How System Integrators Powering Applications with Power over Ethernet (PoE) Can Select the Right Midspan/Injector.

When installing devices that can be powered by Power over Ethernet (PoE) in a venue, it is very important to select the best midspan/injector for each situation.

PoE was invented in 1997 by PowerDsine who came out with the first Power Source Equipment (PSE) Integrated Circuit (IC) to put power on an ethernet cable along with the first Powered Device (PD) IC to take power off of the ethernet cable and put it into the device being powered. Back in 1997, there were no PoE or Powered Network Switches, so in 1998 PowerDsine introduced the first "Midspan" also sometimes known as an "Injector." The Midspan has a port to plug in an ethernet cable from a switch containing data, and a second port which outputs an ethernet cable containing both data and power.

Since that first Midspan, PowerDsine, which today is known as the Microchip Power over Ethernet Business Unit (BU), has been leading the industry through innovation developing not only the first midspan, but also the first outdoor midspan, outdoor PoE switch and much much more. Today, there are many different midspan options including indoor, outdoor, and industrial; single port and multi-port all with data rates ranging from 1 Gbps to 10 Gbps. The real question is why are there so many choices?

The simple answer is different installations require different types of midspans. If you are installing a single device such as a camera or perhaps a security access point, a single PoE indoor midspan would be required. If the camera was being installed outdoors, perhaps a PoE outdoor midspan is a better choice than running a line from indoor; depending upon the camera's placement.

However, if you are installing hundreds of cameras and wireless access points throughout a large venue such as a university or stadium, you do not want to use a single port midspan. The best would be to use multi-port midspans to provide power to as many devices through a single unit. Also, because multi-port midspans are rack mountable, they are easy to install right above the switch and can be up and running adding power to the existing infrastructure.

And that is the key. Today, only 20% of existing network switches provide power. So when power is required over an existing network, a midspan is the best option to supplement power without having to replace the entire switch. Today, only 50% of the network switches being sold are PoE switches able to provide both power and data on a single port. So midpans are required once again to add power to those switches that are not PoE enabled.

Even if switch does have power, it comes with a power budget. This is usually the maximum amount of power available to be used. Rarely, especially in switches with a high number of ports, does the switch have enough to provide full power on all ports. So sometimes even a PoE network switch needs the supplemental power of a midspan.

Matching the proper midspan to the devices being installed is usually the job of a system integrator. There are many system integrators out there extremely familiar and knowledgeable on Power over Ethernet. Others have experience with networks but are only just beginning to get involved in PoE. In the beginning, there were 3 main applications for PoE:

• IP Phones
• IP Cameras
• Wireless Access Points

Today there has been an explosion of devices that can be powered by PoE. From lighting to light and heat sensors; even to the motors that automatically roll up and down shades based upon heat and ambient light in the room, they are all powered by PoE. There are hundreds of devices that can run off of PoE and new ones being introduced every day. This is because PoE is:

• Safe - NEC Class 2 safe from shock and fire not requiring any special conduit or installation.
• International - PoE uses the ethernet cable and connector which is the same around the world; RJ45.
• Cost Effective - Since it is Class 2 electricity, it does not require an electrician to install, anyone can install it.
• Scalable and Flexible - Without needing conduit or an electrician, ethernet cable cable can be easily run anywhere up to 100 meters and if a change is needed, that is simple to implement as well.
• Remotely Managed - PoE, by definition will never deliver power unless there is a request. On top of that, many PoE midspans, especially multi-port midspans have added management features that allows for scheduling, remote control, and automatic error handling.

Midspan manufacturers usually fall into 1 of 3 categories

1. Only producing and selling midspans to PoE device manufacturers as a powering option when the device manufacturer sells their solution. For example, an IP Camera manufacturer wants to offer a way to power their camera when they sell it because they do not know the environment where the camera will be deployed. Although some are quality units, they are mostly not available to system integrators.
2. There are many companies who produce limited types of midspans; usually single port indoor. These units are not usually designed for a commercial environment. They will work well in home or small office installations.
3. Companies producing units that appear to be significantly less expensive. These companies may offer a single port that they offer as PoE "compatible;" yet, they are not PoE compliant. This means they put a constant power level on a cable but have non of the features of PoE. A PoE power source will only turn on when a device requires a specific amount of power. These compatible units are always providing power on the line which can ruin the end device. Another popular approach for multi-ports is isolate the power supply from the unit itself and sell them separately. This will make the multi-port appear much cheaper; however, once the cost of the power supply is added in, the costs will be about the same. And when the ports are isolated from the power supply, it requires the installer to connect the two together.

System integrators can attempt to shop around for the right PoE midspan from the right vendor for every situation, or they can look at the Microchip PoE System Portfolio. Microchip offers single port indoor, outdoor, and industrial units with data rates up to 1 Gbps. It also offers these single indoor and outdoor units in a multi-gig configuration with data rates as high as 10 Gbps. Finally, it offers a complete line of 6, 12, and 24 port rack mountable multi-ports with a choice of 1 Gbps or 10 Gbps data rates. These units are all engineered and manufactured to the highest standards with a worldwide service and support organization ready to back them up.

Microchip PoE midspans are available online at www.microchipdirect.com or through major distributors around the world.