1
$\begingroup$

When I was watching television, especially when I was younger, I sometimes heard a loud noise, followed by either a test message, or a genuine emergency broadcasts, like an Amber alert.

The first signal sounded like short bursts of packets, which usually lasted around 1100 ms. Then there was another 1100 ms pause, and then it would repeat an additional two or three times. Sometimes these bursts are shorter, like around 300 ms long, but the pause is about the same length. Most of the time I would also hear a combination of 853 Hz and 960 Hz tones. I am assuming this is the attention signal.

Since this was before June 12, 2009, I was using over the air analogue television, also known as the national television standards committee (NTSC). Also, I think the encoded marker is also known as a tail preamble.

  • What devices are able to read these messages and display them as text?
$\endgroup$
  • 1
    $\begingroup$ A minute of googling for NTSC "EAS SAME" yielded this list of SDR software with some supporting EAS/SAME. $\endgroup$ – Marcus Müller Feb 19 at 21:51
  • 2
    $\begingroup$ Could probably edit the question, but after looking at that list, it didn’t really help much. I guess I’m tired of wondering if it is there to help people who cannot hear, like the deaf and hard of hearing? Are there any physical hardware devices that can read that’s fitting? $\endgroup$ – HeavenlyHarmony Feb 20 at 0:17
  • $\begingroup$ Well, as said, an SDR + Software can do that. $\endgroup$ – Marcus Müller Feb 20 at 10:46
4
$\begingroup$

Yes, what you are hearing is digital data encoded into the audio stream. These can be decoded by devices that understand the digital data, such as a dedicated weather radio like this one that came up in an Amazon search:

enter image description here

The audio signal does catch the attention of people because it sounds kind of like a warning buzz. But that is a secondary benefit, its primary purpose is to transmit the digital information about what kind of weather alert is coming up where.

$\endgroup$
  • $\begingroup$ Do the NOAA stations broadcast all the same alerts as TV stations, or is it limited to weather events? $\endgroup$ – mrog Feb 20 at 18:52
  • 1
    $\begingroup$ @mrog: I believe EAS is normally all the same alerts. Note that the alerts themselves have location information encoded in them (by county), so a dedicated receiver can be programmed to be more specific than a TV station (which will show alerts for all counties that can receive the broadcast). $\endgroup$ – Greg Hewgill Feb 20 at 18:55

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.