Avaya 1000 Series, Reference

Page: 510 / 700

An automatic switchover is initiated to the reference that recovers first. If the primary recovers
first, then the clock controller tracks to the primary, but switches over to the secondary
whenever the secondary recovers. If the secondary recovers first, then the clock controller
tracks to the secondary.
A time-out mechanism prevents chatter due to repeated automatic switching between primary
and secondary reference sources.
Reference clock selection through software
The 2MB DTI card has the necessary hardware for routing its reference to the appropriate line
on the backplane.
Software is responsible for the distribution of the secondary references and ensures that no
contention is present on the REFCLK1 backplane line. Software designates the 2MB DTI card
as a primary reference source to the clock controller. The secondary reference is obtained from
another 2 Mbps DTI card, which is designated by a craft person. No other clocks originating
from other 2MB DTI packs are used.
The clock controller provides an external timing interface and is capable of accepting two
signals as timing references. In this case, an external reference refers to an auxiliary timing
source which is bridged from a traffic carrying signal. This is not intended to be a dedicated
non-traffic bearing timing signal. The clock controller uses either the two external/auxiliary
references or the 2MB DTI references.
Reference clock interface
The recovered clock derived from the facility is available on the MDF connector. The signals
at these connectors conform to the electrical characteristics of the EIA RS-422 standard.
Switch settings
Various 2MB DTI switch options exist on the NTAK10. These are shown in Table 223: 2 MB
DTI switch options on page 510.
Table 223: 2 MB DTI switch options
Switch Off (Switch Open) On (Switch Closed)
S1-1 — —
S1-2 CC Enabled CC Disabled
S2-1 120 ohms Not Applicable
S2-2 Not Applicable Not Applicable
NTAK10 2.0 Mb DTI card
510 Circuit Card Reference July 2011
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