Three international standards for PoE:
Standard Name | Industry code | Power supply capacity | Plain explanation |
802.3af | PoE | 15.4W | "Snack meal": can only power simple IP phones and ordinary fixed cameras. |
802.3at | PoE+ | 30W | "Standard package": Can power a rotating camera (PTZ) and a dual-band wireless AP. |
802.3bt | PoE++ | 60W / 90W | "Luxury Feast": It can power outdoor PTZ cameras with heaters, smart lighting, and even small TVs. |
Problem points:
1. Will it damage my computer?
This is a concern for many. Standard PoE has a "handshake protocol":
Before supplying power, a switch will "knock on the door" and ask, "Are you a PoE device? How much power do you need?" If the other party does not speak (such as a regular computer), the switch will only transmit data and not supply power.
Warning: There is a type of "non-standard (mandatory) PoE" on the market. This type of power is supplied directly without prior notice, and plugging in the wrong device can really cause damage! When buying, be sure to look for "supports 802.3af/at/bt standards".
2. Are there any requirements for the network cable?
Network cables are like water pipes; thin pipes can't carry large volumes of water.
AF/AT standard: Ordinary Cat5e (Category 5e cable) is sufficient.
BT standard: Cat6 (Category 6 cable) or higher grade pure copper cable must be used, otherwise the power will be lost due to heat before it is delivered to the network cable.
3. Why does the device only receive 25W when the output is 30W?
Because there is path loss when electricity travels through a network cable. The longer the network cable, the greater the loss.
The PoE standard specifies that network cables should be no longer than 100 meters. Beyond this distance, battery life will drop significantly, and the signal will weaken.
