AudioCodes Mediant 3000, User Manual

Page: 303 / 872

Version 6.6 303 Mediant 3000
User's Manual 21. Digital PSTN
21.2.4.2 Configuring BITS Synchronization Mode
The device can use Building Integrated Timing Source (BITS) clock inputs to synchronize
the system to an external BITS source. In BITS synchronization mode, the clock flows from
the BITS to the line interfaces. In this mode, both active and redundant blades are
synchronized by two BITS input trunks. The BITS trunks flow through two SAT blades
(housed in the chassis), each with a designated timing module. Two SAT blades are
required to ensure seamless clock operation in case of failure of one of the SATs timing
modules (i.e., clock redundancy).

To configure BITS synchronization:
1. Configure the external BITS reference transmission type for primary and secondary
interfaces connected to the device. In the System Timing page, set the 'External
Interface Type' parameter (TMExternalIFType) to one of the following:
•
[0] E1 CRC4 (default)
•
[1] E1 CAS
•
[2] E1 FAS
•
[3] T1 D4
•
[4] T1 ESF
•
[5] T12
2. Configure the transmission power between the timing module on the SAT blade and
the T1 external reference clock (External Reference Transmit Line Build Out), using
the TMT1LineBuildOut parameter:
•
[0] = DSX 1.0 to 133 feet 0 dB CSU
•
[1] = DSX 1.133 to 266 feet (default)
•
[2] = DSX 1.266 to 399_feet
•
[3] = DSX 1.399 to 533 feet
•
[4] = DSX 1.533 to 655 feet
•
[7] = DSX 1.0 to 133 feet 0 dB CSU pulse enable transmit and receive gapped
clock
3. Configure the transmission power (in Ohm) between the timing module on the SAT
blade and the E1 external reference clock, using the TME1LineBuildOut parameter:
•
[0] E 75 ohms normal
•
[1] E 120 ohms normal (default)
•
[4] E 75 ohms with high return loss
•
[5] E 120 ohms with high return loss
•
[6] E 75 ohms normal plus enable transmit and receive gapped clock
•
[7] E 120 ohms normal plus enable transmit and receive gapped clock
4. For a BITS reference to return to service, the device must validate the clock. In the
System Timing page, configure the time were reference must have an alarm cleared
before the device declares it as a valid reference, using the 'Reference Validation
Time' parameter (TMReferenceValidationTime).
5. In the System Timing page, set the 'Timing Module Mode' parameter (TMMode) to
External to use BITS inputs.
When one of the BITS reference clock sources fails, the device automatically switches to
the secondary BITS reference source for the device. When a BITS reference clock source
with a higher priority returns to service after failure, the device may either revert to the
higher-priority clock source or continue using the lower-priority clock source. When both
BITS reference clock sources fail, the device enters into clock holdover.