Alarm Functions (Alm Mode); Off-Course Alarm; Border Alarm - Furuno LC-90 Owner's Manual

The Time To Go (TTG) is the amount of time necessary to get to the
desired destination if the present VTD is maintained. TTG is obviously an
estimate, since in the case of a sailboat a series of tacking maneuvers is
usually necessary in order to get to a location, and in the case of a
powerboat the effects of wind and current are usually not constant over a
voyage.
Unlike the Cross-Traek-Error function, the VTD/TTG functions don't
require both a starting and destination waypoint location; only a destination
(Waypoint To) waypoint is needed. However, in the case of a powerboat
especially, the XTE/AC and the VTD/TTG functions are usually used
together, The operator uses the XTE function for instantaneous
information to monitor the short-term deviation from his intended track, and
the VTD and TTG for a long-term evaluation of the progress towards his
destination. Thus it is a good idea to define both a "Waypoint From" and a
"Waypoint To" for VTD/TTG functions as well as for the XTE/AC functions,
using the NAV Mode.
The VTD is displayed in units of nautical miles per hour (knots), and the
TTG is displayed in hours and minutes, up to a maximum of 99 hour s, 59
minutes. Presuming that you have set up a "From" waypoint of 55 and a
"To" waypoint of 56, the display screen below might be typical of what you
would see when you call up the VTD Mode.
Fig. 26 VTD Mode Screen
VTD
ALARM FUNCTIONS (ALM Mode)
There are four conditions that can trigger the audible and visual alarms in
the LC-90: an Off-course alarm which warns you that the Cross-Track
Error has exceeded a preset value; a Border Alarm which warns that you
are approaching too close to the border of an unauthorized zone (such as
the border of another country); an Arrival alarm to signal that you have
arrived near a destination waypoint; and an Anchor-Watch alarm which
warns that the boat may be dragging its anchor. For each of these
functions the operator may preset the limits he wants to work with.
Fig. 2 7 ALM Mode Screen
ALM
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Fig. 27 shows a typical ALM display. The present position is displayed on
the upper two lines. The "ON" or "OFF" on the third line indicates
whether the unit is preset to sound an audible alarm or not. This status
can be changed by using the key sequence of I CLR] 1 + /- I jENT] . The
value for the "Off-Course" or "Border" alarm is entered on the fourth line,
and that for the "Anchor Watch" or "Arrival" alarm is entered on the fifth
line. (A limit of 0.00 means the alarm is off.)
The alarm will sound when the boat crosses the preset alarm zone from
inside or outside. The "In" and "Out" on the bottom two lines indicate
which direction is preset for the alarm function. "In" indicates that the
alarm will sound if the vessel ventures into the area, and "Out" indicates
that the alarm will sound if the vessel ventures outside the desired area.
If an alarm is activated, a visual alarm indication ("WCH" and/or "XTE")
will also appear at the top of the display.
Off-Course Alarm (ALM Mode):
The Off-Course alarm is used when the Cross-Track Error function is being
vised. You may preset the alarm limit from 0.00 n.m. (i.e., the alarm is
disabled) to a maximum låne width of 20 n.m. (that is, 9.99 n.m. each side
of låne center). The Off-Course alarm will sound if you go out of the låne
limits.
For example, the touchpad sequence to use to enter a låne limit of one-half
nautical mile is:
1. Select the fourth line by pressing ^ .
2. Press [CLRi .
3. Confirm that "OUT" is displayed next to the message "XTE". If not,
press ] +/-1 to change the display to "Out."
4. Type [0] tU |ENT| .
Border Alarm (ALM Mode):
The Border Alarm is used when you wish to define, between two waypoints,
a line that you don't wish to cross. The alarm will sound when the boat
comes into the hatched area as shown in the figure below.
For example, assume that you want to draw a line between Waypoints 7 and
8 and that we want to be sure you don't come doser than 1.5 n.m. to
that border. Once you are in the ALM Mode, the touchpad sequence would
be:
1. Select the fourth line by pressing ^ .
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