a track segment is actually caused by malfunctioning of the
corresponding track circuit.
[0041] In this case, a remedy action might consist in merging the damaged track circuit
with the adjacent track circuit, and using the train presence or absence indication
obtained from the correctly operating track circuit as an indication for the track
segment associated with the damaged track circuit.
[0042] The wrong indication of the malfunctioning track circuit is thus hidden in a safe
manner, without causing traffic interruptions either before or during repair of the
damaged or malfunctioning track circuit.
[0043] The invention relates to further characteristics and improvements which form the
subject of the dependent claims.
[0044] The characteristics of the invention and the advantages deriving therefrom will appear
more clearly from the following description of a non-limiting embodiment which is
illustrated in the accompanying drawings, in which:
Figure 1 shows a block diagram of the architecture of the system of the present invention.
Figure 2 shows a block diagram of the architecture of a train detection operating
unit of the present invention.
Figure 3 shows a block diagram of the system in two possible variants of the present
invention, in which the left half includes a processing and control unit for each
interface unit or head, and the right half includes a processing and control unit
that serves multiple interface units or heads.
Figure 4 shows a more detailed block diagram of the structure of the processing and
control unit, according to the variant in which said processing and control unit serves
multiple interface heads.
Figure 5 shows a block diagram of the processing logic section.
Figure 6 shows a block diagram of the transmitter module of the processing and control
logic subsection.
Figure 7 shows a block diagram of the receiver module of the processing and control
logic subsection.
Figure 8 shows a block diagram of the interface unit or head.
Figure 9 is a block diagram of the field interface.
Figures 10 and 11 show the block diagrams of the vital receiver and the AD converter
of said field interface.
Figure 12 shows a block diagram of the structure of a track interface.
Figure 13 shows a block diagram of the track elements.
Figure 14 shows a block diagram of a coding example, using a track circuit type with
non directional joints using DSSS signal coding.
[0045] Referring to Figure 1, a system for train detection, i.e. for occupancy detection
in a railway line, or the like, and for digital communication with trains running
along said railway line comprises at least one track that forms the railway line and
is divided into a plurality of successive galvanically insulated segments having a
predetermined length, known as blocks, which track segments form, in combination with
the control and monitoring subunits 2, 2', 2", an element named track circuit. In
Figure 1, track circuits are indicated as Cdb1, Cdb2 and Cdb3. These track circuits
use rails to send the signals that allow train detection on the corresponding track
segment, and to communicate with a train. Moreover, the signals sent to each track
segment may be used to detect any track failures or damages.
[0046] The system includes a central management and control unit, designated by numeral
1 and indicated as TDM. This management unit generates control signals to execute
procedures for detection of a train T and/or procedures for communication with a train
on said track and/or to execute diagnostic procedures and transmits them to the control
and monitoring subunits 2, 2', 2'' associated with each track block or segment and
forming therewith the track circuit Cdb1, Cdb2 and Cdb3. The subunits 2, 2', 2'' are
operating units that are designed to execute the procedures for detection of the train
T within the associated block, the communication procedures and/or the diagnostic
procedures and transmit the control signals, i.e. the detected information about the
presence or absence of the train T within the corresponding block and/or about proper
communication being established with the train and/or the diagnostic signals relating
to the track circuit to the central control and monitoring unit. Each control and
monitoring subunit 2 is associated with each corresponding block to form a train detection
device in the form of a so-called track circuit Cdb1 Cdb2 and Cdb3, and is connected
to the terminal ends thereof by means of a transmitter 3 and a receiver 4. Each subunit
2 and its respective block, i.e. track segment associated therewith are uniquely identified
by a predetermined identification code.
[0047] Namely, the subunits 2, 2', 2'' named TDH are of the type designed to operate in
insulated double-rail track circuits. In this type of tracks, both rails are mechanically
interrupted, and traction power is returned by inductive connections.
[0048] The control and monitoring subunits 2 are designed for use on two-direction track
circuits and, to this end, a signal transmission reversal feature is provided to propagate
train detection signals and coded communication signals in the direction opposite
to the train running direction.
[0049] A train is detected by injecting a fixed current signal into each track circuit,
i.e. a signal having a fixed current level once it is decoded. The signal transmitted
by the transmitter to the track circuit towards the receiver in a direction opposite
to the train running direction is received if no train is detected. When a train is
present, the rails are shortcircuited by the train itself, and the receiver is not
reached by any signal.
[0050] The control and monitoring subunit 2 can handle (transmit/receive/acknowledge) the
following signals:
codes;
"fixed frequency" signal, which is used to obtain the occupied/unoccupied function
when no code is provided (no path or routing).
[0051] The track circuit is coded by interrupting a carrier frequency a predetermined number
of times per minute (amplitude modulation). This application uses four code types.
These types are obtained by using a 50 HZ carrier interrupted 75, 120, 180 or 270
times a minute (the corresponding code is indicated by the number of interruptions
per minute).
