34TECHNICAL CORNER / Power over Ethernet (PoE) and Megapixel
POWER OVER ETHERNET (PoE)
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.
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MEGAPIXEL
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.
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.
