Rev. B
3-7
HMXMC001013
31-Mar-06
3.4 COMBINING,
CONTINUED
Connecting Subracks
In a combining configuration (figure 3.5), video signals (e.g. cameras) are connected to
the video inputs of the pre-selection subracks. Pre-selection of those video signals are
fed out to the combiner subracks.
In the combiner subrack, the video input (fed out of the pre-selection subrack) is then
selected to the output for display on the monitor. The outputs of the combiner subracks
connect to video output devices, like monitors or VCRs.
Pre-selection subracks used in combining, are denoted by the alpha characters (A T).
Referring to figure 3.5 again, outputs from pre-selection subrack A are numbered 1A, 2A,
3A and so on. Outputs from pre-selection subrack B are also numbered accordingly
(2A, 2B, 2C and so forth).
Video inputs to each channel of the combiner subrack are also labeled (A T). Each
channel only accepts a
single
video input from each pre-selection subrack.
i.e.:
Output 1A, from the
first
pre-selection subrack A, connects to the first input (A) of
channel 1 of the combiner subrack. The second output from the
first
pre-selection
subrack A, 2A, connects to the first input (A) of channel 2 of the combiner subrack. This
goes on until the
N
th
output from the
first
pre-selection subrack A, is connected to the
first input (A), of the
N
th
channel of the combiner subrack.
Likewise, the first output (1B) from the
second
pre-selection subrack B, connects to the
second input (B) of channel 1 of the combiner subrack. The second output, 2B,
connects to the second input (B) of channel 2 of the combiner subrack. This continues
till the
N
th
output of the pre-selection subrack.
In a combining configuration, any video signal traveling from the source to the output of
the combiner subrack, only goes through two subracks. With combining, the video
system can easily accommodate 1024 video inputs to 256 video output channels, and
still maintain very high picture quality.
