Power over Ethernet is a technology that allows IP telephones, wireless LAN Access Points, security network cameras and other IP-based terminals to receive power, in parallel to data, over the existing CAT-5 Ethernet infrastructure without the need to make any modifications. Described by IEEE 802.3af standard.

PoE integrates data and power on the same wires, while keeping the structured cabling safe and not interfering with concurrent network operation. PoE delivers 44-57v of DC power over unshielded twisted-pair wiring for terminals consuming up to 25 watts, depending on the version of the standard in use. There are several common techniques for transmitting power over Ethernet cabling; two of them have been standardized by the IEEE 802.3 committee. Power may be transmitted on the unused (spare) conductors of a cable, since only two of the four pairs are needed for the commonly used 10Mbit/s–100Mbit/s physical layers (Alternative B) or power may be transmitted on the data conductors by applying a common-mode voltage to each pair (Alternative A). 

IEEE 802.3af standard POE pinout:

Pin Alternative A Alternative B
1 Vport Positive  
2 Vport Positive  
3 Vport Negative  
4   Vport Positive
5   Vport Positive
6 Vport Negative  
7   Vport Negative
8   Vport Negative


The original IEEE 802.3af-2003 PoE standard devices provides up to 15.4 W of DC power (minimum 44 V DC and 350 mA) to each device.

The newer PoE+  IEEE 802.3at-2009 PoE standard provides up to 25.5 W of power. Some vendors have announced products that offer up to 51 W of power over a single cable by utilizing all four pairs in the Category 5 cable.

POE devices pinouts of various manufacturers

  Ethernet RJ-45 connector pin number    
Source Voltage 1 2 3 4 5 6 7 8 Load Voltage DC Load Connector  
IEEE 802.3af
using data pairs
48 V DC, protected RX, DC+ RX, DC+ TX, DC- spare spare TX, DC- spare spare (embedded) Industry Standard for active PoE
IEEE 802.3af
using spare pairs
48 V DC, protected RX RX TX DC+ DC+ TX DC- DC- (embedded) Industry Standard for passive PoE
Intel, Symbol, Orinoco Usually
12 or 24 V DC
RX RX TX DC+ DC+ TX DC- DC- (embedded) Most Brands of PoE
(OLD old standard)
48 V DC RX RX TX DC- DC- TX DC+ DC+ (embedded) Older Cisco polarity is
(NEW old standard)
48 V DC RX RX TX DC+ DC+ TX DC- DC- (embedded) New Cisco is IEEE compliant

Cisco   (very unusual)

28 V DC DC+ DC- TX n.c. n.c. TX RX RX (embedded) Seen on Cisco 7936 conference station
D-Link (Adapter) 48 V DC RX RX TX DC+ DC+ TX DC- DC-

or 12VDC@1A

DC coaxial
D-Link PoE Adapter for non-PoE products.
Apple MacIntosh AirPort PoE, Extreme 48 V DC RX RX TX DC?? DC?? TX DC?? DC?? Converted to ??? DC coaxial
Mac Polarity Unknown
HyperLink Many DC Voltages Available RX RX TX DC+ DC+ TX DC- DC- same as input DC coaxial and others available Variety of Options Available to Fit Most Brands of PoE
NYC Wireless
Roll Your Own
12 or 24 or 48 V DC RX RX TX DC+ DC+ TX DC- DC- same as input DC coaxial
or as reqd
New York City Wireless PoE
3Com AirConnect 24 V DC RX RX TX spare spare TX DC+ DC-     3Com AirConnect wireless access points
Alvarion VL 55 Vdc RX RX TX DC+ DC- TX DC+ DC-      
TP-link TL-SF1008P   DC- DC- DC+         DC+      
Polycom IP500 / 501 12V DC RX RX TX DC- DC- TX DC+ DC+     The only difference between regular PoE injectors and the Polycom one is the inverted polarity.

PoE - powered devices should obey following specifications:

Parameter Min Max
Signature Resistance, KOhm 23.75 26.25
Startup Time (till I>10mA), ms   300
Power Consumption, W   12.95
Operating Input Voltage Range, V 36 57
Must Turn on Voltage, V 44  
Must Turn off Voltage, V 30 V  
Input Current (@36Vdc), mA 10 350
Input Current, Peak, mA   400

Maximum length of the cable PoE UTP 5cat.

Input Voltage 9 V: < 30 m

Input Voltage 12 V: < 60 m

Input Voltage 24 V and more answers the quality IEEE 802.3af standard.


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8 pin RJ45 (8P8C) male connector layout
8 pin RJ45 (8P8C) male connector
at the cable