Passive PoE switches

Passive

— the main feature of the passive PoE standard, which distinguishes it from active formats (marked like “802.3**”), is that such power supply does not provide auto-tuning of voltage and power according to the load characteristics. In other words, if the PoE function is enabled in such an output, then power is supplied from it "as is", with unchanged parameters, and even regardless of whether the connected device is PoE-compatible.

The key advantage of the passive standard is its very limited cost compared to active formats. This makes it possible to equip even very simple and inexpensive switches with PoE outputs. On the other hand, the aforementioned lack of auto-tuning makes it much more difficult to coordinate the equipment with each other — especially in light of the fact that different devices can differ markedly in the output / consumption of voltage and current (power). Because of this, when using passive PoE, you need to pay special attention to source and load compatibility in these parameters. If there is no match, then in the best case (if the output voltage / power is lower than required for the load), the power simply will not work, and in the worst case (with excess voltage / power), there is a high probability of overloads, overheating, and even breakdowns with fires — and such troubles can not happen immediately, but after a fairly considerable time. And it is definitely impossible to connect devices with active inputs to passive PoE outputs — for the same reasons.