Glad the info is helpful. I think the system has good potential as another way to get alerts out there if people miss other, traditional channels. Although, if the lines to your local tower are taken out by a tornado, I would hope the alerts go out long before that!

To answer your question, first you have to know about the types of messages that can be sent. The spec uses 30 total message identifiers, which fall into groups such as Presidential, Imminent-Extreme, Imminent-Severe, AMBER, Test, and Reserved. These 30 identifiers are consolidated into these groups before being presented to the user. This is a bit of a simplification, but you can probably get the general idea. The specification says that by default, phones will be subscribed to all alerts, but that they can opt-out of everything except presidential alerts. So maybe this is a small step towards Big Brother, but at least it is one way only! :)

I'm not 100% sure of how the Australian system works, but according to this site it appears to be based on text messages and uses locations based on the billing addresses? It sounds similar in concept but quite a bit different in implementation.

I have no idea how often messages would be sent out using this new system, but the existing emergency alert system on TV is probably a good indicator. This new system does allow for federal, state, and local agencies to send alerts, so I could see the possibility for some abuse. Thankfully, you can turn off almost all the alerts, so this shouldn't be a problem in practice..

I think this is possible; it should be up to the handset vendor to allow for things like this. The spec allows for users to opt-out of things like AMBER alerts, but I could foresee "opt-out" interpreted as "still receive message but don't alert". The spec also allows the message reception on the handset to respect the current volume level -- if you're phone's on silent, you wouldn't hear the tone, for example (it's debatable whether or not this is a good idea!).

In any case, you can opt-out of every alert type except one - Presidential-level alerts. I suppose that if Obama wants you to hear about something, you don't have a choice :)

Yes, that's part of the CBS specification and and the emergency system uses this as well. The messages are broadcast for a set amount of time at a set repetition rate. They also contain serial numbers so that the handsets can distinguish between old and new messages. There is also a provision for sending updates to messages which have already been transmitted.

I'm not sure how granular it will be in practice, but it could technically get down to the individual cell level. Most likely, the carriers know which cells approximately serve which zip codes and would group based on that. The specs don't say exactly how this should be done, except that the "Cell Broadcast Center" should determine the affected cell sites for the geolocation (geo-code, polygon, circle) of the emergency message.

There really isn't much documentation which is publicly available. Here are a few things, although they're short on real details:
Announcements: FEMA FCC CTIA
Standards (paywalled): ATIS 0700006 Joint ATIS/TIA J-STD-100

Sorry I don't have links to the actual specifications content. For some reason, you have to be a member company or pay for them.

I should have referred to the system by its proper name -- in the U.S., it's called the Commercial Mobile Alert System (CMAS). There are similar systems being set up in other countries which closely follow the U.S. specifications, and those systems should be compatible with CMAS (at least that's the plan).

I'm actually working on the handset side of this, so I can answer some of the questions people have about it.

It's really not that complicated of a system. It uses Cell Broadcast Services (CBS) which are part of the existing 3GPP and 3GPP2 standards. Some of you may have seen CBS applications in your phones, but they're typically not used in the U.S. CBS is, as its name implies, a broadcast service.. so obviously it's one-way only. If your phone isn't "subscribed" to the particular message identifier (a kind of topic or category), or your phone isn't on when the message is broadcast, you'll miss it. The system has different classifications for messages, from nationwide alerts, to local alerts (like hurricanes), to AMBER alerts. There can't really be any way for operators to charge for broadcast messages, any more than they can charge for other broadcast resources like paging channels, so I think the only way your bill would be affected would be if they do some blanket 10 cent "government" fee for everyone... By the way, the reason they are using CBS is because it does not place a strain on the network, like sending millions of SMS messages at once would (that's important in a disaster situation when people might be overloading the network).

The special handling on the handset side is to take some specific actions when an emergency message is received.. it has to play a special tone and vibration, among other things. You can opt-out of pretty much all messages, so don't get too worried about being woken up in the middle of the night for AMBER alerts (well, unless you want to receive them). The system supports a monthly test message, but you wouldn't be opted-in to those by default.

The nature of the cell network allows operators to broadcast the messages to specific cells, so you are not going to get alerts for things happening elsewhere in the country. But the design also allows for national (presidential-level) distribution, so yes, in those cases, everybody would get the alert. The network-side of things is more interesting than the handset side, because of how different levels of the government need to be able to send alerts, and this is mostly what the article talks about (although it's short on details).

If you have other questions, reply and I can try to answer them.

I just posted some info on the article:

Maemo 5 default browser on the Nokia N900 (MicroB):
Acid3: 93 / 100
Sunspider Java: 36722.0ms +- 1.5%

It also has full flash support with no jerky playback. Not too bad, and in my opinion it's pretty fast for browsing (if you have 3G or WLAN). Acid3 results make sense because it has a similar engine as Fennec. I just installed the latest Fennec on my N900 and it is a really nice browser, too. Here are its results:
Acid3: 94 / 100
Sunspider Java: 18899.4ms +- 5.5%

I think it's important to count extensibility into the mix as well... I have Adblock Plus installed on my N900 for MicroB and that speeds up browsing a lot!

Roll down the windows? :)

The sad thing is that this excerpt comes from the "features" section of that page. Who wants to be able to run only 3 programs as a *feature*?