Eagle Electronics 245DS User Manual

3 

storage 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 fac-

tory's Customer Service Department; phone numbers are inside the 

manual's back cover. 

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. 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 

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 unit is packed with a Dual Search Skimmer Transducer that can 

transmit at 83 kHz and 200 kHz.