What exactly does POE option "Disable PD" do?

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Mo_
Mo_ Posts: 2
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edited June 2023 in Switch

I have a Zyxel GS1900-24EP. In the options to configure POE for a port, I can select to disable "PD state" (screenshot).

The documentation says: "Select Enable to provide power to a PD connected to the port or Disable so the port cannot receive power from the Switch" (p. 132)


On wikipedia, there is a table with stages of POE: https://en.wikipedia.org/wiki/Power_over_Ethernet

Which of those are perfomed, when POE is set to disabled for a single port?

Should a POE port with "PD disabled" behave exactly the same as a non-POE port on the 24EP?

Thank you.

Picture of the setting in question:

Accepted Solution

  • Zyxel_Melen
    Zyxel_Melen Posts: 1,639  Zyxel Employee
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    Hi @Mo_,

    When the PD state of one port is "disable", the switch will not try to detect PD. In other words, the switch won't send any pulse signal for detection, the voltage is 0V.

    Zyxel Melen

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  • Zyxel_Melen
    Zyxel_Melen Posts: 1,639  Zyxel Employee
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    Hi @Mo_,

    When the PD state of one port is "disable", this means this port will not provide power to any connecting PD. You can say that the behavior of not providing power to the connecting PD is the same as a non-POE port on the GS1900-24EP. In addition, I could not tell you which stage it is in since the switch does not provide any power.

    Zyxel Melen

  • Mo_
    Mo_ Posts: 2
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    edited June 2023
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    Hi @Zyxel_Melen,

    Thanks for the information! This matches with the manual and my observation.
    The reason for my question, however, was that I observed different behavior on POE and non-POE ports on some DIY devices.

    My question is, will the switch even try to detect, whether a PD is connected?

    Maybe a graphic better conveys what concerns me:

    Naively, "PD disabled" could be any Voltage except "On range" (top right).
    I would expect it to be something in the range of Reset (bottom left), but I'm not sure. Hence, the question.



  • Zyxel_Melen
    Zyxel_Melen Posts: 1,639  Zyxel Employee
    First Anniversary 10 Comments Friend Collector First Answer
    Answer ✓
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    Hi @Mo_,

    When the PD state of one port is "disable", the switch will not try to detect PD. In other words, the switch won't send any pulse signal for detection, the voltage is 0V.

    Zyxel Melen