[0052] A nine code coding may be also used. In this case, the above mentioned PWM coded
signal may be added or superposed to an additional signal derived by an identical
PWM modulation of a carrier having a different frequency, i.e. a carrier of 100 to
200 Hz, particularly of 178 Hz.
[0053] The characteristics of the Fixed Current (CF) train detecting signal must ensure
the maintenance of safety conditions even when insulation losses occur at the joints
between adjacent track circuits. A track circuit architecture according to an embodiment
that will be described in greater detail hereafter includes a transmitter for each
track circuit, connected via the operating unit 2, 2', 2'' to the central railway
traffic management unit 1. A modulation is introduced in the CF signal, which is different
between adjacent track circuits and is adapted to ensure safety conditions even when
power is transferred from one track circuit to the following one.
[0054] A possible solution that is also used in prior art, provides different CF signals
(4 sets) to be appropriately allocated to track circuits so as to ensure that there
is not the same signal on adjacent track circuits. In all sets, the signal is composed
of a 50 Hz carrier alternately transmitted in phase and in phase opposition with respect
to a hypothetical 50 Hz reference. The sets are differentiated by the time intervals
between two successive phase steps. Opposed sections are connected via a 90 ms signal
gap, corresponding to 4.5 50 Hz signal periods. By this arrangement, a constant amplitude
signal is always provided at the output of a 50Hz tuned pass band filter, ensuring
occupancy detection anytime.
[0055] The above constitutes one of the possible signal coding arrangements for the signals
transmitted to the track for train detection using the train detection system of the
present invention, which is further illustrated in Figure 2. It shall be noted that
this architecture is also used with different types of train detection devices or
with different track circuit variants. These variants are differentiated by the techniques
they use for coding the transmitted signal and for demodulating the received signal
to retrieve train detection information as well as by the techniques for interfacing
the operating unit 2, 2', 2'' with the track segment which can also use a non directional
joint, that does not impart a unique direction of propagation of the signal transmitted
over a track segment between a transmitter and a receiver of the operating unit.
[0056] Therefore, regardless of the specific signal coding technique and of the particular
prior art track circuit type as described above, all train detection devices intended
in the most general sense as used herein and defined above have the same architecture,
particularly as regards the operating unit 2, 2', 2'' and suffer from the same drawbacks
as described in the general introduction hereto.
[0057] Figure 2 shows in greater detail the block diagram of the train detection system
of the present invention, in which the operating units 2, 2', 2'' have a different
structure.
[0058] According to the present invention, the operating unit 2 is composed of several separate
units, that is:
a processing and control unit designated by numeral 10 and named TDM (Train Detection
Module);
a track segment interface unit or head designated by numeral 30 and named TDH (Train
Detection Head);
and a unit for communication between the above two units 10 and 30, which is provided
in the form of a digital communication network, such as an Intranet network or the
like and is designated by numeral 20 and named TDN (Train Detection Network).
[0059] As mentioned above, this break-up of the operating units allows the train detection
system to have a distributed topology, in which the processing and control units 10
are allocated in a technical room and interact with the track segments via the interface
heads 30, i.e. trackside field units, using a typical digital network communication
protocol through a communication network designated by numeral 20.
[0060] This architectural decomposition also causes the tasks carried out by the traditional
operating units to be distributed among the various processing and control units 10
over the communication network 20 and the track interface units or heads.
[0061] The processing and control unit TDM 10 is a section that provides the processing
platform of the train detection system. On the one hand, this unit receives information
from the interlocking system, i.e. from the central railway traffic management unit
1 using the communication modules PSCOM 110. On the other hand, the processing and
control unit generates the information to be transmitted to the track segments and/or
to the train using the interface units or heads 30 and the communication network 20.
Furthermore, through the network 20, the processing and control unit 10 receives the
signals that the interface units or heads 30 detect from the track segments and transmit
thereto, and processes them to identify the occupancy state of a specific track segment,
i.e. the presence of a train within the specific track segment or to identify other
parameters of the railway system or train, such as the number of axles or to identify
the content of messages transmitted by the train through the track. The result of
such processing is transmitted by the processing and control unit 10 to the railway
traffic management unit 1 through a transmission interface 110. Transmission between
the processing and control units 10 and the central railway traffic management unit
1 may be of the type known in the art as CAN-BUS, that is widely used in transport
systems.
[0062] As better explained below, the processing and control unit is composed of a hardware
and software combination, the hardware part being of substantially general type and
adapted to store and execute several different configuration and task implementation
programs. Therefore, these programs include the instructions for the hardware part,
for the processing and control unit to carry out the above specific tasks, which depend
on the type of train detection device being used, i.e. specifically corresponding
to a particular type of track circuit or axle counter or track to train communication
system. By this arrangement, the processing and control unit exhibit a very high flexibility,
and the detection system features may be changed in very short times and at very low
costs.
[0063] As shown in Figure 3, the architecture may be provided in two general variants. One
of these variants is shown on the left of Figure 3 and only implies that the traditional
prior art operating units are divided into the operating units as mentioned above.
