the lineside railway signal or to the signalling control tower. Balises must be deployed in pairs so that the train can distinguish the direction of travel 1→2 from direction 2→1, unless they are linked to a previous balise group in which case they can contain only one balise. Extra balises can be installed if the volume of data is too great. Balises operate with equipment on the train to provide a system that enhances the safety of train operation: at the approaches to stations with multiple platforms fixed balises may be deployed, as a more accurate supplement to GPS, to enable safe operation of automatic selective door opening. Installation The balise is typically mounted on or between sleepers or ties in the centre line of the track. A train travelling at maximum speed of will transmit and receive a minimum of three copies of the telegram while passing over each Eurobalise. The earlier KER balises (KVB, EBICAB, RSDD) were specified to work up to . The train's on-board computer uses the data from the balises to determine the safe speed profile for the line ahead. Enough information is needed to allow the train to come to a safe standstill if required. The data in the balise can include the distance to the next balise. This is used to check for missing balises which could otherwise lead to a potential wrong-side failure. At the start and end of ATP equipped territory, a pair of fixed balises are often used to inform the onboard ATP equipment to start or stop supervision of the train movements. Usage Eurobalises are used in: ETCS – the European-wide train protection system Chinese Train Control System versions CTCS-2 and CTCS-3, used on high speed rail lines in China EuroSignum – a variant of the earlier Swiss Integra-Signum train protection system EuroZub – a variant of the earlier Swiss ZUB 121 train protection system SCMT – an Italian train protection system TBL1+ – a train protection system used in Belgium GNT – the system to control tilting trains in Germany ZBS – a new rapid transit control system for the S-Bahn Berlin TASS - a system to control the tilting of trains on the West Coast Main Line Balises other than Eurobalises are used in: KVB - a train protection system used in France ASFA - a train protection system used in Spain ACSES - a train protection