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Figure 85. DPLL Implementation on Active Ports
Note
Since the jitter is removed from the signal before entering the backplane, the
signal received from the backplane would only have a small amount of jitter
accumulated on the backplane.
The signal received from the backplane goes through the narrowband PLL
before being transmitted out of the port.
The passive module switching modules do not use DPLLs on each port. Instead,
a Jitter Attenuation Daughter Card (JADC) is required which implements an
enhanced DPLL function which can receive and eliminate a greater amount of
accumulated jitter.
Note
Ports 17 and 18 on the 18-port active modules can be set up as either RI/RO
or lobe ports using the jumpers provided on the module. When these ports
are configured as RI/RO ports and your 8260 is connected via these ports to
a non-8260 hub, a JADC must be installed on these modules to ensure that
the jitter accumulated on the non-8260 hub, is reduced before it enters your
8260.
140 8260 Multiprotocol Intelligent Switching Hub