Smart Buildings Systems for Architects, Owners and Builders

The current standard is sufficient to power many low-powered devices.
However, the power rating is insufficient to power devices such as video sur-
veillance cameras using pan, tilt, and zoom (PTZ) capabilities and video tele-
phones. A second standard, IEEE 802.at, also known as “POE Plus,” is now
being developed and will offer higher power levels although still within the
low-voltage range.
Expectations are that the standards for POE Plus will have a power rating
of at least 30 watts, basically doubling the existing standard. One concern with
the development of the standard is that higher power generates more heat on
the cable pair(s), resulting in an increase in the attenuation of the cable; the
result could be that cabling runs be shortened to comply with the standards
of ANSI/TIA/EIA-568.
POE products started with VoIP telephones and wireless access points but
have rapidly expanded into hundreds of certified products. These include sur-
veillance cameras, clocks, intercom systems, paging systems, access control
card readers, time and attendance systems, and touch-screen flat panels.
Descriptions of some of POE’s numerous benefits follow.

Lower cost—The cost of a typical power outlet includes conduit, wire, a back-
box for the outlet and the labor of an electrician. If a power outlet does not
have to be installed for the device the cost of installation and construction is
reduced. Some organizations have saved $350 to $1000 per location by not
having to install power. Others have estimated that the average cost to

Signal Pair

Signal Pair

48 V Rx

Tx Rx

DC/DC

Converter

Tx

+

−

Spare Pair

Power Sourcing

Equipment Powered Device

4 5 1 2 3 6 7 8

4 5 1 2 3 6 7 8

Spare Pair

Figure 2.12 POE using the spare cable pairs.

The Foundations of a Smart Building 29