[EAS] EAS time stamp usage

[Harold Price]

Sean,

The comment you referenced points out an area that needs further 
discussion.  It isn't entirely correct in its interpretation of the 
existing Part 11, however.

That comment makes a lot of references to "time of transmission".  In 
fact, Part 11 contains the string "time of transmission" only once, 
in 11.44(c):

"Key EAS sources (NP, LP, SP and SR) and Participating National (PN) 
sources that remain on the air during a National emergency must carry 
Presidential Messages "live" at the time of transmission or 
immediately upon receipt. Activation of the National level EAS must 
preempt State and Local Area EAS operation."

Part 11 doesn't further define time of transmission, and doesn't link 
it to JJJHHMM. Common sense would define it as "when it was 
sent".  Immediately upon receipt is also pretty clear.  It says 
nothing about holding on to it until the JJJHHMM time occurs, or 
appears to occur, at the receiving site.

My interpretation of Part 11.44, and in fact any alert, is it becomes 
sendable when received, if it passes all the other rules.  JJJHHMM is 
used to show the effective time and the ending time (for the canned 
text), but it isn't a "hold for release" time.  Nowhere does Part 11 
call for, or even hint at, using JJJHHMM to queue alerts for later 
transmission.

One might ask if there is a "rule" saying when an alert is 
valid.  There are passages about displaying the valid time for a 
message, but nothing about holding it for transmission until it is 
valid. There are only discussion about valid and invalid messages, 
not messages that might become valid in the future. Also note that 
Part 11 is derived from the NWS SAME protocol, they have even more 
types of time.  A tornado warning can be issued for 2pm until 
4pm.  The warning can be transmitted at 1:00pm.  Is it reasonable to 
wait until 2pm to put it on the air? Of course not.

In the real world, clocks drift.  Even today, you can have an EAS/CAP 
device at a remote location with only a one-way link to deliver CAP 
messages, and no local time standard.  Sage (and some other vendors) 
allow for some clock drift when comparing the time at the receiver 
and the time at the originator.  The fuzz time isn't standardized, it 
could and should be.

Comments about some vendors "ignoring" JJJHHMM are a little 
overstated.  A little fuzz isn't the same as "ignoring JJJHHMM".

The EAS/CAP industry, FEMA, and the FCC do need to nail down these issues.

Regards,
Harold Price
ECIG and CSRIC member

At 10:58 PM 12/18/2011, Sean Donelan wrote:
>A comment was submitted to the FCC about the usage of the EAS time stamp
>field (JJJHHMM) in the EAS protocol.
>
>http://fjallfoss.fcc.gov/ecfs/document/view?id=7021750843
>
>The comment does a good job covering a lot of time issues.