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FAQ

What is the PoE power pins assignment mode A & B?


Answer:

There are two modes of PoE, A and B. Mode A delivers power on the data pairs of 100BASE-TX or 10BASE-T. Mode B delivers power on the spare pairs. PoE can also be used on 1000BASE-T Ethernet, in which case there are no spare pairs and all power is delivered using the phantom technique.

In mode A, pins 1 and 2 form one side of the 48 V DC, and pins 3 and 6 form the other side. These are the same two pairs used for data transmission in 10BASE-T and 100BASE-TX, allowing the provision of both power and data over only two pairs in such networks. The free polarity allows PoE to accommodate for crossover cables, patch cables and auto-MDIX.

In mode B, pins 4–5 form one side of the DC supply and pins 7–8 provide the return; these are the "spare" pairs in 10BASE-T and 100BASE-TX. Mode B, therefore, requires a 4-pair cable.

faq_switchpin.png

The PSE (power sourcing equipment), not the PD (powered device), decides whether power mode A or B shall be used. PDs that implement only Mode A or Mode B are disallowed by the standard.

Updated in September 2017

 

Mode A

Mode B

ER52000

V

 

ER58000

V

 

ER59000

V

 

EX74000

 

V

EX75000

 

V

EX76000

 

V

EX78000

V

V

EX78602

V Port 5, 6

V Port 1~6

EX78162

  V

EX78900

V

V

EX34000

 

V

EX45900

V

 

EX42300

V

 

EX38000

 

V

EX45000

 

V

EX46900A

V

 

EX46100

 

V

EX48000

 

V

EX48000A

 

V

EX49000

 

V

EX49000A

 

V

EX17008

V

 

EX17016

V

 

EX17082

V

 

EX17162

V

 

EX17242

V

 

EX17908

V (Port 2,4,6,8)

V (Port 1,3,5,7)

EX17044A

V

 

EX17008A

V

 

EX17016A

V

 

EX17082A

V

 

EX17162A

V

 

EX17908A

V (Port 2,4,6,8)

V (Port 1,3,5,7)

EX24402

 

V

EX26182

V

 

EX26262

V