American Telecom AM64/128A - Manual (Page 20)

Test Menu AM64/128A User Manual
20
With a G.703 interface fitted, the application of a loopback will apply a loopback to line at the remote
slave unit (known as an LTU loop on the G.703 linecard and standalone units).
Note : It is not possible to “Hardwire” a G.703 loop at the G.703 interface connector.
5.4.3. Remote Loop
Remote loop involves turning on a BBM loopback, but from the other end of the link (see figure 5.4.3).
This can only be menu activated from a BBM with a X.21bis interface. It is available from the DTE however,
in either X.21 or X.21bis.
5.4.3.1 Remote Loop from menu
On applying the loop, the TM LED should light and the top level status display should show ‘Loop Active’.
To apply the loop select the item T> Rem Loop Off
Press SELECT and the display should change to T> Rem Loop On
Note: As this feature applies a loop at the remote end, it is possible that in some circumstances (mainly
fault conditions) that the actual loop can be removed without the local BBM realising it. In these cases the
display will show Rem Loop On when in fact no loop exists. If the loop has been cleared by a transient fault
condition it can of course be reapplied by deselecting the Remote loop and then re-selecting it. The data
flow with the loop applied is as shown in figure 5.4.3.
Note : In order to apply a remote loop back to line at the remote end of a BBM to BBM link from the local
end, when operating with an X.21 or G.703 interface at an unstructured rate ie : 64kbps (bit or byte
timing) or 128kbps, use the communication channel loop back (see section 5.4.9).