User's Guide

Some Cisco switches support both IEEE 802.3af/at PoE or their own proprietary version. Their default

mode is called “auto”. In “auto” mode, the switch will try to automatically detect what type of PoE the

plugged in device supports. The Cisco switch auto method does not work with passive PoE equipment in-

cluding plugging into the data input ports of Rajant PoE devices that are used with the ME4, LX5, and JR2.

The link will not come up or will “flicker” up and down.

To connect a Cisco PoE switch to a Rajant PoE capable device, you must turn off the PoE capability of this

port. You must set the “power inline” setting of the port to “never”. http://www.cis-

co.com/c/en/us/td/docs/switches/lan/catalyst4500/122/25ew/configuration/gui de/conf/PoE.html in-

cludes information for configuring the port.

Remarks:

Do not attempt to combine Cisco automatic PoE detection with the input port of Rajant passive PoE de-

vices used with the ME4, LX5, and JR2 models. Set the “power inline” setting of the port to “never”. Con-

tact a technical support representative for further information.

Page 1 of 1

G.5 Never Apply Power to the Data Input Port of a Rajant Mid-Span Power over

Ethernet (POE) Power Supply

IMPORTANT

This applies to all Rajant BreadCrumb models using passive PoE power supplies.

Product TSB Notice No.: 03-100162-001

TECH SERVICE BULLETIN

Never Apply Power to the Data Input Port of a Rajant Mid-Span Power over Ethernet (POE) Power

Supply

Summary:

With exception to the Rajant VHDC-24V50W-GbE, never connect the data input port of any Rajant sup-

plied mid-span POE power supply to a POE powered data port. Rajant 10/100 POEs will not work proper-

ly, and Rajant 10/100/1000 POEs will be permanently damaged causing the Ethernet data link to fail.

Background:

Many Rajant BreadCrumb models including KM3, ME4, ME3, LX5, LX4 and the JR family do not support

802.3 af/at automatic power negotiation. These BreadCrumb models must be powered from Rajant-ap-

proved passive mid-span POE power supplies. Rajant mid-span POE power supplies do not support 802.3

af/at automatic power negotiation. With exception to the Rajant VHDC-24V50W-GbE, the data input port

of all other Rajant POE power supplies must never be connected to a POE powered data port.

The Ethernet data lines of the Rajant 10/100/1000 AC/DC mid-span POE power supply are protected by

low voltage TVS diodes. These protection diodes are intended to prevent damage to equipment from

short duration voltage transients, such as electrostatic discharge. The TVS diodes will fail to a permanent

short circuit condition if continuous DC voltage is applied. When the TVS diodes are damaged, the POE

data path will no longer work. The Ethernet data link will fail, or will never form.

Field Test:

Use the following procedure to test a Rajant mid-span POE for data path damage.

1. Remove the AC power cord from the Rajant POE.