Control, Transmission, and Synchronization Interfaces
5-26 Issue 8.0 July 2002
Externally Timed/Externally Timed Configuration 5
In the externally timed/externally timed configuration (Figure 5-15), both FT-2000
OC-48 Add/Drop-Rings Terminals time their transmitted signals from internal
oscillators that are locked to the DS1 external synchronization reference.
Since this configuration requires local office clocks at each terminal, it is most
suited to interoffice applications. The network must have all DS1 references
traceable to a common primary reference source (for example, outstate trunking)
or to multiple primary reference sources (for example, a carrier-to-carrier
interface). The use of multiple primary reference sources is referred to as
plesiochronous operation. If synchronous (EC-1, OC-3, IS-3 or OC-12) low speed
interfaces are present, external sources must be traceable to a stratum 1 clock.
The externally timed/externally timed configuration applies to all OC-48
Add/Drop-Rings Terminal applications (with or without the FT-2000 OC-48
Repeater Bay).
The LAA18 TG3 (DS1) circuit pack can also provide DS1 synchronization outputs
to the office BITS clock or other central office equipment. For more information
about platform timing modes, refer to "Platform Synchronization" in this section.
Figure 5-15. Externally Timed/Externally Timed Configuration
FT-2000
Stratum 3 or better
OC-48
BITS
Clock
Central Office
Equipment
Other
FT-2000
CO CO
Externally Timed
Externally Timed
DS3/EC-1/OC-3/IS-3/OC-12DS3/EC-1/OC-3/IS-3/OC-12
To Next Page
Loading...
Need help?
General