JRC JFE-400 Instruction Manual page 101

4) The alert instance identifies the current instance of an alert to distinguish alerts of
the same type (Alert identifier) and from the same source (e.g. dangerous target).
Alert instance is maximum a 6-digit integer from 1 to 999999, the number '0'
indicates that the command is intended for all alert instances. Except for number
'0', the number of alert instance can be freely defined by the manufacturer as long
as it is unique for one type of alert (alert identifier). It is not permitted to modify the
alert instance within a life cycle of a distributed alert (from 'active and
unacknowledged' state until 'normal' state is reached). It can be also a null field,
when there is only one alert of that type.
5) This should not be a null field
acknowledge: A
request / repeat information: Q
responsibility transfer: O
silence: S
6) This field should be "C" and should not be a null field. This field indicates a
command. A sentence without "C"is not a command.
7) ACK – Acknowledge alarm(Legacy Alert sentence)
$--ACK,xxx*hh<CR><LF>
1
1: Unique alarm number (identifier) at alarm source.
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10.Appendix