[EAS] The Daisy Chain

[Harold Price]

Dave,

This time, not as close as you usually are.

The Sage ENDEC has always worked as I describe below, back to the 1996 release of the 1822.

Once two of the three headers in an alert have matched each other, and the ENDEC has decided that this alert is eligible to air (not log -only or no matching filter), then it turns on its recorder and also starts looking for the two-tone signal or the 1050 hz signal.  If it is detected, then the recorder is "rewound" and restarts once the signal goes away (with a small debounce capability for a short dropout).  There is a  maximum  time the ENDEC looks for the signal until it assumes there isn't one (it is longer for an NWS input), and a maximum length of tone it is willing to believe.  After the above, alert sequence proceeds.

Takeaways:
1) We don't require the attention signal to record audio - if it is present and detected, it is removed.
2) Only the first tone is removed.  If the upstream station sent two attention signals, then you will relay two signals,- the first is removed and regenerated, the 2nd is included as part of the recorded audio.  If the upstream station's tone was not detected, or more than one was sent, then the 2nd attention signal (s) will be present in the ENDEC's logged audio, you will hear it if you click play or download.
3) The attention tone filter threshold is a settable parameter, see the levels tab.  It should be around 7.  Anything higher can lead to not detecting a noisy tone.

As Dave said, an attention signal that is clipped or distorted, or has noise or dropouts, or is way too low, will not be detected.

Harold

On Mon, Aug 16, 2021 at 6:33 PM Dave Kline dklinefmtv at gmail.com wrote:
As I recall, from my busted old memory, SAGE boxes need the two-tone attention signal or they don't record the audio message. (Even less sure how the other guy's boxes work.) Something about the end of two-tone triggers the recording??? (Lots of question marks.)
And again, for SAGE (and maybe the others) the incoming two-tone level needs to be within a certain range.
If it's too hot it gets distorted and doesn't get decoded as the two-tone attention signal. Same with being too low???
-Was I even close Harold?-