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Technical Specifications
Issue 3 June 2001
10-53
Synchronization 10
BBF2/BBF2B Synchronous Timing Generator (TGS) 10
The TGS circuit pack meets the specifications of GR-253-CORE, SONET
Transport Systems Generic Criteria. The TGS circuit pack supports three timing
modes:
â– External timing: Locked to external Stratum 3
(±4.6 ppm) or better DS1 reference.
â– Line-timing: Locked to recovered clock from an OC-N signal.
â– Free-running: Timing derived from high-stability temperature-compensated
voltage-controlled crystal oscillator (TCVCXO) with a long-term accuracy of
±15 ppm and temperature stability of ±8.8 ppm (−40°Cto+75°C).
Holdover mode is entered on failure of external timing or line-timing reference,
providing a temperature stability of ±8.8 ppm (−40°Cto+75°C). Holdover
capability for 24 hours will be better than ±4.6 ppm.
The DS1 timing output used for network synchronization (BBF2B only) provides
long-term accuracy traceable to the OC-N signal.
SONET synchronization messaging is used to output DS1 AIS when clock
traceability is lost (Release 5 and later). Jitter on the DS1 output is less than 0.06
unit interval peak-to-peak.
BBF4 Synchronous Timing Generator 3 (TG3) 10
The TG3 Stratum 3 circuit pack meets the specifications of GR-253-CORE,
SONET Transport Systems Generic Criteria. The TG3 circuit pack supports three
timing modes:
â– External timing: Locked to external Stratum 3
(±4.6 ppm) or better DS1 reference.
â– Line-timing: Locked to recovered clock from an OC-N signal.
â– Free-running: Timing derived from high-stability temperature-compensated
voltage-controlled crystal oscillator (TCVCXO) with a long-term accuracy of
±4.6 ppm and temperature stability of ±2 ppm.
Holdover mode is entered on failure of external timing or line-timing reference,
providing a temperature stability of ±2 ppm (−40°Cto+75°C) or ± .3 ppm
(0°Cto+70°C). Holdover capability for 24 hours will be better than ±.37 ppm.
The DS1 timing output used for network synchronization (BBF2B or BBF4)
provides long-term accuracy traceable to the OC-N signal.
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