SACHET emergency alert system: At around 11.40 am on Saturday, many smartphones across India suddenly played a sharp beeping sound, accompanied by vibrations. A pop-up message flashed on screens in English, Hindi and other languages with the headline ‘extremely severe alert’. While many may have been taken aback by the sudden vibrations and sound, this was essentially a pan-India test of a mass broadcast system — called cell broadcast — to alert people during natural or manmade disasters. Currently, the government already issues disaster alerts through SMS. But unlike SMS alerts, which may be missed by many, the cell broadcast technology used on Saturday is unmissable. It mirrors the technologies used in countries such as Japan (which issued tsunami alerts). While tests have been on for some time now in India, this was the first time this took place on such a scale. Here’s what cell broadcast technology is, how it works, and why it’s crucial for a country to have such an alert system.…