Proceedings 2002/2003 - IRSE

CTRL SIGNALLING AND COMMUNICATIONS 75
TECHNICAL DESCRIPTION
ITCS Architecture
The ITCS is designed in such a way that the
system can be used on different sites as well as on
lines for which the signalling principles are different.
Three layers have therefore been implemented:
• A generic layer including all necessary hardware
and software and in particular the generic software
ensuring the required safety. This layer is
the same whatever the signalling principles
applied or the sites.
• An application-specific layer corresponding to
the signalling principles applicable to a network
or a line.
• A data layer specific to each site (geographical
data). This layer can be modified with no need to
change the other layers.
Generic Layer
The generic equipment is modular in order to be
adaptable to each site whatever the amount of
equipment to be controlled. The generic layer
includes:
• a processor unit ensuring all the functional
process;
• interfaces with the adjacent interlockings;
• interfaces with the track.
Processing Unit
The safety critical processes are performed by
three computers with a two-out-of-three architecture.
These computers are checked by coded
mono-processors of which there are two to ensure
system availability. This unit handles the links with
the Route Control Centre and the local control unit (if
any), the adjacent ITCS, the input/output interfaces
and local maintenance equipment.
Input/Output Interfaces
This equipment is managed by the processing
unit. The number depends on the site configuration.
Based on a coded mono-processor, they include
input and output racks for the interfaces with the
other equipment within the signalling room or the
trackside equipment, and manage the links with the
track interfaces cubicles.
The safety of inputs is ensured by “SACEM” type
coding using a coded mono-processor. The safety of
the output is ensured by recreate-reading and comparison
with the control by the coded mono-processor.
Track Interfaces
These interfaces concern the necessary equipment
for the functioning of:
• track circuits;
• intermittent transmission loops.
Track Circuit Equipment
This equipment includes the transmitter, the
receiver, cable compensation and orientation
devices. The transmitter receives the TVM information
to be sent to the train through the input/output
interface cubicle, and forms the message to be put
into the track. This transmitter consists of two
distinct elements, a digital one to form the signal and
an analogue one to amplify it. Cable compensation
reduces the level of the signal for a track circuit close
to the signalling room, so that the tuning depends
only on the track circuit itself and not on the distance
between the track circuit and the signalling room.
There is compensation both for the transmitter and
for the receiver. The orientation device allows the
exchange of the transmitter and receiver depending
on the direction of travel, to ensure that the transmitter
always feeds in front of the train.
The receiver provides the function of track circuit
reception, giving the inputs/outputs interface coded
mono-processor the signal characteristics allowing
it to determine if the track circuit is free or occupied.
In addition it ensures the rereading of the TVM code,
transmitting it to the input/output interface coded
mono-processor which compares it with the control
and inhibits the transmitter in case of discrepancy.
Intermittent Transmission Loop Transmitters
The transmitter receives the message number to
be transmitted via the inputs/outputs interface
cubicle. This is calculated by the processing unit and
forms the signal to be put into the loop. These transmitters
also check the status of the loops, and give
this status to the processing unit.
Application Specific Layer
The Application Specific Layer is formed of ele-