IP surveillance with Power over Ethernet

An increasing number of businesses, school districts and healthcare facilities are delving into Smart Ethernet switches with Power-over-Ethernet (PoE) technology—and reaping big benefits for their IP Surveillance networks. Power over Ethernet technology describes a system to pass electrical power over Ethernet cabling, along with data. This means that a network device can be powered and operated using the same cable as for network connection, eliminating the need for power outlets close to an IP camera, for example. However, in order to save money on installation and increase the security level by using PoE, it's important to keep certain key points in mind when dealing with the technology. This article will guide you through equipment and standards within PoE that will help you succeed in the field.

Power over Ethernet, or PoE, is not a new technology and it's already widely utilised in networking, for example in IP phones, wireless AP's and IP cameras. The first successful design and implementation of a proprietary PoE system was accomplished by Cisco in the year 2000. Their technique of putting 48V DC power on the LAN data cable along with the data traffic helped them overcome their customer's objections to wall adapter powering – and in the end also helped them to sell a lot of VoIP phone systems.

The PoE scheme

In a PoE scheme, two different types of devices are involved: power sourcing equipment (PSE) and powered devices (PD). A PD is a PoE enabled network end device, such as an IP security camera, equipped to accept low voltage power transmitted over Ethernet cabling.

A PSE on the other hand, is a device that provides ("sources") power to the Ethernet cable. Power is supplied in common mode over two or more of the differential pairs of wires found in Ethernet cables and comes from a power supply such as an Ethernet switch. There are two types of PSEs which can add PoE to your network: endspans and midspans. Endspans are Ethernet switches that include the power over Ethernet transmission circuitry and are commonly called PoE switches. Midspans are power injectors that stand between a regular Ethernet switch and the powered device, injecting power without affecting the data.

IEEE standards In June 2003, the IEEE working group released the ratified IEEE 802.3af PoE standard. It provides up to 15.4W of DC power (minimum 44V DC and 350mA) to each powered device. The maximum current of IEEE 802.3af is 360mA. The output voltage range of IEEE 802.3af is from 44V DC to 57V DC.

In 2010, IEEE ratified a new PoE standard, 802.3at, which provides 30W of DC power to the PD. The maximum current of IEEE802.3at is 600mA. The output voltage range varies from 50V DC to 57V DC. The IEEE 802.3at standard is also known as PoE+ or PoE plus.

The four PoE phases Every PSE is responsible for managing four basic aspects (or phases) of PoE:

1. PD detection
2. PD classification
3. Power-up
4. Power-removal

PD detection and PD classification are carried out through complex signaling protocols which make sure that power is delivered to the PD according to the classification. It prevents powering when no PD is connected and assures prompt power removal when a PD is disconnected. The protocols also maintain a stable DC current flow at all voltage levels. A PoE enabled PSE provides a low power signaling mechanism that constantly monitors for a 802.3 powered device (PD) to appear at the end of the LAN cable. If a non-powered network device is connected, the PSE can function just as a non-PoE and perform an "ordinary" link to the networked device. However, if an 802.3 PD is connected, the PSE will quickly recognise this and begin the process of powering it up.

Cables The IEEE standard for PoE requires Category 5 cable (CAT-5) or higher for high power levels, but can operate with Category 3 cable for low power levels. But still, even high quality outdoor Category 5 cable (CAT-5) is much cheaper than USB repeaters or AC wire.

Fault protection To minimize the possibility of damage to equipment in the event of a malfunction, the more sophisticated PoE systems employ fault protection. This feature is good to have and shuts off the power supply if excessive current or a short circuit is detected.

UPS PoE can increase your security level through a so called central UPS (Uninterrupted Power Supply) in the monitor room or central control room where the PoE Ethernet switch is located.

In case of a power outage, critical networking devices will become inoperable unless they are protected by a UPS with battery backup. Having the networked equipment distributed throughout your building or campus requires the distribution of several UPS systems. With PoE, a single, centrally managed UPS can be used to supply backup power to your PSE equipment. All the distributed PD networking devices can then receive battery-backed power even in power outages.

