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Networking Fundamentals · Intermediate

Power Sourcing Equipment (PSE)

The device that supplies PoE power, such as a PoE switch (endpoint PSE) or a midspan injector.

Definition

The PSE detects whether a connected device is PoE-capable using a signature resistance, classifies its power needs, and supplies power within its budget. Endpoint PSEs are switches; midspans sit between a non-PoE switch and the device.

Example

A 48-port PoE+ switch with a 740 W budget is the PSE for phones and APs.

Exam tip

The PSE never sends power to a non-PoE device because detection fails first.

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