Furuno FR-1500 MARK-3 Series User Manual page 74

2.11.3 Guard zone alarm
When a target comes in a guard zone, the audible alarm comes on with the visual indication
GUARD ZONE. The intruding target is denoted by an inverted triangle mark. If the target leaves
the zone, it changes to a normal tracking symbol (O).
You can set the guard zone as follows:
1. Press the [MENU], [7], [7] to display the PLOT menu.
2. Press the [0] key twice.
3. Press the [3] key to select GUARD ZONE.
4. Press the [3] key again to select SET and press the [ENTER/SELECT] key.
5. Set the cursor on one boundary of the guard ring and press the [ENTER/SELECT] key. Set
the cursor on the other boundary and press the [ENTER/SELECT] key.
The default (setting at switching on) Guard Zone covers 3.5-4 nm in a sector ±45° of the heading.
The range and sector of the GZ may be adjustable to cover full 360° as selected by the operator.
To disable the guard zone, select OFF at step 4 in the above procedure and press the
[ENTER/SELECT] key.
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