• United States
by Michael Day

Some PoE vendors play fast and loose with standards terminology

Sep 20, 20044 mins

* Power over Ethernet: It's a standard, not a euphemism

Many of you may remember the newsletter I wrote touting the benefits of Power-over-Ethernet devices and how they could be the next big thing in networking for hard to reach places (see newsletter link below).  That story prompted some manufacturers to write to me telling me of their wares, and opened my eyes to a disturbing trend. I have had the opportunity to try out several so-called PoE-enabled devices and, because of that, I’ve become very disenchanted with the marketing folks’ loose use of industry standards terminology.

As stated on the Power over Ethernet Web site (, “The voltage is nominally 48V, and about 13W of power is available at the Powered Device. An isolated DC-DC converter transforms the 48V to a lower voltage more suitable for the electronics in the Powered Device, while maintaining 1500V of isolation for safety reasons.”

“PoE-enabled” is not interchangeable with “802.3af compliant,” and that’s where the buyer needs to pay close attention.

The IEEE 802.3af standard specifies how switches, routers and hubs should deliver power over standard Ethernet cabling to devices like IP phones, security systems and wireless LAN access points. There are no laws or even guidelines dictating that a product labeled “PoE-enabled” has to comply with the industry standard. For some applications, non-standard devices may be a good fit, but if you’re designing an 802.3af-based network, be sure to read the fine print. If it doesn’t say 802.3af, there is no guarantee that it will conform to the standard.

In the two months since I first wrote about the standard, I have seen and tested products stating they are PoE-enabled, coming from manufacturers the world over. I have discovered that “PoE-enabled” covers a much broader spectrum of products than does “802.3af compliant.” Is that a bad thing? That depends on your perspective.

If you are setting up a network and are looking for the plug-and-play fit guaranteed by a standard, then yes. If you are merely looking for the ease of installation and convenience of PoE-enablement, then no. I guess what I’m having trouble with is the way some companies use PoE in a manner that would imply adhering to the standard. A device can be PoE-enabled and not be 802.3af compliant, but if a device is 802.3af compliant, it is definitely PoE-enabled.

Many PoE device vendors play by the rules.  My experience has shown that when companies like PowerDsine, Cisco, 3Com and Axis say that their new products are PoE-enabled, you can be assured that they follow the 802.3af standard. Some, like Cisco, which made pre-standard PoE devices, have built intelligence into their newest PoE wares. The newer products can actually sense the pre-standard devices, and power them accordingly, while allowing 802.3af devices to operate as expected.

Here’s an example of what some manufacturers are pulling. We evaluated a camera that came with an injector and a splitter to handle the camera’s non-standard power requirements. The packaging said “PoE-enabled.”  Nevertheless, I’m less than thrilled with the company’s implementation of PoE.

Here is what is wrong with that practice. Let’s say I’m setting up a strict 802.3af compliant, PoE-enabled surveillance system. I’ve already planned the camera placement, purchased housings for the ones that are to be mounted outdoors, calculated and purchased the required cabling, determined switch and/or injector placement and purchased them. I’ve begun installation and then I realize my housings aren’t large enough to contain the camera and custom, non-compliant splitter (or tap).

And as if that weren’t enough of a headache, I’ve also come to realize that I’m now going to need the services of an electrician to supply me with enough AC outlets to plug all those custom injectors into.

PoE is a technology with a lot of potential.  It’s a shame that some manufacturers are cutting corners and ignoring the international technical standard that would allow for a fairly straightforward installation.  Instead, their non-standard implementations force us to customize our networks to accommodate their products.

My advice to you is: buyer beware.  If you are starting to dabble with PoE devices, read the product specifications carefully and look for assurances that the product adheres to the 802.3af standard.

Michael Day is CTO for Currid & Company.  You can write to him at