Power over Ethernet, a.k.a. PoE or 802.3af, and its new big
sibling Power over Ethernet Plus, a.k.a. PoE+ or 802.3at, are
forms of “inline power.” Inline power refers to providing power,
either AC or DC, over the same cable that the data signals are
travelling. An example of inline power you may be more familiar
is USB-powered devices — devices that can be powered through a
USB port, like mice, keyboards, small disk drives, reading
lights, and that also to do battery recharging on headsets,
smartphones, and other devices. (This requires the USB port
being supplied with enough power. On some notebooks, not all the
USB ports also provide power; similarly, on some desktops, USB
ports in the back will also provide power but not the front
ones.) Another example which might not be obvious to people who
grew up using mostly cell phones is the non-wireless home table-
top telephones and wall phones, which not only didn’t need
batteries or AC adapters, but kept working when the neighborhood
power went out because they