Cell broadcast alerts in India: SACHET and CAP

Your phone buzzes, makes an unfamiliar loud sound and shows a message that says it is a test. You did not subscribe to anything. This is a cell broadcast alert in India, and since 2023 many people have seen one without knowing where it came from. This article explains how the cell broadcast alert system in India works, how it relates to SACHET (the National Disaster Management Authority's alert platform) and to the Common Alerting Protocol (CAP), and what the official sources actually say. We stick to what government documents state, with their dates.

What is a cell broadcast message?

A cell broadcast message is a one-to-many message sent by the mobile network to every compatible handset within a chosen area, rather than to a list of phone numbers. The Department of Telecommunications (DoT) describes it as a technology that sends time-sensitive disaster-management messages "to all mobile devices within a designated geographical area, irrespective of whether the recipients are residents or visitors" [1].

The difference from SMS is worth spelling out:

The "sent at once" point is stated in the DoT's announcement of June 2025: unlike individual SMS alerts, cell broadcast messages "are sent to all mobile phones in a particular area at once" [3]. Because the network does not have to send millions of separate messages, a broadcast is intended to stay fast even when networks are congested, which is exactly when a warning matters. We do not have a measured figure for general conditions, so treat that as the design intent rather than a guarantee.

What is SACHET?

SACHET is India's integrated alert system run by the National Disaster Management Authority (NDMA). Its full name is the "Common Alerting Protocol Based Integrated Alert System" [2]. The SACHET portal states that it is developed and maintained by the Centre for Development of Telematics (C-DOT) [10], the research and development centre of the DoT; the cell broadcast system is also being developed and implemented by C-DOT [3]. In the DoT's announcement of 30 June 2025, SACHET is described as an existing SMS-based NDMA alert system that is "operational in all 36 states and Union Territories" [3].

In a written reply in the Rajya Sabha on 21 August 2025, the Ministry of Earth Sciences described the alert chain as having three parts [2]:

1. Alert-generating agencies: the India Meteorological Department (IMD), the Central Water Commission (CWC), the Forest Survey of India (FSI), DGRE, INCOIS and others, as listed in the reply.
2. Disseminating channels: cellular networks, radio, television, the Internet, satellite and so on.
3. Recipients: the general public and responders.

The same reply says that after a pilot project in Tamil Nadu, pan-India implementation of Phase I of the CAP project was sanctioned by the Government, and that the State Disaster Management Authorities use the NavIC satellite system to send warnings [2]. SACHET is therefore best understood as the platform in the middle. Agencies feed alerts in; SACHET sends them out through several channels. SMS is one channel and cell broadcast is another.

What is the Common Alerting Protocol (CAP)?

CAP is an open, non-proprietary digital format for describing an alert. The OASIS standard, version 1.2, published on 1 July 2010, defines it as a format for "all types of alerts and notifications", independent of the application or the network that carries it [4]. The International Telecommunication Union (ITU) has adopted it as Recommendation ITU-T X.1303 (CAP 1.1, 2007) and X.1303 bis (CAP 1.2, 2014) [5][6]. SACHET is described by the DoT and by Parliament replies as built on CAP as recommended by the ITU [2][3].

The value of a common format is simple. An IMD cyclone warning, a CWC flood bulletin and a tsunami message all use the same fields. One message can then be converted into an SMS, a cell broadcast, a siren trigger, a television crawl or an app notification without anyone retyping it.

What is inside a CAP message?

A CAP message has an alert block with the message identity, and one or more info blocks describing the event, and an optional area and resource. According to the standard, the fields every alert must carry are an identifier, the sender, the time sent, a status, a message type and a scope [4]. Each info block must state the category, the event, and the urgency, severity and certainty [4].

The status field is why a test message can be recognised as a test by software, and the msgType field is how a warning is later updated or cancelled. The area block gives the geography, typically as a polygon, a circle or a code [4]. That geographic target is what a cell broadcast system turns into a list of mobile towers.

Here is a small, illustrative fragment. The identifiers and place are made up to show the structure:

<alert xmlns="urn:oasis:names:tc:emergency:cap:1.2">
  <identifier>EXAMPLE-0001</identifier>
  <sender>example-agency@example.org</sender>
  <sent>2026-01-15T10:30:00+05:30</sent>
  <status>Exercise</status>
  <msgType>Alert</msgType>
  <scope>Public</scope>
  <info>
    <category>Met</category>
    <event>Flash flood</event>
    <urgency>Expected</urgency>
    <severity>Severe</severity>
    <certainty>Likely</certainty>
    <headline>Illustrative exercise message</headline>
    <area><areaDesc>Example valley, example district</areaDesc></area>
  </info>
</alert>

How do cell broadcast alerts reach your phone in India?

The path, as far as the official sources describe it, runs in four steps:

1. An authorised agency or disaster management authority prepares the alert and selects the affected area.
2. The alert is placed on the national platform in CAP form and routed to a cell broadcast system.
3. Each telecom service provider's network transmits the message only from the towers covering the chosen area.
4. Handsets in range show the message, usually with a distinct sound and vibration.

