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B1 Vital Relays

Gravity-Based Fail-Safe Electromechanical Relays for Railway Signaling

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B1 Vital Relays are used in railway signaling where a clear mechanical response is required under fault conditions. Their operation is based on gravity, allowing the armature and contacts to return to a safe position naturally whenever power is lost or an abnormal situation occurs.


Because of their open mechanical layout, the movement of contacts can be visually checked during inspection, a characteristic that has kept B1 relays in service for decades. They are commonly found in track circuits, interlocking arrangements, and other vital signaling functions that depend on predictable, purely mechanical behavior.

  • B1 Flasher
  • B1 Light-Out Neutral
  • B1 Lamp-Control
  • B1 Power Transfer
  • B1 Code Responsive
  • B1 Switch-Overload Neutral

Polarized magnetic stick relay operating as a B1 vital relay in railway signaling applications

Polarized Relay/Magnetic Stick

  • Used in signaling systems where it is necessary to detect the direction of the current or maintain a safe position even when power is removed.


  • This relay is polarized to respond to different current directions, ensuring that any failure drives the system to a safe position


Neutral line relay configured as a B1 gravity-operated vital relay for railway signaling

Neutral Line Relay

  • Employed in signaling systems where precise and secure control of signal positions is required.


  • Types of Neutral Line Relays:

 - Flasher Relays

 - Switch Control Relays

 - Switch Overload Relays

 - Power Transfer Relays

AC vane relay used as a B1 gravity-based vital relay in railway signaling systems

AC Vane Relay

  • Used in track circuit signaling systems.