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PoE Switches for IP Surveillance

How to use PoE technology for your network cameras?

Conventionally, a security network camera requires two different types of cable for network connection. The one is Ethernet cable to transmit data, the another is power cable for power transmission. The requirement of power cable connection is always a barrier for deployment of network devices, either placing the device near to power source, or installing new electrical socket near the network camera. PoE (Power over Ethernet) technology perfectly solved this problem and greatly improved the flexibility of devices.


l Since the first release of PoE IEEE802.3af standard, PoE market has already significantly increased. According to the statistics from Infonetics, the PoE enabled devices increased from 25 million to 63 million, also can be expected to exceed 100 million in 2015. PoE technology can transmit both data and power supply through the same Ethernet cable, which greatly make installation become convenient and greatly reduced the demand for power cable.

Since the improvement of manufacturing, chips become more and more smaller, also support extreme low power consumption, the total power consumption of network devices gradually become smaller. This greatly expanded the PoE technology's applicable scope.

What's Power over Ethernet?

PoE technology can transmit not only data, but also power supply through an Ethernet cable. Inside the Cat 5 Ethernet cable, there are four pairs UTP (unshielded twisted pair). In a typical network connection, only using two pairs UTP to transmit data (Gigabyte connection uses all four pairs UTP for data transmission). PoE uses two pairs to transmit power supply. For fast Ethernet, both data and power supply will transmit over the same two pairs UTP (check Figure 1).

PoE Working Theory
Figure 1. PoE Working Theory

Power sourcing equipment, such as PoE switch or PoE injector, PoE midspans, to provide power supply for powered device. Powered device (PD) include wireless LAN Access Point (AP), IP cameras, IP telephone, RFID devices. Based on power consumption, IEEE802.3af classifies powered devices into different categories, so that ensure power sourcing equipment (PSE) is able to provide sufficient power to PD.

As the power source, PSE features the following three functions:

  • Detecting powered device to determine how much power consumption required
  • Providing sufficient power supply
  • Monitor and stop providing power supply according to environment
PoE 802.3af Device Categories
Figure 2. PoE 802.3af Device Categories

Enhanced PoE standard (PoE+)

The growing demand of PoE power accelerates the development of IEEE 802.3at (also called PoE+) standard. PoE+ makes the Power over Ethernet technology become possibility to high power consumption devices. Now, PoE powered device includes PTZ network cameras, video intercom, HD monitors and low-power embedded systems. The new standard is backward compatible with 802.3af, the available maximum power increased to 25.5 watts, and allow powered devices to coordinate their exact maximum power.

Since no power cables and sockets required, enterprises can increase the flexibility of equipment deployment, to provide power supply to the locations where conventional AC power can't reach. The installation and usage of PoE technology has a significant growth; as more powered devices enter the market, PoE will become a user must have features in many small and medium-sized enterprises. 

PoE Technology Applications
Figure 3.PoE Technology Applications

PoE IP video surveillance system

If you decide to build an IP video surveillance system, the selection and setup of cameras, network video recorders (NVRs), network switches and routers play an important role in building a reliable IP video surveillance system. PoE technology is being used and deployed to provide cost-effective network connection. PoE technology can bring many benefits to your IP video surveillance system. To setup a such system, there are many different ways.

PoE IP cameras + NVR with PoE ports

Both network cameras and NVR support PoE technology, just using an Ethernet cable connect cameras to Ethernet ports of NVR, no need to use extra devices. This is the simplest way to setup a cost-effective IP surveillance system. However, if your NVR breaks down, the whole system will shut down. Currently, there are only 4 channel, 8 channel and 16 channel NVRs are equipped with PoE inside the NVR. For more than 16 channels such as 24 channel, 32 channel, users have to use the regular NVR.

PoE IP cameras + PoE switch + NVR

Between NVR and IP cameras, there is a PoE switch, the POE switch can not only provide data switching function, but also carry power to your network cameras. PoE switch is powered by independent power source, even NVR breaks down, the IP cameras and PoE switches can keep working. However, since you need to use PoE switch, this is a medium cost solution.

A PoE switch is a network switch has built-in Power over Ethernet injection. Simply connect network cameras to the PoE switch as normal, and the switch will detect whether they are PoE-compatible and enable power automatically. POE switches are available to suit all applications, from low-cost un-managed edge switches with a few ports, up to complex multi-port rack-mounted units with sophisticated management. Generally, PoE switch adopts rack-mountable housing for easy installation.

IP cameras + PoE splitters + NVR with PoE ports (or PoE switch + NVR)

This is the method to upgrade your existing regular IP camera system to PoE. The PoE splitter can make your regular IP camera to take advantage of Power over Ethernet technology. The POE splitter is patched in to the camera's network connection, and taps off the POE power, which it converts into a lower voltage suitable for the camera. 

What's Midspans and PoE splitters

Midspans and splitters (also known as active splitters) are equipment that enable an existing network to support Power over Ethernet.

The midspan, which adds power to an Ethernet cable, is placed between the network switch and the powered devices. To ensure that data transfer is not affected, it is important to keep in mind that the maximum distance between the source of the data (e.g., switch) and the network video products is not more than 100 m (328 ft.). This means that the midspan and active splitter(s) must be placed within the distance of 100 m.

A splitter is used to split the power and data in an Ethernet cable into two separate cables, which can then be connected to a device that has no built-in support for PoE. Since PoE or PoE+ only supplies 48 V DC, another function of the splitter is to step down the voltage to the appropriate level for the device; for example, 12 V or 5 V.

How to choose a PoE switch?

Since using PoE technology is the best choice, what are factors should we consider when choosing a PoE network switch? For selecting right PoE network switches based on two major factors: PoE standard (802.3af or PoE+) & power requirements, bandwidth & ports requirements.

IP surveillance system uses PoE switches
Figure 5. IP surveillance system uses PoE switches

PoE standard & Power requirements

  • PoE (802.3af) provides up to 15.4W per port, with up to 12.9W available to the IP camera
  • PoE+ (802.3at) provides up to 30W, with up to 25W available to the IP camera

Most IP cameras are designed to accept Power over Ethernet with 802.3af standard. For high power consumption network cameras such as PTZ network camera they utilizes PoE+ (802.3at) standard. When choosing a PoE switch, the PoE standard must match each other.

Ports & Bandwidth requirements

You need to know the quantity of network cameras will be in the network. This determines how many ports the switch will need. One port per camera, today there are 4 channel, 8 channel, 16 channel, 24 channel, 32 channel PoE switches available in the market.

Thereafter, you need to figure out what the average bandwidth required per camera. The bandwidth requirement depend on many factors, primarily the resolution, the frame rate. Using this camera bandwidth calculator, you can estimate the required network bandwidth for video streaming. After knowing the average bandwidth required per camera, you can calculate the total bandwidth required per switch.

Average bandwidth per camera x total number of cameras = total bandwidth required

Adequate bandwidth for data transmission and resilience, security are key factors required to ensure a successful surveillance network. Undoubtedly, the network is an important element in any network surveillance installation, because it enables system function, not only transmitting video stream so they can be viewed and stored, but also carrying power to the cameras via a Power over Ethernet feature.

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