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C Timing Options
Overview
The flexibility and complexity of the timing options for the DeskTop
T1 DSU require explanations that are more detailed than those
normally provided. This appendix therefore describes details and
applications of the DeskTop T1 DSU timing options:
•
Receive Timing
•
Internal Timing
•
DTE Timing
•
DTE Split Timing
Each description is accompanied by an illustration that shows how the
timing clock is distributed throughout the network. The timing option
descriptions are followed by some representative network applications
that show how to apply the timing options in a variety of network
configurations.
Timing Option Descriptions
In synchronous networks, all device transmitters and receivers are
usually referenced to a single master timing source. This timing
source, or clock, is frequently provided by the network and is highly
accurate and stable. The DSU recovers the embedded clock from the
data stream and uses it to synchronize its own internal timing reference
to the master clock. This allows the DSU to extract the data reliably
and further to distribute timing to other devices connected to it.
(Timing is embedded in the data stream on the network port, but is
provided on a separate lead in the DTE interface.) The network clock
is the preferred timing source, but the DeskTop T1 DSU supports other
timing options as well, for use in applications where timing from the
network clock is either not available or not applicable.
GDC 048R154-000
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