One of the oft-mentioned benefits of network/security convergence is the relative ease of installation as a result of being able to use existing cabling and infrastructure. One of the necessary components of this infrastructure is power. It used to be our cameras and other devices required two cable paths, one for data/video and one to power the device. Then, as more and more devices migrated onto the network, a way was needed to deliver both the power and data signals down the same cable.
The solution came in the form of a new network standard — power over Ethernet. PoE is exactly what it sounds like: The ability to power a device simply by plugging in the Ethernet cable. PoE was developed primarily for the introduction of IP phones. In order for IP phones to be quickly deployed, a way was needed to eliminate an extra power cable/supply whenever possible.
Cisco had PoE implementations long before it ever became a standard. As one of the pioneers of IP phones, the networking specialist immediately recognized the need, and moved to fill it. As other devices moved to the edge of the networks, the need for integrated power continued to grow. Both cameras and IP access control devices Let’s examine how PoE works and what you need to know to optimize solutions for your clients.
SWITCH AND MID-SPAN DEVICES
For the most part, when you need to supply power over Ethernet, the primary device you are going to look at is the network switch. PoE-capable switches are becoming more and more popular, and less and less expensive.
PoE-capable switches come in all sizes and price levels. Some of the less expensive models might only have a select number of network ports able to supply PoE.
More expensive models now can supply PoE on all ports, up to hundreds. Pay attention to detail when you purchase a PoE-capable switch. As just mentioned, not all ports may actually supply PoE, and in some cases the total wattage available to each port may vary, depending on how many devices are connected and how much power each one is drawing.
What do you do if a PoE switch isn’t available? Let’s say you are adding an IP access control system to an existing network that doesn’t have PoE switches. What can you do?
Fortunately there are a number of solutions to this. All of them involve some kind of “injector” placed between the network switch port and the device needing the power. This is called a mid-span device.
A mid-span injector plugs into main power and has “in” and “out” network ports. The “in” generally gets hooked into the switch side of the network, and the “out” goes out to the edge device. The injector takes the Ethernet signal through and adds the power onto the correct pairs of the “out” link, powering the device.
Mid-span solutions come in single and multichannel configurations. Some devices have other touches like auditing and logging. Here again, it is important to know that the mid-span device you are using can supply sufficient power to all the devices you need to attach to it.
So you have a PoE switch and a PoE device. Now all you need to do is plug it in and walk away, right? Not exactly.
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The Convergence Channel with Steve Payne ·