Extending Power-over–Ethernet technology for security

PoE solutions reduce power consumption, simplify installation of security devices


Security professionals worldwide are increasingly turning to Power-over-Ethernet (PoE) solutions as demand for enhanced security monitoring technology continues to rise. Advancements of the technology have made it more convenient to deploy network devices by enabling both power and data to be delivered over the existing Ethernet cabling in a unified infrastructure that is easier to expand, upgrade and maintain. PoE, which delivers safe, uninterrupted power over the existing local area network (LAN) infrastructure, has become an important tool for simplifying network deployment while improving remote-management capabilities, security benefits and overall energy efficiency.

Today’s security systems demand consistent, 24/7 operation. PoE provides power and data to a system’s power devices (PDs) over a single RJ45 connector, eliminating the need for a local alternating current (AC) outlet and enabling wireless access points, video surveillance cameras, access control systems and other PDs to be installed wherever they are needed. This can include difficult-to-reach locations, regardless of whether or not there is an electrical outlet nearby. Not only does PoE power ensure installed cameras operate reliably day and night, it also features a centralized architecture that provides the ability to back up the security system. In contrast, if AC power is used, which cannot be backed up, cameras will not operate if there is a power interruption. Given these significant advantages, in addition to those addressed further below, it’s no surprise that the majority of today’s IP cameras are PoE-compatable.

The original, low-power IEEE 802.3af PoE standard used two of the four pairs of wires in the Category 5 (Cat 5) cable to deliver up to 15.4 watts (W), while the latest PoE standard can deliver 30W over two pairs and even 60W when using all four pairs. The four-pair powering also helps maintain high levels of power efficiency thanks to the lower current levels used compared to two pairs. But perhaps one of the most exciting advancements in PoE for security professionals is the ability to expand the distance PDs can be placed from the data and power source with PoE extension technology.

The appeal of extending PoE

PoE extension is particularly important for security applications like access control and video surveillance where power is needed in hard-to-reach places. With Ethernet, each device must be installed 100 meters (m) between the switch (typically located in the communication room) and any device connected to it, such as an IP camera. Data integrity cannot be guaranteed beyond this distance. If an additional camera is needed to monitor a company’s parking lot, for example, the company would need to build another communication room or install a switch in every 100-meter segment, generating potentially expensive additional costs. But PoE extenders can help solve the distance dilemma.

PoE extender devices enable network administrators to deliver both data and power to network devices such as WLAN (wireless local area network) access points (AP) and network cameras at baseline distances of 200m, which is an additional 100m to the original Ethernet segment as defined by IEEE specifications (Fig. 1).

Extenders can also be cascaded to span even longer distances. If a daisy chain is used, in which multiple devices are wired together in sequence, power can be distributed even further, up to 500m. These flexible solutions can be installed wherever they’re needed—even difficult-to-reach walls and ceilings—to ensure they’re in the best place for their usage despite the presence of a nearby power outlet.

The most important advantage of a PoE extender over a PoE switch is that the PoE extender does not need local powering; it gets the power from the original PoE source (PoE switch or midspan). The extender will use small portion of the power and forward the remaining power to the PD. This feature enables the PoE extender to be small, as no internal AC-to-DC or DC-to-DC conversion is needed.

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