Just use the concept which discuss in the track circuit part to divide the track into many blocks, then AWS system is formed. The system mainly divided into two parts, three lights version and four lights version, below is the operate process of three lights version:

1. When every block is clear, the signal light will show Operate signal. (Green)

2. After the train move to block A1, signal A1 sense by track circuit, then turn Red to prevent other train pass though these block area.

3. After the train move to block A2, signal A2 turns to Red and signal A1 changed to Yellow, this changes let the other train entry block A1 in limited speed and stop in signal A2.

4. After the train moves to block A3, signal A1 turns to Green and let other train to pass though. Signal A2 turns to Yellow and so on.

Four lights version system:

Same concept of three lights version, Yellow-Yellow is added. This design is main used in faster speed line to shorter each block and increase the frequency of the train.

AWS ramp:
The signal system discuss above are just the instruction to the train move or stop, whatever if the train don¡¦t obey the signal? Then that¡¦s no use to have a signaling system! To ensure safety, AWS ramp is use to ensure the train follows the light signal to operate. The front part of AWS ramp is a permanent magnet, the rest part is a electro-magnet, and the whole AWS ramp are install in the track wood, when the train pass, the front part permanent magnet will then inform the warning system and braking system of the train to get ready, if the signal light is Green, the electro-magnet of AWS ramp will then magnetic, and after the sensor receive the magnetic signal will then inform the buzzer in the control room, and the indicator will then turn to Black which indicate the train can use the normal speed to operate, but if the signal light are Yellow or Red, the electro-magnet will then disconnect, the sensor sense the disconnect of magnetic and cause the alarm inside control room turn ON, the indicator will show Yellow and Black frequently, if the driver not press the CANCEL button to turn Off the alarm, the braking system will then turn ON automatically to stop the train. Press CANCEL button means that the driver knows the warning! AWS is depends on this to ensure the train follows the signal light.

Furthermore, AWS ramp is not located beside the signal light, it¡¦s locate in the distance which is equal to the braking distance, to prevent the accident train hit the train which in the next block area.

Location of AWS ramp