19

The wikipedia article (https://en.wikipedia.org/wiki/Power_over_Ethernet) explains it quite nicely: Standards-based power over Ethernet is implemented following the specifications in IEEE 802.3af-2003 (which was later incorporated as clause 33 into IEEE 802.3-2005) or the 2009 update, IEEE 802.3at. A phantom power technique is used to allow the ...


12

Like many standards, the initial standard is never sufficient to the developing technology. Once people have the "ability" to do something, they will often find new (and previously unexpected) ways of using that ability. 802.11 wireless is a prime example as no one originally expected it to develop into a "wired replacement" that we are heading towards ...


10

it sends %CDP_PD-2-POWER_LOW: All radios disabled to the console... Question: How can I make this AP turn on the radios? I talked with a Cisco Wireless Consulting SE... The first problem is that the recovery image (i.e. rcv-w8 image) does not have the firmware for Dot11 radios... so I had to upload new firmware. I normally use archive download-sw /force-...


7

Some ways to check if you have PoE on the network: On a Cisco switch, log in and enter show power inline and if it supports PoE, you should get output showing which ports are drawing power, a summary of configuration, etc. Any managed PoE switch should have a similar command. Do a web search for your network equipment's model/line and see if it lists PoE as ...


7

I know this is an older question, hopefully you've solved it by now, but I wanted to toss in my two cents, for the benefit of future generations if nothing else. First of all, yes, ethernet and PoE specs mean you can do exactly what you're trying to do, and run two PoE cameras over a single Cat5e. First up, there are very, very, VERY few IP surveillance ...


6

They need to be powered either by PoE or a power adapter. PoE is going to be either a PoE switch or an inline PoE injector. The PoE injector still requires a wall outlet like the power adapter will.


6

Some 3600's do require 802.3at power and it looks like this one does, and for some reason it is only drawing 802.3af power levels. Not sure if there is a bug in either the switch or AP code that could cause this, but here are a couple things to try. In some cases (usually with non-Cisco devices) I have had to add on the following on the interface (shut the ...


6

If only phones are connected to the switch, you should be fine. If you also have PCs connected in tandem (switch<->phone<->PC), then you need to worry about QoS capabilities on the switch.


5

Adding to what YLearn already said, show power inline is how you can quickly retrieve that information from the cli to see if your hardware supports it. A non-PoE supported device would display the output below if it were available. MHN00642AN01#show power inline Module Available Used Remaining (Watts) (Watts) (Watts) ------ --...


5

As I know the main problem of transporting power over ethernet cables is temperature rise and resistance. 802.3af defines the max power as 12.95 W and max current as 350 mA over 2 pairs. 802.3at defines the max power as 25 W and max current as 600 mA over 2 pairs. For both of them the typical wire (24 AWG) supports the temperature rise. Lower diameters ...


5

Ylearn's answer is good, but I don't think it's the full answer for this part: Why could they not just do 60 watts from the inception of POE? Cisco's UPOE gets 60 watts mainly by doing 30W on two pair-of-pairs, something that 802.3af couldn't do as it was planned to support 10/100Mb Ethernet which both only use two pairs, and it was a design requirement ...


4

There's a good overview of UPoE in this video: https://vimeo.com/52203711 From what I remember of the conversation, the quality of the UTP cable makes a huge difference in the capability of power transmission. Now that we have Cat6 (or better) it is capable of carrying higher wattages of power to the 100m max distance.


4

The Wikipedia answer Teun posted is correct but is pretty dense and hard to follow for someone who is not up on EE terminology. Here is my attempt at a less jargon heavy version. Signals are transmitted as a voltage difference between the two wires in a pair while power is transmitted as a voltage difference between two pairs. Ethernet is transformer ...


4

You cannot convert switches so they become POE. But you can use special devices that are called "POE Injectors" in addition to the switch. They exist in 24 and 48 ports (and other size) versions.


4

If 100 Mbit/s is enough for camera to work, You can try split single 4-pairs cat5 cable in two 2-pairs links. It can be done by 2 Ethernet splitter or by proper cable crimping. "This adapter brings 4-5-7-8 to the second port's 1-2-3-6. This is, technically, a spec violation, but over short distances, it does work." 100BASE-TX Ethernet works definitely, but ...


4

Patch cable has a smaller effective diameter (usually AWG 26-28) and a larger serial resistance than horizontal (rigid) cable (AWG 22-24). This causes a higher voltage drop from end to end. With 30+ m it is likely to exceed the tolerance of PoE. 50 m patch cable will also very likely exceed the specifications for 100BASE-TX and 1000BASE-T (maximum ...


