Nortel Networks Circuit Card 사용자 설명서
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NTAK20 Clock Controller daughterboard
System clock specification and characteristics
Since the accuracy requirements for CCITT and EIA Stratum 3 are different,
it is necessary to have two TCVCXOs which feature different values of
frequency tuning sensitivity. See Table 238.
it is necessary to have two TCVCXOs which feature different values of
frequency tuning sensitivity. See Table 238.
EIA/CCITT compliance
The clock controller complies with 1.5 Mb EIA Stratum 3ND, 2.0 Mb CCITT
or 2.56 Mb basic rate. The differences between these requirements mainly
affect PLL pull in range. Stratum 4 conforms to international markets
(2.0 Mb) while Stratum 3 conforms to North American markets (1.5 Mb).
or 2.56 Mb basic rate. The differences between these requirements mainly
affect PLL pull in range. Stratum 4 conforms to international markets
(2.0 Mb) while Stratum 3 conforms to North American markets (1.5 Mb).
Monitoring references
The primary and secondary synchronization references are continuously
monitored in order to provide autorecovery.
monitored in order to provide autorecovery.
Reference switchover
Switchover occurs 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 is out of specification and the other
reference is still within specification, an automatic switchover is initiated
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 is out of specification and the other
reference is still within specification, an automatic switchover is initiated
Table 238
System clock specification and characteristics
System clock specification and characteristics
Specifications
CCITT
EIA
Base Frequency
20.48 MHz
20.48 MHz
Accuracy
+ 3 ppm
+ 1 ppm
Operating Temperature
0 to 70 C + 1 ppm
0 to 70 C + 1 ppm
Drift Rate (Aging)
+ 1 ppm per year
+ 4 ppm in 20 years
Tuning Range (minimum)
+ 60 ppm min.
+ 90 ppm max.
+ 10 ppm min.
+ 15 ppm max.
Input Voltage Range
0 to 10 volts, 5V center
0 to 10 volts, 5V center