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AM64/128A User Manual Test Menu
21
5.4.3.2 Remote loop from DTE
When the BBM receives an ART pattern (00110011) from the DTE (in X.21), or when circuit 140 is active
(in X.21bis) the loopback is applied on the remote BBM similarly to the above. To apply a remote loop in
this fashion refer to your DTE handbook for details.
The BBM can be in any menu when this loop is applied, it does not have to be in the Test Menu.
Note that the Test Menu
Rem 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 above case.
The data flow with the loop applied is shown in figure 5.4.3.
It is possible to have a BBM menu selected remote loop operational at the same time as a DTE remote loop.
In this case the loop itself 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).
5.4.4 Binary Patterns
It is possible to transmit three different patterns to the remote BBM:
(1) All 1's with status ON
(2) All 0's with status ON
(3) Alternate 1’s and 0’s with status OFF (Controlled Not Ready’s or CNR’s)
The CNR pattern (3) is sent by pressing ‘TX NRDY’ on the front panel. Patterns (1) and (2) can only be
activated from the test menu.
Default state is sending no patterns when the display is : T> Bin Keys Off
If the SELECT key is pressed then binary 0's are sent : T> Sending Bin 0
If the SELECT key is pressed again then the binary 1 pattern is sent : T> Sending Bin 1
A third press of SELECT returns the function to its default (off) state.
Note : several factors may prevent the binary pattern being transmitted. The test menu display shows only
that a binary pattern will be transmitted if the BBM is capable of it.
Factors preventing transmission are:
(1) Fault conditions
(2) Loop back active
(3) Local loop active
(4) TX NRDY key active
With most rates the patterns are sent with status ON. If an unstructured rate, such as 64kbps, is used, there
is no status line. In this case binary 1’s become effectively a AIS signal, and binary 0’s become a UNR signal.