900 Series™ Introduction; How Sonar Works - Humminbird 917C Installation And Operation Manual

900 Series™ Introduction
Your 900 Series™ Ultra Wide Screen Fishing System comes in several
different configurations. See the following list of products, all of which are
covered by this manual, to find your 900 Series™ configuration:
• Humminbird® 917c Combo: Ultra Wide Screen Fishing System with
Chartplotter (Maps) and DualBeam PLUS™ 200/83 kHz Transducer,
GPS Receiver included
• Humminbird® 957c Combo: Ultra Wide Screen Fishing System with
Chartplotter (Maps) and QuadraBeam PLUS™ 200/83/455 kHz
Transducer, GPS Receiver included.

How Sonar Works

Sonar technology is based on sound waves. The 900 Series™ Fishing System
uses sonar to locate and define structure, bottom contour and composition,
as well as depth directly below the transducer.
Your 900 Series™ Fishing System 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.
1
SONAR is an acronym for SOund and
NAvigation Ranging. Sonar utilizes 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.
When all the echoes are viewed side by side,
an easy to interpret "graph" of the bottom, fish
and structure appears.