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TECHNICAL CORNER / Power over Ethernet (PoE) and Megapixel
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POWER OVER ETHERNET (PoE)
MEGAPIXEL
One cable for transmitting video, audio* and power.
With a network video solution, you have the option of
using the same Ethernet cable both for data
communications and power. This feature makes it
easier to install products since an electrician is not
required and the network video product is able to
operate even when there is a power failure if the PoE
source is connected to a UPS.
*depending on camera model
PoE technology is regulated in a standard called IEEE
802.3af and is designed in a way that does not degrade
the network data communication performance or
decrease the network reach. The power delivered over
the LAN infrastructure is automatically activated when
a compatible terminal is identified, and blocked to
legacy devices that are not compatible. This feature
allows users to freely and safely mix legacy and PoE-
compatible devices on their network.
The higher the resolution, the more details can be seen
in an image. This facilitates the identification of objects
and persons – important considerations in video
surveillance. Megapixel resolution allows the same
scene to be viewed in greater detail, or a larger scene
to be viewed at a maintained resolution. The higher
resolution also means that digital pan/tilt/zoom can be
used without causing a drop in resolution.
After the video signal from an NTSC or PAL analog
camera has been digitized, the maximum resolution
will be 0.4 megapixel. New network camera technology
makes higher resolutions possible.
One common megapixel format is 1280x1024, which
gives 1.3 megapixel resolution, 3 times higher than
analog cameras. Cameras that provide up to 3
megapixel are also available. It is, however, important
to bear in mind that higher resolutions generally lead
to reduced light sensitivity, because of the smaller
pixels in the image sensor as compared to conventional
cameras.
Network switch
with PoE
Axis network camera
with built-in PoE
Power over Ethernet (PoE)
The full 1600x1200 resolution provided by AXIS 223M Network
Camera gives more than 4 times the number of pixels compared to a
high resolution analog camera.