Centrally managed power also enables remote shutdown or remote reset capabilities. Through managing a PoE-enabled LAN switch via a web browser or by SNMP, remote networking devices can be easily reset or shut down saving the time and expense of dispatching a technician.

PSE Conformance Test is important despite the various requirements described for PD detection signaling in the 802.3 specification, there is considerable room for design variation. In practice, detection pulses and detection measurement schemes do vary significantly across PSE interface technologies. The 802.3at specification leaves considerable room for implementation dependent behaviours. Additionally, many vendors of PSE will choose to go outside the 802.3 specification in ways that will affect the ability to power and maintain pure 802.3at PDs. This high degree of variation adds a number of PoE compatibility issues, such as problems with voltage levels.

PoE challenges design and test engineers a great deal. Evaluating the quality of a PSE comes down to having to work with "smart" multi-channel DC power sources that are activated and deactivated through signalling protocols operating over several power delivery and polarity configurations. The application and management of DC power over multiple local area network connections must be completely transparent, safe, non-destructive, and non-disruptive to the traditional data transmission behaviours of those network connections and associated network equipment.

for example, has over ten years of PoE Ethernet switches design experience, and in the quality assurance lab every PSE needs to pass the PSE Conformance Test Suite offered by Sifos Technologies. The test suite for 802.3at produces up to 115 test parameters depending upon PSE capabilities. These parameters are measured in 23 distinct tests that cover over 95 percent of the PSE PICS (conformance check list items) in the IEEE 802.3at specification. The test is widely used throughout the networking community as the industry "norm" for PSE specification compliance.

Due to the fast pace of this sector, with most equipment having a realistic lifespan of around five years, it is most important to buy a fully qualified system. If you buy equipment which is not fully conformant to IEEE 802.3at or IEEE 802.3af, you might end up having to deal with a real nightmare in the future.

A few of the advantages with PoE

• Equipment can be placed in the most optimal location instead of choosing one where power is available.
• Network installations can be accomplished cheaper, easier and faster.
• Network changes, such as adding, removing or moving something, can be made much easier.
• Using a PoE infrastructure enables centralised power management capabilities for critical network devices.
• PoE can be used in security applications where USB or AC power is unsuitable, inconvenient or too expensive to use.

Selecting a PoE Switch

You just picked up some new Power over Ethernet devices – a few of the hottest new IP cameras. However, after opening the box you run into a series of unexpected problems. No its a really powerful decision.

First: Each camera comes equipped with its PoE injector capable of supplying the appropriate level of power.  However, prior to even mocking up your panel it becomes clear – four PoE injectors and a standard Ethernet switch will not fit.
In an effort to maintain a reasonable panel size, you ditch the PoE injectors in favor of a Power over Ethernet switch, a single product that will replace all four injectors and provide Ethernet switching.  So far so good.

Second: After deciding that a PoE switch will best suit your need, you set out on a search for the cheapest PoE switch you can find.  Before long you realize the injectors were provided so that the cameras receive the exact amount of power they are optimized to run at.  With this new concern in mind, the search moves from the “cheapest switch” to the ”right switch.” In order to identify the right switch, you will need some information… but where do you look?

You are able to find a small label printed on the bottom near the Ethernet port of the camera – something that specifies how this camera can be powered. Now you have some numbers to shoot for, but what exactly do they mean?

While listed on the label in the above order, Power over Ethernet is best addressed in this order:-

1.     Is this a Power over Ethernet device?

A.     Will the device accept Power and data through the Ethernet port? Has the device been designed to make use of Power over Ethernet.

2.     Is this device IEEE 802.3af or IEEE 802.3at compliant?

A.     How much power will the device draw? Both IEEE 802.3af and 802.3at are based off +48VDC voltage but differ in wattage.