[0064] Here, at least two interface units or heads 30 are provided for each track segment
designed to form a track circuit or a different circuit or device for detection of
the train or other operating parameters or conditions of the train and the track segment,
and one dedicated processing and control unit 10 is provided for each interface unit
or head 30. All the processing and control units 10 communicate via the same communication
network 20 with the corresponding track segment interface unit or head. This variant
embodiment is defined as Single Track Topology and already provides considerable advantages
as compared with prior art architectures.
[0065] Referring to the right side of Figure 3, the broken-down architecture of the system
of the present invention provides a variant topology in which one processing and control
unit serves and is thus connected with multiple track segments through the corresponding
interface units or heads associated with each track segment.
[0066] As mentioned above with reference to prior art, each track segment, and hence each
track circuit or other device for detection of or communication with the train including
the track segment, is identified by a unique identification code, wherefore the processing
and control units 10 and the track segment interface units functionally associated
therewith can acknowledge and cooperate with each other without interfering with other
pairs of processing and control units 10 and interface units 30 within the system.
[0067] Concerning the interface units, these are dedicated to track management and are located
close to the corresponding track segment, or block. The interface units or heads receive
control signals from the central or dedicated processing or control unit 10 depending
on the selected one of the variants of Figure 3.
[0068] The controls contain information about the signal type that has to be generated and
transmitted to the track segment.
[0069] Furthermore, the interface units transmit the signals received from the track segment
to the processing and control unit 10 irrespective of whether the latter is a central
unit or dedicated, as required by the use of a single-track or multi-track topology
respectively, illustrated in Figure 3.
[0070] The connection allowing communication of the interface units 30 with the processing
and control unit 10 relies on a digital communication network and shall be deemed
an important part of the system architecture, because such communication section provides
advantages in terms of system logic and power distribution.
[0071] Concerning the types of train detection devices that can be used with the train detection
system of the present invention, these include:
jointless audio frequency track circuits;
low frequency track circuits with mechanical joints
pulse signal track circuits with mechanical joints axle counters.
[0072] The above list is provided for illustration purposes only and shall not be deemed
to limit the configuration flexibility of the train detection system of the invention.
[0073] It shall be further noted, for example, that the joints 130 for connection of the
track segment interface units may be of directional type, wherefore the track circuit
operates like the one known in the prior art and described with reference to Figure
1 in which, depending on the train direction, the signal is injected to either end
of the track segment and received at the opposite end of the same track. Otherwise,
the track circuit type may include joints 130 with no directional feature, that cause
two-way propagation of the signal injected at each block and hence from each interface
unit 30 in the track. In this case, the signal transmitted to the track and the signal
received therefrom will be coded and decoded in different manners, allowing to precisely
and uniquely identify the relation between one component of the received signal and
a given track segment.
[0074] The detailed construction of the processing and control units/s 10 is shown in the
block diagram of Figure 4. Referring to Figure 4, the processing and control unit
10 has a processing and control section 210 with a two out of two configuration, also
known as 2oo2. The processing and control section 110 has two processing logic subsections
A and B, designated by numerals 310 and 310', which are connected via an internal
bus to respective CPUs A and B, designated by numerals 410 and 410'. The two processing
sections 310 and 310' also communicate with each other via a communication line, designated
as xport. This port is used for synchronization of processes and exchange of vital
data and is part of the 2oo2 platform. Likewise, the two CPUs A and B, designated
by numerals 410 and 410', communicate with each other by a serial link line, designated
by numeral 510.
[0075] The processing and control section further includes a power supply subsection 510
and a configuration subsection 610 which stores the configuration parameters of the
detection devices that the processing and control unit has to use in combination with
corresponding interface units 30.
[0076] The processing and control section 210 is connected to a communication interface
PSCOM, designated by numeral 110, whereby said section 210 communicates with the central
railway traffic management unit 1.
[0077] Furthermore, the processing and control section 210 has network communication interfaces
A and B, designated by numerals 710, 710', connected to each of the processing logics
310 and 310'. The processing and control section 210 communicates via the network
communication interfaces 710 and 710', through the network 20, with the individual
interface units or interface heads 30, each of which is in turn designed to be connected
with one of the track segments.
[0078] The CPUs 410 and 410' operate as a CAN BUS interface with a processing platform 2oo2
and manage the information generated by the corresponding processing section 310,
310'. These processing sections may be considered as interface drivers for interfacing
with the external sections, i.e. the interface heads 30, and for access thereto for
control and signal transmission and reception via the connector sections A and B 710
and 710'.
[0079] The CPUs 410 and 410' communicate with other sections of the processing and control
unit 10 using internal bus modules or the CAN BUS.
[0080] Figure 5 shows in greater detail the structure of the processing sections 310 and
310' that have identical constructions.
[0081] Each processing section 310, 310'.
[0082] One of the relevant subsections is the digital signal processing section named DSP
and designated by 311. This subsection is the receiving part of the processing engine
and has the following tasks:
Digital processing of signal flows coming from the interface heads 30;
Generation of test signals to validate the receiving chains of the interface heads
30;
Mathematical signal processing (RMS measures, FFT, i.e. Fast Fourier Transform analysis),
etc.;
Determination of the occupancy status of the various track circuits and/or information
designed to be detected by a particular train detection device, such as an axle counter
or a track to train message communication unit.
