What Is A PoE Injector?

What is a PoE Injector?

Power over Ethernet (PoE) delivers both power and data concurrently via twisted pair Ethernet cabling. This technology improves network agility and scalability in efficient and cost-effective ways. There are several types of PoE devices, for example, the PoE switch, PoE splitter, PoE injector, etc. This article focuses on the PoE injector: What is it? What does it work? Are there different types? How is it installed?

What is a Power over Ethernet (PoE) injector?

Let’s start with a definition. PC Magazine defines the PoE injector as follows:

A device that adds power to an Ethernet cable for Power over Ethernet (PoE) equipment. Although Ethernet switches are available with PoE capability, millions of regular “non-PoE” switches are in use and continue to be installed. . .1

As stated above, these (also called midspan or PoE adapter) are used to make a non-PoE LAN switch port work with PoE devices. A PoE injector is ideal for low-power devices that need to be installed in hard-to-reach places where there are no power outlets available. This affords power with no impact on existing building structures at a minimal cost.

How does a PoE injector work?

These devices connect a wireless access point (WAP), PoE lighting, IP camera, or any IEEE 802.3af, IEEE 802.3at, and IEEE 802.3bt-powered device (PD) to a network switch. Power is then “injected” into an Ethernet cable. Typically, a PoE injector converts AC to DC to power these low-voltage PoE devices.

PoE Injector Application

A PoE injector usually has two RJ45 ports, one labeled Data In and one labeled PoE/Data Out. Following is an overview of what each of these ports does.

Data In port

Let’s use the example of an IP security camera. The Data In port connects the security camera to the local network, the NVR camera port, or a network switch. If this port is not connected to the security camera, the local network is unreachable.

PoE/Data Out port

This port has two functions: 1) It delivers power to the IP security camera, and 2) it completes the network, so data is transmitted successfully. If this port is not connected to the security camera, it will not power up and will not connect to the NVR/network.

Setting this up usually requires three devices: 1) a connection to the network (E.g., a router or a switch), 2) the PD, and 3) the PoE injector itself.


Are there different types?

Active PoE Injector

Conforms to the PoE standard of IEEE 802.3af, IEEE 802.3at, or IEEE 802.3bt is considered to use active PoE. During the initial handshake, if the PoE injector does not receive the proper acknowledgment, it will not power up, ensuring the device’s safety. The typical 802.3at/af/bt PoE voltage is 44 to 57 volts (V) DC.

Passive PoE Injector

Adopts PoE technology that does not conform to the 802.3at/af/bt standard is considered to use passive PoE. Generally, passive PoE devices run on 18 to 48 volts. It is important to note that it may likely cause permanent electrical damage to the device if the wrong voltage is connected.

12 Volt, 24 Volt, and 48 Volt PoE Injectors

Depending upon the output power voltage a PoE injector supplies, it is put into one of three types: 12V, 24V, or 48V. The voltage of a PoE injector must be taken into account as its voltage and the voltage standard of the PoE device must be compatible.

In addition, they can also be typed by the number of ports they have (e.g., one-port PoE injectors, eight-port PoE injectors, etc.)

How do you install a PoE injector?

Let’s continue to use the example of an IP security camera. There are six steps to follow:

  1. You will need the following equipment: an IP camera, a PoE injector, a standard network switch, and Cat5e, Cat6, or Cat6a Ethernet cabling.
  2. Test to make sure the IP camera, PoE injector, and the IP camera’s management work properly.
  3. Make sure all video and network configurations are made before mounting the IP camera.
  4. Plug the Ethernet cable into the PoE injector’s PoE/Data Out port, then connect the other end of the cable to the IP camera’s PoE port.
  5. Mount the IP camera where there is adequate light to ensure it can capture a clear image on the screen.
  6. Plug another Ethernet cable into the PoE injector’s Data In port, then connect the other end of the cable to the Ethernet switch.
  7. Plug the PoE injector’s power cord into a local AC outlet.

How does a PoE injector benefit you?

There are three major benefits:

  1. Easy installation: A simple play-and-plug solution to your PoE needs.
  2. Flexible network expansion: PoE injectors add PoE capability to non-PoE switches, thus extending the network distance. Also, the use of Ethernet cabling allows for better end device connections.
  3. Saves time and money: With a PoE injector, there is no need to perform the labor-intensive task of running both data and power cable from the network switch to the PD. PoE is fast and cheap—saving both time and money.

What things should I consider when purchasing a PoE injector?

When you are ready to purchase, make sure you have thought about the following three things:

  1. The number of PDs: If there is only one PD, a PoE injector with a single port will do. However, if there are several PDs, make sure you have a sufficient number of ports.
  2. PoE port power supply: The PoE injector’s PoE standard must conform with the PD. There are three primary PoE standards—802.3af (PoE) supplies power up to 15.4 watts (W); 802.3at (PoE+) supplies power up to 30 W; and 802.3bt (PoE++) supplies power up to 100 W.
  3. Power supply voltage: Just as with the PoE power supply, the PoE injector’s voltage must be compliant with the PDs. This compliance will prevent overloads or operating issues.

A Last Word

Versa Technology has a line of high-quality PoE injectors that will enable you to couple non-PoE power sourcing equipment (PSE) with PoE PDs.

Contact us Contact us. We will be happy to advise you as to which PoE injector is best for your project.

1: PC Magazine Encyclopedia