B.     IEEE 802.3af = “Standard PoE” = devices consuming up to 12.95W of PoE power IEEE 802.3at = “PoE Plus, High-Power PoE” = devices consuming up to 25.50W of PoE power

3.     Which class of Powered Devices (PD) is the device a member of?

A.     PoE capability and power level compliance – the class level of Powered Devices further specifies how much power the device will draw

Class 1 = 0.44 – 3.84W “Very low power”
Class 2 = 3.84 – 6.49W “Low power” 
Class 3 = 6.49 – 12.95W “Mid power” 
Class 4 = 12.95 – 25.5W “High power, suitable only for IEEE 802.3at PoE”

Translating the above power label again we find:

1.     Is this a Power over Ethernet device? Yes, this camera can accept PoE

2.     Is this device IEEE 802.3af or IEEE 802.3at compliant? IEEE 802.3af – the maximum it will draw is 12.95W at 48VDC

3.     Which class of Powered Devices (PD) is the device a member of? Class 2 – this device will draw between 3.84 and 6.49W – it is a “low power” device

After finding a Power over Ethernet switch that will provide suitable power conditions on a per-port basis, there is one final element to consider – power budget.

Will the switch you choose provide enough power per port for each camera? You bought four cameras to use four cameras, not to use just one or two.  Your choice in a Power over Ethernet switch needs to reflect this… Will the switch provide suitable power to all ports at all times?

Finally, after considering space in your panel, power demands of one camera, power ability of a switch for one port, and powering ability of a switch across all ports, you are prepared to make a decision!

Power Over Ethernet - Way to Go

Power Over Ethernet May Be The Way to Go

Power over Ethernet (PoE) is a technology that powers a remote Ethernet device by transferring electrical power over the same standard twisted-pair Ethernet cable that used to also send Ethernet data communication.

Here are some benefits to using PoE:

Simple – A single cable can supply power and network connection
Space – Only one set of wires to deal with saves space and simplifies installation
Maintenance – Easier to deal with low voltage issues
Easy –Very easy install cameras and extend your network
Reach – Supports longer camera runs with Ethernet cable (ft.)
Savings – Cost savings on many levels (installs, labor, etc)
Look into Power over Ethernet injectors or switches to assist you in transmitting electrical power, along with data, to remote devices over your network. The benefits could be endless!

There are two main types of PoE, active and passive.

1. Active PoE is standardized by the IEEE 802.3af (PoE) and 802.3at (PoE+ which provides more power). Active PoE requires negotiation between the device and the power source. Double check if this matters, but I am pretty sure this is supported to the supported length of cable for ethernet of the particular type (100Mbps or gigabit). Active PoE is mostly the domain of enterprise stuff. It's not generally inexpensive. In general[1] you can plug a non 802.3af/at PoE device in to network port that has power being provided to on that standard and all will be fine.



Typical Application





2. Passive PoE is simplistic and simply uses a pair of the 8 wires in an ethernet cable for running power. How much power this can provide and how far the device can be from the power source varies wildly. There are some "standards" but they are by convention rather than formalized. It's generally bad (tm) to plug a device that is not expecting passive PoE in to a port that is powered as such. If you have a well designed network device, it might not fry the device, but it really shouldn't work.

In standard cat-5 cabling for 10Mbit or 100Mbit Ethernet only 4 of the 8 wires are actually used.

Power over Ethernet is a technique to use the unused pairs: (4,5 and 8,7) to carry DC power to the device.

Some devices contain the circuitry to actually be powered directly; in other cases you need to split the power off the Ethernet cabling and feed it into the equipment the normal way.

Intel, Ayaya, Orinoco, Wavelan, 3Com and Symbol use 4,5 = ground and 7,8 is positive

Cisco aironet use 7,8 = ground, 4,5 = positive.

