From the Manufacturer

The Linksys 12 Volt Power Over Ethernet Adapter Kit lets you put your access points almost anywhere, by removing the requirement of nearby power outlets. By using the existing Category 5 Ethernet cabling to deliver power to many standard 12 volt access points and other network devices, you save the time, hassle, and expense of running AC power to the access points installation location.

The best position for a wireless access point is usually on the ceiling, in the center of the area to be covered. Second best would be high on a nearby wall. Unfortunately, theres usually no easily accessible AC power plugs available in these locations. With the Power Over Ethernet Adapter Kit, installing the access point in these preferred spots becomes far less trouble.

The 12 Volt Power Over Ethernet Adapter Kit is a two piece set. The "Injector" sends both power and data over one Category 5 cable to your access point, wireless router or bridge. Then the tiny "Splitter", placed at the remote location, separates the network data and DC power back into two cables, and delivers them to the access point. The Injector can also be used by itself with POE-enabled network devices that accept 48 volts directly on a POE port.

When its time to expand your wireless network, let the Linksys 12 Volt Power Over Ethernet Adapter Kit simplify your installation.