"Andrew Gabriel" wrote in message
.. .

When I originally did my home structured cabling, I made a point
of putting A and B wires onto one of the pairs not used by
10/100 ethernet, so I didn't blow up any ethernet ports by
plugging in a POTS line by mistake. However, I'm not all gigabit
ethernet (uses all 4 pairs) so I just have to be more careful.

No need.. Ethernet is a transformer coupled interface and there are
isolating transformers at each end of each pair.
They should be good to at least 1500V to meet the standard.
It why you can't blow old stuff up if you plug it into POE port.