Contrôle de vitesse par balises (KVB)

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Contrôle de vitesse par balises (KVB)
Frequencies 4.5 MHz
Frequency Range 4.5 MHz - 4.5 MHz
Modulation AM
Emission Designator
Bandwidth 100 kHz
Location France, United Kingdom
Short Description "Speed control by beacons" railway safety system used in France and the Channel Tunnel line in the UK.
I/Q Raw Recording
Audio Sample

Contrôle de vitesse par balises (Speed control by beacons, abbreviated to KVB) is a railway safety system used in Mainland France and in the United Kingdom between London and the Channel Tunnel. The passive beacons are placed trackside and store line information that is transmitted to the train as it passes over. A signal similar to the Eurobalise downlink is constantly transmitted from the train which energizes the beacon and clocks the data with a OOKOn-Off Keying Modulation signal. The reply to the train is coded by the beacon by selectively echoing a ring at 1/6th of the carrier frequency.


Power and clock downlink to beacon: 27.115 MHzMegaHertz (MHz) 10^6 Hz carrier, 50kHz AMAmplitude Modulation
Data uplink to train: 27.115 MHzMegaHertz (MHz) 10^6 Hz / 6 ~= 4.5 MHzMegaHertz (MHz) 10^6 Hz, 50kHz AMAmplitude Modulation


The analog version of the system continuously repeats a 32-bit frame with a fixed 8-bit start marker, and a 12-bit payload doubled by its complement. Most beacons transmit fixed data. Some are connected to light signals to transmit variable data depending on their state.

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