Signal Crossing Prevention System (Automatic Train Stop, ATS): KFS SIL2 system

Système de Contrôle Ponctuel de Vitesse Autonome (KPVA)

This is a signal crossing control system (a signal such as a red light, for example), an ATS, which comprises three parts:

a KSF beacon installed on the track in interface with the signals, an onboard sensor, fixed on the truck, which receives data from the beacon and finally an onboard calculator has the task of sending the data from the sensor and issues an emergency stop command to the train.

Documents and ISA* Certification

    Operating principles of the KFS SIL2 (ATS)

    KFS SIL2 is an Automatic Train Stop (ATS), developped by CLEARSY. The KFS system operates from three elements:

    • an onboard KFS sensor
    • a KFS beacon installed on the ground on the track
    • an onboard KFS processing block or rack

    The principle behind it is simple: the onboard KFS sensor detects an electro-magnetic (or magnetic) field, emitted by a KFS beacon, installed on the ballast between the running rails via the intermediary of an external chassis, and relayed to the manoeuvre protection signal. The KFS sensor sends the information picked up at the KFS processing block, which is responsible for decoding it and passing on the information for the emergency braking or the driver’s alarm, which in turn triggers the halting of the tramway.

    The KFS system is compatible with the KPVA beacons. When those beacons detect an unexpected high speed, they send a signal to the KFS sensor that is installed on the train. The KFS controller immediately trigger an emergency braking.

    CLEARSY proposes to install a sensor at the end of the factory line in order to detect potential remaining pieces, that may damage or tear the KFS and KPVA beacons that are set up on the tracks.

    KFS system components

    KFS Sensor

    Its main objective is to detect two types of fields: one is magnetic from an electric magnet or permanent magnet, the other is low frequency electromagnetic from an antenna, generated by the RPS, KPVA or KFS Beacons assembled on the track between the train rails. The KFS sensor sends the information it receives to the KFS block, which decodes it and transmits the information to the emergency brake system or the driver’s alarm.

    KFS Block or Rack

    The KFS block is an onboard ; its main objective is to:

    • Decode information from the magnetic onboard KFS sensor, which is generated by the RPS, KPVA or KFS Beacon installed on the track between the train’s rails,
    • And transmit the information to the emergency braking system (VACMA).
    • The KFS block receives two types of electrical signals from the magnetic sensor:


    The analogical KFS Beacon is an integrated autonomous system for electrical and thermal railway systems (train/urban subways/RER/tramway).Its main function is to provide information on a crossing at a traffic signal (red light/green light)

    It is installed on a ballast between the tracks via the intermediary of an external chassis with anti-vibration resilience.

    The electrical equipment attached to the traffic signal provides the Beacon with red light information (which is the same when there is no light) or green light information.

    A permanent magnet creates a constant magnetic field. The presence of this magnetic field alone informs the onboard sensor and its treatment block that the Beacon, in other words the related traffic light (red light or no light), must not be crossed.

    When the light is green, this magnetic field runs in parallel to the electro-magnetic emission of two F1 and F3 frequencies, informing the onboard sensor and its block of an authorization to pass.

    Three Beacons are available:

    • The KFS mp Beacon (anti-signal crossing prevention system for the Paris subway system) is a functional equivalent of the RPS permanent magnet Beacon used on the urban subway system in Paris.
    • The KFS rp Beacon (anti-signal crossing prevention system for the Paris RER) is a functional equivalent of the RP electromagnet Beacon used on the RER system.
    • The KFS Beacon (integrated anti-signal crossing prevention system) is a functional equivalent of the RPS subway and RER Beacons, as well as their associated electronics.


    • CORSE: in operation since 2006 – Number of units: 35
    • RHÔNEXPRESS: in operation since 2010;  11 balises KFSI SIL2, 7 capteurs et racks. Installation: Vossloh
    • VALENCIENNES TRAMWAY: in operation since 2014 ; Number of copies: 28 balises KFSI SIL2, 28 capteurs et racks – Installation: INEO
    • NICE TRAMWAY: in operation since 2019 – Installation: Mobility
    • CORSE: renovation of the Corsican railroad signalling

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