Emergency broadcast messages explained

Emergency Alert Messages
By Adam Zeis on 26 Jul 2012 12:03 pm EDT

Just what is the Commercial Mobile Alert System (CMAS) and Wireless Emergency Alert (WEA)? We'll break it down for you.

Last week we noted that many users received an emergency alert on some devices for a storm that passed through the East coast. In the comments it was noted that a bevy of other users across North America had also received alerts in the last few weeks. The messages are part of the Commercial Mobile Alert System / Wireless Emergency Alert (or CMAS / WEA respectively). This system is setup through carriers to broadcast alerts to users for sever weather, Amber alerts and presidential alerts. Keep reading as we look at just where these alerts come from and what makes them tick.

CMAS / WEA Explained

While some users assumed that these alerts are basic SMS, that isn't quite the case. The messages are part of the Cell Broadcast Service, which differs slightly from standard SMS. 

From Wikipedia:

Cell Broadcast is designed for simultaneous delivery of messages to multiple users in a specified area. Whereas the Short Message Service-Point to Point (SMS-PP) is a one-to-one and one-to-a-few service(requires multiple sms message, as each message can only carry one phone number), Cell Broadcast is a one-to-many geographically focused messaging service. Cell Broadcast messaging is also supported by UMTS, as defihttp://crackberry.com/node/add/blogned by 3GPP. 

Essentially CBS is a "one to many" service while SMS is a "one to one" service. CBS dedicates part of a given network to messages all the time. If an SMS were sent to everyone in an area for an emergency, it would eat up network resources and cripple it, thus rendering it useless (also why cellular data is better than voice). Having dedicated resources, CBS allows for messages to be sent to many users at any time while still leaving the network open for other data like email and phone calls.

The alerts are issued by the President of the United States and agencies such as the National Weather Service, FEMA, the Department of Homeland Security and the Telecommunications Industry Association.

Ultimately it's up to the carriers and regulators to decide what alerts are sent out to customers at any given time, and they will only be received by those who have devices that support CBS (most newer devices do). The alerts are sent to geographic locations based on the location data from your SIM or device.

In most cases you also have the ability to disable all but the Presidental alerts, so you can choose not to receive threat or Amber alerts. And if you're in Canada for example, you won't receive US Presidential alerts since you're not in the US.

Lastly - that annoying tone that accompanies the alerts? It's mandated by the carriers - right down to the tone frequency -- so unfortunately you can't change it. It's sure to get your attention though!

If you're on a newer device running OS 7+ you can access your emergency alert settings by clicking on the Emergency Alert Messages icon, the press the Menu key and choose Options.

Adam Zeis Adam Zeis "Mobile Nations Content Strategist" 3740 (articles) 2892 (forum posts)

Reader comments

Emergency broadcast messages explained


Weird, on my 9930 (recently upgraded to that leaked version with bundle nr. 1333) i no longer see Cell Broadcast in the menu.

Anyone know of an alternative place where to enable / disable this?

This is a wonderful feature to have, however no one has answered my question from last week; how come some received the alerts and others (like my wife and I) did not when based on the posts people share the same carrier and both had o/s7??? and yes my 9850 and my wife 9930 are both set up to receive all alerts. Also so are the "Regulators"??


You ask a wonderful question. I was wondering the same thing last week when a severe thunderstorm came through New York...that some received on T-MO and some didn't (like myself).

Exactly, my wife and I were traveling in the storm from Jersey Shore to our home in Queens and while I understand other Verizon customers receive alerts, neither of us received an alert.

Seems to me that if it's based on location, maybe it's somehow tied to the GPS and your phone didn't have a fix or location services weren't on. Just a guess

I would think it would not be tied to your GPS but to what cell tower you are attached to, this would be easier to find just the phone attached to the tower instead of having to find the phones via the tower, find their GPS position, then go back to the tower to send the message.

Today my wife (9930) and I (9850) received our first alerts from our carrier Verizon in New York. Alert came through once, short siren like notifier. All in all not bad. I differ with other bloggers, in case of an emergency the more information the better. Hoping everyone else is having positive results.

Best regards.

Today my wife (9930) and I (9850) received our first alerts from our carrier Verizon in New York. Alert came through once, short siren like notifier. All in all not bad. I differ with other bloggers, in case of an emergency the more information the better. Hoping everyone else is having positive results.

Best regards.

On the dumb question of the day>>> where is the Emergency Alert Messages icon? can't find it... :(

Anyone can help this techologically blinded guy?

Learn something new every day, very cool. I saw this on my phone and I never knew exactly what it was for until now. Thanks CB Adam!!

Gf has this on her new 9350 although she has never had a alert as of yet and we live in Baltimore Maryland were a bad storm tore stuff up just a week or so ago.

I can make an educated guess: Some cellular towers are probably misconfigured. If you are in a high coverage area, like a city or dense suburb, you could have two devices next to each other which could be on two different towers. If one of those towers is misconfigured to have cell broadcasts disabled, that would explain the phenomenon you and other observed.

I think this is a great idea, and more countries should adopt it and make it mandatory. We don't carry televisions, or FM radio with us at all times. But we sure do take our phone everywhere we go. Plus, for most people, myself included, their phones are on 24/7. Of course there has to be law so that the government don't misuse the system for propaganda.

Great idea, but worthless to me right now since it isn't functioning in Louisville or Southern Indiana area. Probably they are still in the implementation process and it hasn't hit the good old midwest, yet.

i've never received one of these so i wouldn't know... what is the battery meter app on the notification bar?

Annoying tone is putting it lightly. Had just reached the edge of the first storm in MA, hail, wind, end of days look to the sky and then the tone! Had no idea where it was coming from at first, thought the car had been hit by lightning.

I am with Rogers wireless (Canada) I do nt see the icon in my menu. Is this active in canada? If someone knows how to access this please let me know.

If I remember correctly, you have to have your sound profile set up a certain way as well in order to get these messages, at least the tone.

I've got this feature on my phone, but it's yet to go off, as we've not really had any bad weather here recently to trigger the EAS system which in turn would trigger these messages.

It may have something to do with where the phone thinks you are as well.

i got at least 10 of these the last time there was a storm, the same message sometimes within seconds of each other. disabled.

great , just what i need when travelling to the US. idiots like FEMA telling me there is an impending disaster assuming I don't know how to get a weather forecast or another idiot like US President Obombya clogging up my inbox.

This site is suppose to be about technology and apps not disrespect. so Mr or Ms. Crazy Canuck you do not have to come to the U.S.A., you can uncheck the alert services on your BlackBerry, but respect our country and our presidents, whether it Washinton, Adams, Jefferson, Lincoln, Johnson, Roosevelt, Wilson, Truman, Kennedy, Reagan, Bush, Clinton, etc. and Yes our current sitting President Mr. Barack Obama (All 44 of them).

In northern virgina, both my 9930 and my bionic went nuts at the same time. Never mind the numbnuts naysayers, this is a GREAT feature for phones to have.