On October 7, Mumbai’s civic body issued a brief press note with an unusual request. Sirens would be sounded in south Mumbai’s Fort area on October 8 and 9, it said, and citizens should not panic or misunderstand the sound. The test was pre-planned, and there was no actual emergency or threat.When the sirens sounded the next day from the Old Secretariat building, what few realised was that similar tests had been carried out in Rajasthan’s Jaisalmer on September 30 and in Bihar just two days earlier, on October 6.The Mumbai test was part of a larger, nationwide exercise. After Operation Sindoor, states had rushed to buy air raid sirens, often without any specifications. Now the Centre wants to replace that patchwork with a single, advanced air raid warning system for the whole country, one that can be set off with a text message. Now the Centre wants to replace that patchwork with a single, advanced air raid warning system for the whole country, one that can be set off with a text message.Leading the effort is a team from the Centre for Development of Telematics (C-DOT), under the Department of Telecommunications (DoT), working with the Director General, Civil Defence, New Delhi. Along with Civil Defence officials, the team has been travelling across the country, listening to sirens being played out and taking copious notes.The trials began in border states such as Rajasthan and have now moved to coastal states such as Maharashtra. Punjab is likely to be next month.At each stop, officials note how far the sound carries, how long the siren goes off, its technical connectivity and the type of noise it makes, along with the varying needs of the local area. The aim is to see whether the prototype needs any changes before it is finalised as the device for “centralised siren triggering”.A rush after ‘Operation Sindoor’The push for one system grew out of the tense weeks of May 2025. After the Pahalgam terror attack in April, India launched Operation Sindoor on May 7, striking terror camps in Pakistan and Pakistan-occupied Kashmir. Pakistan responded with drone and missile attacks on Indian border areas, and the hostilities lasted until a ceasefire on May 10.Story continues below this adOn the day the strikes began, the Union Home Ministry ordered civil defence mock drills in 244 districts across the country, the first such nationwide exercise in decades. Air raid sirens were central to the drills, and to the fear that cities could come under attack. But in many places, the sirens had long fallen silent.“After Operation Sindoor when there was the possibility of a threat, various states had purchased sirens without any specifications. There was a rush to purchase these as most states had stopped the use of sirens so departments purchased whatever they could as the old sirens were not working,” an official from Maharashtra said.Once the urgency passed, the focus shifted to uniformity. “After the demo took place following instructions by the Centre due to the possibility of attacks post Operation Sindoor and the urgency passed, a need was felt to ensure that there was uniformity in the sirens used and there be a prototype using which the necessary specifications could be defined for future purchase,” the official added.A siren switched on by textAt the heart of the prototype is cell broadcast technology developed by C-DOT. The same technology was launched nationwide for disaster management on May 2, 2026, when alerts were sent to mobile phones across the country. It is now being evaluated for a second use — activating sirens installed at different locations from a single central system.Story continues below this adIn simple terms, a text message would flip the siren’s switch, instead of someone having to operate it manually. Geo-fencing would allow sirens to go off only in a particular area, rather than across an entire state or the country.A note by Maharashtra Civil Defence said C-DOT had successfully conducted the operational trial and field testing in Mumbai at the Old Secretariat Annexe Building on October 8, as part of modernisation of the Civil Defence Air Raid Warning siren system. During the trial, the note said, the system demonstrated “real-time, centralised and geo-targeted dissemination” of cell broadcast messages, with geo-fenced activation of the siren. The siren was activated multiple times through cell broadcast messages.Why one size may not fit allEven a standard system will have to bend to local conditions. In Mumbai, the problem is the skyline.“Every state has their own unique issue. For instance, in Mumbai, where there are many skyscrapers, keeping a siren on the third floor will not be effective as adjacent buildings will block the sounds. Hence, state or city specific factors will also have to be taken into consideration before coming up with a final decision,” the official said.Story continues below this adSound output and activation are among the technical parameters being examined, and officials and experts recorded their observations during the trial to help improve the system. The siren system, an official said, serves as a vital medium for issuing timely warnings to the public in a potential emergency. For now, the technology remains in the prototype and testing phase, with its capabilities and possible improvements being assessed at different locations.