There are 3 standard in IEEE802.3 PoE specification (IEEE802.3af/at/bt). Each standard specifics the maximum power budget in the PoE system. The PD negotiation process can classify which standard will be applied before the power source equipments (PSE) releases the power to the remote IP devices. Usually the higher standard is backwards compatible with lower standard. For example, IEEE802.3at PoE injector can supply power for IEEE802.3af devices, but the power budget is set to IEEE802.3af.
IEEE802.3af PoE Injector 15.4W
IEEE802.3at PoE+ Injector 30W
IEEE802.3bt PoE+ Injector 90W
95W IP device: smart lock, wireless access point, Thin-client, Remote digital signage display, AIO(All-in-One) touch PC, PTZ Speed Dome
30W IP device: smart lock, IP camera, wireless access point, VoIP etc.
15.4W IP Device: VoIP, IP camera, wireless access point etc.