Lucent Technologies Release 7 User Manual

Issue 4

June 1999

Maintenance Object Repair Procedures 

9-1564

SYNC (Synchronization) 

coming from the PPN to the EPN over the standby fiber link). If another loss of 
signal occurred after the Tone-clock circuit pack switched to receive timing from 
the standby EI, the Tone-clock circuit pack will run on its local oscillator. The 
yellow LED on the Tone-clock circuit pack flashes at the 2.7 seconds on and .3 
seconds off rate (mostly on) if timing is received from an external source (an EI in 
this example). Otherwise, if the Tone-clock circuit pack is running on its local 
oscillator, the yellow LED flashes at the .3 seconds on and 2.7 seconds off rate 
(mostly off).

The TN722 DS1 Interface circuit pack does not provide a synchronization 
reference as reliable as the TN767 or TN464C circuit packs. Therefore, it is 
recommended that the TN767 or TN464C circuit packs are used as primary or 
secondary sources instead of the TN722 type DS1 circuit packs.

Figure 9-92

 illustrates one possible configuration of Stratum 3 synchronization.

For Stratum 3 synchronization, an external clock provides a timing signal to a 
TN780 Tone-Clock circuit pack, and the TN780 provides timing to all circuit 

DS-1

INTF

Clock

STRATUM 3

External

TONE/

TN780

CLOCK

and

standby

fiber

link

standby

fiber

link

active fiber link

timing info

active fiber link

and

timing info

PPN

* The EPN to EPN fiber link does not carry timing

standby

active

fiber link

fiber link

EPN

EPN

DS1 References

DS-1

INTF

DS-1

INTF