Humminbird 748 3D Operation Manual page 17

about the area under your boat, including the following items:
Bait Ball
Hollow Fish Symbol (see Fish ID+™)
Thermoclines - Layers of water with different
temperatures that appear at different depths
and different times of the year. A thermocline
typically appears as a continuous band of gray
levels moving across the display at the same
depth.
Structure - Where fish may be hiding.
Fish - The Fishing System displays fish as
arches and/or fish icons, and can be set to
alarm when a fish of a certain size is
detected. When a target is detected, a Fish
ID+™ symbol appears on the display with
the depth displayed above it. The size of the
symbol indicates the intensity of the sonar
return. The unit will clearly show schools of
Bait Fish as "clouds" of different shapes and
sizes, depending on the number of fish and
boat speed.
Active Cursor
RTS (Real Time Sonar) Window™
Battery Voltage - The voltage of the boat's
battery. It can be set to alarm if the voltage
falls below a certain point.
either device is connected to the Fishing System. If both devices are connected, then only
9 What's on the 2D Sonar Display