Grass Valley NV8256-Plus v.1.2 - Manual (Page 28)

18 Rev 1.2 • 20 Oct 08
2. Introduction
Active Cards
The input card receives 16 signals from the local coaxial connectors. Each input is forwarded to an
analog-to-digital converter that converts the signals to digital. Each digital input is forwarded to
one of 16 distribution amplifiers, which distributes three copies of the signal. One copy is sent to a
buffer and then the motherboard, which forwards the signal to the crosspoint card in the left slot
(inputs 1–256). The second copy is sent to a cable driver and then the motherboard, which forwards
the signal to the expansion connectors. When two routers are connected together, the signals are
forwarded to the second router through the expansion connectors. The third copy is sent to a 2×1
MUX and then the motherboard, which forwards the signal to the crosspoint card in the middle slot
(redundant crosspoint). For more information on each crosspoint card and crosspoint card slot func-
tions, see
Crosspoint Cards on page 18.
If two routers are connected together, the analog-to-SD input card also receives 16 inputs from the
expansion connections. Each input is forwarded to one of 16 cable receivers, which create two cop-
ies of the signal. One copy is sent to a 2×1 MUX and then a buffer. The buffer forwards the signal
to the motherboard, which forwards the signal to the crosspoint card in the middle slot (redundant
crosspoint). The other copy is sent to a buffer and then the motherboard, which forwards the signal
to the crosspoint card in the right slot (257–512).
Figure 2-15 shows the signal flow for an analog-to-SD input card.
Figure 2-15. Analog-to-SD Input Card Block Diagram
Crosspoint Cards
Crosspoint cards (EM0439) receive signals from the input cards (via the motherboard). The cross-
point card then performs switching as directed by the control card, sending signals to the output
cards (via the motherboard). Each crosspoint card can receive and distribute up to 256 individual
SD, SWB or 3Gig signals (signal rates from 10 Mb/s to 3.0 Gb/s).
The crosspoint card slot into which the crosspoint card is installed determines which signals are
managed.
Left and Right Slot Functions
When facing the front of the router, crosspoint cards installed in either the left or right slots manage
signals as follows:
Inputs
from
coaxial
connectors
(16)
Motherboard
Connector
Buffer Distrib.
Amp.
Cable
Driver
Crosspoint
LEFT
2x1
Mux
Motherboard
Connector
Expansion
Connectors
Motherboard
Connector
Buffer Crosspoint
MIDDLE
Inputs
from
Expansion
Connectors
(16)
Motherboard
Connector
Buffer Crosspoint
RIGHT
A/D
Converter
A/D
Converter
Distrib.
Amp.