4

No. This isn't possible. The switch itself negotiates the amount of power to be provided when it comes up, and beyond the obvious non-starter of two data lines being paralleled to each other (two transmits connected to each other?) there is no accommodation in the various PoE specs to be splitting power. Indeed, you'd potentially end up in a situation ...


4

With gigabit endpoints (1000BASE-T) your injector needs to be gigabit capable as well. Cheap injectors insert power on the pairs unused by 10BASE-T and 100BASE-TX while disrupting the data transmission on these pairs. This only works when one of the endpoints falls back to 100BASE-TX - while this is quite common it's not to be taken for granted. The ...


4

The PSE decides on which pairs power is supplied. A compliant PD needs to be able to use either pairs. Connecting a power supply to the spare pairs (only possible with 10BASE-T and 100BASE-TX) is not compatible with IEEE PoE. While most devices would probably work, some won't, and some may even break. My advice is to use a proper PoE injector and modify it ...


4

The cable category defines the high-frequency parameters of the cable (mostly attenuation and crosstalk). For PoE, the serial resistance of the cable matters which isn't defined by category. Good plenum cable grew somewhat thicker by custom from Cat-3 over Cat-5 to Cat-6(A), patch cables vary greatly down to 30 AWG. Essentially, the thicker the cable (...


4

The 468508-002 is a short-wave (850 nm) 8Gb SFP+ transceiver for Fibre Channel. It is not compatible with Ethernet switches and won't ever work in a 2520. Provision switches like the 2520 series accept their own family of transceivers, e.g. J4858C (1000BASE-SX), J4859C (1000BASE-LX), J8177C (1000BASE-T). Check the transceiver compatibility guide and the ...


4

IEEE PoE (Power over MDI) is the only standard for running power over a network cable, consisting of the original PoE 802.3af (12.95 W), the improved "PoE+" 802.3at (25.5 W) and the latest "4PPoE" 802.3bt (71 W). There is a large number of proprietary variants out there as well. Most of them are not interoperable and it's possible to damage the hardware ...


3

A little late to the party on this one, but just came across this myself today. Plug the VoIP phone into the PoE switch like normal. Then have the port from your VoIP phone that is labeled "PC" connect to your non-PoE switch and distribute to the rest of your PCs with the rest of the open ports from your non-PoE switch. This may be what PsychoData is ...


3

Your question: We have been led to believe that BT Business Broadband blocks IP Phones other than their own. Is this true? is off topic here. You will need to ask BT, but it doesn't matter if you are not going to send VoIP traffic over the BT network (outside of your network). If your phones need PoE, they must be directly connected to a PoE switch, ...


3

Twisted pair Ethernet is transformer isolated. To allow the signals to pass through the transformers (which block DC and low frequencies). the signal is transmitted at high frequency and coding schemes are used to avoid DC and near DC components in the signal. This applies regardless of whether POE is in use. POE with power on the signal pairs (POE mode A ...


3

While wireless is a good, convenient, possibly necessary thing for a company to have and use, you don't own the airwaves, and you must be willing to accept any interference that disrupts your Wi-Fi, even if it disrupts your business. Having a wired infrastructure can save your business a lot of money. I don't think you really want to bet the company on ...


3

It's your network, do whatever compromise is required by you, your management, and their budget. I agree with comment above: don't mess with hidden wire, do it close to the phone or in the patch panel. [EDITED re safety] Be aware any legal consequence of non-professionally made cabling, especially as regards fire hazards. But because the power is allowed ...


3

From the fact that Phone 2 works with long cable into port 10 but not 9, and that the switch doesn't enable power when plugged into port 9 ... It does indeed look like the cable. POE sensing is a fiddly business which to simplify a little is as follows: the switch puts a voltage down the cable and senses the resistance. If it measures as a characteristic ...


3

There are some poorly designed or constructed devices. We experienced this with some devices that had pins shorted in a way that requested PoE from the switch, but the devices could not handle PoE, and they blew up when connected to a PoE switch interface. This was a design defect in the devices, and we needed to disable PoE on the switch interfaces where ...


3

So-called "passive PoE" is really just power-over-cat5 and really isn't compatible at all with 802.3af PoE. Even the cheaper supposedly conforming PoE splitters can have issues with isolation and grounding -- which I've seen cause (literal) sparks on the receiving equipment. Most non-standard PoE equipment only works with mode B power, and usually only ...


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