Verilink IMUX (880-503137-001) Product Manual - Manual (Page 41)

Diagnostics
Verilink IMUX User Manual 5-3
Figure 5-3 IMUX Loopbacks
Table 5-2 IMUX Loopbacks
Loopback Type Definition
Payload Loopback (PLB) A PLB loops the signal intended for the DTE back
toward the far-end at the data port. It tests the
T1 channels and the IMUX module up to the data
port.
Equipment Loopback (ELB) When used with an M1-3, the DTE signal is
looped back to the DTE. This test isolates the
equipment cable and DTE as possible trouble
locations.
IMUX
Equipment
Loopback
DTE IMUX M1-3
Payload
Loopback
IMUX M1-3
MLS
Midplane