B.Verify that the data terminal equipment is operating properly and can be used for a test. If a fault is indicated, call a technician or replace the unit.
C.Perform a BER (bit error rate) test on each unit using a separate BER tester. If the BER test equipment 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 1090.
5.3.2REMOTE DIGITAL LOOPBACK (RDL)
The Remote Digital Loopback (RDL) test checks the performance of both the local and remote Model 1090',and the communication link between them. Any characters sent to the remote Model 1090 in this test mode will be returned back to the originating device.
To perform an RDL test, follow these steps:
Figure 7. Remote Digital Loop
A.Activate RDL. This may be done in one of two ways: First, by moving the front panel toggle switch DOWN to “Remote”. Or, second, by raising the RL signal on the terminal interface (for pin numbers, see Appendix D).
B.Perform a BER (bit error rate) test on the system, using BER testers on both ends.
C.If the BER test equipment indicates a fault and the Local Analog Loopback test was successful for both Model 1090s, you may have a problem with the line between the Model 1090s. You should inspect the line for proper connections.
5.3.3 LOCAL DIGITAL LOOPBACK (LDL)
The Local Digital Loopback (LDL) test checks the local and remote 1090s and all communication paths. In LDL, the TX/RX circuit of the local 1090 closes, thereby allowing characters sent from BOTH the local terminal and remote terminal to loop back (echo) to themselves (See Figure 8, below). To accurately perform LDL diagnostics, technicians must send characters (or BER diagnostics) from each end. To perform a LDL, follow the instructions below:
Figure 8. Local Digital Loop
A.On the bottom of the unit, turn
B.Enable LDL by moving the front panel toggle switch up to “Local”, Or, by raising the signal LL on the terminal interface(for pin numbers, see Appendix D).
C.Perform a BER (bit error rate) test on the system, using BER testers on both ends.
D.If the BER test equipment indicates a fault and the Local Analog Loopback test was successful for both Model 1090s, you may have a problem with the line between the Model 1090s. You should inspect the line for proper connections.
NOTE: LDL will only work when
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