Speed Calibration (Advanced, With Temp/Speed Only); Demonstration; Sound Control - Humminbird 748 3D Operation Manual

Speed Calibration will adjust the speed readout by the percentage entered,
and will appear in the menu if a Temp/Speed Accessory is connected and the
paddlewheel has moved at least once.
Demonstration controls whether the Demonstration Mode is visible or off. The
Demonstration Mode appears on the screen if you don't press any keys during
the warning screen at power up. Menu settings cannot be saved in
Demonstration (see Power On and Start-Up Options Menu).
Sound Control allows you to set when the control head will beep or sound
because of key presses and/or alarms.
Speed Calibration
(Advanced, with Temp/Speed only)
Settings: -20% to +20%, Default = 0%

Demonstration

Settings: Off, Visible, Default = Visible

Sound Control

Settings: No Sounds, Alarms Only, All Sounds, Default =
All Sounds
61 Setup Menu Tab