Advanced Pstn Configuration; Clock Settings - AudioCodes Mediant 2000 User Manual

SIP User's Manual
11

Advanced PSTN Configuration

This section discusses advanced PSTN configurations.
11.1

Clock Settings

In a traditional TDM service network such as PSTN, both ends of the TDM connection must
be synchronized. If synchronization is not achieved, voice frames are either dropped (to
prevent a buffer overflow condition) or inserted (to prevent an underflow condition). In both
cases, connection quality and reliability is affected.
The device's clock settings can be configured to one of the following:

Network:
clock source for transmit on all interfaces

Internal/BITS: uses the internal oscillator for its transmit
Note:

To use the device's internal clock source,:
1. TDMBusClockSource = 1
2. ClockMaster = 1 (for all trunks)

To use the recovered clock option:
1. TDMBusClockSource = 4
2. ClockMaster_x = 0 (for all 'slave' trunks connected to PBX#1)
3. ClockMaster_x = 1 (for all 'master' trunks connected to PBX#2)
The above assumes that the device recovers its internal clock from one of the 'slave' trunks
connected to PBX#1 and provides clock to PBX#2 on its 'master' trunks. In addition, it's
necessary to define from which of the 'slave' trunks the device recovers its clock:

TDMBusPSTNAutoClockEnable = 1 (device automatically selects one of the
connected 'slave' trunks)
- Or -

TDMBusLocalReference = # (trunk number, where 0 is the first trunk - and the default)
Note:
Version 5.8
recovers a clock from one of its physical PSTN E1/T1 trunk interfaces as a
The device terminates the E1/T1 down to 64-kbps timeslots and hence, can't
tolerate different clock sources for its physical interfaces. Different clock
sources can lead to performance errors and voice disturbances.
When the device is used in a 'non-span' configuration, the internal device
clock must be used (as explained above).
11. Advanced PSTN Configuration
471 October 2009