Eurobalise downlink
From Signal Identification Wiki
An Eurobalise is a specific variant of a balise being a transponder placed between the rails of a railway. These balises constitute an integral part of the European Train Control System, where they serve as "beacons" giving the exact location of a train as well as transmitting signalling information in a digital telegram to the train. The downlink uses an amplitude modulation on the 27.095 MHzMegaHertz (MHz) 10^6 Hz frequency. This frequency is used to power the passive balises (it is the intermediate channel 11A in CB radio).