[0083] The DSP subsection 311 may execute various signal processing techniques, in the form
of software programs to be executed by said DSP subsection and incorporating specific
signal processing or treatment steps according to the processing or treatment methods
as selected or required for the type of train detection device to be used. Therefore,
a memory 311 is connected to the digital signal processing DSP subsection 311, for
storage of the processing software or programs to be executed by said DSP subsection
311.
[0084] The other section, also programmable, is the configuration subsection 312 which allows
configuration of the interface heads managed by the processing and control section
310.
[0085] Such configuration subsection 312, as well as the digital signal processing DSP subsection
311 communicate via an internal bus with a track to train communication logic subsection,
for determining the direction and status of the interface heads, which is designated
by numeral 313 and manages the information exchanged with the CPU A and CPU B sections
410, 410' through a communication bus 314. The TDM bus is a bus located in the processing
and control unit 10 which manages the communication between modules and subsections,
as well as the redundancy of the 2oo2 architecture and the vital protection of messages.
[0086] The management of information exchange by the subsection 313 includes management
of message transmission from the interface heads 30 to the train, determination of
the direction of propagation of the transmitted signal for each interface head 30
when a directional joint is provided as used in prior art and described with reference
to the prior art of Figure 1, and such management further includes the status of the
track segment relative to each interface head.
The interface heads 30 communicate with the processing and control sections 310 via
the connector subsections 710, 710' which are in turn connected to the processing
and control subsection 310 via a connector interface 315.
[0087] The latter is connected to the subsection 313 via a transmitter module 316 and to
the digital signal processing DSP subsection designated by numeral 311 via a receiver
module 317.
[0088] The purpose of the transmitter module 316, which is shown in greater detail in Figure
6 is to generate the train detection signal, e.g. including bit message modulation
and phase control, to code the information and the messages of the transmit signal
to be transmitted to the interface heads 30, to set the direction of propagation of
the transmit signal for each interface head associated with a track segment.
[0089] Each transmitter module 316 comprises a main logic subsection 160 whereby it communicates
with the track to train communication logic subsection 313 for determining the direction
and the status of the interface heads. This main logic subsection 160 of the transmitter
manages three subsections having different tasks, i.e. message coding, configuration
of the transmit signal to be injected into the track signal, and check of the transmit
signal to be injected into the track segment.
[0090] The configuration subsection includes a frequency generator 161 which, in this example,
can provide two carriers of different frequencies F1 and F2, giving the symbols bit
= 1 and bit = 0 depending on the configuration that has been read by the internal
bus of the processing and control module.
[0091] The module 162 generates a FSK (Frequency Shift Keying) type modulation of the signal
to be transmitted to the track segment using as an input the message provided by the
bus subsystem TDM 314 and using the carrier signals with the frequencies F1 and F2
generated by the generator 161.
[0092] On the other hand, the signal checking module 164 determines the amplitude and phase
of the signal transmitted to track circuits and the switching module 165 of the track
determines the setting of the transmit signal propagation direction from the setting
of the switch that sets the signal input end of the track circuit, when the joint
of the track segment interface units is of the directional type.
[0093] The signal at the output of the FSK modulation module 163 is provided to a coding
module 166 which adds signal phase and amplitude information to the signal to be transmitted
to the track segment, and the signal so coded at the output of the coding module 166
is provided to a network interface 167 wherefrom it is provided to the connection
interface subsection 315 for communication with a corresponding interface head 30
through the network 20.
[0094] Fig. 7 shows an exemplary receiver module 317. The receiver module communicates with
the digital signal processing subsection 311 via an internal bus and comprises an
interface for communication via said bus, designated by numeral 171. On the other
hand, the receiver module 317 communicates with the interface heads 13 through the
network 20 and via a network interface 172.
[0095] On the one hand, the receiver module transmits test signals to a data coder 174.
The signals to be transmitted to the track segment are packed with information about
the test signals that are used to certify the operation of the interface heads 30.
[0096] On the other hand, the receiver module receives from the interface head 30 the signals
that the latter has received from a corresponding track segment and transmits them,
via the network interface 172, to a data decoder 173. Such data decoder processes
the signal received from the circuit with information about the recheck signals used
to certify the operation of the interface heads 30 and the track occupancy status,
whereas a demultiplexing subsection 175 demultiplexes the data from the decoder 173.
In the particular example of Figure 6, the demultiplexing operation provides data
to the bus interface 171.
[0097] An exemplary structure for the interface units or heads 30 is shown in Figure 8.
[0098] The interface unit 30 includes a field interface 301 for communication with the processing
and control unit 10, which comprises the means for performing tasks of signal transmission
and reception to and from the track segment; a track interface 302 whereby it communicates
via track elements 303 with a track segment or block. The track interface 302 comprises
the elements required for interconnection with the track segment, such as the tuning
unit, wheel detectors, or the like. The track elements include track or rail parts,
such as joints, capacitors and other devices, that are directly mounted to the track
or the rails.
