American Telecom AM64/128A - Manual (Page 19)

AM64/128A User Manual Test Menu
19
With a G.703 Interface fitted, the application of a local loop will cause G.703 data to be looped back to
the G.703 network at the G.703 interface (known as a Loop B / LCB loop on the G.703 linecard and
standalone units) as shown in figure 5.4.1.2 below.
5.4.1.2 Local loop from DTE
To apply a local loop in this fashion refer to your DTE equipment handbook for details on how to send the
pattern. The BBM can be in any menu when this loop is applied, it does not have to be in the Test Menu.
Note : The Test Menu ‘Loc Loop’ message does not reflect the state of a loop applied from the DTE, but
the status menu display and the TM LED will be set as in the diagram figure 5.4.1.1.
It is possible to have a BBM Menu selected local loop operational at the same time as a DTE local loop. In
this case the local loop will only be removed when both the Menu item has been deselected and the DTE
has cancelled its loop, (i.e. the loop is removed by the last releasing action).
5.4.2 Loopback
The loopback feature places a loop on the local BBM in the opposite sense to the local loop, i.e. data
coming from the line is looped back. The DTE is effectively cut off and receives a Not Ready signal.
Loopback is applied by selecting the display: T > Loopback Off
Pressing SELECT activates the loop, indicated by: T > Loopback On
The TM LED should then light and the top level status display should show ‘Loop Active’.
The data flow for this loop is shown in fig 5.4.2.1 below :
This loop cannot be activated from the local DTE, only by the remote DTE, and in this case it is termed a
Remote Loop, (see section 5.4.3).