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2. RADAR OPERATION
2-42
2.25.8 CPA/TCPA alarm (ARP)
When the predicted CPA of any target becomes smaller than a preset CPA
alarm range or its predicted TCPA less than a preset TCPA alarm limit, an audio
alarm sounds, which you may silence with the [CLEAR] key. In addition, the
target plot symbol of the offending target changes to a triangle and flashes
together with its vector. Press the [ALARM] key and the message COLLISION
ALARM appears. Press the CLEAR ALARM soft key to acknowledge the alarm.
The flashing of the triangle plot symbol continues until you intentionally terminate
tracking of the target. The ARP continuously monitors the predicted range at the
Closest Point of Approach (CPA) and predicted time to CPA (TCPA) of each
target to own ship.
Provided that this feature is used correctly, it will help prevent the risk of collision
by alerting you to threatening targets. It is important that gain, A/C SEA, A/C
RAIN and other radar controls are properly adjusted and the ARP is set up so
that it can track targets effectively.
CPA/TCPA alarm ranges must be set up properly taking into consideration the
size, tonnage, speed, turning performance and other characteristics of own ship.
CAUTION
The CPA/TCPA alarm should never be
relied upon as the sole means for detect-
ing the risk of collision. The navigator is
not relieved of the responsibility to keep
visual lookout for avoiding collisions,
whether or not the radar or other plotting
aid is in use.
Follow the steps shown below to set the CPA/TCPA alarm range:
1. Press the [MENU] key followed by the ARP SETUP soft key.
2. Operate the cursor pad to select CPA.
3. Press the EDIT soft key to show the CPA window.
CPA
▲
▼
OFF
0.5nm
1nm
2nm
3nm
5nm
6nm
CPA window
4. Select a CPA limit desired by the cursor pad.
5. Press the ENTER soft key. The ARP SETUP menu reappears.
6. Press the cursor pad to select TCPA.
7. Press the EDIT soft key to show the TCPA window.