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High Availability Single Section Digital Axle Counter "SSDAC-G36R" Versatile High Availability Dual Redundant Axle Counting System 2x2oo2 Architecture


G36R is a fail-safe 2x2oo2 microcontroller based axle counting system for High Availability section proving in Railways. G36R can be configured to various versions using fool-proof method thus prevents wrong configuration at site, ensures highest degree of safety. Operating mode like preparatory, clear and occupied, configuration status, wheel counts and error messages are constantly displayed on the system LCD status panel and interactive Reset box.

Dual Redundant Magnetic sensors detects the axle counts and direction of train movements that is transmitted to the other end of the system to verify and clear the block. Wheel sensed at one DP will cleared at any DP. The section status can be fed directly to further controlling systems through vital relay contacts. Each section has two or three detection points based on configurations. System unit is housed near the track with its DP placed at a variable distance of 15 Mts.

Reliable communication between systems with a cable loss of 30dB using V.23 FSK modem at 1200bps, assured by CRC check with redundant messages. Fixed pair communication along with interlocked addressing between units ensures fail-safety. Built-in event logger logs normal and error data that can be downloaded on to a PC using RS232 serial port. Additional FSK modem available in event logger card connected to interactive Rest Box at station (requires extra pair in quad cable). User-friendly GUI aids to print reports.

RDSO Approved and Complies with RDSO/SPN/177/2005 Ver 2.0 with amendment 1. G36R works on 24 VDC power supply, integrated with lightening surge protectors.

Stable operation at adverse environmental conditions from –10°C to 70°C. Reliable train detection by sensors exposed to water clogging due to heavy rains.

SSDAC G36R System

Web Mounted Tx Rx Coils



  • Microprocessor based fail-safe embedded system
  • Detection of axles and direction of train movement
  • Fixed pair communication, CRC check & unique addressing of units ensures fail-safety
  • User friendly GUI aids to download events via RS232 port
  • Units are housed in location boxes near the tracks

Axle Detectors

  • Web mounted on track, works with 90-R, 52Kg, 60Kg rails
  • Phase detection principle employed
  • Signals fed at 21Khz and 25Khz to Tx coils at 60V RMS
  • Axles above 550mm are detected

Dual Reset Box

  • Amended as per RDSO Ver 2.0 Specification
  • Interactive RESET Box with Separate status LCD display for individual axle counting system on single quad cable multidrop mode and common Resetting
  • Independent system status and combined parallel Section
  • Stores events locally to download at station only

Technical Specifications

  • Complies to RDSO/SPN/177/2005 Ver 2.0 with amendment 1
  • IV&V of system software meets stringent CENELEC 50128, SIL-4
  • Mature and rugged with inherent fail-safety, highest reliability, availability, and maintainability as per CENELEC standards
  • Supports below configurations
    • 2DP Confugaration
  • No TP circuit required for push trolley with spoke wheel
  • Scalable to higher configuration with same hardware and software
  • Communication using V.23 FSK modem with cable loss of 30dB
  • Built-in event-logger logs up to 14000 events
  • Train detection up to 250Kmph
  • 24VDC working
  • Protected against lightning surges
  • Stable operation at –10 to 70oC and RE area
  • 2 Independent safety electronics in a single card frame for high availability
  • 2 separate output Vital Relays for paralleling to achieve highest availability
  • Configurable as common wheel sensing detectors for both axle counting electronics
  • Track occupancy information available at each detection point
  • Trolley protection circuit not required
  • Works with 90-R, 52kg, 60kg and worn-out rails
  • Local or remote data logging for 15000 events


2DP Configuration

  • Operation on straight lines - station or block section
  • Communication using one pair quad cable per system
  • Preparatory Reset configurable either with or without piloting
  • PR and VR contacts at detection points

Automatic Reset Philosophy

  • Any failure of single SSDAC initiates Resetting automatically to normalise the failed SSDAC without affecting system working
  • Manual Resetting required only when both SSDAC fails
  • Reset configurable either with or without piloting
  • Auto Resetting counter for analysis

SSDAC-G36R typical Automatic Resetting circuit