Keep in mind that the closer the update rate matches your boat speed, the more accurate is the graphic depiction of the terrain beneath your boat. Use the UP and DOWN ARROWS to select the desired update rate. The Display Speed setting is remembered when the unit is powered off. Battery Alarm. The Battery Alarm Option allows you to select the voltage level at which the Battery Alarm activates. At the Battery Alarm menu (under options), you will note that the default setting is OFF. Push the DOWN ARROW BUTTON to select the feature ON. Push the DOWN ARROW BUTTON again to move into the ADJUST BATTERY ALARM setting. Using the UP and DOWN ARROW BUTTONS, select a voltage between 9.0 and 12.0. When the voltage drops below your selected voltage, an audible alarm will sound, and a battery alarm icon will be displayed on screen with current voltage level. Bottom Black. There are two selections available: OFF and ON. The factory setting is OFF. With this setting, the 250DX displays the bottom using Structure ID. This allows you to determine the texture and relative hardness of the bottom. Selecting Bottom Black “ON” causes the unit to blacken in the display below the bottom. This gives the user easiest recognition of the bottom location, even from a great distance. The 250DX remembers the Bottom Black setting when powered off. USING THE 250DX MENU FUNCTIONS Fish ID. There are three selections available: OFF, ID+ ON, and ADJUST. The factory setting is ID+ ON. With Fish ID OFF, sonar returns are displayed as “raw” information. There is no interpretation made by the unit. Selecting ID OFF also disables the fish alarm. ID+ ON enables the 250DX to interpret the raw sonar data and, using a variety of techniques, depict appropriate target returns as one of three different size fish symbols. Further identification shows whether the fish is in the wide or narrow beam. The 250DX also displays the depth beneath the surface with the corresponding fish symbol. Bottom Black View Selecting Adjust and making incremental changes enhances the fishfinder’s ability to identify sonar returns as fish symbols. Increasing the value to a number greater than zero shows more fish symbols on-screen. In this case smaller sonar returns will be depicted as fish symbols. This is useful for identifying many smaller sonar returns (such as baitfish) as fish symbols. Decreasing the value to a number less than zero shows fewer fish symbols on-screen. In this case smaller sonar returns are disregarded. This is useful for eliminating many small sonar returns when seeking larger species of fish. The 250DX remembers this selection even when the unit is powered off. Raw Sonar ID+ On USING THE 250DX MENU FUNCTIONS Numeral Size. Two options are available: BIG and SMALL. The factory setting is BIG. With this setting, the digital depth and speed and temp numerals are drawn large enough to be read from across the boat. The big numerals occupy space on the display that could be used for the graphics area. Hence, the small numerals option. With small numerals selected, a greater amount of the display area is available for the graphic view. This effectively increases the display resolution of the unit. Numeral Size settings are remembered when powered off. Diagnostic. Two options are available: HIDE and SHOW. The factory setting is HIDE. Selecting SHOW brings up the Diagnostic screen. See the Using Diagnostic section for more information. Units. The Units function allows the user to select the units of measurement for the depth and speed readout. Metres/KTS, (metres/nautical miles per hour), Metres/KPH (metres/kilometres per hour), FEET/MPH (feet/statute miles per hour) and FEET/KTS (feet/nautical miles per hour), are available.The 250TX remembers this selection even when the unit is powered off. Languages. The language menu displays one of two sets of languages. Language set A includes: English, French, Italian, German, Norwegian, Swedish, Spanish, and Finnish. Language Set B provides Hungarian, Danish, Polish, Portuguese, Dutch and English. To select your language, push the UP or Down Arrow Buttons to scroll through the list. USING THE 250DX MENU FUNCTIONS Speed Offset. The Speed Offset option allows the user to compensate for differences in hull design, and its effect on the accuracy of the speed measurement. If there is a discrepancy between the indicated speed and another speed measurement device on the boat, the speed measurement can be varied to improve accuracy. Remember, the speed paddle wheel measures speed through the water, not speed over ground. Speed offset is remembered after power is disconnected. Depth Offset. The Depth Offset allows the user to select the point on the boat from which the depth measurement is made. Selecting a positive value adds distance to the measurement. If the transducer is mounted 3 feet beneath the waterline, a positive 3 will show the correct depth from the surface of the water. Another frequent use of depth offset is to show ...