Furuno FR-8111, FR-8251 manual Watch Alarm, Echo Average, 25 How to set the guard alarm

Guard zone to set

A D A

B C

Set cursor on point A (or B) and

(1)press GUARD ALARM.

(or GUARD2)

GUARD1

IN

(or OUT)

Press

GUARD

ALARM.

(4)

Guard zone

(or GUARD2)

GUARD1

SET

(2)

(or GUARD2)

GUARD1

SET

Set cursor on point C (or D).

(3)

1.29 Watch Alarm

The watch alarm works like an alarm clock, sounding an aural alarm and blinking a visual indication "T ALM" at the predetermined time interval. When the alarm sounds, you can silence it by pressing the AUDIO OFF key.

You can select time interval (3 min, 6 min, 12 min, 15 min, or 20 min) on the TIME ALM menu.

1)	Press the MENU key.
2)	Select the TIME ALM menu.
3)	Press the ENTER/SELECT key.
4)	Select TIME ALM and press the ENTER/SE-
	LECT key.

Figure 1-25 How to set the guard alarm

Note: When the radar range is less than one half of the guard zone range, the guard zone disap- pears and the indication of active guard zone (GUARD1 or GUARD2) appears in highlighted video. If this happens, raise the range to re-display the guard zone.

Silencing the aural alarm

When a target violates the guard zone, the target flashes and the aural alarm sounds. You can si- lence the aural alarm by pressing the GUARD ALARM key. When this is done, ACK replaces IN (or OUT). This means the aural alarm is tem- porarily deactivated; but, the target still flashes. Press the key again to reactivate the alarm.

Canceling the guard zone and guard alarm

Press and hold down the GUARD ALARM key about two seconds until the guard zone disap- pears.

5)	Select time interval (or OFF).
6)	Press the ENTER/SELECT key.
7)	Press the MENU key.

1.30 Echo Average

The echo average feature effectively suppresses sea clutter and other random noise. Echoes re- ceived from stable targets such as ships (if not moving at high speeds) appear on the screen at almost the same position every rotation of the antenna. On the other hand, unstable echoes such as sea clutter appear at random positions.

To distinguish real target echoes from sea clutter, this radar performs scan-to-scan correlation. Cor- relation is made by storing and averaging echo signals over successive picture frames. If an echo is solid and stable, it is shown in its normal in- tensity. Sea clutter is averaged over successive scans and reduced in brightness. This makes it easier to discriminate real targets from sea clut- ter.

To properly use the echo average feature, first properly suppress sea clutter with the A/C SEA control and then select echo average function as follows;

How to turn on echo averaging

1)Press the MENU key.

2)Select the ECHO SIG menu.

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