The news has crept out and, finally, dribbled into the more-worriable Right: Uncle Sam's gonna try to blow the dust off the national-level mechanisms of the Emergency Alert System, with a test of three-and-a-half minutes duration. It's only that long because they're concerned the three-minute audio buffer in some units may not fail gracefully and they want to find out.
That might not be the headline you saw; the examples I have seen range from "One Man Can Shut Off U.S. Broadcasting?" and escalate from there.
I'm usually pretty coy about what I do for a living but let's just say -- 'cos it's true -- that I have been in virtual attendance at every FEMA teleconference for this test and I know how the hardware works; I've installed a dozen of the things over the years. (They're commercially made by 5 or 6 companies, by the way; Uncle Sam just defines the alert tone and data bursts. You could look up the dope in 47CFR, Parts 70-79 and build your own -- but why?)
At the most invasive, EAS hardware can include an "interrupt box" that grabs the audio going to the transmitter. That's all the control it's got; the station could beat it with a patch cord or, at worst, a pair of side-cutters.
But it hasn't even got that much control; the devices can be operated in "automatic" or "manual." Most are kept in manual because in automatic, when they get an alert for their area or a relayable test, they do just "take over," no matter what might be on the air, even commercials. This is not what you would call acceptable, if those commercials paid your salary, and unless the station is low-budget or had ijits at the controls (hey, they work cheap!), it's better to run the EAS box in manual; then when tests or alerts come in, only the d00d in the control room hears them and, at the end of that commercial or hot hit tune, he or she pushes the magic "manual forward" button to play it on the air. (So why is the magical interrupt box even there? Sometimes it isn't, but however things are wired up, part of the EAS message is a databurst that carries the specific event code and location, and it works best if it gets sent at the proper volume; relying on that d00d or d00dete to set the volume level...not always the best idea).
So there's your "Federal control" at the last step before end-user level. Let's back up and see how Uncle Sam pushes his diabolical red button!
Turns out there is some Sooper Sekrit Stuff here but after you've read about it, you may see why. The FCC decided -- based on EMP studies and a lot of experience -- that the entire country can be reached via a few dozen powerful AM stations. They picked 'em and gave them some kind of multiple-redundant link back to Washington; one path is via satellite but it's not the only connection and the details are not public. All it carries is the same EAS info any other link in in system carries: voice-grade audio, with an alert tone and databurst, and it talks to the same kind of interrupt box, which, yes, is in automatic mode. Yes, there's your Big Red Button and that is all it does -- if it even does that; that part of the system has never been tested on the air. The feds are indeed cagy about their links to these AM stations; they use their own security protocols, it's not on the Internet -- and I don't blame 'em. If that got hacked, it would be a huge mess -- or at least awkward; the one mistaken activation known was at a single station, quickly caught, and wasn't a problem.
...And why wasn't it a problem? Because the next stage is a whole bunch of other stations, with their own guys at the controls, who looked at the incoming message, compared it to reality (gee, nothing on the newswires, nothing on the network feed, nothing on the Internet) and stifled it. You still don't want it happening every time some code kiddie in Duluth gets bored, which is why our Uncle Sam ain't talkin' about the details.
Downstream of the few dozen AM stations, it's all open-source. There are no hidden links, no hidden codes, nothing; it happens over the air where anyone can hear it. If the government -- Federal, State or local -- abused the EAS system, they'd get massive non-compliance; they are counting on actual voluntary compliance, thousands of individuals of all stripes, all across the country, each one of whom decides if they will push that button or not.
The fed.gov ain't "takin' over" anything -- because they can't.
Personally, I'd advise you to listen to your $PERSONAL MUSIC PLAYER unless the weather looks bad. Or the to Internet.
4 weeks ago