RJ45 Pin #	Wire Color	10Base-T Signal	PoE
	(T568A)	100Base-TX Signal
1	White/Green	Transmit (+)	Mode A +
2	Green	Transmit (-)	Mode A +
3	White/ Orange	Receive (+)	Mode A -
4	Blue	Unused	Mode B +
5	White/ Blue	Unused	Mode B +
6	Orange	Receive (-)	Mode A -
7	White/ Brown	Unused	Mode B -
8	Brown	Unused	Mode B -
Power over Ethernet Pinout
Same As The Straight-Through Cable Pinout for T568A

It eliminates the need for power outlets at the camera locations and enables easier application of uninterruptible power supplies (UPS) to ensure 24 hours a day, 7 days a week operation.

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 standard provides power up to 15.4W on the switch or midspan side, which translates to a maximum power consumption of 12.9W on the device/camera side - making it suitable for indoor cameras. Outdoor cameras as well as PTZ and dome cameras have a power consumption that normally exceeds this, making PoE functionality less suitable. Some manufacturers also offer non-standard proprietary products providing suitable power for these applications as well,but it should be noted that since these are non-standard products, no interoperability between different brands is possible. The 802.3af standard also provides support for so-called power classification, which allows for a negotiation of power consumption between the PoE unit and the devices. This means an intelligent switch can reserve sufficient, and not superfluous, power for the device (camera) - with the possible result that the switch could enable more PoE outputs.

PoE network camera in Global market

Development of PoE network camera in Global market

Since the launching of Power over Ethernet (PoE) standard, global enterprise are eager to utilize this emerging technology in just a few years. According the latest survey, in just six years from 2008 to now, the annual increasing rate of power equipment with PoE technology will reach 33%. In 2014, global market of power devices with PoE technology will be over $5.2 billion, compound annual growth rate will be 38%.

Along with the development of worldwide security market, users start to consider deploying some network cameras and other network security devices. Network surveillance based on PoE is more and more accepted by users and have great development.

PoE (Power over Ethernet) means keeping the current Ethernet cat-5 deployment, assure interface AP for wireless network security cameras and other IP signal devise based on IP signal, at the same time, it is able to power ac electric for those kinds of devices. PoE technology use one general Ethernet cable to transmit Ethernet signal and ac electrical source simultaneously, allowing power and date to be integrated into the same cable system. In the case of guaranteeing the construction cable safety, keep normal answer operation. PoE network camera use PoE technology to realize the network video surveillance, which has power device function to use direct current main provided by power device equipment to transmit to power device via twisted-pair.

Compared to normal network camera, PoE network camera has following advantages: apart from power the connected device through Ethernet cable, PoE reduce the investment cost, as a result, it decrease the overall the deployment costs to  organize the device based on IP infrastructure. Poe not only provide the need for installing wall power connection, which dramatically reduce the plug costs related supporting end devices but also install the network connection device on the place where is hard to deploy the local alternating current power supply, to some content, provide more flexibility. We can separate PoE network camera form power device end in the practice, which can be divide into two types, normal cameras and PoE adaptor. Front end has Ethernet switch for PoE power, and back end has PoE adaptor, which will transmit the twisted cable power to network camera for the working power. Because power device is able to identify the rate of power, when we use ups to power, the advantage of saving energy is more obvious.

How fiber optic cabling combined with PoE converters allows long-distance IP camera placement

Power over Ethernet (PoE) technology enables powering IP surveillance cameras through the transfer of DC electrical power along with data over standard unshielded twisted pair (UTP) cabling. This cabling connects to a network device through an RJ-45 port that injects the power from power sourcing equipment such as a PoE switch or midspan PoE injector. PoE provides a flexible and convenient means of powering devices that are located in out-of-the-way locations, and saves money by eliminating the expense and difficulty of direct electrical wiring. A challenge with PoE is reaching remote locations outside the distance limitation of UTP cabling. According to the TIA/EIA 568-5-A standard for category 5e cable, the maximum length for a cable segment is 100 meters (328 ft), and PoE power injectors or midspans do not increase the distance of the data link.

