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Pro-Bel Ltd
Technical manual
The AES level has a dedicated AES
reference
generator that determines the
appropriate instant to switch noiselessly
between
audio sources
.
It is only enabled
when a crosspoint trigger pulse occurs on the F/SYNC line. In other words, the
audio
switches
at the first appropriate point during a field interval.
• 6.2 Salvo switching
In a salvo, the sources may be configured to switch using different trigger
methods. The software will set batches of cross points related to the trigger
method
configured.
The order of events is
given
below:
•
set up crosspoints to be Forced
•
set up crosspoints to be switched timed to 625 reference
•
enable 625 SYNCS and wait until field pulse occurred or timeout
•
disable SYNCS
•
set up crosspoints to be switched timed to 525 reference
•
enable 525 SYNCS and wait until field pulse occurred or timeout
•
if timeout occurred then force SYN
CS
to take crosspoints
•
set up crosspoints to be switched timed to TTL pulse
•
enable TTL reference and wait until trigger pulse occurred
• 6.3 Handshaking and error reporting
Freeway
Card handshakes are obtained by utilising part of the crosspoint set
mechanism
.
The order of events is as follows:
1. Write Level and Destination
2. Read HSHAKE line
The HSHAKE line is common across all switcher modules but is only as
serted
from
the module pertaining to the
level
and destination sent.
On power-up the 2440 control software will ch eck if the auto-
configure
switch
(sw
2_6)
is in the ON position (DOWN)
.
If it is, th
e
system reads
a
ll handshakes and
then enables
crosspoints for
the modules th
at
were
detected.
If in the OFF
position (UP) the system uses the last module configuration as the template for
enabling cros s p oints . Thu
s,
for parts of the router
where
no handshakes have
been detected crosspoints will be inhibited.
6540T-00 Nov 97
47
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