While traveling in Indian Railways, you must have seen a red chain hanging in every coach. It is not a common rope, but is part of an emergency system, called an emergency chain or alarm chain pulling (ACP). You must have thought that how does such a big train stop by pulling this small chain? Which technology works behind it? Let’s know the whole story.

What happens when the chain is pulled?

When passengers pull this chain, a mechanical valve opens which is connected to the brake pipe of the train. This pipe is part of the air brake system of the train. Most of the trains of Indian Railways use air brake systems, in which the compressed air connecting coaches continues to flow.

This compressed air maintains a certain pressure so that the brakes of the train remain open. As soon as a chain is drawn, the valve opens and the air comes out from this pipe. This reduces the pressure of the system and is identified as an emergency. As soon as the pressure is reduced, the brakes automatically start, and the train stops slowly.

How does the driver know?

In new trains, the loco pilot ie the driver immediately receives information through alarm or light on which coach the chain is drawn. After this, the guard or railway staff go to that coach as soon as the train stops.

Chen drawing rules and punishment

If the chain is drawn without any legitimate reason (eg – someone’s health, security crisis etc.), then it is a legal offense. In such cases, a person convicted may be sentenced to heavy fines or jail.

Railways is making technical upgrade

Indian Railways is now making this system more smart.
CCTV cameras are being installed in some trains
Electronic alarm system that can monitor chain pulling
Sensor based brake cylinders, who record the exact location of chain drawing.