10.Appendix
10-9
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.
10) The revision counter is the main method to follow up-to-date status. Revision counter is
also unique for each instance of alert. Revision counter starts with 1 and the step for
increment is 1. The count resets to 1 after 99 is used. Revision counter increments on each
change of content of any field of the alert.
11) The escalation counter is presenting the number of alert escalations after time expiration
during the state active-unacknowledged. The escalation counter starts with 0 and the step
for increment is 1. The count resets to 1 after 9 is used. The alert escalation can be the
escalation from warning into warning (activation of audible signal only), the escalation from
warning to alarm or the escalation from alarm to alarm with activation of backup navigator
alarm.
12) This field is used for Alert title which is mandatory and for additional alert description which
is optional.
• The first ALF sentence transmits the Alert title. Alert title is maximum 16 characters short
form of the alert text.
• The optional second ALF sentence transmits the additional alert description. Additional alert
description is the long description of the alert. The additional alert description contains more
information for decision making (i.e. alert description text).
• The second ALF sentence uses null fields for Time of last change, Alert category, Alert
priority, and Alert state to allow longer text. The actual number of valid characters should be
such that the total number of characters in a sentence does not exceed the “82”-character
limit.
• Some equipment standards specify alert text longer than 16 characters (for example the
AIS standard has defined some alerts to be coded with ALR sentence and with text longer
than 16 characters). In such cases the first ALF sentence is used for the first 16 characters
of the alert text as alert title and the second ALF sentence to carry the full alert text.
10) ARC – Alert command refused
$--ARC,hhmmss.ss,aaa,x.x,x.x,c*hh <CR><LF>
1 2 3 4 5
1: Time 1)
2: Manufacturer mnemonic code 2)
3: Alert identifier 3)
4: Alert instance, 1 to 999999 4)
5: Refused alert command, A, Q, O or S 5)
Note;
1) Release time of the Alert Command Refused. (e.g. for VDR purposes), optional, can be a
null field. Sender is allowed to use all alternatives defined in Table 5 Field type summary.
Receiver is allowed to ignore content of this field. If receiver does not ignore this field it
should support all alternatives defined in Table 5 Field type summary.
2) Used for proprietary alerts defined by the manufacturer. For standardized alerts this should
be a null field.
3) The alert identifier is unique within a single alert source. The alert identifier is a variable
length Integer field of maximum a 7-digit integer. It identifies the type of the alert, e.g. a “lost
target” alert. Standardized alerts use unique alert identifiers described in equipment
standards. Number range 10000-9999999 is reserved for proprietary alerts. Alert Identifier
examples: “001”, “2456789”, “245”
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