Selecting the timing source – Paradyne ACCULINK 336x E1 User Manual

Page 54

Operation

3-33

3360-A2-GB20-20

December 1996

Selecting the Timing Source

The E1 NTU provides the ability to select a primary

clock (timing) source that is used to synchronize all of the
E1 and data port interfaces on the E1 NTU. The clock for
each interface is at the appropriate rate for that interface
(e.g., 2.048 Mbps for the E1 interfaces, the configured
port rate for the data ports), and it is independent of the
primary clock rate. This means that the primary clock rate
and the E1 NTU interface rates may be different.

The E1 NTU automatically falls back to the secondary

clock when a failure of the selected primary clock is
detected. If a secondary clock failure is detected, the E1
NTU falls back to its internal clock.

The clock source configuration options enable you to

select either the network interface, a synchronous data
port, the internal clock, the G.703 DTE interface, or an
external clock. If external clocking is selected, you must
use the clock rate configuration option to specify the clock
rate.

Figure 3-12

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

External clock and secondary
clock sources are only available
for 2-port and 4-port E1 NTUs.