[0099] Figure 9 is a block diagram of the field interface 301.
[0100] A subsection 100 named COM has the purpose of managing transmission and reception
and of coding and decoding the data flow of communication with the processing and
control unit 10.
[0101] More in detail, in this example, the data flow is functionally broken down into the
following signals:
- Transmit signals: these are data flows that represent the information used to build
or generate the signals to be transmitted or injected to the track segment;
- Test signals: these signals are transmitted and received from the processing and control
unit 10 to certify proper operation of the field interface section 301;
- Receive signals: these signals come from the track segment and are the track segment
response to the transmit signals. These signals are processed by the processing and
control unit 10 to retrieve information about the occupancy state of a track segment.
[0102] The transmit signals are provided to a power driver interface 101 which adapts the
signal level and processes the messages from the processing and control unit 10 to
control the power amplification subsection 103. This power amplification subsection
103 amplifies AC and pulse signals to ensure compliance thereof with the power requirements
for the control of the various track interfaces. Particular advantages can be achieved
by the use of a subsection that can dynamically adjust amplitude, frequency and phase
of the signal to be transmitted. This section provides a transmit signal portion,
named Transmission rechecker, which is designed to be checked by the vital receiver
subsection 104. By this arrangement, the transmit signal transmitted to the track
segment can be safely checked. The power amplifier 103 receives power from a power
section 106 that generates the power amplification signal and converts the power source
to be used for the power amplifier.
[0103] The identification key module 105 contains the unique identification key of the track
circuit and has the purpose of checking the identity of the field interface.
[0104] The vital receiver provides test signals and receive signals to the processing and
control unit 10 and communicates with a diagnostic data acquisition section 107.
[0105] The output of the power amplifier 103 provides the signal to be transmitted to the
track segment and to a track switch 108. The latter is also connected to an input
of the vital receiver 104, and the receive signal acquired from the track segment
is provided to said receiver through it.
[0106] The input and output of the track switch 108 are connected to the track connection
interface section on the left side 200 and the track connection interface section
on the right side 200' of the track interface 302.
[0107] This block is only used when a Signal to Train feature is required, and the associated
feature consists in connecting the transmit and receive signals with the right and
left ends of the track segment to transmit information to the train in the direction
of propagation towards the train, depending on the train direction over the track.
The switch 108 is controlled by the processing and control unit 10 using the transmit
signal itself.
[0108] The vital receiver 104 provides vital monitoring of all the parameters required to
ensure safe operation of the system. Its main tasks are to acquire and manage the
following signals:
- Receive voltage from the track segment (RX_Track signal);
- Adapted transmit signal (TX_Recheck signal);
- Test signal used for safe operation of the receiver (TEST SIGNALS signal);
- Identification key (ID_KEY signal);
- Power supply (POWER SUPPLY RECHECK signal);
- Time base and reference voltage for A/D and D/A conversion;
- Diagnostic data (DIAG_DATA signal).
[0109] The vital receiver 104 has the purpose of managing analog to digital conversion of
the signals transmitted and received to and from the track segment.
[0110] The safe architecture is based on a MooN platform, where M and N are natural numbers
and particularly M = N = 2 in the minimum configuration of the present example. In
the 2oo2 configuration, each section, each module and each signal are replicated once.
[0111] Figure 10 shows the structure of the vital receiver in greater detail.
[0112] The vital receiver comprises two adders 41, 42. These adders separate the input signals
into two individual A/D conversion channels designated by numerals 40 and 40' and
particularly separate the signals that come from the track segment TX-TRACK from the
check signal TX-RECHECK signal that comes from the power amplifier 103. Also, the
adders inject the amplitude test signal by providing an analog addition of the input
signal and two test signals (TEST_V1 e TEST V2) for each A/D conversion channel. An
external clock 43 generates an independent time base that is used as a reference frequency
for the A/D conversion channels. These channels perform analog/digital conversion
of the following signals:
- RX-TRACK 1,2: signals received from the track segment with the test signal used to
certify safe operation of the section (signals TEST_V1 and TEST-V2) superposed thereupon.
- TX-RECHECK 1,2: signals coming from the power amplifier 104 with the test signal used
to certify safe operation of said amplifier (signals TEST_V1 and TEST-V2) superposed
thereupon;
- DIAG DATA: Diagnostic data acquired by the diagnostic section and designed to be transmitted
to the processing and control unit 10. These acquired parameters include, for example:
temperature of the field interface devices 301, temperature of the track segment,
current consumption, noise measures in- and out-of-band;
- IDENTIFICATION KEY: - information about the identity of the section (ID_KEY signal);
- POWER SUPPLY: - Information about the reference power supply values (POWER SUPPLY
RECHECK signal);
- TEST_F1, TEST_F2: signals used to certify proper A/D conversion.
[0113] The structure of the A/D conversion channels 40 and 40' is shown in Figure 11.
