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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:
NOTE: Only the 987c SI Combo model comes with GPS and built-in cartography.
• Humminbird® 981c SI: Ultra-Wide Screen Fishing System with Side Imaging and
Dual Frequency Transducer, optional GPS support
• Humminbird® 987c SI Combo: Ultra-Wide Screen Fishing System with
Chartplotter (Maps) and Side Imaging and Dual Frequency Transducer, GPS
Receiver included.
HOW THE 900 SERIES™ 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 ¼ of a second. It is unlikely that your boat can
"outrun" this sonar signal.
SIDE IMAGING SONAR
Your 900 Series™ 987c SI Combo and 981c SI use Side Imaging sonar to provide a wide
yet precise survey of a large area of water, including detailed bottom topography and
fish-attracting structure orientation. The Side Imaging transducer returns are
processed into an image similar to an aerial photograph. Typically, the Side Imaging
sonar searches an area that is 240 feet wide, with a depth limitation of 100 feet. See
What’s on the Side Imaging Display and Understanding Side Imaging for more
information.
DUALBEAM PLUS™ SONAR
Your 900 Series™ is shipped with a 200/50 kHz DualBeam PLUS™ sonar system with
a wide (74°) area of coverage. DualBeam PLUS™ sonar returns can be blended together,
viewed separately or compared side-by-side. DualBeam PLUS™ is ideal for a wide
range of conditions - from shallow to very deep water in both fresh and salt water.
Depth capability is affected by such factors as boat speed, wave action, bottom
hardness, water conditions and transducer installation.
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