ZyXEL Communications ES-2024PWR Support Notes page 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)
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PoE Support Note
3