Grass Valley MRC v.1.2 - Manual (Page 152)

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Tutorials
Routing
Each of the individual inputs and outputs of a device is assigned to a distinct level. A router
can be partitioned into physical levels, in different ways, depending on the router. Some
routers switch both video and audio signals. Such routers might have two physical levels,
one for video and one for audio.
NV9000-SE Utilities defines “virtual” levels. A virtual level is an abstraction that corresponds
to a signal type occurring in many different physical devices. (MRC does not deal with virtual
levels, only physical levels.)
A source device is one that send signals to a router (or routers). A destination device is one
that receives signals from a router or (routers).
We say that destinations are sets of outputs. But we also remember that physical destination
devices have inputs connected to those outputs!
Similarly, sources are sets of inputs, and we remember that physical source devices have out-
puts connected to those inputs!
Usually routers manage hundreds or thousands of incoming and outgoing signals.
To manipulate the incoming and outgoing signals — how they are switched in the router —
operators use control panels. Commands from the control panels are sent to the routers telling
the routers how to switch the signals. Status from the routers is returned to the control panels.
What is a Router?
Suppose you have two VCRs and one TV. You want to be able to view a movie from either VCR.
So you plug the cable from one VCR into the TV. When you want to use the other VCR, you have
to change cables. After a while, that gets a little tiresome. Wouldn’t it be easier if you had a
switch you could flip?
Now suppose you have a dozen TVs and a dozen VCRs plus cable service. You want to be able to
direct any program from any VCR or from the cable company to any of the TVs.
That is what routers do: direct the content from a number of inputs to selected outputs.
A router is a device that switches (i.e., routes) incoming signals to different outputs under soft-
ware control. A router usually has a substantial number of inputs and outputs, and uses a
crosspoint matrix to perform the switching.
In the crosspoint matrix, any input can be connected to any or all outputs. However, no output
can be connected to more than one input because routers do not mix input signals.
• • •
VCR
Cable
Router
VCR
VCR
VCR
VCR
TV
TV
TV
TV
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• • •
• • •
• • •
Controls