Furuno NavNet TZtouch3 Series Operator's Manual page 231

7. FISH FINDER (SOUNDER)
[Zero Line Rejection]: Turn the zero line (transmission line) on or off. When turned
on, the transmission line disappears, which allows you to better watch fish echoes
near the surface. The length of the transmission line changes with transducer used
and installation characteristics.
Note: If the sounder source is [DFF3], adjust [Zero Line Range] (below) to set the area
where to reject the zero line.
[Zero Line Range]: This feature adjusts the transmission line so that the transmission
line disappears when the menu item [Zero Line Rejector] is turned on. Available with
DFF3 and DI-FFAMP. The setting range is 1.4 to 2.5 for DFF3; 1.4 to 3.8 For DI-
FFAMP. For a long tail, increase the value. If the transmission line does not disappear,
lower the TX power. Applicable to Network Sounder DFF3.
[Transducer Draft]: Set the distance between the transducer and the draft line to
show the distance from the sea surface (Setting range: 0.0 to 99.9 ft).
[Salt Water]: Select [ON] to use this equipment in salt water.
[Fish Finder Source]: Select the fish finder used.
[Transducer Setup]: Select the method to setup the transducer, by model, manually,
or TDID (transducer ID). See the installation manual for details.
[Transmission Format]: Select whether to transmit high frequency and low frequency
simultaneously or with a time difference (DI-FFAMP exclusive menu item). [Parallel]
transmits the frequency simultaneously. [Sequential] transmits with a delay between
transmissions. Use [Sequential] if [Parallel] is generating interference.
[Transmission Power]: Interference can appear on the screen when the fish finder
on your ship and one on a another ship have the same TX frequency. To prevent this
interference, lower your TX power and ask the other ship to lower their TX power. For
the DI-FFAMP, the setting range is 0 (off) to 10. For the DFF1-UHD the settings are
"minimum" and "maximum".
[External KP]: Turn on to sync with external keying pulse, for DFF3, DFF1-UHD, DI-
FFAMP. The default setting uses the internal sync pulse. For external keying pulse
synchronization, set this item to [ON].
[Bottom Level HF (MF, LF)]: The default bottom level setting (0) determines that two
strong echoes received in sequence are bottom echoes. If the depth indication is not
stable in the default setting, adjust the bottom level here. The setting range is -40 to
40. If vertical bars appear on the bottom line in the bottom expansion display, lower
the bottom level until the vertical bars disappear. Be careful not to lower the level ex-
cessively; bottom fish may be judged as the bottom echo.
[Gain Offset HF (MF, LF)]: If the gain setting is wrong, or there is a difference in the
gain between the low and high frequencies, you can balance the gain for the two fre-
quencies here.
[Auto Gain Offset HF (MF, LF)]: If the auto gain offset is wrong, or there is a differ-
ence in the gain between the low and high frequencies, set an offset here to balance
auto gain for the two frequencies.
[STC HF (MF, LF)]: Delete unnecessary echoes (plankton, air bubbles, etc.) near the
surface that hide the fish near the surface. The setting range is 0 to 10, and 0 is off.
10 deletes unnecessary echoes from the surface to approximately 16 ft. Make sure
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