Poe switch, how to measure voltage

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Buxtehude

Reputable
Sep 18, 2014
2
0
4,510
Hi,
I have an old LinksysSLM2008, where port 1, supports Poe, port one works fine for data, but when I connect an Trendnet TV-IP311PI, with a cat6 cable, nothing happens.

I can't figure out, whether the camera is dead, or the port isnt supplying, the needed voltage.

Does any one know which wires to measure if the current is correct or none existant. BR
 
Solution
B
You can't really. The switch and the camera are both 802.3af...this really is PoE unlike what some device claim.

It runs on 48 volts but because 48 volts will blow stuff up sometimes the switch only delivers the power when it is asked to. This where 802.3af comes in. This is a special protocol that the end device can request a certain amount of power. Now in advanced systems a device may ask for more power than the switch has left so it will not honor the request. In your case with a single port and a single device and both devices are 802.3af compliant it should just work. I would see if there are any setting in the switch that maybe turn this on and off or if it indicates there is some problem.

It just normally works.....now...
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bill001g

Titan
Aug 9, 2012
28,363
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You can't really. The switch and the camera are both 802.3af...this really is PoE unlike what some device claim.

It runs on 48 volts but because 48 volts will blow stuff up sometimes the switch only delivers the power when it is asked to. This where 802.3af comes in. This is a special protocol that the end device can request a certain amount of power. Now in advanced systems a device may ask for more power than the switch has left so it will not honor the request. In your case with a single port and a single device and both devices are 802.3af compliant it should just work. I would see if there are any setting in the switch that maybe turn this on and off or if it indicates there is some problem.

It just normally works.....now the part I forget is how you can trick the switch into delivering power. It is testing for a certain resistance on certain pairs and then it delivers partial power which is then modified based on the requirements.

 
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Solution
B

Buxtehude

Reputable
Sep 18, 2014
2
0
4,510
Hi,

I did check to see if Poe could be activated in the switch, but no.

I contacted Trendnet support, the guy claimed my switch did'nt support Poe, I answered then why does the user manual state it supports IEEE 802.3af. It was a tiresome conversation.

I am not inclined to buy Trendnet products, with that level of support. The supporter spoke, if possible even worse english, than yours truly.

Thanks!
 
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