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What Is Power Over Ethernet (PoE) And What Is It Used For?

What Is Power Over Ethernet (PoE) And What Is It Used For?

Power over Ethernet (PoE) is a standard that allows Ethernet cables to simultaneously transmit data and power using a single network cable. This allows system integrators and network installers to place electrical devices in locations without electrical circuits. Additionally, PoE eliminates the expense of installing additional electrical wiring by requiring professional electrical installers to ensure strict piping regulations are adhered to.

PoE technology delivers 10/100/1000 Mbps data and power budgets up to 15W, 30W, 60W and 90W to devices over Cat5e, Cat6 and Cat6a. Cat7 and Cat8 Ethernet cables for maximum distance of 100m.

PoE technology is based on IEEE 802.3af, 802.3at, and 802.3bt standards set by the Institute of Electrical and Electronics Engineers and govern how network equipment must operate to support interoperability between devices.

PoE-enabled devices can be power supply equipment (PSE), electrical appliances (PDs), or sometimes both. The power transmitting device is a PSE while the power device is a PD. Most PSEs are network switches or PoE injectors intended for use with non-PoE switches.

General areas of use

  • IP Phones
  • IP Cameras
  • Wireless Access Points

But it can also power other devices, including:

  • Lighting
  • ATMs
  • IP intercoms
  • Security card readers
  • IP hours

What are the 802.3af and 802.3at standards?

The Institute of Electrical and Electronics Engineers (IEEE) creates PoE standards. Click here to learn more about IEEE’s standardization process. There are currently three PoE standards available. The 802.3af standard supports 15.4W of power. However, although 802.3at power supply equipment (PSE) can deliver 15.4W of power, electrical devices (PDs) can only reliably receive 12.95W of power due to power dissipation.

In 2009 IEEE introduced the 802.3at standard (PoE+). This standard supports 30W of power, but similar to the 802.3af standard, power delivery causes PDs to receive a slightly lower amount of power, specifically 25.5W of power.

802.3bt (also known as PoE++) was certified in 2018 and has two types (Type 3 and Type 4) that offer higher power. The 802.3bt (Type 3) standard supports 60 W power with PDs receiving 51 W. The 802.3bt (Type 4) standard supports 100W, dissipating up to 71.3W at the receiving end. This new standard combines Mode A and Mode B to achieve a higher voltage and support 10 Gbps connections.

PSEs and PDs

Power supply equipment (PSE) refers to devices that provide power to connected devices, such as switches, hubs, and injectors. Electrical devices (PDs) receive power from PSEs. A few examples of PD include IP cameras, phones, and wireless access points (WAPs).

Mode A and Mode B

PoE devices often use different power pinout pairs. These two methods are “Mode A” and “Mode B”.

With Mode A, data pin pairs 1-2 form one side of the DC source and pin pairs 3-6 form the other side, making output pairs 4-5 and 7-8 unusable. Units that use Mode A are sometimes referred to as “last span” units.

Unlike Mode A, Mode B leaves no data pinout pairs unused. Pin pairs 1-2 and 3-6 send data. Pin pairs 4-5 form one side of the DC supply and pin pairs 7-8 form the other side. Units that use Mode B are also called “mid-span” devices.

While the differences between Mode A and Mode B are minimal, they are important to consider, as ignoring which power pins are used to transmit and receive power can lead to non-functioning connections.

Why is there so much emphasis on 100W?

A higher power budget is especially critical for PoE lighting systems and platforms and other smart technologies currently being adopted. As businesses move towards innovative technologies, automation is also advancing step by step. For example, smart PDs are automatic, and automation requires more power. Savvy device customers are realizing what is possible with Ethernet power delivery and the IEEE 802.3bt standard and are taking steps to upgrade their supporting infrastructure accordingly.

Some of the important applications for high power PoE include:

  • LED lighting and sensors
  • PTZ cameras
  • High performance WAPs
  • Thin client computers
  • VoIP Phones
  • IP security cameras
  • Facility monitoring controls
  • digital signal
  • point of sale kiosks

What are the advantages of PoE?

Cost efficiency: Eliminates the cost of hiring professional electrical installers.
Fast deployment: Network cables must be plugged into the appropriate equipment to function properly.
Flexibility : Network administrators can distribute electrical devices almost anywhere. Shielded cabling can be used for outdoor environments. For industrial environments, industrial grade electrical devices can be used.
Safety : Because it uses a relatively low voltage, it offers low risks of electrical hazards.
Reliability : Covered by IEEE’s stringent 802.3 standard specifications.
Scalability : Makes it easy to add new equipment to a network.

Reduces installation costs

Installation costs are much lower than traditional cabling installation and operating costs are much more efficient. A twisted pair cable provides both data and power to devices. Existing copper from old telephone systems can also be reused.

Additionally, PoE injectors and splitters save money by allowing IT professionals to combine older devices with newer, more efficient PoE network components. It also allows organizations to add remote devices without having to install electrical infrastructure. Injectors and splitters are designed to supply power to and from equipment that is not PoE compatible. These inexpensive units will add years to an older system and save thousands of dollars by skipping the installation of electrical outlets in remote locations.

Why is it faster?

PoE devices adapt to changing environments. They can be easily portable, reconnected at the switch level, and integrated into changing network configurations. It is plug and play. An entire network should not be shut down to add or remove devices.

Is PoE Safe?

PoE Type 3 voltages are typically less than 60V and Type 4 are less than 90V. Ducts and metal cladding are not required. Fewer steps and hazards and the simple use of an Ethernet cable eliminates the need for a trained electrician.

What are their data collection capabilities?

PoE technology is perfect for data collection. For example, analytics software can help facility groups determine when a space is occupied and when LED lighting and HVAC components can be turned off. As a result, operating costs can be much lower depending on actual usage.

What are the limits of PoE?

Limitations are few but should be taken into account when adopting for the first time:

  • It only transmits 100 m.
  • Incompatible devices require additional equipment.
  • Power budgets can reach levels found only in older equipment.

Can I Connect a Device That Doesn’t Support PoE to the PoE Port?

IEEE 802.3af/at/bt compliant PoE technology is secure. PoE injectors and switches will not harm any equipment, even if the devices do not support receiving power over Ethernet. Before sending any power to a connected PD, the PSE initiates a negotiation procedure that determines the power needed by the connected device. This procedure uses low voltage and is harmless to any connected devices, with or without PoE. If the handshake is completed, the PoE injector or switch sends power, which triggers the PD to start. If this handshake is not completed, the PSE will never send any power. This built-in feature of all IEEE 802.3af/at/bt compliant devices makes PoE technology inherently secure.

What is PoE Switch (Power over Ethernet Switch)?

Power over Ethernet (PoE) is an access layer technology that combines data signals and electrical power in a single Ethernet cable connection to enable remote powering the device. PoE switches provide PoE power and network connectivity to access points, surveillance cameras, and other IoT devices over twisted-pair cable.

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