Emerson 1420 Technical Note

Technical Note

00840-1600-4420, Rev AA

Smart Wireless Gateway 1420 with Power over

Ethernet (PoE)

The new Gateway hardware supports IEEE 802.3af and IEEE 802.3at PoE.

1

Introduction

With the growth of ethernet, many have wanted to save time and cost on wiring by sending

power down to an ethernet device over the same ethernet cable used to haul data. This is

possible because there are four extra wires in an ethernet cable that are typically not used. In the

past there was no formal standard, people came up with their own wiring schemes for using

these wires to provide power. This resulted in a number of different schemes to exist and lead to

confusion as people were damaging their computers because they did not know there was

power available over the ethernet cable.

In 2003, IEEE 802.3af standard for PoE was adopted. It specified:

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2

There are two types of IEEE 802.3 PoE devices

1.

2.

The Gateway can be configured by jumpers to work in either one of the modes referenced

above. Therefore the Gateway can source power or be powered via the ethernet cable.

Note

The Gateway cannot be a PSE and a PD at the same time. PoE can only be configured on one

Gateway port at a time.

Smart Wireless Gateway 1420 with Power over Ethernet (PoE)

The wires that would carry power and how

Devices that could source power and devices that could be powered

Supplied wattage would be up to 15 Watts (in 2009, IEEE 802.3at was adopted, which

allowed power up to 25 Watts)

The voltage used

A method of protecting against damaging non-PoE devices

(Power Sourcing Equipment) is a device that acts as a voltage source and supplies

PoE to devices via the ethernet cable.

(Powered Device) is a device that is supplied with power via PoE from a PSE device

via the ethernet cable.

May 2015