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Home> News> How to judge whether a PoE switch supplies power for standard PoE?
April 01, 2020

How to judge whether a PoE switch supplies power for standard PoE?

Before understand how to determine whether a PoE switch is powered by standard PoE, you need to figure out what a POE switch is.

A PoE power supply switch refers to a switch capable of providing network power to a remote power receiving terminal through a network cable, and includes two functions of a network switch and PoE power supply. It is a relatively common power supply device in a PoE power supply system.

Classification of POE switches

1.Standard POE switch

Complying with IEEE802.3af and 802.3at standards, it is a standard POE switch (commonly known as 48V). The complete POE includes two parts: power supply equipment (PSE, Power Sourcing Equipment) and power receiver equipment (PD, Power Device).POE switch is a kind of equipment of PSE. PSE is a device that supplies power to the terminal, and the manager of the POE Ethernet power supply process. PD is a terminal device that accepts power (48V national standard equipment contains PD chips).

2.Non-standard POE switches

It is a non-standard POE switch if non-standard is 48V, 24V, 12V, 5V and etc.

Main application areas of POE switches

The POE switch mainly provides the network and power for monitoring (powering the Camera), wireless coverage (powering the AP), and wireless transmission (powering the bridge).

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Working process of standard POE power supply switch

1. Detection: The poe switch first outputs a very small voltage, and it detects that it contains power receiving end equipment that supports IEEE802.3at / af standard chips (supporting IEEE802.3at / af standard chips for short "PD").

2. PD classification: After detecting the PD, the poe switch classifies the PD device and evaluates the power of the PD device.

3. Power supply: During the startup period (usually less than 15 μs), the poe switch supplies power to the PD from a low voltage until the voltage required by the PD is sufficient to supply stable and reliable DC power to the PD equipment.

4. Power failure: If the PD device is disconnected, the poe switch will stop powering the PD quickly (generally within 300-400ms) and repeat the detection process to detect whether the cable terminal is connected to the PD device.

Multimeter test method for true and false POE

Start the device and set the multimeter to the voltage measurement position.Then,use the two multimeter pens to touch the PSE device power pin (usually 1/2, 3/6 or 4/5, 7/8 of the RJ45 port).It is a non-standard product if the device with a stable output of 48V or other voltage values (12V, 24V, etc.) is measured. Because PSE does not detect the power receiving equipment (multimeter)and directly uses 48V or other voltage values to supply power in this process.

Conversely, if the voltage cannot be measured and the multimeter's hands jump between 2 ~ 10V, it is standard PoE. Because the PSE is detecting the PD end (multimeter) and the multimeter is not a legitimate PD at this stage. The PSE will not supply power and no stable voltage is generated.

After mastering the above judgment methods, you can distinguish whether a PoE switch is powered by standard PoE.

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