So, how do you get beyond that 100-meter limit? Once answer is through fiber optics. Fiber optic cabling is an effective method to overcome the distance and bandwidth limitations of UTP, and media converters are a commonly used to integrate copper network equipment and fiber. Since DC power cannot be conducted over fiber, PoE media converters are the solution to extend network distances via fiber to remote IP cameras. A PoE media converter converts the fiber to copper, and sends DC power to the camera over the UTP cabling.

How PoE Media Converters Work
On the main article image/PoE schematic that appears at right, an Ethernet switch with RJ-45 ports resides in a control room or data closet. The copper UTP cabling is converted to fiber with a standard media converter. The fiber is run a long distance to the PoE media converter located near a convenient AC or DC power source, where it converts the fiber back to copper UTP. The PoE media converter also functions as a power-sourcing mini switch, and injects PoE (DC power) over the UTP cable. At the other end of the UTP cable is the IP camera, located up to 100 meters away from the PoE media converter.
PoE media converters are available with Gigabit Ethernet and Fast Ethernet data rates and can support PoE (15.4 watts) or PoE+ (25.5 watts). PoE media converters function like PoE mini-switches, and are available in a variety of multi-port configurations, including dual RJ-45 and dual fiber ports. They can support fixed fiber connectors or small form pluggable transceivers.
To understand those power specifications, it’s worth knowing that in 2003, the IEEE ratified the 802.3af PoE Standard. That standard provides up to 15.4 watts of power per port. Late in 2009, the IEEE ratified the 802.3at PoE Standard known as PoE+ that provides up to 25.5 watts of power for each port. PoE+ can be required to power IP cameras with Pan-Tilt-Zoom (PTZ) / Speed Dome Camera capabilities, and weather-hardened cameras used in cold environments that feature blowers and de-icers.

Leverage the Benefits of Fiber
There are several solutions available to extend the distances of PoE network links, including LAN extenders that convert Ethernet to DSL, UTP to coax converters and wireless technology. When you’re going long distance, however, fiber optic cabling provides several advantages over these technologies.
Unlike copper, fiber extends network distances up to 87 miles (140 kilometers) per link with no data deterioration over distance (signal deterioration is to be expected in copper cabling). LAN extenders can only extend network distances about 3,300 feet, but a data rate of 100 Mbps can drop by 70 percent at longer distances.
Fiber cabling provides security benefits as well. It is a secure medium that generates no electro-magnetic emission and is very difficult to tap. Fiber is also very reliable because it is not susceptible to electrical interference, or data loss due to temperature or atmospheric conditions.

Understanding Power over Ethernet for video surveillance

PoE was, and is, supposed to make the powering of devices easy. You take your camera or other device that accepts power via the Ethernet port, you plug in the RJ45 jack to the port, and you walk away. Inside the head end, you plug the other end of the same Ethernet cable into a PoE switch or PoE injector and voila, power is magically delivered to the device along with the data connection. In theory, all of the normal worries are gone. AC power or DC power is irrelevant, and you don't even have to worry about over-powering a camera that, were you to fry it, could potentially set you back a few thousand dollars in equipment costs and man hours!

PoE was supposed to be this way, but practical reality has diverged from the perfect world concept in such a way that the actual installation is almost never that easy. So set aside the “perfect world” notions you have, and let’s start with the basics, so you can understand how PoE works.

There are four classes of PoE: Class 1, 2, 3 and 0. Each PoE classification denotes a range of power that is available to the end device as well as the power that must be available on the port of the power sourcing equipment (PSE):

PoE Classifications

• Class 1 --  4.5 watts at PoE port; 3.84 watts at device
• Class 2 --  7.5 watts at PoE port; 6.49 watts at device
• Class 3 --  15.4 watts at PoE port; 12.95 watts at device
• Class 0 --  15.4 watts at PoE port; .44 to 12.95 watts at device

In the world of PoE there are two kinds of switches that can provide PoE; the kind that operates with a “guarantee per port” and the kind that operates with a “total power budget”. Both kinds of switching are useful but there is a significant difference between them. If you happen to have a switch nearby, look at it and see if you can tell into which one of the above two categories your switch falls.

