"ACD is non-signal equipment. In the Railways, station masters are provided with enough electronic protection against wrongdoings and unsafe things, but there is nothing much for drivers and guards. ACDs provide this protective layer and are additional lookout devices," Rajaram, who invented and patented the device, told mid-day. Pic/AFP

"An ACD system is at the station too. The top speed condition is directly taken by the ACD through direct independent wiring, not set to the mainline. The station ACD and the loco ACD communicate with each other from a range of 1.3 km, independent of any signal condition. The device acts to drop speed to 20 kmph. The ACD network works independently of red signal, etc. The only objective is to avoid dangerous collisions at high speed. The network of ACDs detects unusual train behaviour within a 1.3-km range. ACDs observe and talk to each other and as a network of a minimum four or six at a time," he explained. Pic/AFP

Sources said in 2003, the technology got approved after extensive trials and proving tests spread over five years and was finally cleared for large-scale implementation in the Northeast Frontier Railway zone. In fact, National Geographic conducted a trial, by asking the inventor to stand between two colliding trains and see if he would be saved by the technology. They monitored the loco driver to see that he did not apply the brakes. It was a success and the documentary capturing the feat has been viewed by millions. Pic/PTI

In March 2023, a locomotive carrying Vaishnaw and the then-Railway Board Chairman V K Tripathi raced towards each other on the same track and the latest Kavach version had triggered and applied automatic brakes 200 metres apart, thus avoiding a collision. Pic/AFP

Railway officials refuted the claim and said that no technology, including Kavach, could have averted what happened in Odisha, as the response time for the driver was as short as 23 seconds after the train got diverted to the loop line when the signal was set for the main line. Officials said the latest version of Kavach incorporates all features and is certified at the highest level of safety integrity, which implies that the possibility of hazardous error happening is less than once in more than 10,000 years.  Pic/AFP