Maintenance
4-24 3160-A2-GB21-80
March 1999
Starting a Payload Loopback
The Payload Loopback command (PLB) loops the received signal on the network
interface back to the network. The signal is looped back as close to the DTE
Drop/Insert (DSX-1) port as possible (after it has passed through the framing
circuitry of the DSU/CSU). Framing CRCs and BPVs are corrected.
496-14316-02
CSUDSU
NETWORK
INTERFACE
DTE
(DSX-1)
ALL 1s
PLB
PORT 1PORT 2
ALL 1s
ALL
1s
Procedure
To perform a Payload loopback:
1. From the top-level menu screen, select Test.
2. From the Test screen, select Lpbk.
F1
Test:
Rlpbk Lpbk Ptrns
F2 F3
3. From the Loopback screen, select PLB.
F1
Loopback:
Abort LLB PLB
F2 F3
Test Started appears on Line 2. If a Payload loopback is already in
progress, the Already Active message appears. If an invalid combination
of loopbacks is in progress, the error message Invld Test Combo appears
(see Table 4-8 for valid loopback test combinations).