1957.) A sonar consists of a transmitter, transducer, receiver and dis- play. 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.
How to use this manual: typographical conventions
Many instructions are listed as numbered steps. The keypad and arrow "keystrokes" appear as boldface type. So, if you're in a real hurry (or just need a reminder), you can skim the instructions and pick out what menu command to use by finding the boldface command text. The fol- lowing paragraphs explain how to interpret the text formatting for those commands and other instructions:
Arrow Keys
The arrow keys control a horizontal line depth cursor on the sonar screen. The arrow keys also help you move around the menus so you can execute different commands. They are represented by symbols like these, which denote the down arrow key, the up arrow, the left arrow and the right arrow: ↓ ↑ ← →.
Keyboard
The other keys perform a variety of functions. When the text refers to a key to press, the key is shown in bold, sans serif type. For example, the "Enter/Icons" key is shown as ENT and the "Menu" key is shown as MENU.
Menu Commands
A menu command or a menu option will appear in small capital letters, in a bold sans serif type like this: DEPTH CURSOR. These indicate that you are to select this command or option from a menu or take an action of some kind with the menu item. Text that you may need to enter or file names you need to select are show in italic type, such as data type.
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