[EAS] Differences between EAS units

[Sean Donelan]

Inter-station signalling and programming content have been a challenge
for every warning system, including EAS, EBS, etc.

Most EAS boxes try to do something reasonable with corner cases, but
interoperability can be interesting when they choose different reasonable 
options.

Overlapping and preempting of in progress EAS messages is stated in the 
FCC rules, but what actually happens at the protocol level on different
boxes?

   How should the message in progress be aborted at the protocol level?

   How do you detect that a mesage was incomplete because it was aborted?

   For example, in the middle of a TOR message from the NWS you receive a 
EAN header from an EAS box installed in series at the NWS transmitter to
relay local area alert messages.

   For example, in the middle of an EAN from a PEP you receive a RMT header 
(i.e. lower priority).

   For example, in the middle of an EAN from a PEP you receive an EAT or 
another EAN (i.e. similar priority).

What is the minimum delay between consecutive EAS messages?  How 
do you handle multiple messages on the same or different monitoring 
sources received while an EAS message is pending or in progress?

   For example, if immediately after the EAN ends (EOM) but before the 
message is completely relayed, you receive another EAN header on the same 
or different monitor source?  A corner-corner case of overlapping 
messages.

Handling station and hardware failures was specified in the EBS rules but 
not in the automation EAS rules.

   If a station is off the air when an EAN arrives, how should it sign on
the air while the EAN is in progress?

   If more than a few minutes have passed and missed the beginning of the 
EAN?

   If the EAS boxes reboots when it originally tried to relay the EAN, can 
it resume relaying the EAN?

   If a station has a hardware problem during an EAN, how should it 
sign-off the air so downstream monitoring stations switch to another 
source?

If the audio or carrier is lost in the middle of an EAN message before
an EOM, or another monitor source just has a better quality signal, how 
would to switch between EAN sources?