Introduction

Overview

Introduction

Power Over Ethernet connections to embedded computers will allow much cheaper installation (no AC cabling, lower labor costs), facilitate updating the installation and repositioning of sensors without electricians, while main­ taining full control over every node through the Internet, with VoIP and webcam telephony. Functionality can be changed by downloading new software through the network.

Figure 1 shows a typical system implemented to power telephones. The PoE Ethernet switches are installed to supply power over the twisted pair LAN cables to run phones or other appliances as required.

Mitel 3300 IP PBX

5300xl

HP PoE switch

HP PoE switch

Figure 1-1. Example of a Typical Implementation

Here are some reasons why you might want to do this:

■Only one set of wires to bring to your appliance - simplifies installation and saves space.

■There is no need to pay for additional electrical power runs or to delay your installation schedule to make them- saves time and money.

■The appliance can be easily moved, to wherever you can lay a LAN cable - minimal disruption to the workplace.

■Safer - no AC voltages need to be added for additional network devices.

■As well as the data transfer to and from the appliance, you can use SNMP network management infrastructure to monitor and control the appliances.

■Appliances can be shut down or reset remotely - no need for a reset button or power switch.

■When implementing wireless LAN systems it simplifies the RF survey task, as the access point can easily be moved and wired in.

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