Railway signalling · Train detection
Single Section Digital Axle Counter (SSDAC)
SIL 4 compliant train detection for a single track section with one to four detection points: terminal lines, sidings, block sections and point zones. Independently assessed by Bureau Veritas Italy; designed and manufactured in Bengaluru.
SIL 4 compliant, assessed by Bureau Veritas Italy · RDSO approval in progress
How it works
The SSDAC decides whether a track section is clear or occupied by counting axles in and out of it. The section is reported clear only when both counts match and the equipment is healthy. Any defect, missing sub-assembly or power failure withdraws the clear indication, so the system always fails to a safe, occupied state.
Rail-mounted axle detectors at each end of the section feed trackside field units, which communicate over copper quad cable or a voice channel in optical fibre and drive the vital relay output for the section.
Configurations
One detection point
Terminal lines and sidings.
Two detection points
Straight-line block sections.
Three or four detection points
Point zones.
Consecutive single sections
Chained for automatic signalling territory.
Key specifications
Parameters per RDSO/SPN/176/2013 Ver. 3.0, to which the system is designed and type-tested. The full specification is in the brochure.
Detection performance
| Parameter | Value |
|---|---|
| Train speed range | 0 to 350 km/h |
| Maximum axle count per section | 1024 |
| Occupancy response time | Less than 1.0 s |
| Clearance time after train leaves | Less than 2.5 s |
| Error rate | Not more than 2 per 1,000,000 axles, with no unsafe outcome |
| Trolleys and dip lorries | Not counted; no trolley protection track circuit needed |
Equipment and power
| Parameter | Value |
|---|---|
| Axle detector | Web-mounted, two Rx and one Tx coil, no moving parts; 52 kg/m, 60 kg/m and 90 R rails |
| Detector ingress protection | IP66 and IP68; unaffected by track flooding |
| Field unit architecture | 2-out-of-2 |
| Communication | Quad cable (IRS:TC-30), min. 1200 baud, up to 20 dB loss |
| Field unit supply | 24 V DC, +20% to −30%; 0.6 A nominal |
| Protection | Over-voltage, under-voltage and reverse polarity |
Environment and reliability
| Parameter | Value |
|---|---|
| Operating temperature | −10 °C to +70 °C |
| Traction systems | Non-electrified, 25 kV AC, 1500 V DC and 750 V DC |
| Event logger | Minimum 40,000 time-stamped events |
| MTBF (equipment) | Not lower than 70,000 hours |
| Service life | Not less than 20 years |
Testing and support
SIL 4, independently assessed
SIL 4 compliant, assessed by Bureau Veritas Italy. Developed to CENELEC EN 50126, 50128 and 50129, so that any failure results in a defined safe state, never a hazardous one.
Testing on every unit
Type, acceptance and routine tests, with 100% environmental stress screening of every board.
Support
Supervised commissioning, training, spares and controlled software updates.
Covering a station yard or many sections? See the multi-section Digital Axle Counter (DAC / MSDAC).
Planning a block section or siding?
Tell us the number of detection points, cable lengths and the application, and we will propose the right configuration.
Talk to our engineers