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2018-08-16

For units with SYNCH IN and SYNCH OUT ports

v. 43.0.1125


1 TDM Sync Feature

The TDM Sync feature provides a means to synchronise the operation of T1/E1/BRI circuits spanning across multiple units and to specify which port of a unit should be used as the reference.

All ISDN ports must be synchronised. When using one device, it is possible to specify a "source" port for the clock on which the other ports can be synchronised on. With several devices, the ports of the different units can also be synchronised. Therefore, it is very helpful to have a special TDM Sync port, with the clock, which can be shared between the devices.

Bad synchronisation can cause, for example:

  • Choppy video communications
  • Failure of fax transmissions
  • Lost of audio frames

The Sync signal transferred between units is a Single Ended 8 KHz Frame Sync Pulse.


1.1 Cabling Several Units for TDM Synchronisation

Context

Cabling is done using straight cables in a daisy chain.

Before You Start

The common practice is to have the first unit act as the Clock Master. However

Steps

  1. Connect a standard Ethernet cable to the SYNC OUT port of the first device.
  2. Connect the other end of the Ethernet cable to the SYNC IN port of another device.
  3. Connect all your units in the same fashion.
  4. Connect a standard Ethernet cable in the SYNC OUT port of the last unit.
  5. Connect the other end of the Ethernet cable in the SYNC IN port of the first unit.

    Note

    There must always be a link between the last and first unit even if the first unit is the master because it may lose its source and then another unit in the chain will become the master.

Result

Next Step

1.2 Selecting the Port Used for Synchronisation

1.2 Selecting the Port Used for Synchronisation

Context

If you are not familiar with the meaning of the fields and buttons, click Show Help, located at the upper right corner of the Web page. When activated, the fields and buttons that offer online help will change to green and if you hover over them, the description will be displayed.

Steps

  1. Access the DGW Web interface of your unit.
  2. Go to System/Hardware.
  3. In the Clock Reference Configuration table, from the Suggestion selection list, choose SYNCIN.

Result

The unit will be synchronised on the SYNCIN port.