LOTC | The Loss of Transmit Clock LED lights |
| when |
| the unit detects that there is no transmit |
| clock. |
ALM | The alarm LED indicates the loss of carrier, |
| i.e., no activity on the network. |
ERR | The error LED is not used in Model 2702. |
TST | The test indicator LED blinks with a specific |
| pattern depending on the type of test mode. |
| When the unit is in local analog loop, the |
| LED will blink on briefly. When the unit is in |
| remote loop, the TST LED will blink off |
| briefly. The test mode is V.54 Loopback & |
| Local loopback. |
PWR | The power indicator LED will remain lit while |
| the unit is powered. It turns off when the |
| unit is not powered. |
5.2 LOOP (V.54 & TELCO) DIAGNOSTICS
The Model 2702 offers two V.54 loop diagnostics and is compati- ble with two Telco loop diagnostics. Use these diagnostics to test the NTU and any communication links. These tests can be activated via signals on the DTE interface.
5.2.1 Operating Local Loopback (LL)
The Local Loopback (LL) test checks the operation of the local Model 2702, and is performed separately on each unit. Any data sent to the local Model 2702 in this mode will be echoed (returned) back to the user device. To perform a LL test, follow the steps below.
1.Activate the “LL” signal on the DTE pin L. 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. If the BER test equip- ment indicates no faults, but the data terminal indicates a fault, follow the manufacturer’s checkout procedures for the data terminal. Also, check the interface cable between the terminal and the Model 2702.
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5.2.2 Operating Remote Digital Loopback (RL)
The Remote Digital Loopback (RL) test checks the performance of both the local and remote Model 2702, as well as the communication link between them. To perform a RDL test, follow the steps below.
1.Activate the “RL” signal on the DTE pin N. If you are not sure which lead is the “RL” signal, please refer to Appendix D.
2.Perform a bit error rate test (BERT) 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.
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