Meridian Nortel 1 Option 11C Technical Reference Manual page 508

Page 508 of 544
Table 159
System clock specification and characteristics
Specifications
Base Frequency
Accuracy
Operating Temperature
Drift Rate (Aging)
Tuning Range (minimum)
Input Voltage Range
553-3011-100 Standard 14.00
NTAK20 clock controller
System clock specification and characteristics
Since the accuracy requirements for CCITT and EIA Stratum 3ND are so
different, it is necessary to have two TCVCXO which feature different values
of frequency tuning sensitivity.
0 to 70 C + 1 ppm
+ 1 ppm per year
0 to 10 volts, 5V center
EIA/CCITT compliance
The clock controller complies with 1.5 Mb EIA Stratum 3ND, 2.0 Mb CCITT
or 2.56 basic rate. The differences between these requirements mainly affect
PLL pull in range. Stratum 4 conforms to international markets (2.0Mb) while
stratum 3 conforms to North American market. (1.5 Mb).
Monitoring references
The primary and secondary synchronization references are continuously
monitored in order to provide autorecovery.
Reference switchover
Switchover may occur in the case of reference degradation or loss of signal.
When performance of the reference degrades to a point where the system
clock is no longer allowed to follow the timing signal, then the reference is
out of specification. If the reference being used is out of specification and the
other reference is still within specification, an automatic switchover is
initiated without software intervention. If both references are out of
specification, the clock controller provides holdover.
January 2002
CCITT
20.48 MHz
+ 3 ppm
+ 60 ppm min.
+ 90 ppm max.
EIA
20.48 MHz
+ 1 ppm
0 to 70 C + 1 ppm
+ 4 ppm in 20 years
+ 10 ppm min.
+ 15 ppm max.
0 to 10 volts, 5V center