Appendix
C
Display Systems
C-5
Sync
This term refers to the part of the video signal that
is used to stabilize the picture. Sync can take
three forms:
1)"Composite sync" when the horizontal and
vertical components are together on one cable.
2)"Sync on green" when the sync is part of the
green video.
3)"Separate sync" or "H.SYNC and V.SYNC"
when the horizontal and vertical components of
the sync are on two separate cables.
Sync Width
The duration of each sync pulse generated by a
computer. The sync width is part of the blanking
time.
TTL Video
A type of RGB video with digital characteristics.
Terminated
A wire connecting a single video source to a
display device, such as a projector, must be
terminated by a resistance (usually 75
Ω
for
video).
Throw Distance
Also called "Projector-to-Screen Distance", the
distance between the front of the projector's
green lens and the screen.
Variable Scan
The ability of a projector to synchronize to inputs
with frequencies within a specified range.
Vertical Frequency
The frequency at which images are generated.
Vertical frequencies vary amongst sources. This
term is also called vertical scan rate.
Video
The signal that is used by display devices (such
as projectors) to generate a picture. This term
also refers to the output of video tape/disk players
and computers.
Video Decoder
A device that converts NTSC, PAL, SECAM or
NTSC 4.43 video to RGB video (Marquee Multi-
standard Decoder).
Viewing Angle
Screens do not reflect equally in all directions.
Most light is reflected in a conical volume which is
centered around the "line of best viewing".
Maximum brightness is seen when you are
positioned within the viewing cone. The
horizontal and vertical viewing angles are the
horizontal and vertical angles of the cone.
White Balance
White Balance refers to the color temperature of
white used by the projector.
White Field
A white field is the area of an image that is white
only. For example, a full white field is an image
that is white everywhere. A 10% white field is a
white area (usually rectangular) that occupies
10% of the image; the remaining 90% is black.
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