[0114] The ADC analog to digital conversion section 410 and the multiplexer MUX 411 are
controlled by a driver unit 412. The following signals are provided at the input of
the multiplexer 411:
TEST_F: this signal is generated by the section 414 which receives at its input the
signal of the external clock 43 and is used to certify the time base of each analog-to-digital
conversion 40, 40';
TEST_PS: this test signal is generated by a power source monitoring section that receives
at its input the power source signal;
TX_RECHECK: this signal is used to certify the signals to be transmitted to the track
segment and is generated by the power amplifier 103 of the field interface 301 with
the adder 41, 42 superposing thereupon the test signal TEST_V1 or TEST_V2 depending
on which of the two digital conversion channels is used. The signal produced by the
adder 41, 42 is provided at the input of the multiplexer 411 after being filtered
by an antialiasing filter 415;
RX_TRACK: These signals are received from the track segment through the track elements
303 and the track interface 302, with the adder 41, 42 superposing thereupon the test
signal (TEST_V1 or TEST_V2 depending on the A/D channel being used) and are provided
at the input of the multiplexer 411 after being filtered by an antialiasing filter
416.
[0115] A voltage reference signal for the analog-to-digital converter 410 is further provided
at the input of the multiplexer. This reference signal is generated by a section 417
that is part of the analog-to-digital converter 410.
[0116] Finally, diagnostic parameters acquired by the diagnostic subsection 107 are provided
to the multiplexer 411.
[0117] The test signals TEST_V (i.e. TEST_V1 and TEST_V2 a depending on the A/D channel
being used) are generated by two DAC sections 418 that are controlled by the processing
and control section 10 using the TEST V signal to certify safe operation of the analog-to-digital
conversion process.
[0118] The analog-to-digital conversion section 410 turns the analog signals from the track
segment into digital signals and transmits them through the network interface module
100 and through the network 20 to the processing and control unit 10 once the signals
converted into digital form have been coded with the identification key in a section
located at the output of the AD converter 410 and designated by numeral 419. Likewise,
the test signals TEST_V and TEST_F are generated from TEST signals that come from
the processing and control unit 10 in a section 420 specially designed therefor.
[0119] The track interface module 302 is shown in Figure 13 and consists of the part of
the system that is designed to perform the tasks of interconnection with the track
in terms of impedance matching and signal level adaptation to the track.
[0120] The present example has been only described with reference to track circuit features.
However, when using axle counters and any other different train detection devices,
such as devices for communication between the train and a wayside unit, the structure
will be modified according to the peculiarities of these devices which are known in
their general structure, wherefore adaptation to the system architecture of the present
invention is well known to those of ordinary skill in the art, once adaptation has
been described for the track circuit, which is one of prior art train detection devices.
[0121] The track interface 302 receives the transmit signals TX-SIGNALS, i.e. the signals
to be transmitted to the track segment from the field interface 301 and provides them
to the track elements 303 as TX_TRACK signals, after submitting these signals to the
following steps:
cable adaptation 500: this step allows impedance matching between the signals provided
by the field interface 302 and the cable impedance at which the signals are physically
provided to the track to minimize power losses caused by impedance mismatching.
[0122] Galvanic insulation 510: electrical separation between the system and the track and
particularly between the track and the field interface and the processing and control
unit 10.
Preshunt 520: preshunt prevention features.
Joint impedance matching 530;
Overvoltage protection 540;
Track connection 550.
[0123] These steps are also carried out with the signals received from the RX_TRACK track
through the track elements 303 and provided at the input of the field interface 302.
[0124] Concerning the track elements, these are schematically summarized in Figure 14. The
track elements physically consist of the components or devices of the system that
are located close to the track and are used to balance traction return currents, to
compensate for track impedance, to ensure safe operation and to implement electric
joints.
[0125] Electric connection with the track rails is provided by an electric receive and transmit
joint 600. This joint is used to electrically separate adjacent track segments and
balance the traction return current.
[0126] Obviously, the rails 610 that carry the track circuit signals and the traction return
signal of the train are also to be considered as a track circuit element and hence
as a track element.
[0127] The impedance joint 620 ensures continuity of the return current and ground connection
of the rails.
[0128] The compensation capacity 630 allows equalization of the frequency response of the
track and affords longer track segments of the track circuits.
[0129] Referring to the communication network 20 between the processing and control unit/s
10 and the track segment interfacing unit/s 30, this is a typical digital connection
network that can be of various types and operate according to various protocols.
[0130] Without excluding other types, protocols or architectures of existing and future
networks, a star topology is currently preferable for the logic network and possibly
also for the power network. Alternatively, the power network may also have a ring
topology.
[0131] In the former topology, power distribution and logic connections will be provided
by the same cable. If fiber optic is used for logic connection, a mixed cable will
be used, comprising the fiber optic cable and a conduction cable for power distribution.
However, if different topologies are used for the logic and the power networks, like
in the above variant, two separate cables will be provided and the power network will
have a power cable laid along the track. A network structure example from the point
of view of communication techniques is the ISO-OSI layer model. The network model
is preferably, but without limitation, a client/server network model in which the
processing and control units 10 act as servers and the track segment interfacing units
act as clients. The communication technique is of the message passing type.
