Eagle Electronics FISHSTRIKE 1000C - Manual (Page 13)

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NOTE:
The memory capacities refer only to the unit's on-board memory.
The amount of GPS or sonar data you can record and save for recall
later is only limited by the number of MMC cards you have.
NOTICE!
The storage and operation temperature range for your unit is from -
4 degrees to +167 degrees Fahrenheit (-20 degrees to +75 degrees
Celsius). Extended storage or operation in temperatures higher or
lower than specified will damage the liquid crystal display in your
unit. This type of damage is not covered by the warranty. For more
information, contact the factory's Customer Service Department.
Phone numbers are listed on the last page.
How Your Sonar Works
Sonar has been around since the 1940s, so if you already know how it
works, skip down to read about the relatively new technology of GPS.
But, if you've never owned a sonar fish finder, this segment will tell you
the underwater basics.
Sonar is an abbreviation for SOund NAvigation and Ranging, a
technology developed during World War II for tracking enemy
submarines. A sonar consists of a transmitter, transducer, receiver and
display. Here’s an explanation of how it finds the bottom and the fish.
The transmitter emits an electrical impulse, which the transducer
converts into a sound wave and sends into the water. (The sound
frequency can't be heard by humans or fish.) The sound wave strikes an
object (fish, structure, bottom) and bounces back to the transducer,
which converts the sound back into an electrical signal.
The receiver amplifies this return signal, or echo, and sends it to the
display, where an image of the object appears on the scrolling sonar
chart. The sonar's microprocessor calculates the time lapse between the
transmitted signal and echo return to determine the distance to the
object. The whole process repeats itself several times each second.
Your sonar unit can record a log of the sonar signals that scroll across
the screen and save them to the MMC memory card. (These recordings
are also called sonar charts or sonar graphs.) You can replay this sonar
log in the unit using the Sonar Simulator function, or play it back on a
personal computer using our free Sonar Viewer. The viewer is available
for download from the Eagle web site, www.eaglesonar.com.
You can save several different sonar log files, erase 'em and record new
ones, over and over again. The size of your sonar recordings are only
limited by the free space available on your MMC.