3com Switch 4500 PWR 50-Port User Manual

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 2: I

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WITCH

The -48V DC power will take priority over the AC mains and will power 
the Switch if it is connected.

Use the earthing cable that accompanies your Switch if the length is 
suitable. Alternatively use the earthing cable specification as defined in 
Appendix B on page 91.

The recommended cable length should not exceed 3 metres (9.84 feet).

The RPS status LED on the front of the Switch 4500 PWR indicates the 
status of the RPS and AC supplies as shown in Table 9.

Table 9   RPS LED Colors

The Switch 4500 Power over Ethernet (PoE) units can supply power to 
any IEEE 802.3af compliant device through any of its 10/100 ports over a 
Category 5 or Category 5e Ethernet cable. The same cable connects the 
device to the network.

Power over Ethernet is a self-configuring protocol. When you plug a PoE 
compliant device into one of the ports on the Switch, the Switch will 
supply the power required to the device, providing that the total power 
budget for the Switch would not be exceeded by doing so.

A PoE Switch combines the functionality of a standard Ethernet Switch 
with a single power supply that can power multiple devices. Using a PoE 
Switch has the following advantages over an unpowered network:

■

Reduced Cabling — a PoE (802.3af) compliant device which has its 
power supplied over its ethernet cable does not require a separate 
power supply. If, for example, the Switch is used to connect a 3Com 
11 Mbps Wireless LAN Access Point 8500 to the network, then only a 

AC and RPS supply connected.

AC failed or not connected. RPS supply is ok.

There is no RPS supply connected.