The DoT's 2025 review of the year records what happened in practice. In February 2025 C-DOT and NDMA signed a memorandum of understanding to implement an indigenous cell broadcast system across all Indian telecom networks. C-DOT then integrated its platform with all four major service providers, achieving "more than 95% pan-India network readiness", and the system was used live during Cyclone Montha in October 2025 in Andhra Pradesh and Odisha, where alerts in regional languages were disseminated "within 2–3 seconds", according to the DoT [7]. Those are the DoT's own reported figures for that event, not a general promise for every alert.

When did cell broadcast alerts start in India, and what was the testing?

The documented timeline, in order:

• 20 July 2023: the DoT announced, with NDMA, tests of the Cell Broadcast Alert System on each telecom service provider, to be repeated from time to time in various regions. Each test alert would be labelled "SAMPLE TESTING MESSAGE" [8].
• 28 September 2023: a second release said the tests were being run state by state, with Punjab next on 29 September [1].
• October 2023: press coverage reported a test with a message in Hindi and English saying that it was a test requiring no action [9].
• February 2025: C-DOT and NDMA signed the memorandum of understanding for the indigenous system [7].
• 30 June 2025: the DoT announced nationwide testing for about two to four weeks, with test messages in English and Hindi. After testing, alerts would go out through cell broadcast and SMS in multiple Indian languages. Only phones with the test channels enabled would receive test messages, and some people might get the same test more than once because all towers were being covered [3].
• October 2025: live use during Cyclone Montha, reported by the DoT [7].

Why did my phone show an emergency alert that said it was a test?

Because the DoT and NDMA have been running planned tests since 2023. The July 2023 release said people "may receive simulated emergency alerts", that these were part of the planned testing and did not indicate an actual emergency, and that each would be labelled "SAMPLE TESTING MESSAGE" [8]. Press reports of an October 2023 test described messages in Hindi and English saying that no action was needed, and some users reported the alert notification appearing several times [9]. The June 2025 announcement added that only phones with the test channels enabled would receive test messages, and that some people might get the same message more than once because all towers were being covered [3].

If you want to know whether your own phone can show such alerts, look in its notification or alert settings. Where they sit differs by make and software version, so follow your phone's own help. In CAP terms, a message with status set to Test or Exercise is a rehearsal and needs no action [4].

What cell broadcast cannot do

Cell broadcast reaches phones. It does not reach people without a handset, phones that are off, or devices without alert support, and it says nothing about what to do unless the message is written well. Messages are short, so the instruction has to be short too. A flood warning that reaches a phone still needs a clear action, a place and a time. That is why alert systems pair cell broadcast with sirens, local authorities and community networks; see early warning dissemination: sirens, SMS and CAP and how a flood early warning system works. The colour categories that IMD uses inside the warning text are explained in India's colour-coded weather warnings.

Key points

• Cell broadcast sends one message to every compatible phone in a defined area, whether the person lives there or is visiting [1].
• SACHET is the NDMA's CAP-based integrated alert system, developed and maintained by C-DOT; its SMS service is reported operational in all 36 states and Union Territories [2][3][10].
• CAP is an open message format (OASIS CAP 1.2, ITU-T X.1303 bis) that lets one alert feed many channels [4][6].
• DoT and NDMA began cell broadcast testing in July 2023; C-DOT and NDMA signed a memorandum for an indigenous system in February 2025; the DoT reports live use in Cyclone Montha in October 2025 [7][8].
• A message labelled as a test needs no action [3][8].

Where ClimMaTech fits

At ClimMaTech we build river monitoring and warning equipment, and many warnings begin from a river level or rain reading that has to be turned into a message people trust. The Rakshak Control Centre can take in alerts from agencies in CAP format and, with authorised approval, link them to local warnings such as Rakshak sirens and voice messages; it is available for demonstration. Official public alerts themselves remain the work of the authorised agencies.

References

1. Press Information Bureau, Ministry of Communications, DOT and NDMA collaborate to enhance emergency communication with Cell Broadcast Alert System testing, 28 September 2023. pib.gov.in
2. Press Information Bureau, Ministry of Earth Sciences, Parliament question: Expansion of NavIC-based Early Warning System (Rajya Sabha written reply), 21 August 2025. pib.gov.in
3. IANS, Govt begins testing new mobile alert system for real-time disaster warnings, reporting the Department of Telecommunications announcement of 30 June 2025. ianslive.in; also All India Radio News, 1 July 2025, newsonair.gov.in
4. OASIS, Common Alerting Protocol Version 1.2, OASIS Standard, 1 July 2010. docs.oasis-open.org
5. ITU-T, Recommendation X.1303 (09/07): Common alerting protocol (CAP 1.1). itu.int
6. ITU-T, Recommendation X.1303 bis (03/14): Common alerting protocol (CAP 1.2). itu.int
7. Press Information Bureau, Ministry of Communications, 2025 Year End Review for Department of Telecommunications, 19 December 2025. pib.gov.in
8. Press Information Bureau, Ministry of Communications, DoT to conduct Cell Broadcast Alert System testing to enhance emergency communication during disasters, 20 July 2023. pib.gov.in
9. Voice&Data, PAN-India Emergency Alerts test conducted by DoT, 11 October 2023. voicendata.com
10. National Disaster Management Authority, SACHET: Common Alerting Protocol Based Integrated Alert System (portal footer: developed and maintained by C-DOT). sachet.ndma.gov.in