Power over Ethernet commonly referenced as PoE for short is a method of transferring power along with data on twisted pair Ethernet cabling (cat5e, cat6, etc). A PoE injector supplies power to a security camera by “injecting” power into the Ethernet cable. Typically speaking, a PoE injector will plug into a standard wall outlet and then convert the alternating current (AC) into Direct Current(DC) so it can power the low voltage network security camera.
The PoE Injector for an IP camera
A PoE injector will almost always have two RJ45 Ethernet ports, one will be labeled Data in and the other port will be labeled PoE/Data Out. The typical use of a PoE injector will require 3 devices. The PoE injector itself, A connection to the network, usually a router, or a switch, and the device that requires the PoE injector in this case an IP security camera.
Data In Port
The Data In port is used to connect the security camera to the local network. In most cases, this will be your home router, the NVR camera port, or a network switch. Without this port connected the camera will be unreachable from the local network.
PoE/Data Out Port
The PoE/ Data out port does two things, it provides power to the camera and also completes the network so data transmission can be complete. Without this port connected the camera will not power up, and will not connect to the NVR/network.
How much power can the PoE Injector provide to the IP camera?
Two are the main standards for PoE devices:
- 802.3af. PoE standard provides up to 15.4 W of DC power. This is the older standard of the two but many cameras will have this as a listed specification still and most of regular IP cameras work on this standard.
- 802.3at. PoE standard also known as PoE+ or PoE plus, provides up to 25.5 W of power and is backwards compatible with 802.3af devices. The PTZ cameras need a PoE injector that supports this standart (since the PTZ cameras require a lot of power to function properly).
| PoE Standard | PoE Common Name | Power Output | Comment |
| IEEE 802.3af | PoE | 15.40 W | 12.95 W power available for connected device (PD) |
| IEEE 802.3at | PoE+ | 30 W | 25.50 W power available for connected device (PD) |
| IEEE 802.3bt Type 3 | 4PPoE, Ultra PoE | 60 W | 51 W power available for connected device (PD) |
| IEEE 802.3bt Type 4 | Ultra PoE | 100 W | 71 W power available for connected device (PD) |
Diagram to connect an IP camera via a PoE Injector
As you can see in the diagram we need three devices to do the setup: the PoE injector itself, a connection to the network (usually a router or a switch) and the device that requires the PoE injector in this case an IP security camera.
Recommended PoE Injectors for CCTV IP cameras
TP-LINK PoE Injector
TRENDnet Gigabit PoE Injector
