Eagle Electronics 320C manual How Sonar Works, Notice

Surface water temp: ..... Yes, built into transducer. Optional addi-

tional temp sensors for live well, bait well, etc. are available.

Speed/distance log: ....... Yes, with optional speed sensor.

NOTICE!

The storage and operation temperature for your unit is from -4 de- grees to +167 degrees Fahrenheit (-20 degrees to +75 degrees Cel- sius). Extended storage in temperatures higher or lower than speci- fied will damage the liquid crystal display in your unit. This type of damage is not covered by the warranty. For more information, con- tact the factory's Customer Service Department; phone numbers are inside the manual's back cover.

How Sonar Works

Sonar has been around since the 1940s, so if you already know how it works, skip ahead to the next segment on the typographical conventions used in this manual. 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 technol- ogy developed during World War II for tracking enemy submarines. (Ea- gle developed the world's first transistorized sportfishing sonar in 1957.) A sonar consists of a transmitter, transducer, receiver and display. In simple terms, here's how it finds the bottom, or the fish:

The transmitter emits an electrical impulse, which the transducer con- verts 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

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