Furuno BB FAR28x7 - Manual (Page 157)

3. ARP OPERATION
3-25
When an ARP or AIS target violates the guard zone, the message “GUARD”
appears (in red) at the right side of the display and the offending target is
marked with an inverted triangle. Further, the AIS display is automatically turned
on.
Note 1: If you wish to create a guard zone having a 360-degree coverage
around own ship, set point B in almost the same direction (approx. ±3°)
as point A and then push the left button.
Note 2: If the range scale is changed to less than half of the guard zone, the GZ
box reads “GZx OUT.” If the left button is pushed in this state, the guard
alarm zone goes into “sleep” state and the guidance box reads “GZ
WORK L = DELETE.”
Note 3: The default guard zone is fan shaped. It may also be a polygon having
3-10 points. For details, see paragraph 3.13.5.
Note 4: Two more alarm zones (No. 1 and No. 2 Guard Alarm Zones) may be
added in addition. This means a maximum 4 alarm zones are available
at a time. ARP symbols are not changed to inverted triangles in the
guard alarm zone, only those in guard zone do so.
3.13.2 Sleeping, deactivating a guard zone
1. Roll the trackball to choose the appropriate GZ box.
2. Sleep or deactivate the guard zone as appropriate:
Sleep guard zone: Push the left button momentarily to remove the guard
zone from the screen. The indication in the GZ box changes from “GZx
WORK” to “GZx SLEEP.” To reactivate and display the guard zone, repeat
this procedure to display “GZx WORK.”
Deactivate guard zone: Push and hold down the left button until the GZ box
goes blank.
3.13.3 Acknowledging the guard zone alarm
To acknowledge and silence the guard zone audible alarm, press the [ALARM
ACK] key, or choose the ALARM ACK box and then push the left button.