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SYNCHRONIZATION OF DIGITAL FACILITIES
5-31
The slip count provided by the interface should also be used in the process of choosing a healthy
clock reference. However, when the interface terminates on a D4-channel bank (or equivalent) that
is not locked to the AT&T reference frequency for its timing, then the interface should not be used
for synchronization.
Line-Only Mode DS1/DMI-BOS (TN767)
When using a line-only mode interface for synchronization purposes, the following facts should be
known:
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Since the D4-channel bank (or equivalent) at the far end will be timed to the signal received from
a DS1/DMI, no slips should occur on a line-only mode DS1/DMI facility. Because of this, slip
counts from line-only mode DS1/DMI should not be used in the process of determining the health
of a clock reference (that is, they would tend to make the reference appear to be in better
condition than it may be).
Line-only mode DS1/DMI should not be used as system clock references unless it is known for
certain that the incoming DS1/DMI signal is locked to the AT&T reference frequency. Normally,
a DS1/DMI facility terminating directly on the far end D4-channel bank will not be locked to the
AT&T reference frequency.
Trunk-Mode DS1/DMI-MOS (TN767)
For Generic 1, DS1/DMI-MOS (TN767) will only terminate at a compatible computer. The
computer must always obtain its timing from the switch. The switch should never select the DMI-
MOS link as a timing reference.