[0132] The above description only related to the example of track circuits. As explained
above, the structure as described herein will not change in its general form with
axle counters and other devices for detection of or communication with a train through
the track. Changes or integrations may be required as would be obvious to those skilled
in the art.
[0133] It shall be further noted that the above description relates to a specific track
circuit example in which, like in Figure 1 showing the prior art, the joint for connection
to the track is of the directional type, with signals being always transmitted along
the track segments from one end of said segment to the opposite end in a direction
opposite to that of the train, so that the transmitted signals propagate towards the
train that enters or runs over the track segment.
[0134] The above disclosure and architecture, as well as the division of the operating units
into interface units and processing and control units, both being programmable depending
on the system configuration and the type of track circuit and signal coding being
used, allow the system as described above to be changed to obtain a non directional
track connection type. In this case, the signals transmitted to the track segments
propagate in all directions and the received signals include various signal components
deriving from the signals transmitted to the track segments.
[0135] In order to identify the receive signal associated with a transmit signal for a specific
track segment, in this case the transmit signals are coded. First, two different frequencies
are used for the transmit signals provided to the track. The transmit signals with
the two different frequencies are distributed over the track circuits so that signals
with different frequencies, corresponding to these two frequencies, are transmitted
to two adjacent track segments.
[0136] Also, the transmit signals with different frequencies are coded, coding being also
carried out using two different codes, each of said two codes being only used for
coding signals having one of these two frequencies.
[0137] Signal coding is advantageously a Direct Sequence Spread Spectrum (DSSS) or a Frequency
Hopping Spread Spectrum (FHSS) coding, allowing determination of the receive signal
component associated with a particular track segment by decoding the receive signals
through relation with the signal that is deemed to be associated with the relevant
track segment.
[0138] The block diagram of Figure 15 shows the above principle, the same reference numerals
being used therein to denote the same parts as in the previous figures.
[0139] It will be appreciated that this track circuit variant is obtained, according to
the present invention, by only changing the track connection joint from a directional
design to a non directional design and by storing a logic processing and control program
in the processing and control unit and/or in other programmable units, the execution
of which program causes the processing and control unit to operate according to the
track circuit variant and a configuration program. This allows the system to be changed
as desired by the customer, and as required by the track and weather conditions, by
only storing a different processing and control program and without requiring heavy
hardware changes.
1. A system for detection of and communication with trains, comprising:
a) a railway line having at least one track, which track is divided into a plurality
of successive track segments, known as track blocks,
b) means for generating signals for detection of or communication with the train being
provided for each of said track segments;
c) and means for receiving from the track block said detection and communication signals
produced by a train by active signal generation or change of the detection and communication
signals transmitted to the track block;
d) means for processing the detection signals or the communication signals received
from the track block to determine the operating or working conditions of the train
and/or the track block based on the changes found in the received signals with respect
to the transmitted signals and/or on the information contained in the communication
signals transmitted by the train,
e) means for generating signals indicative of the operating or working conditions
of the train and/or the track block and for transmitting said status signals to a
central railway network control unit, known as central Interlocking System, which
is connected to said detection and communication unit and receives signals therefrom,
indicative of the conditions of the train and/or the track block,
f) means for receiving control signals for detection of or communication with the
train from said central control unit,
characterized in that
g) one or more local heads are associated with each track block for interfacing with
a corresponding track block, which include:
means for generating and transmitting signals for detection of or communication with
the train to the corresponding track block
and means for receiving from the track block said detection and communication signals
produced by a train by active signal generation or change of the detection and communication
signals transmitted to the track block;
h) said local interface heads further include an interface for digital message communication,
according to a predetermined communication protocol, with a separate central processing
and control unit;
i) said central processing and control unit includes a digital message communication
interface which operates with the same communication protocol as the local track block
interface heads;
j) and said processing and control unit includes hardware in whose memories a processing
and control program is stored, to be executed by said hardware and whereby said processing
and control unit generates and transmits the control signals to the local track block
interface heads for triggering said local interface heads to generate and transmit
predetermined detection and/or communication signals and for receiving detection and/or
communication signals;
k) and whereby the processing and control unit processes the detection and communication
signals received from the local interface heads to determine the operating or working
conditions of the train and/or the track block based on the changes found in the received
signals with respect to the transmitted signals and/or on the information contained
in the communication signals transmitted by the train, and generates signals indicative
of the operating or working conditions of the train and/or the track block;
l) whereas said central processing and control unit communicates with the railway
traffic management unit for transmitting thereto said status signals or messages transmitted
by the train and for receiving therefrom control signals and/or messages to be transmitted
to the train.
2. A system as claimed in claim 1, characterized in that the interfaces for communication between the track block interface heads and the
central processing and control unit operate with a network communication protocol,
a communication network being provided.
