GROUND SUB-SYSTEM
Technical specsDescription
The trackside subsystem (SST) provides the transmission of information about signal aspects and other fixed data (line speed, braking curves, distance to next signal, speed restrictions) to the on-board subsystem via a microwave link.
The transmission of data is performed by suitably located information points. The transfer of information on board is said to be discontinuous, as it only takes place when the train encounters these information points.
The information points, directly connected to relay based, dichroic mirror and LED signals, allow the aspect of the signal to be acquired by means of an encoder, and the transmission of information to the transponder about the signal, line speed characteristics and braking curves as well as information about the distance to the next signal and subsequent information points.
The power supply for the equipment at an Information Point is taken from the signal that is connected to this. Furthermore the information points are not intrusive and given the importance of the task being performed, they ensure a safety integrity level of SIL 4 (CENELEC EN 50129). equal to that of SIL4. The processor is the core part of the Encoder that is realised from a two-out-of-two fail safe architecture (2oo2) In order to guarantee the safety integrity of the information about the signalling system and to ensure that all the functions provided by the SSC are performed correctly.
The transponder sends a microwave signal to the on-board equipment, containing information in the form of telegrams that are structured according to a safety related communications protocol and interpreted by the on-board equipment.
The information points are functionally correlated so that the failure of a single information point is detected. When it is necessary to start this correlation a special information point called Data TAG is used.