Digital Block

Digital Block is used for exchanging permissions in fail safe way for sending / receiving trains between two stations

Digital Block


  • Completely safe – CENELEC SIL-4 certified
  • High reliability – Inbuilt 2 out 3 Architecture
  • Improved availability
    • Woks with variety of media – OFC (dark fibre) / Copper cable / E1 Channel / Voice channel – equipped with redundancy of media selection
    • Protection against surges
    • Redundant power supply
  • Flexible – Fit for DC/AC/Diesel traction territories
  • Easy to deploy – Embedded, prewired modules
  • Least operations – Saves operations time
  • Fast operations – Takes few seconds
  • Easy to maintain & troubleshoot – Completely electronic, deskilling of trouble shooting with extensive diagnostics
  • Reduced cost of maintenance – By Remote Condition Monitoring


Operational Benefits

  • Automatic TOL – block failure due to premature TOL operation eliminated.
  • Automatic Line Close – Elimination of operator involvement results in time saving and immediate block closure.
  • Block closing provision after push back operation, avoids block failure for next train.
  • Audio-visual alarms on section occupancy and clearance.
  • There is no block length limitation as equipment supports OFC.

Maintenance Benefits

  • No periodic over hauling as there are no mechanical parts.
  • Less number of relays used – improved reliability.
  • Error code displayed numerically for ease of understanding.
  • Status of all relays indicated by LED – reduces MTTR.
  • Diagnostic LED indications provided on the PCB facia makes troubleshooting easy.
  • Sufficient space provided in the equipment rack for keeping spares to reduce MTTR.


  • 2 out of 3 Architecture ensures safety as well as availability.
  • Inclusion of watch dog and mine fields for controlled software flow.
  • Bi-state and de-bounce validations for inputs.
  • Independent 2 out of 3 Architectural Voter card for placing validated outputs.
  • Critical Power Control module using twin relays for assisting safe shutdown.
  • Latching nature of TGTR and TCFR QL1 Type relays is tested for its every operation.

Additional Benefits

  • Block instrument clock is synchronized with GPS.
  • Extra Modem is provided for communication between data logger and Digital Block.
  • Industrial grade, components provided to ensure reliability.
  • Communication lines and power supply lines are protected with SPDs.
  • Burn-in and temperature cycle tests in the manufacturing process ensures zero fault production.
  • Each processor card is provided with independent power supply system – ensures reliability.


Digital Block Architecture
Digital Block Installation