PoE power sourcing equipment (PSE)
PSEs can come in various forms. The most common, convenient, and preferable is in the form of a PoE enabled switch that delivers both network connectivity and PoE to a PD. Other than a PoE switch, PSEs also take the form of:
- Midspan - An intermediate device between a non-PoE switch and a PD that delivers power to the PD. Midspans typically have the same number of ports as the non-PoE switch that it connects to, although this is not strictly necessary.
- PoE injector - A device that "injects" power into an Ethernet connection. It works much the same way as a midspan, but delivers power to a single device.
Both of the above devices plug in to mains power and have a transformer that enables them to deliver power to the PD.
Typically, PoE switches will conform to some standards-based PoE, or "Active" PoE. Most PoE injectors will usually use passive PoE although you may find standards-based injectors as well. Both active and passive PoE midspans are generally available.