Control, Transmission, and Synchronization Interfaces
Issue 8.0 July 2002
5-11
Two TG3 (DS1) circuit packs are located on each Low Speed Shelf and support
the synchronization needs of the FT-2000 OC-48 Lightwave System. The
FT-2000 OC-48 Repeater Bay does not require TG3 (DS1) circuit packs. The TG3
(DS1) circuit packs are 1x1 (revertive) protected, protecting against circuit pack
failures. The DS1 synchronization references are revertively protected. For more
information about synchronization protection, refer to Volume I, Section 9,
"Maintenance Description."
Free Running Mode 5
In the free running mode (Figure 5-5), the TG3 (DS1) circuit packs on the Low
Speed Shelf - System Controller derive timing from a highly stable crystal
oscillator. This oscillator has a long-term accuracy better than ±4.6 ppm. The TG3
(DS1) circuit packs distribute 155.52 MHz timing signals to the low speed
interface circuit packs on the Low Speed Shelf - System Controller and the OC48
Transmitter (OC48 TRMTR) circuit packs on the Enhanced High Speed Shelf (or
High Speed Shelf).
In the free running mode, the DS1 reference input interface (TIMING IN PRI and
TIMING IN SECY) and DS1 reference output interface (TIMING OUT 1 and
TIMING OUT 2) located on the interconnection panel of the Low Speed Shelf -
System Controller are not used.
Figure 5-5. Free Running Synchronization
1
2
TG3
155.52 MHz
25.92 MHz
1
2
TG3
155.52 MHz
155.52 MHz
Complementary
(Optional)
System Controller
OC48 TRMTR
Low Speed
Interfaces
Low Speed
Interfaces
Low Speed Shelf -
Low Speed Shelf -
Enhanced
High Speed Shelf
(or High Speed Shelf)
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