Ethernet Power
- By Daniel Feldman
- Jun 01, 2009
Power-over-Ethernet technology, which enables networked devices to be powered over the
same Ethernet cabling infrastructure as data, provides important benefits in security applications.
It eliminates costly AC outlet installation and allows network cameras to be deployed in
difficult-to-reach locations. It also simplifies the job of resetting and repositioning equipment,
and delivering emergency backup power. PoE’s advanced line terminal detection ensures
that a faulty camera or access control terminal can be detected and shut down, preventing
damage to expensive switches and patch panels.
Now, with the advent of products supporting the latest IEEE802.3at-draft4.1 high-power
specifications, network administrators have new capabilities for powering a broader range
of terminals. The new standard roughly doubles what power-sourcing equipment can
deliver, and powered devices can receive to 30 watts and 25.5 watts, respectively. It also
increases PSE output voltage to between 50 and 57 volts, and boosts maximum ongoing
current to 600 mA.
Midspans offer the easiest approach for quickly deploying high-power PoE, simply by inserting
them between an existing switch and PDs. The most efficient midspans deliver power
over all four pairs of Ethernet cable, rather than just two, enabling a 600 mA current level --
rather than 1.2 amps -- to be maintained while delivering high power. This cuts power dissipation
nearly in half while reducing costs almost 15 percent as compared to two-pair solutions.
The latest high-power PoE midspans also improve power management. For instance,
Microsemi’s PowerDsine® PD-9000G units include an option that supports both IPv4 and
IPv6 addressing and enables energy-efficient remote device control and monitoring. Other
options include the ability for interconnected midspans to back each other up in case of
a power-supply failure and flexible powering options from AC, DC or another midspan. DC
inputs can be used with external power supplies to increase midspan power capacity or
provide redundancy.
The latest high-power midspans offer many advantages and, with their system efficiency
options and remote power-management capabilities, make it significantly easier to power and
manage the network security infrastructure.
This article originally appeared in the June 2009 issue of Network-Centric Security.
About the Author
Daniel Feldman is the director of marketing and telecom at Microsemi Corp.