Editor’s note:I am pleased to have Victor Chertakovsky back on Planet Analog. Below, he is sharing a good tutorial and refresher on Power over Ethernet (PoE). I think this is a good topic of discussion especially in light of the many industry demands for the standardization of higher power PoE.
What is Power over Ethernet?
Power over Ethernet (PoE) is a technology that allows network cables to carry electrical power. With PoE, power can be supplied either by a PoE switch or from a PoE injector (a small power supply placed between a switch and a powered PoE device).
For example, a digital security camera or an indoor/outdoor home security health care device normally requires two connections to be made when they are installed:
- A network connection, in order to be able to communicate with video recording and alarm signal acquisition systems
- A power connection, to deliver the electrical power the camera or other security devices need to operate.
However, if this equipment is PoE-enabled, only the network connection needs to be made, as it will receive its electrical power from this cable as well.
Why use POE?
Specifying Power over Ethernet brings many advantages to an installation:
- Time and cost savings are achieved by reducing the time and expense of having electrical power cabling installed. Network cables do not require a qualified electrician to fit them, and can be located almost anywhere.
- Flexibility: Without being tethered to an electrical outlet, devices such as IP cameras, wireless access points and indoor/outdoor home security & health care devices can be located wherever they are needed most and repositioned easily if required.
- Safety: PoE delivery is intelligent, and designed to protect network equipment from overload, under-powering, or incorrect installation.
- Reliability: PoE power comes from a central and universally compatible source, rather than a collection of distributed wall adapters. It can be backed-up by an uninterruptible power supply, or controlled to easily disable or reset devices.
- Scalability: Having power available on the network means that installation and distribution of network connections is simple and effective.
Devices that use Power over Ethernet
POE has many applications, but the three key areas are:
- VoIP phones: This is the original PoE application. Using PoE means phones have a single connection to a wall socket, and can be remotely powered down, just like with the older analog systems.
- IP cameras: PoE is now ubiquitous on networked surveillance cameras, where it enables fast deployment and easy repositioning.
- Wireless WiFi and Bluetooth APs and RFID readers are commonly PoE-compatible, to allow remote location away from AC outlets, and relocation following site surveys.
The main advantage of using PoE for security device powering is for powering of Home Security & Health Care Devices. Usually, inside and outside the house, Home Security & Health Care Devices are powered from batteries. The ability to replace batteries by PoE makes it possible for the user to save a great deal of cost on Alkaline Batteries and prevent the waste of sending dozens of used batteries into our environment during the year. The PoE replacement will avoid the pollution caused by discarded Alkaline Batteries.
Besides the simplicity of reduced cabling and the convenience of eliminating the need for direct power in difficult locations, PoE offers some other benefits. Almost any device can occasionally require a restart to restore functionality. How many times have you had to climb a ladder or a flight of stairs to power-cycle a device? You’re not alone. With a full-featured PoE switch, an administrator can power-cycle a device from the switch’s built-in management interface.
It is cheaper and simpler to deploy Ethernet cable data points than to mount additional AC outlets, since a typical electrical installation of a single device is $200-$750 on average.