Desktop, Plugtop

PoE is the designation used for power transfer via a standard Cat. 5/6 twisted pair cable, and not only al ows for the saving of the additional mains power line but also, thanks to the safe low voltage, can be laid by a non-professional. PoE works with voltages of less than 60 V and is therefore classified as SELV (Safety Extra Low Voltage). A distinction is drawn between injectors (PSE – Power Sourcing Equipment), which in turn can be designed as Midspan or Endspan, and consumers (PD-Powered Device).

Midspans use the spare pairs 4|5 and 7|8, while Endspans transfer power only via the data lines, pairs 1|2 and 3|6. In principle, there are two power classes according to IEEE: IEEE802.3af (15.4 W per port), and IEEE802.3at (30 W per port). There are also special classes: Ultra/Mega - PoE with 60 and 95W per port respectively.

Desktop and Plugtop versions are straightforward injectors, which in most cases are configured with IEC320-C14 (cold device plugs) or, in rare cases, also as plug-in power units. Likewise, Midspans, i.e. hubs, are often designed as tabletop units, in order to impose power on an existing Ethernet switch. In this case there are 4, 8, 16 and more channels to choose from, with power values of up to 60 W per port.