Railway signalling · Train detection
Digital Axle Counter (DAC / MSDAC)
A multi-section digital axle counter, also called MSDAC, built to be SIL 4 compliant. For station yards, ladder layouts and automatic signalling, with one central evaluator for up to 40 detection points and 39 track sections. Currently in development; designed and manufactured in Bengaluru.
How it works
The DAC decides whether each track section is clear or occupied by counting axles in and out of it. A 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.
Clamp-mounted axle detectors feed trackside field units, which report to a 2-out-of-3 (2oo3) Central Evaluator over optical fibre cable (OFC) or quad cable. The evaluator drives a vital relay output for every section and connects to a reset unit, event logger, diagnostic terminal and electronic interlocking.
Built for complex layouts
Up to 40 detection points
Per evaluator, covering large station yards from one location.
Up to 39 track sections
Each with its own vital relay output.
Interlocking ready
RS-232 interface to Electronic Interlocking per RDSO/SPN/192, plus a separate data logger port.
Ladder layouts
Multiple detection points across crossovers and ladder configurations.
Automatic signalling
Consecutive sections for automatic signalling territory.
Built to be SIL 4 compliant
2-out-of-3 (2oo3) Central Evaluator, developed to CENELEC EN 50126, EN 50716:2023, EN 50129 and EN 50159.
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 | 9,999 |
| 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 |
Evaluator and interfaces
| Parameter | Value |
|---|---|
| Architecture | 2-out-of-3 (2oo3) Central Evaluator |
| Detection points per evaluator | Up to 40 |
| Track sections per evaluator | Up to 39, one vital relay output each |
| Interlocking interface | RS-232 to Electronic Interlocking per RDSO/SPN/192 |
| Data logger interface | Separate port, protocol per RDSO/SPN/99 |
| Communication | Optical fibre cable (OFC) and quad cable (IRS:TC-30) |
| Vital relay | 24 V DC, 1000 Ω, plug-in type |
| Power supply | 24 V DC from IPS per RDSO/SPN/165; over-voltage, under-voltage and reverse polarity protection |
Axle detector, environment and reliability
| Parameter | Value |
|---|---|
| Axle detector | Clamp-mounted, no moving parts; 52 kg/m, 60 kg/m and 90 R rails; IP66 and IP68 |
| Operating temperature | −10 °C to +70 °C |
| Traction systems | Non-electrified, 25 kV AC, 1500 V DC and 750 V DC |
| Event logger | Minimum 1,00,000 (one lakh) time-stamped events |
| MTBF (equipment) | Not lower than 70,000 hours |
| Service life | Not less than 20 years |
Testing and support
Independent assessment planned
Hardware and software validation and RAMS analysis will be carried out by an accredited independent safety assessor, to be finalised.
Testing on every unit
Type, acceptance and routine tests, with 100% environmental stress screening of every board and burn-in of components and assemblies.
Support
Supervised commissioning, training, spares and controlled software updates under formal configuration management.
Need a single section only? See the Single Section Digital Axle Counter (SSDAC).
Planning a yard or automatic signalling project?
Tell us the number of detection points and sections, cable lengths and where the evaluator will sit, and we will propose the right configuration.
Talk to our engineers