3Com Switch 4500 Family Manual page 139

If the cable is in normal state, the displayed length value is the total length of the cable.
If the cable is in any other state, the displayed length value is the length from the port to the faulty
point.
Pair impedance mismatch
Pair skew
Pair swap
Pair polarity
Insertion loss
Return loss
Near-end crosstalk
By default, the system does not test the cable connected to the Ethernet port.
Currently, only cable status and cable length can be tested. A hyphen (-) indicates that the
corresponding test item is not supported.
Examples
# Enable the system to test the cable connected to Ethernet 1/0/1.
<Sysname> system-view
System View: return to User View with Ctrl+Z.
[Sysname] interface Ethernet 1/0/1
[Sysname-Ethernet1/0/1] virtual-cable-test
Cable status: normal, 0 meter(s)
Pair Impedance mismatch: -
Pair skew: - ns
Pair swap: -
Pair polarity: -
Insertion loss: - db
Return loss: - db
Near-end crosstalk: - db
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