WEEK 4 : DAY 5 COMMUNICATION EQUIPMENT

4.5 EQUIPMENTS

        Here, we will learn about the internal details of equipments used by the Railways including the Control Office Equipment (COE), Way Station Equipment (WSE) and emergency control which are required for the functioning of the railways.

4.5.1 Control office equipment

• It is a 4 wire/2 wire Train Traffic control equipment with DTMF.
• Spec No. Rs:TC:60/2007
• Way-station equipment 4-wire
• More information here.   

  

4.5.2 Way Station equipment

     Way station equipments consists of a PCB followed by a telephone.

4.5.2.1 WSE PCB

WSE PCB

        Way station PCB has following main parts:-

1. DIP switch 1 & 2 :- used to assign a station code to W.S.E station.
2. Group DIP switch :- used to assign a group code to W.S.E station.
3. Telephone Terminals :- used to connect W.S.E telephone to the W.S.E PCB.
4. Line Terminals :- used to connect channel to the W.S.E PCB.
5. Decoder :- It decodes the DTMF frequencies it gets into binary numbers
6. Divider :- It compares the decoded signal with the value of station code assigned to the station or WSE equipment.
7. Logic Circuit :- It decides what to do with the signal. e.g :- If the decoded signal doesn't match with the station code it will glow a red LED to indicate that the station code does not match.

4.5.2.2 Working of WSE PCB

• First coded signal in the form of DTMF signals are decoded by decoder and converted into 4-bit binary number.
• Then the divider compares the decoded DTMF signals with the station code and gives output false if they are not equal and vice versa.
• Then the logic circuit decides what to do according to the output of divider.
• If the output of divider is true the logic circuit will switch on the relay and the WSE telephone will ring.Also a green LED glows to indicate that the code is correct
• If the output of divider is false Red LED glows indicating that station code does not match.

4.5.2.2 Types of WSE PCB

       There are two types of WSE PCB

1. Logic-circuit based WSE PCB:- In this logic gates are used to implement decoder divider and logic circuit. They form separate blocks in this PCB
2. Microprocessor based WSE PCB :- In this microprocessor is used to implement decoder divider and logic circuit. They are implemented in the same microprocessor so separate blocks are not required. It contains a watchdog which checks for any error in the microprocessor and corrects it or reset it as required.

4.5.2.3 Station code and group code assignment

• As we all know by now that every station has a station code. But the point is how to assign it.
• Station codes and group codes are assigned using the DIP switches in the PCB.

DIP SWITCHES ON WSE PCB 

• As evident from the figure there are three set of DIP switches two are for station code ranging from 0 to 9 and one is for assigning group code. For more info visit here.
• Station code is two digit number so each set DIP switch are assigned to one digit. So we have to simply put the DIP switch of the corresponding number to "On position".
• For example:- If station code is 54. Then dip switch corresponding to 5 in "DIP SWITCH 1" in the figure is put in "on position" and dip switch corresponding to 4 in "DIP SWITCH 2" in the figure is put in "on position".
• Similarly for the group codes the dip switch correspond to that group in "DIP SWITCH 3" in the figure is put in "On position

4.5.2.4 Telephone and line terminals

Line Terminals

• Tx : - Transmitting wire is connected to it
• Rx : - receiving wire is connected to it.
• Gnd : - Ground
• +12 V : - Power supply

Telephone Terminals

•  NC :- No connection
• +12V : - Power Supply
• MIC : - Microphone
• Gnd : - Ground
• Rx :- Receiver
• Buzz :- Buzzer i.e the device which rings when we receive a call.
• LED :- Led which after ringing stops.

NEXT | HOME | PREVIOUS