Tektronix Grass Valley 3000 - Manual (Page 113)

3-5
Crosspoint Bus
Crosspoint Bus
A crosspoint bus consists of a group of switches called crosspoints,
each with a different video or key input. The row of switches has
a common output called a bus.
The various crosspoint buses on the switcher’s control panel
make up the Source Select Subpanel (the large matrix of buttons
that occupies the left 1/3 of the control panel), which is used for
connecting the video and key input buses to the crosspoint output
buses that feed transition and effects circuits.
The pushbuttons at the intersections between the input buses and
the output buses are called crosspoint buttons
Crosspoint buses include the following:
■ A and B background buses and the Key buses on the M/Es
■ PGM (Program) and PST (Preset) background buses and the
DSK (Downstream Keyer) bus on the PGM-PST/DSK section
■ PVW (Preview)/Mask/Aux (auxiliary) buses
The background buses feed the video mixers, allowing you to
select background sources and do transitions between them. The
key buses feed the keyers, allowing you to set up keys which are
also fed to the mixers for keying over the background. Lastly, the
aux buses select signals and send them directly to switcher
outputs for feeding external devices such as digital picture
manipulators; this makes the same inputs that are available to the
switcher also available to the external devices.