IBM 6091 Set Up And Operation Manual page 24

Depending on the length of the video cables to the next display, noticeable signal
loss may result. To compensate for this signal loss. set the gain switch at the display
driving the video signal.
The gain switch, located at the back of the 6091-023 display (see Figure 3-5 on
page 3-6 for the location of this switch) has three positions: 0, 1, and 2. This
switch affects the OUTPUT signal level. The OUTPUT signal is the signal received
by the next display on the video link.
As an approximate guide, use gain position 0-for video cable lengths up to 20
meters; position 1 for cable lengths between 20 and 60 meters; and position 2 for
lengths between 60 and 100 meters.
CORRECT
NORMAL IMAGE
I
<f-GRAY
SCALE
LIGHT
-i>IDARK
WHITE GRAY
I
I
I
INCORRECT
WHITE
GRAY BLACK
I I
I
COMPRESSED IMAGE
LOSS OF GRAY SCALE
GAIN SWITCH SET TOO HIGH
BLACK
I
I
Figure 3-6. Correct and Incorrect Gray Scales (Color Bar Test Pattern)
Observe the gray scale. The pattern should show white at the left with 6 shades of
gray and black at the right. If the black (background) appears gray, reduce the
setting of the brightness control. (Normally this control should be at the center
detent)
CHAPTER 3. Operating the 6091 Color Displays
3-7