EMU coaches have some cables that run the entire length of the train. These cables carry the control signals for brakes, train lighting (powering the lights and fans in the coaches) etc. In the attached picture (Source: click here I have highlighted the cables in the red box.The present generation of AC/DC EMUs running in Madras have five such cables running throughout the length of the rake. These 5 cables (and the sockets they plug into) are labeled as A,B,C,D and E. Earlier EMUs had these cables dangling outside the motor car (as in the attached picture), however SR started modifying...

Life Line of ChennaiChennai Beach Chengalpattu EMU train approaching, Maraimalai Nagar RS. In spite of having considerable space for passengers to stand inside, few travelers prefer to travel in foot board risking their life.