Using Alarms - Raymarine DSM250 Owner's Handbook Manual

6-8
MULTI GAIN
MANUAL
15%
STC

Using Alarms

ALARMS MULTI
Setting a low value produces wide band for the weakest color, but
a small signal band for the other colors; setting a high value gives
a wide band for the strongest color, but a small signal band for the
other colors.
Note: On a color LCD, the sounder also provides a COLOR THRESH-
OLD control to reduce the number of colors displayed. Use COLOR
THRESHOLD with COLOR GAIN to determine how echoes are displayed.
The DSM250 provides automatic or manual COLOR GAIN adjust-
ment. Automatic adjustment displays colors based on current con-
ditions, with as many colors as possible, while minimizing noise
and clutter. As conditions change the auto-color gain adjusts. If
you select manual adjustment, you will need to re-adjust the gain
as conditions change.
STC
STC (Sensitivity Time Control) reduces surface clutter by reducing
the gain in the top 100 ft of the display. This function is useful for
reducing noise (caused by air bubbles and floating debris) that
often appears in shallow water. A low STC value has little effect on
gain in shallow water; a high STC value decreases the gain in shal-
low water so that only the strongest echoes are displayed.
Although you can manually set the STC level, Raymarine recom-
mends letting the sounder module choose the proper level for you
by selecting AUTO STC. Automatic STC mode takes advantage the
hardware's advanced DSP technology, which typically achieves a
sharper image in auto mode than is possible in manual mode.
STC is not available in Sonar Simulator mode.
The ALARMS key is used to set up alarms; three alarms are avail-
able to alert you of fish, shallow water, and deep water. Each
alarm can be toggled ON and OFF and you set the depth at which
shallow and deep water alarms are triggered: ranging from
2–3000 ft (or 2–4900 ft for high performance transducers).
You may want to use the shallow and deep water alarms when you
are anchored. Set the limits to just above and below your anchor
depth; the sounder triggers an alarm if the anchor drags and the
boats moves into shallower or deeper water.
DSM250 Digital Sounder Module