NTP [Network Time Protocol]
Unit 4, 2-8 South St
Rydalmere, NSW 2116
T: 13 14 91
F: 1800 659 025
W: www.simplextime.com.au
NTP definition & Application
Document: NTP.doc Issued: October 2008
Q: What is PoE?
A: Power over Ethernet is a communications network standard, called IEEE802.3af,
introduced in 2003. It extends existing Ethernet standards, and offers the first truly
international standard for power distribution and data distribution on the same cable.
Delivering both data and power over one set of wires simplifies installation, saves space and
eliminates the need for separate electrical and data outlets.
The voltage supply distributed over the cable is between 36–57 VDC, nominally 48VDC. The
maximum load power 15.4W. The power source can be configured to current limit between
10-400mA.
The PoE will experience a voltage drop on long cable runs and is therefore limited to 100
meter runs.
Q: How can PoE installations save money?
A: The data/power cable combination is economical per meter. PoE eliminates the need for
costly and cumbersome AC outlets at every device.
There is no need for annual battery replacement or battery maintenance, Daylight Savings
Time configuration can be done from a Computer terminal on the network. A network
administrator can easily control one or hundreds of clocks individually from any PC on the
network with a simple Telnet session. The option of centralized integrating a UPS backup into
the PoE network provides for a greater level of uptime and reliability.
Q: What Do I Require to Support PoE?
A: There are two ways to provide PoE.
Option1: In the switch room, existing rack switches can remain and additional midspan
power injector racks need to be installed to inject power at the server location.
Option2: Insert a single power injector near the end device on long cable runs.
It is advisable to label all PoE ports to visually identify them and differentiate between normal
ports, otherwise PoE devices may not operate when connected to normal ports. Existing
cabling can be retained.
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