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ACCULINK 316x DSU/CSU
3-32 January 1997 3160-A2-GB21-50
Selecting the Timing Source
The DSU/CSU provides the ability to select a master
clock (timing) source that is used to synchronize all of the
T1 and data port interfaces on the DSU/CSU. The clock
for each interface is at the appropriate rate for that
interface (e.g., 1.544 Mbps for the T1 interfaces, the
configured port rate for the data ports), and it is
independent of the master clock rate. This means that the
master clock rate and the DSU/CSU interface rates may
be different.
The clock source configuration options enable you to
select either the network interface, a synchronous data
port, the internal clock, the DTE Drop/Insert (DSX-1)
interface, or an external clock. If external clocking is
selected, you must use the clock rate configuration option
to specify the clock rate. Figure 3-11 shows some
common clocking configurations. Two sample procedures
for configuring timing are given in the following sections,
Configuring for Network Timing and Configuring for
External Timing. For more information on configuration
options, refer to Appendix C.
NOTE
The external clock source is only
available for 2-port and 4-port
DSU/CSUs. For carrier-mounted
DSU/CSUs, the external clock
provides timing for up to eight
slots in the carrier. Each Auxiliary
Backplane must have its own
external clock input.
496-14341-03
NETWORK
CLOCK: NETWORK CLOCK: NETWORK
CLOCK: NETWORKCLOCK: INTERNAL
CLOCK: EXTERNAL CLOCK: NETWORK
PBX
CLOCK: DTE (G.703) CONNECTOR
CLOCK: NETWORK
TERMINAL
EQUIPMENT
CLOCK: PORT 1, 2, 3, OR 4
CLOCK: NETWORK
Figure 3-11. Common Clocking Configurations