Patton electronic 2710 user manual Loop V.54 & Telco Diagnostics, Operating Local Loopback LL

5.2 LOOP (V.54 & TELCO) DIAGNOSTICS

The NetLink-T1™ offers three V.54 loop diagnostics and is com- patible with two Telco loop diagnostics. Use these diagnostics to test the CSU/DSU and any communication links. These tests can be acti- vated via the software control port (See Section 3.2.3 System Diagnostics) or via signals on the serial port interface.

5.2.1 Operating Local Loopback (LL)

The Local Loopback (LL) test checks the operation of the local

NetLink-T1™, and is performed separately on each unit. Any data sent to the local NetLink-T1™ in this test mode will be echoed (returned) back to the user device (i.e., characters typed on the keyboard of a ter- minal will appear on the terminal screen).

To perform a LL test, follow these steps:

1.Activate LL. This may be done in one of two ways:

a. Enter a Local Loop from the System Diagnostics/Statistics menu and toggle the <Spacebar> until “LL” appears next to the a Local Loop option.

b.Activate the “LL” signal on the DTE. If you are not sure which lead is the “LL” signal, please refer to Appendix D.

2.Verify that the data terminal equipment is operating properly and can be used for a test.

3.Perform a V.52 BER (bit error rate) test as described in Section 5.3.3. If the BER test equipment indicates no faults, but the data terminal indicates a fault, follow the manufactur- er’s checkout procedures for the data terminal. Also, check the interface cable between the terminal and the NetLink- T1™.

5.2.2Operating Remote Digital Loopback (RL)

The Remote Digital Loopback (RL) test checks the performance of both the local and remote NetLink-T1™, as well as the communication link between them. Any characters sent to the remote NetLink-T1™ in this test mode will be returned back to the originating device (i.e, char- acters typed on the keyboard of the local terminal will appear on the local terminal screen after having been passed to the remote NetLink- T1™ and looped back).

To perform an RDL test, follow these steps:

1.Activate RDL. This may be done in two ways:

a. Enter b Remote Loop from the System Diagnostics/Statistics menu and toggle the <Spacebar> until “RL” appears next to the b Remote Loop option.;

b.Activate the “RL” signal on the DTE. If you are not sure which lead is the “RL” signal, please refer to Appendix D.

2.Perform a bit error rate test (BERT) using the internal V.52 generator (as described in Section 5.3), or using a separate BER Tester. If the BER test indicates a fault, and the Local Line Loopback test was successful for both NetLink™s, you may have a problem with the twisted pair line connection.

5.2.3Central Office Loops

The NetLink-T1™ also responds to central office initiated loop com- mands. When in D4 framing mode, the NetLink-T1™ will implement the “loop up” command 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.

When operating in ESF framing mode, loopback commands are issued via the Facility Data Link (FDL). The line loop message will cause a loop back before data enters the framer portion of the CSU. The payload loop message will cause the NetLink-T1™ to loop data after the framer portion of the CSU.

The NetLink-T1™ will respond to Universal Loopback De-activate to clear all central office loops.

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