3. A system as claimed in claim 1 or 2, characterized in that multiple parallel processing and control units are provided, which are arranged along
a railway line, each controlling and processing the signals of a subset of local interface
heads that are connected to corresponding track blocks of a subset of track blocks,
whereas each processing and control unit communicates independently with the central
railway traffic management unit, each local interface head and/or each track block
and each processing and control unit being uniquely identified by an identification
code that is associated to the signals for communication between the interface heads
and the corresponding processing and control unit and between said processing and
control units and the central railway traffic management unit.
4. A system as claimed in one or more of the preceding claims, characterized in that the interface heads, interfacing with each track block constitute the transmitter
unit and the receiver unit of a so-called track circuit, for generating a train detection
signal and transmitting said signal to the track block and for receiving said train
detection signal from said track block, whereas the processing and control unit is
the unit that controls the transmitter and receiver units and the means for processing
the detection signals received from the track block for determining the presence or
absence of a train on said track block.
5. A system as claimed in claim 4, characterized in that the interface heads and/or the track block and the processing and control unit have
means for diagnostic check of their operating conditions.
6. A system as claimed in claim 5 characterized in that the processing and control unit has means for generating signals for simulated indication
of the presence or absence of the train within one or more track blocks.
7. A system as claimed in claim 5 or 6, characterized in that the processing and control unit has means for integrating two or more track circuits
corresponding to two or more adjacent track blocks in a single composite track circuit
and, in case of failure of one of said two or more track circuits, the transmitter
and receiver units of the faulty track circuits are replaced by at least one transmitter
unit and one receiver unit among those of the working circuit/s, said at least one
transmitter unit and at least one receiver unit serving the assembly of two or more
integrated track circuits.
8. A system as claimed in one or more of the preceding claims 5 to 7, characterized in that the diagnostic means and the means for integrating two or more track circuits are
a diagnostic program and a track circuit integrating program which is stored and executed
by the processing and control unit or a subsection of said unit.
9. A system as claimed in one or more of the preceding claims, characterized in that the interface heads for interfacing with each track block constitute the sensor of
a so-called axle counter, whereas the processing and control unit constitutes the
control unit of the axle counter sensor and the unit for determining the number of
axles by processing of signals received by said sensor, a software program being stored
in said processing and control unit for processing signals of axle counting sensors
and for controlling said axle counting sensors, which software program is executed
by said processing and control unit.
10. A system as claimed in one or more of the preceding claims, characterized in that the interface heads for interfacing with each track block constitute the units for
transmitting and receiving communication messages to and from a train unit, which
also has a transmitter and receiver unit, said communication messages being transmitted
through the track blocks over which the train passes, whereas the processing and control
unit constitutes the unit for controlling transmission and reception of the communication
signals and the unit for generating the messages to be transmitted to the train and
interpreting the messages received from the train, a software program being stored
in said processing and control unit, for generating and interpreting messages and
controlling the transmission and reception of messages to and from a train, which
software program is executed by said processing and control unit.
11. A system as claimed in one or more of the preceding claims, characterized in that the track circuit is of the type with mechanical joints, in which the track segments
are mechanically and electrically separated, i.e. galvanically insulated from each
other.
12. A system as claimed in one or more of claims 1 to 10, characterized in that the track circuits are of the jointless type.
13. A system as claimed in one or more of the preceding claims 1 to 12, characterized in that the interface heads in the track circuit are connected to the corresponding track
block via directional joints, which define the signal direction over the track segment
from one end to the other of said track segment, by associating at one end the interface
head for transmission and at the other end the interface head for reception.
14. A system as claimed in one or more of the preceding claims 1 to 8, characterized in that the interface heads in the track circuit are connected to the corresponding track
block via non directional joints, which do not define the signal direction over the
track segment from one end to the other of said track segment, signal transmission
and reception occurring according to Direct Sequence Spread Spectrum (DSSS) or Frequency
Hopping Spread Spectrum (FHSS) communication techniques.
15. A system as claimed in claim 14, characterized in that each track block of a succession of track circuits arranged along a track has a joint
for connection of the transmitting and receiving track block interface heads, which
is of the broad frequency band type, and the transmitting interface heads transmit
a signal coded according to one of two different codes and having one of two different
frequencies to the track block through the associated joint, the signals transmitted
by adjacent detection heads being respectively coded with two different codes and
said signals having two different frequencies, whereas each receiving interface head
receives all the signals transmitted over the track from the different transmitting
interface heads, the correct receive signal, having the frequency and code expected
for the receiving interface head of a predetermined track circuit, i.e. a predetermined
joint, being determined by relating the received signal with the signal having the
expected code and frequency for the receiving interface head of a predetermined track
circuit, i.e. a predetermined joint.
16. A system as claimed in claim 15, characterized in that the coding sequences are sequences with pseudo-orthogonal properties used for modulation/demodulation
of the signal transmitted over the track circuit by DSSS (Direct Sequence Spread Spectrum)
or FHSS (Frequency Hopping Spread Spectrum) techniques, with such configurations as
to maximize protection from typical noise emitted by DC and AC powered trains, while
also maximizing mutual interferences between the track circuits.