Railways Signaling & Safety Equipment

• The system provides individual vital relay output for each section / point zone based on the principle of counting of axles.

• It can be deployed for simultaneous monitoring of following track sections in a station or yard area:

  •  LOOP LINE

  •  MAIN LINE

  •  PLATFORM LINE

  •  GOODS LINE

  •  COMMON LINE

  •  STABLING LINE

  •  POINT ZONE

  •  DEAD END

   

• SYSTEM BRIEF: The MSDAC comprises of

  • Axle Detectors

  •  Electronic field units

  •  Central Evaluator

  •  SM's Reset panel

  •  Monitoring Unit

  The Central Evaluator of the system has been designed and developed with a modular structure. (5 sets of cards). Each set of cards can be connected to minimum 2 and maximum 8 f field units. The complete system with all the 5 sets of cards can be connected to maximum 40 Nos. of field units. Therefore, the system has the provision to scale up or scale down according to the requirement at station.

• PRINCIPLE OF WORKING
  The Axle Detectors are installed at both limits of a track section along with their electronic field units on track side. Each of them is called a detection point. The total no. of detection points is to be decided by Railways to cover the station area as per the total no. of track sections to be brought under monitoring by means of the MSDAC. The field units are connected with Central Evaluator by means of 1/2 Quad cable. The Central Evaluator is to be installed in Station/Cabin. The 24V power supply is connected to Central Evaluator and also taken to the field units by means of a separate power cable. The Axle Detectors work on high frequency (21K Hz & 23 KHz ) according to the proven method of electro magnetic wheel detection. When a train wheel enters between the Axle Detectors, it influences the electromagnetic field and the wheel is detected, The Axle Detectors and electronics associated with it is working on the principle of Phase Modulation for detection of wheels. A separate small length DC Track circuit is not required for trolley suppression. The detected wheels of a train are converted into pulses and these pulses are counted and stored at the entry and exit field units of the track section. The stored counts as well as the health from the field units are continuously transmitted by means of telegram packets to Central Evaluator on 1/2 quad cable. After evaluation of counts received from entry and exit field units of each section, the track "Clear" decision is arrived in Central Evaluator. If the evaluation of counts is equal, the Vital Relay (VR) is energized to pick up. Otherwise the VR is dropped and the track section is shown as "Occupied". The contacts of VR is to be provided into the signaling circuits of the station. The VR for point zone is picked up after evaluating counts from all the field units of that particular section.

• The TAWD system supports single line, double line and multiple line configurations. It is based on the Digital Axle Counter.

• It operates on battery. Solar panels are used to charge the battery bank. ½ quad cable is required for communication between the Gate unit and the Remote Unit. This cable also carries power between Gate unit and Remote Unit.

• PRINCIPLE OF WORKING:  The TAWD system comprises of following subsystems.

  1.  Gate Unit

  2.  Remote Units

  3.  Decision Units

  4.  Gate Man monitoring Unit (Audio Visual Alarm Subsystem)

  5.  Station Master Monitoring and Reset Panel

  Line Side Equipment consists of Gate unit(s) and Remote units. One Gate unit and two Remote units are required for one line. When approaching train touches the advance sensor i.e. Remote unit, Gate unit starts incrementing its wheel counts. When train leaves the section from Gate unit, the Gate unit decrements the wheel count. The successful passage of train will result in zero count registered in the Gate unit indicating that the section is clear. And on leaving the remote unit of other side, counts are not registered in the gate unit.
  
  Gate unit continuously transmits the section status and health information to the Decision unit’s acquisition card. Acquisition card processes the received information and generates the driving signals for the audio-visual cards which finally drive the external audio visual signals for the road user.
   

  Data logger card of Decision unit keeps collecting the information and this information is transmitted periodically to the Gate man indication panel and to Station Master Monitoring and Reset Panel.
  
  The transmission to the station master monitoring and reset panel is the query and response system. Station Master Panel generates the periodically query for each gate. The respective Gate Decision unit responds to the query meant for it. Independent channels are set for handling the station A and station B.
  
  Health of the vital parts is monitored continuously by the Decision unit. Any failure is reported back to Station Master Monitoring and Reset Panel immediately and to the Gate Main indication panel. In case of error in the Line side equipment, visual information for the road user is also with drawn and both gate man indication panel and station master reset panel shows the error in the system.