Power over Ethernet (PoE) technology was first ratified by the Institute of Electrical and Electronics Engineers (IEEE) in 2003 and has increasingly been used for powering network devices ever since. PoE has been proven to provide huge benefits such as easy installation, saving capital expenditures (CapEx) and operating expenses (OPEX), and offering a reliable and safe power standard for all types of networks worldwide.

PoE’s main limiting factor for use with new applications is the amount of power available. While standard PoE’s (IEEE 802.3af) 15.4 watts (W) availability is sufficient for applications such as IP cameras, VoIP phones, and Wireless Access Points (WAPs), it does not supply enough wattage for IP video phones, pan-tilt-zoom(PTZ) cameras, and alarm systems. As a result, the IEEE released the 802.3at (PoE+) standard of 30W.

These days, there is high demand for devices that require even more power (e.g., point-of-sale (PoS) systems, digital signage, connected LED lighting, etc.). This is where the IEEE 803.2bt standard comes in.

PoE Terminology

It is important to define common PoE terms before talking more specifically about Hi-PoE.

PoE, PoE+, PoE++, and Hi-PoE

There are three standards that define four types of Power over Ethernet technology.


PoE is also called standard PoE, IEEE 802.3af, or Type 1 and is the first standard ratified by the IEEE in 2003. This standard supplies a maximum of 15.4W of power to applications such as IP cameras, VoIP phones, and WAPs.


Also called IEEE 802.3at or Type 2, the IEEE released this PoE standard in 2009. PoE+ supplies up to 30W of power to devices such as alarm systems and PTZ cameras. This standard is backward compatible with PoE (Type1).


PoE ++ is IEEE 802.3bt/Type 3, was ratified in 2018 by the IEEE, and supplies up to 60W to applications such as video telephones and thin clients. 


Hi-PoE is also known as IEEE802.3bt/Type 4 or high-powered PoE. It was ratified along with PoE++ in 2018 and supplies up to 100W of power to POS systems and LED lighting applications. IEEE 802.3bt Type 3 and Type 4 are backward compatible with the PoE and PoE+ standards.

PoE Types

Powered Device (PD)

Any network device powered by PoE technology is referred to as a powered device or PD. Examples of PDs range from low-wattage IP security cameras to more power-hungry applications such as LED lighting.

Power Sourcing Equipment (PSE)

Power sourcing equipment (PSE) are devices that send both power and data over a single Ethernet cable to a connected PD. PSEs have two classifications: they are either an “endspan” or a  “midspan” device.


Also known as an “endpoint,” the typical endspan device in a PoE network is a PoE switch. The PoE switch (PSE) sends power to the connected device (PD).


The most common midspan PSE device is a PoE injector. Here’s how it works: If a network has a non-PoE-enabled switch, a PoE power source (PSE) must be added to the system to use a PoE PD. This device (e.g., a PoE injector) is positioned between the non-PoE switch and the PoE PD—hence, the term “midspan” or “in the middle.”

POE-171A-95 End Span or Mid Span

IEEE 802.3bt (Hi-PoE)

The IEEE ratified the 802.3bt standard in September 2018. It defines two standards of PoE: PoE++ (Type 3) and high powered PoE (or HI-PoE/Type 4). Type 3 provides up to 60W at each PoE port, with 51W available to the powered device (PD). The power reduction happens because of power loss during the transmission process. Type 4 supplies a maximum output of 100W (with 71W available to the PD).

IEEE 802.3bt: A New Generation of PoE

PoE technology transmits power and data over standard Unshielded-Twisted Pair (UTP) cables. UTP cables consist of four pairs of twisted-pair wires (a total of eight wires). The IEEE 802.3af (PoE) and 802.3at (PoE+) standards use two twisted pairs for power connection, while all four pairs can deliver data. 

In contrast, the newest PoE generation (IEEE 802.3bt) uses all four twisted pairs to transport power. Using all eight wires is an improvement as it minimizes power loss during the transmission process—thus, supplying an increased power budget which allows more higher-power PDs to be added to the network.

IEEE 802.3bt Introduces New Types and Standards

This latest PoE standard introduced two new PoE types: POE++ (Type 3) and Hi-PoE (Type 4), as well as four additional classes (Class 5-8).

IEEE 802.3 PoE technology has a class system. Each PoE type is assigned a class that “is determined by the lowest common power level that can be supported by both the PSE and PD. This is achieved by the PSE detecting the power requirements of the PD using Link Layer Discovery Protocol (LLDP), which essentially analyzes bi-directional data packets between the PSE and the PD.”

There are nine classes that range from 0 to 8. For example, Type 1 and Type 2 support Class 0-4, Type 3 supports Class 5-6, and Type 4 supports Class 7-8.

The main reason for using this class system is to better manage a PSE’s power budget. For example, if a PSE is Class 8, but the PD is only Class 7, the system is classified as Class 7, so the PSE delivers only the power that the PD requires rather than outputting more power than necessary.

Single and Dual Signature

Along with new types and classes, the IEEE 802.3bt standard brings two new PD typologies: single signature and dual signature.

The PoE and Poe+ standards do not distinguish between single-signature and dual-signature PDs. IEEE 802.3bt introduced this new concept to designers and manufacturers of PoE equipment. An Ethernet Alliance white paper describes single/dual signature PDs as follows:

At a high level, a dual-signature PD has two separate detection circuits and two separate classification circuits. In contrast, a single-signature PD has a single detection circuit and a single classification circuit.

Dual-signature PDs enable applications that require up to the same maximum power level as single-signature PDs, but with the additional flexibility of different load configurations and either a parallel or staggered power-up sequence across Modes. The following are typical applications for dual-signature PDs:

  • A PD that consists of two independent, isolated loads with distinct Class requested over each Mode.
  • A PD that consists of two independent, isolated loads with the same Class requested on both Modes and where only one of the loads is operating while the other provides redundancy.

POE-171A-95 PoE InjectorPLANET USA’s PoE-171A-95 is a Single-Port 802.3bt Power over Ethernet Injector with a maximum of up to 95W of power output. It is equipped with 10M/100M/1G/2.5F G/5GBASE-T

RJ45 copper interfaces that can handle extremely large amounts of data transmission. 

The POE-171A-95 is designed to meet the demands for higher power required by network equipment, such as:

  • PTZ speed dome
  • All-in-One touch PC
  • Remote digital signage display
  • Other network PDs that require higher power to work

To learn about Planet USA’s high-quality products, visit our website.