Humminbird 787C2 Operation Manual page 61

531476-1_A - 787c2_Eng.qxd 11/22/2005
Chart Speed: Chart Speed is a user-controllable feature that sets the speed at which
sonar information moves across the display. A faster setting displays sonar information
from more pings and shows more detail, but the information moves quickly across the
display: a slower setting permits viewing of more sonar history, but does not display as
much detail. The best setting is often the user's personal choice.
Cone Angle: The cone angle is the angular measurement of the sonar beam at a specific
dB down point (i.e. -10 dB). See dB Down Point.
Customizable Digital Readouts: Customizable Digital Readouts is a Humminbird®
feature that permits the user to select the specific digital information that appears in
the main Sonar view (i.e. Speed, Temperature, Barometric Pressure, TripLog, etc.)
Dead Zone: The dead zone is the area of the sonar beam that receives the sonar signal
after the main bottom return. Fish and other objects close to the bottom that fall within
the dead zone will probably not be visible in the sonar beam. Precision sonar beams,
such as the Humminbird® 20° beam, have a smaller dead zone than wider sonar beams.
Decibel: A Decibel is the measurement for sound pressure level, or "intensity" of the
sonar return. See dB Down Point.
dB Down Point: The dB Down Point is the standard decibel level at which the sonar cone
angle is measured, and is written as "@ -10 dB" or "@ -3 dB". Measurements at smaller
down points (bigger negative numbers) indicate that the less intensive sonar signals are
being used for the measurement.
Display, FSTN: FSTN is an acronym for Film Super-Twist Nematic. FSTN is a monochrome
display technology characterized by black, high-contrast pixels. All monochrome fixed
mount Humminbird® products use FSTN technology.
DualBeam PLUS™: DualBeam PLUS™ is a Humminbird® sonar configuration that uses
two sonar beams simultaneously, and combines the information from both beams into
one view by overlapping the data on-screen, or shows each beam individually side by
side, or permits each beam to be viewed individually full screen.
Feature Memory: Feature Memory is a Humminbird® feature that retains the user's
menu settings in permanent memory. Settings are retained even when the unit is
powered off indefinitely.
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Fish Arch: A Fish Arch is the apparent "arch" that appears on the display when any object
moves through the sonar cone. The arch results from a gradual decrease in distance to
an object as it moves into the sonar cone. The distance to an object changes due to the
conical shape of the sonar beam, which causes the distance to be greater at the edges
of the beam than at the center of the beam. When this distance change is graphed on
the display, an arch appears.
Fish ID+™: Fish ID+™ is a Humminbird® feature that uses advanced sonar processing
algorithms to determine if a detected object is likely to be a fish. When the sonar signal
from an object meets strict parameters, the unit draws a Fish Symbol (or icon) and the
digital depth of the target. On DualBeam and DualBeam PLUS™ units, fish detected in
the narrow center beam are shown as shaded symbols, and fish detected in the wider
beam are shown as hollow symbols.
Fish Symbol: A Fish Symbol is the graphic that is displayed on the screen when Fish ID+
determines that a sonar return is likely to be a fish. See Fish ID+.
Freeze Frame: Freeze Frame is a Humminbird® feature that pauses the sonar scrolling
so that the image on screen can be studied with greater detail. See Instant Image
Update.
Frequency: Frequency is a measure of the number of sound wave cycles per second of a
sound impulse transmitted underwater. A typical frequency for fishfinders is 200 kHz,
which offers a good balance of performance under many conditions. Lower frequencies,
such as 50 kHz, are capable of penetrating to greater depths, but with less resolution.
Higher frequencies, such as 455 kHz, offer greater resolution, but are limited in depth
performance. Humminbird® uses a variety of frequencies that are optimized for specific
applications.
Grayscale: Grayscale is the use of varying shades of gray to represent the strength of the
sonar signal on the display , and is a very intuitive method of presenting information.
Traditionally, the strongest sonar signals are represented in black, and progressively
weaker signals are represented in progressively lighter shades of gray.
Grayscale, Inverse: Inverse Grayscale is a Humminbird® feature that reverses the
correlation of sonar signal strength and the shade of gray typically used to represent it.
The strongest sonar signals are represented by "white", and progressively weaker
signals are represented in progressively darker shades of gray. While somewhat counter-
intuitive, this method makes the sonar images crisper, and has the benefit of enhancing
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