Humminbird 300 SERIES 345C DI - Manual (Page 11)

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How Sonar Works
Sonar technology is based on sound waves. The 300 Series™ Fishfinder uses
sonar to locate and define structure, bottom contour and composition, as well
as depth directly below the transducer.
Your 300 Series™ Fishfinder sends a sound wave signal and determines
distance by measuring the time between the transmission of the sound wave
and when the sound wave is reflected off of an object; it then uses the reflected
signal to interpret location, size, and composition of an object.
Sonar is very fast. A sound wave can travel from the surface to a depth of
240 ft (70 m) and back again in less than 1/4 of a second. It is unlikely that your
boat can “outrun“ this sonar signal.
SONAR is an acronym for SOund and
NAvigation Ranging. Sonar uses precision
sound pulses or “pings“ which are emitted
into the water in a teardrop-shaped beam.
The sound pulses “echo“ back from objects
in the water such as the bottom, fish, and
other submerged objects. The returned
echoes are displayed on the LCD screen.
Each time a new echo is received, the old
echoes are moved across the LCD, creating
a scrolling effect.
How Sonar Works