Specifications

CSU/DSU MS DBU

12.2.2 T

ROUBLESHOOTING

NSTALLATIONS

Before initiating diagnostics on a newly installed unit and/or DDS circuit and

before contacting Black Box Technical Support, please check the items in

Table 12-2 to ensure the unit is configured properly.

After verifying the items listed in Table 12-2, the unit should operate properly

and display the following:

DATA MODE

LOOP IS NORMAL

If a status message other than DATA MODE LOOP IS NORMAL is shown,

begin performing the diagnostics described below the table.

Table 12-2. Troubleshooting New Installations

Configuration

Item to Check Option Selection Action

DTE Type EIA-232 or V.35 From the Configuration menu, select the

type of DTE interface option to connect to

the DSU/CSU.

Loop Rate Auto, 2.4 to 64 kbps From the Configuration menu, select the

DDS loop rate of the DDS circuit.

Data Format Async or Sync From the Configuration menu, select the

type of data to be used.

DTE Cable N/A Verify DTE cable connection to the proper

DTE connector on the DSU/CSU.

Telco Cable N/A Verify the telco cable is securely connected

to the DSU/CSU and wall jack.

Power the unit N/A Verify the unit passes self-test during

Off, then On. power-up (displayed on the LCD).

Test Sequence for Troubleshooting New Installs or Existing Circuits

If your DSU is suspected of having problems, perform a self-test to determine

whether the unit is in good health. Either use the ATZ command or turn the

CSU/DSU off, then on again. The LCD will show whether it passes the self-test.

If your DSU is receiving excessive errors requiring retransmission of data, first

perform a DTE with Test Pattern test (Section 12.3.4) to determine whether the

unit’s internal transmitter and receiver are operating error-free. If the problem

persists, perform a Remote Test to verify the connection between the local and