MSDAC has a mechanism to reset a particular track section to recover from an error or a failure condition. This is done through the SM's reset panel. The section is to be physically verified by the SM to be unoccupied and then the reset command is to be given from the reset panel. This command is received by the central evaluator and it then sends the command to the respective field units to zero their counts.
The wheel-detection events are converted into pulses and these pulses are counted by the field units. These counts are stored here as well. The stored counts as well as the health of the track sensors are monitored and are continuously transmitted by the field unit, by means of telegram packets to Central Evaluator on the ½ Quad cables that also powers the field unit. The central Evaluator receives the count from each of the field unit it is connected to and it then takes the decision of the track section is occupied or not. This decision is taken based on 2003 voting logic in a fail safe manner. MSDAC signals the occupancy of the track section by means of an electro-mechanical relay called VR relay. The contacts of VR are used in the signaling circuits of signaling system at the station.
Therefore, the system has the provision to scale up or scale down according to the requirements at station.
The system consists of the following components:
Ø Axle Detectors
Ø Electronics Field Units
Ø Central Evaluator
Ø SM's Reset Panel
Ø Monitoring Unit
The Axle Detectors are installed at the limits of a track section along with their electronic field units on track side. The number of detection points is decided based on the track circuiting requirement of a station. The field units are connected with Central Evaluator by means of ½ Quad cables. The Central Evaluator is installed at the station and is powered by 24V DC local supply. The field units are also powered using 24V DC that is derived from the power source that powers the central evaluator. The Axle Detectors operates on high frequency (21 KHz & 23 KHz) electromagnetic wheel detection technology. When a train wheel passes over the Axle detectors, the change in electromagnetic field is sensed. This change triggers a complex algorithm that decides if a wheel has passed over the axle detector. The Axle detectors and the electronics associated with it is working on the principle of Phase Modulation.
The Central Evaluator of MSDAC-730P has been designed to be modular. The system can be configured for up to 40 field units in steps of 8.
It is used for detecting railway track occupancy primarily in a station. It is used for track circuiting a whole station. MSDAC-730P is modular in design and can be used with 40 detection points per chassis. Each detection point has a track sensor that identifies a track section boundary. A track section can be defined with 2/3/4 detection points.
MSDAC-730P is a multi-section digital axle counter system that is designed using the principles of fail-safety and has a two-out-of-three fail safe architecture. It is microcontroller based and has redundant power supply arrangement. Its modular nature allows you to plan your upgrades and extensions without any problem. It is extensible with 8 detections points in a module set. It provides an easy to use GUI for configuration.
It is designed in accordance with the RDSO specification No. Specification No. RDSO/SPN/176/2005 to meet CENELEC SIL-4 standards.