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10 votes
Accepted

Multiple POE over a single cable

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 ...
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  • 116
7 votes

How Can I Easily Tell If My Network Has Power Over Ethernet?

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 ...
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  • 26.7k
6 votes

What is the minimum diameter for Power over Ethernet?

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 ...
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  • 4,417
6 votes

Connect a POE VoIP phone to a non-POE Switch

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.
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6 votes

Is a 10/100 switch sufficient for Voice?

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.
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  • 62.1k
5 votes
Accepted

How Can I Easily Tell If My Network Has Power Over Ethernet?

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 ...
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  • 5,449
4 votes

POE is compatible with Gigabit Ethernet?

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 ...
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  • 11.6k
4 votes

Enable PoE on Cisco non-PoE switches

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.
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  • 18.3k
4 votes

Multiple POE over a single cable

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-...
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  • 724
4 votes

Strange POE Behaviour

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 ...
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  • 69.8k
4 votes
Accepted

Join two PoE Splitters

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 ...
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  • 6,018
4 votes
Accepted

Verifying 802.3 auto negotiation

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 ...
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  • 69.8k
4 votes

Feeding a PoE capable device with variable power supply over TIA568 A cable (DC spares)

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 ...
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  • 69.8k
4 votes

HP ProCurve 2520G Switch not accepting HP transceiver SFP

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 ...
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  • 69.8k
4 votes

PoE only data and power over network

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....
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  • 69.8k
4 votes
Accepted

In practice, how much can the 100m ethernet limit be pushed?

The "100 m Ethernet limit" you refer to exists for twisted-pair copper only. Fiber Ethernet over single-mode fiber (SMF) easily reaches over many kilometers. 800 ft/240 m is far beyond the ...
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  • 69.8k
3 votes
Accepted

Connect a POE VoIP phone to a non-POE Switch

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" ...
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  • 46
3 votes
Accepted

PoE Query - IP Phones

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 ...
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  • 93k
3 votes
Accepted

POE - How does Mode A work?

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 ...
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  • 11.6k
3 votes
Accepted

Mostly wireless campus vs. VoIP

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, ...
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  • 93k
3 votes
Accepted

Changing ethernet wiring for Cisco pre-standard PoE

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 ...
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  • 15.9k
3 votes
Accepted

Strange POE Behaviour

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 ...
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  • 15.9k
3 votes
Accepted

Why is there a warning on some PoE Switches, non-PoE might suffer damage?

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, ...
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  • 93k
3 votes

Active POE Injector with passive POE Splitter

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 ...
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  • 15.9k
3 votes
Accepted

PoE losses: Cat5e vs Cat6

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 ...
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  • 69.8k
3 votes
Accepted

Is temperature sensor on zero enough to prove PoE Control Module is failed?

(converted from comments) The "Total Power" figure should show what the PSU can deliver, regardless of what's currently in use. The "0 W" pretty clearly shows there's something wrong. Possibly, the ...
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  • 69.8k
3 votes

C3560CX-8PT-S UPOE

The Catalyst WS-C3560CX-8PT-S is a PD/PSE product, which means that the switch can behave like both a Power Device (PD) and Power Source Equipment (PSE). This switch will be powered on by the PoE ...
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  • 1,700
3 votes
Accepted

What does "inline" mean in the context of cable testing?

“Inline” refers to PoE, not to the position of the tester. So this with this tester you can check cables doing power over Ethernet. You would still place the tester at the ends of the cable.
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  • 15.6k
3 votes

Why is a PoE circuit limited to 328 feet?

IEEE PoE is an option for IEEE 802.3 twisted-pair Ethernet which is generally limited to 100m in total - up to 90m of rigid, solid-core cable and up to 10m of flexible, stranded cable. If you use ...
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  • 69.8k
2 votes

100BASE-TX, PoE and PSTN over a single UTP Category 5 cable?

I just wanted to add a quick note to answer one of your last remaining questions: Standard Fast Ethernet (100BASE-TX) calls to use Pair 2 and 3, which correlate to pins 1&2 and pins 3&6, ...
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  • 13.9k

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