I was sure that in Chinese network equipment with POE, the 48 volt supply voltage is transmitted over the blue and brown pairs of network wires that are not used in a 100 megabit network. I was wrong.
I measured the voltages on one of the POE ports of the recorder from the POE video surveillance kit (https://ammo1.livejournal.com/1170220.html). Instead of the expected 48 volts, the multimeter showed a constantly changing voltage of 10-15 V, and not only between the blue and brown pairs, but also between the orange and green pairs, through which data is transmitted.
If so, I decided to perform a brutal experiment with dismemberment. :)
We connect the camera to the recorder. Everything works, the picture is there.
And now we cut the blue and brown pairs in the cable.
We connect again and everything works!
Power along with data is transmitted over two pairs. Apparently, this is the POE IEEE 802.3af standard.
By the way, in this case, the very 48 V appear between the unused blue and brown pairs. As far as I understand, the blue and brown pairs allow you to transfer more power through the POE, but everything works without them.
I tried to connect the camera with such a four-wire cable via POE Switch / Splitter (https://ammo1.livejournal.com/1173125.html) and it worked again. So it also supports this POE standard.
I was misled by the fact that the Chinese do not indicate the POE standard in the description of the equipment (it is not indicated in the description of the kit and in the description of the switch).
Numerous POE standards are described on Wikipedia.
By the way, since POE works on four wires in Chinese cameras, it is quite possible to use one cable that is not very large lengths for connecting two cameras, crimping two connectors on each side - for orange / green and brown / blue pairs.
P.S. It was found that following the link in my review of the POE video surveillance kit (https://ammo1.livejournal.com/1170220.html) now sell a kit with other cameras with worse image quality and possibly without support for detecting people and faces in the frame (the sensor is not Sony, but the Chinese SC).
© 2020, Alexey Nadezhin
The main topic of my blog is technology in human life. I write reviews, share experiences, talk about all sorts of interesting things. My second project - lamptest.ru. I test LED bulbs and help figure out which ones are good and which are not so good.