Operation

3-33

3162-A2-GB20-30 March 1999
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 3-18
shows some common clocking configurations. For more information on
configuration options, refer to Appendix C.
496-15012-01
NETWORK
CLOCK: NETWORK CLOCK: NETWORK
CLOCK: NETWORKCLOCK: INTERNAL
CLOCK: EXTERNAL CLOCK: NETWORK
PBX
CLOCK: DTE DROP/INSERT (DSX-1) CONNECTOR CLOCK: NETWORK
TERMINAL
EQUIPMENT
CLOCK: PORT 1 CLOCK: NETWORK
Figure 3-18. Common Clocking Configurations