G.703/G.704 NTU W/V35
20
Figure 7. Remote Loop in a Network Extension Application
There are two Remote Loops that can be initiated from the MT335A: (1) V.54
Loop, and; (2) CSU Loop. The user can select the type of loop that can be initi-
ated by Switch S2-4. When a loopback is initiated this is the type of loop that the
unit uses to loop up the remote unit and which type of loop the unit will
respond to.
To perform an RDL test, follow these steps:
1. Activate RDL. This may be done in two ways:
— Activate the “RL” signal on the DTE. If you are not sure which lead is
the “RL” signal, please refer to Appendix B.
— Set the front panel switch to “Remote”.
2. Perform a bit error rate test (BERT) using the internal V.52 generator (as
described in section “Using the V.52 (BER) Test Pattern Generator”), or
using a separate BER Tester. If the BER test indicates a fault, and the
Local Line Loopback test was successful for both devices, you may have
a problem with the twisted pair line connection.
4.9.33 CSU L
OOP
Although CSU Loop is predominantly a T1 function, the MT335A responds to
central office initiated loop commands. Customers can use this facility when the
Central Office network switch supports CSU loops over an E1 interface.
When CSU Loop is selected, the MT335A will implement the “loop up” com-
mand when it recognizes the pattern “10000” in the data stream for a minimum
of 5 seconds. The “loop down” command is implemented by the pattern “100” in
the data stream for a minimum of 5 seconds.
Serial
Device
Serial
Device
Receive
Recover
Clocking
Internal
Clocking
Cable Span
G.703/G.704 NTU
MT335A
G.703/G.704 NTU
MT335A
Clock/
Data
Clock/
Data
Clock/
Data
Data
Data
