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CPA / TCPA Alarm 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
In the system, targets are categorized into two types: tracked / activate AIS targets and dangerous targets. 
The grade of danger can easily be recognized on the display at a glance. So the officer can easily decide which 
target he should pay attention to. 
The types of target and alarm are shown below. 
 
 
CPA / TCPA Alarm 
 
Status  Symbol on display  Alarm characters  Alarm sound  Conditions 
Dangerous target 
 
 
 
 
 
 
 
 
 
 
Red blinking 
CPA / TCPA 
Beep sound 
(pee-poh)   
Alarm 
acknowledgeable
 
x  CPA d CPA LIMIT, 
x  0 d TCPA d TCPA LIMIT 
 
An alarm is issued when all the 
conditions are met. 
The AIS targets that issues 
alarm refer to Section 5.1.5 
“Setting Collision Decision 
Criteria (CPA/TCPA Limit)”.
 
CPA Limit and TCPA Limit: The Setting Values 
12 
AIS12 
Since  these  alarms  may  include  some  errors 
depending on the target tracking conditions, the 
navigation officer himself should make the final 
decision  for  ship  operations  such  as  collision 
avoidance. 
Making the final navigation decision based only 
on  the  alarm  may  cause  accidents  such  as 
collisions. 
Caution