Eurobalise

thumb|A Siemens Eurobalise in Germany A Eurobalise is a specific type of a balise installed between the rails of a railway. Eurobalises are part of the European Train Control System (ETCS). The balises are pre-programmed and contain information that is read by train antennas. One of their many functions is to allow a train to determine its location.

== Overview == A balise typically needs no wayside power source. Coupling between the balise and the vehicle-mounted antenna is by magnetic induction, similar to a transformer - although operating at frequencies typical of radio, it is not a radio system. In response to "telepowering" by means of a 27 MHz, CW-modulated magnetic field transmitted by a (BTM and its associated antenna) mounted under a passing train, the balise transmits information to the train (uplink) by means of a 4.234 MHz FSK-modulated magnetic field. The original provisions for Eurobalises to receive information from the train (downlink) have been removed from the specification. The transmission rate is sufficient to transmit at least three copies of a 'telegram' to be received by a train passing at any speed up to 500 km/h. The BTM may be integrated into the on-board antenna or a separate electronic module, according to the preference of the system vendor.