When executing a command, the keyfob's LED blinks
red once to indicate transmission of the command to the
control panel. If the operation is successfully
completed, the green LED lights momentarily and a
"success tune" is heard. If the operation fails or
cannot be completed, for example, when the system
is "not ready", the red LED lights steadily and a "failure
tune" is heard
,
see KF-234 PG2 User's Guide,
“Panel Response to Keyfob Commands” section
3.2.