PoE Support Note
All contents copyright (c) 2011 ZyXEL Communications Corporation.
3
EndSpan & MidSpan
There are two kinds of PoE solutions in the world, Endspan and Midspan. Usually a PoE
switch would be an endspan solution, while a PoE Injector would be a midspan solution. (ex.
PoE-12, PoE-80)
Alternative A is also called “Endspan”, which means that data and power are in the same
twisted pairs. Power is carried over the data pairs (1/2 & 3/6)
Alternative B is also called “MidSpan” which means that data and power are NOT in the
same twisted pairs. Power is carried over the spare pairs (4/5 & 7/8)
