Power over Ethernet (PoE) Basics - Active POE
Power over Ethernet (PoE) is a technology initially introduced by Cisco in the early 2000s. It enables the transmission of electrical power alongside data signals over standard Ethernet cables. It allows network devices, such as IP phones, wireless access points, Point-of-Sale devices, and security cameras, to receive power directly from a PoE-enabled network switch or injector, eliminating the need for separate power cables.
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There are two term to familiarize with before beginning our discussion, these are the IEEE 802.3 categorizations for power device types:
- Power Sourcing Equipment (PSE) - any electronic device that provides electrical power over standard ethernet cables (Cat 5, 6, 7 etc.) to a PoE enabled device.
- Powered Device (PD) - this is any electronic device that is powered via PoE (any device powered by a PSE).
Broadly put we have two major categorizations for PoE:
Refers to any type of PoE that will perform a negotiation between the power supply equipment and the powered device. It will only relay power when the PD requests for it, transmitting at the negotiated voltage and power required by the device. The implication is that your non - PoE devices are safe when connected to an active PSE.
The power available for use is typically between 15W - 100W, which is enough for many use cases.
The standards under active PoE are regulated by the IEEE 802.3 standards to enforce compatibility among the different manufacturers. A PSE might be a midspan (PoE injector) or endspan (PoE network switch) device.
- Passive/ Non-Standard PoE
It can lightly be referred to as an old school standard. It delivers PoE to the PD but without a handshake (negotiation), the PSE will just consistently transmit its available power irrespective of device requirements. It's not covered by the IEEE 802.3 working group standards.
These will be devices such as wireless access points, VoIP phones, security cameras, Point of Sale devices etc.
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