SIL4 Timer relay

Timer for delaying the attraction of an N.S1 signaling relay

Timers are used to delay the attraction of a “N.S1” type signaling relay. They are usually used with track circuits to suppress possible nuisance caused by point-and-track kills.

Placed as an interface between an N.S1 relay and its command, the relay can only activate following a continuous command of a selected minimum duration. Any disappearance of the command, however short, resets its time delay and drops the relay if the latter is active.

This block has a SIL4 security level. In the absence of a command, a fault cannot cause the output relay to activate. Likewise, faults cannot shorten the selected time delay.

BKFU Relais N.S1 Agence Marseille SCLE
BKFU Relais N.S1 Agence Marseille SCLE
BTE relais N.S1 Agence Marseille
BTE relais N.S1 Agence Marseille


  • Hides short commands, avoiding untimely activation and relay “chatter”
  • For track circuits, delays release of tracks
  • Guarantees relay does not activate immediately on appearance of the command
  • Can delay the activation of a permissive signal, control push button or other


  • Safely filters out shunt-type command noise
  • SIL 4 safety level
  • Signaling device powered by 24V DC from the substation
  • Galvanically insulates the control output relay supply and the substation supply
  • Very robust, reliable and available device
  • Maintenance-free, its case and connections are in N.S1 format, simplifying exchange in the event of a failure


SNCF Réseau

Downloadable files

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for more information

Nathalie Sévikian

+33 4 91 03 04 24 rf.elcs@naikives.eilahtan


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