Busting myths about power-over-ethernet

Power-over-ethernet (PoE) technology integrates power and data across standard UTP cabling, enabling power to be supplied to network devices, such as IP phones, network cameras and wireless access points through a single network cable. With the ability to install endpoints in any location, PoE technology provides a scalable and flexible networking infrastructure geared for growth and efficiency.

Myth #1: PoE switches can provide all the power needed

Today, most switches are merely PoE-enabled. This means the majority rely on power management to share available power across the switch ports. The switches are designed with a smaller power supply that is typically capable of powering the switch itself and providing the required 15.4 W of power over a limited number of ports. For example: a 24-port PoE switch with power management typically has a 195 W power supply. After the 40 W needed to power the switch, approximately 155 W remains. If 12 of the 24 ports are used to connect end devices using 11.5 W each, only 17 W remains to provide power on the last 12 ports.
Myth busted: A PoE switch is often not the best and most cost-effective solution.

Myth #2: Midspans and PoE switches are the same

PoE Midspans are not switches. Midspans are additional PoE power sources that can be used to offer full power to all endpoint devices. PoE Midspans (power hub or power injector) pass data from a switch and ‘inject’ safe power acting as a patch panel of sorts. Midspans are commonly used with PoE and non-PoE switches in networks.
Myth busted: Midspans don’t switch — they make use of existing switches and inject safe power across all ports.

Myth #3: Only switches with built-in PoE should be used to power devices like IP phones, access points and IP security cameras

PoE switches are designed with power management and have to distribute different power as required to ports, but there often isn’t enough power for all devices plus the power required for the primary task of switching. Networks with multiple devices quickly go beyond the limited capacity of managed power PoE switches. As PoE devices grow in capability and deployment, this managed power limitation will become more evident. In contrast, Midspans were designed to provide full power on every port and deliver safe and reliable power based on the IEEE 802.3af/at standards.
Myth busted: Rather than relying on power management in switches, use Midspans that can deliver full power (15.4 W) to every port for all PoE-enabled devices.

Myth #4: Non-PoE-enabled ethernet devices can’t be powered using PoE technology

Many devices don’t directly accept PoE, but can still use PoE technology. If devices use less than 12.5 W (802.3af) or 50 W (802.3at+) and connect to ethernet, PoE splitters can be used to accept PoE power from any IEEE 802.3af/at-compliant switch or midspan and then separate the data and power onto two separate cables. Data is connected to end devices through standard RJ45 plugs, while power is connected using standard adapter plugs. Splitters can also convert the input voltage to the required voltage for a non-PoE device.
Myth busted: PoE splitters can be used with PoE midspans and switches to provide data and power connectivity required by most endpoint devices.

Myth #5: Additional PoE switch ports are needed to power IP cameras and high-power PTZ cameras

Today, many devices have evolved into more advanced solutions with higher power requirements. The traditional approach was to endure a ‘forklift upgrade’. This meant buying new PoE switches and physically swapping the existing switches to meet higher power requirements or add more powered ports. A more cost-effective way is to separate the data and power in the wiring closet. It is more efficient and costs less to separate data and power allowing the business switch to be retained for IP needs and supplement it where required with midspan technology to power the endpoints.
Myth busted: A PoE switch is often not the most cost-effective solution.