A switch that guarantees a certain wattage per port -- 15.4 watts per port, for example -- means that you can be sure that no matter how many Class 3 or Class 0 devices are plugged in, the switch will be able to power them. Of course, these switches tend to be bigger, more expensive and ill-suited for use outside of a nice climate controlled room, but they do prevent errors in power planning.

The second type of switch mentioned above -- the kind with a total power budget -- can only power as many PoE devices as it has power to spare. Imagine that you are working with a 4-port switch that carries a total power budget of 30 watts. This kind of switch could power four Class 2 cameras (4 devices x 7.5 watts = 30 watts needed). It could also easily power four Class 1 devices (4 devices x 4.5 watts = 18 watts needed). Continuing with that math, it would be able to power Class 3 or Class 0 devices, but it could only power two of those types of devices.

Power planning is where the rubber meets the road, and it brings up a challenge in our industry.

What happens if a chosen device (i.e., a PoE powered camera) does not clearly specify the PoE class and instead simply gives an operating wattage? You might think that this is OK since a camera which says “6.01 watts” is within the Class 2 specifications and therefore must be Class 2. But that’s where reality often diverges from common sense. In theory, what is supposed to happen is that a device is clearly labeled with a PoE classification so that when said device is plugged into a PSE device, the power budget has been worked out such that each device will receive its required PoE.

What I believe the security industry needs – right now, since PoE is happening today -- is clear labeling of the correct classification of PoE on each and every device that uses PoE. It is all well and good to place the operating or maximum wattage on the device, but industry manufacturers need to take the next step!

Manufacturers should label the device, print it on in large type and with bold colors, CLASS 1, CLASS 2, CLASS 3, CLASS 0, or whatever PoE Plus will hold as a classification. It's OK if your device actually only draws 3 watts during normal operation but for some reason is Class 0. Just tell your integrator channel partners and end users by labeling the device in the manner in which it was intended to be used. This lets system designers know the classification so that they might properly create a power plan and buy the correct devices. No one wants to be in the field trying to get a project done on time and only then realize that their switches don’t have enough power for the devices they’ve purchased.

While I am solidly standing on my PoE soapbox, let me also make a plea for PoE classification to be a priority on data sheets and marketing slicks. Some camera manufacturers make wonderful versions of these spec sheets. You’ll find photos, technical illustrations, cross reference charts, and more -- and often not a hint of PoE classification to be found anywhere. As someone who works with PoE, it sometimes seems as though PoE has become the crazy uncle that everyone has and who no one wants to invite to the party. Unfortunately for all of us, the crazy uncle could actually be the life of the party -- he makes it easy to entertain the guests and always has enough cash to pay for pizza -- but we haven't managed to take advantage of him yet!

PoE is supposed to make things easy, and between the standards bodies, the independent PoE offerings, the lack of classification usage, the errors in PoE chip usage within devices, and the propensity of some manufacturers to create Class 0 signatures in devices that draw minimal wattage, PoE's original purpose has been obfuscated in a way only rivaled by the current explanation of the financial bailout.

Why has it become so complex? Who knows! Unfortunately it has, and confusion has also shared a taxi with a lack of education on the road to PoE's widespread acceptance. People see a label on a device that says “802.af” or “IEEE Compliant” and then automatically assume that they can plug it into a PoE switch or midpsan and have it work with no problem. What makes the education problem worse is that often it does work with no problem, and this leads people to the assumption that PoE is really nothing more than Windows “plug and play” for power. Unlike Windows, however, there is no “blue screen of death” when using PoE. Instead there is a device that does not power on, or (in rare cases) a device that does power on followed by smoke, the smell of singed chip boards and fried capacitors, and then what was a very expensive security device becomes an equally expensive paperweight.