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Transponder

Device, equipped with an internal antenna, which recognizes an external query and emits response signals. It can receive energy for activation from the same external source. Used in railway applications both on the ground and on board vehicles. If it is installed on the track, in order to transmit information to the traction equipment, it can also be defined as buoy or balise. In this last case it is used in the railway circulation with ATC and ERTMS, constituting the Information Points and therefore allows the realization of the discontinuous digital repetition channel of the data from ground on board. The information capacity of the buoys can be of different lengths for various applications: – 12 useful bits (with separate edge hardware for the discontinuous channel and for the continuous channel); – 180 useful bits (with distinct edge HW for the discontinuous channel and for RSC); – 1024 useful bits, for the realization in Europe of a standard system of command and control in safety. The 12 or 180 bit buoys are called KER buoys, the 1024 bit buoys are the European standard buoys (EUROBALISE). The digital buoys are energized when the train passes through an antenna that continuously emits a radio signal that activates the same buoys which, in turn, reflect a signal, containing the various information, to the train. The buoys can be of the fixed, semi-fixed and variable type. The former are used to encode fixed data, information not subject to change. The second, semi-fixed (configurable, using wired connectors called “Plug”) are used to encode data that is inserted in specific occasions by programming. The third, variable type (switchable), are connected to an Encoder and are used to encode variable data, information regarding the status of the signals and other data concerning the circulation. The switchable buoys receive the messages transmitted by the encoders and when they are energized, when a train passes, they transmit the message on board; each buoy also has a stored message, called a “default” message, which sends the trains restrictive information that guarantees safety when the buoy does not receive, in the event of a connection failure, information from the encoder. The buoys generally transmit three words (X, Y, Z) of four data bits: the first X is permanently encoded using a hardware key and is used together with the X of the successive buoys to define only the type of information point to which it refers; the second Y and the third Z can be coded as fixed or variable; if they are variables they have an appropriate connection to the encoders. The transponders can include from one to three so-called “plugs” for the coding of the codes they must send to the on-board sensor: in the “plugs” there are the “plug” coding keys, of 14 different types. There are four types of Transponder: F, with the words X, Y and Z fixed; Y, with the word Y in variable coding and X and Z fixed; Z, with the word Z with variable coding and Y and fixed X; Y/Z, with the words Y and Z with variable coding. See Air Gap Interface

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