The evolution of PoE, a self-powered Ethernet connection, is yet another example of the adaptability of Ethernet technology that uses the inherent ability of a copper based connection to transmit both data and power from point A to B over UTP cable. The list of applications for self-powered Ethernet connections is long. A relevant example is the adoption of Ethernet technology within industrial-based networking systems. Prior to looking at this example it is necessary to explain how PoE systems evolved as an alternative solution to a Plain Old Telephone Service (POTS).

Supplying power over an Ethernet UTP cable was originally developed to duplicate the functionality of the POTS, where the analogue telephone is self-powered via a UTP connection from a remote Central Office (CO) or local Private Branch Exchange (PBX). For new installations, Information Technology (IT) managers prefer to install a Voice over Internet Protocol (VoIP) telephone system rather than the alternative, the outdated POTS. The deployment of a VoIP telephone system allows IT managers to significantly reduce the complexity of the system and the number of systems they need to maintain and repair. More importantly, a VoIP telephone system reduces installation costs by deleting the need for a separate analogue telephone system and a PBX. Maintenance costs are similarly reduced by utilizing the power of an Internet Protocol (IP) address, allowing users greater facility to move desks without the need of a telephone technician to swap wiring loom connections within the Main Distribution Frame (MDF) telephone patch panel.

Industrial-based networking systems are adopting Ethernet as the preferred communication bus structure. The adoption of Ethernet-based communications accelerated by the development of Compact PCI PICMG 2.16, offers the additional feature of a redundant switch configuration and improving system efficiency in the event of system or power outage failures. Using Ethernetbased
TCP/IP protocols within an industrial network environment allows unrelated Processor Line Device Cards (PLDC) to communicate directly with one another for the first time using each manufacturer's TCP/IP protocol, eliminating the need to implement expensive software or hardware to interface the competing systems together. In the past, for field-based devices, the preferred communication method for connecting a sensor or transducer to the central control or management system was via an RS485 or RS232 bus connection. Using a RS485 or RS232 connection was simple and cost-effective to set up with no expert knowledge required for cable installation.

RS485 and RS232 bus connections are gradually being displaced with the emergence of Smart Device Servers (SDS). The presence of a self-powered Ethernet connection is driving the adoption of a SDS. A powered Ethernet connection gives the field device or SDS the ability to be self-powered via the same Ethernet connection. A SDS is an embedded PC located at the device that converts serial data into Ethernet packets, providing a bridge between the proprietary device data and an open environment. This allows standard IT tools to communicate directly with the field device. Providing a remote field device with an Ethernet connection offers the same benefits as a RS485 or RS232 connection, namely, low installation and commissioning costs. But an Ethernet connection gives field devices the additional feature of direct access to the Internet which permits more complex tasks and algorithms (normally too complex to carry out in the field) to be performed on the raw data.

PoE is an innovative technology that allows next generation SDS to receive power and data over the same UTP cable, eliminating the time, cost and effort required to install a separate 110/220 Volts Alternating Current (VAC) power to the remote SDS. Using the power derived from the Ethernet connection eliminates the need for a localized battery back-up, preventing any data loss or security breaches. All SDS devices can be protected by a single, centralized, UPS.