I received a Cisco 3750X the other day. I went to go plug it in for testing and found that the standard three prong female power connector is no longer compatible with the power supply. Cisco has added a notch to their power supply port making the standard cable incompatible with their 3750X C3KX-PWR-1100WAC power supply.

Here is a picture of the required cable below that does fit the 3750X switches. Notice the notch on the female end.

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My question: Is there a specific reason as to why Cisco has done this? Is there some sort of specific power requirements that the "standard" power cable cant handle that this compatible cable can? Or, is this simply Cisco being Cisco and making something proprietary because it can.

1 Answer 1


The cable pictured is a standard: IEC320-C15. The difference is in the temperature rating of the cable. These are rated to 120C, while the "ordinary" ones (IEC320-C13) are 70C.

I believe the increased load for PoE switches requires the higher temperature rating.

  • What you are looking at looks to me like a true Kettle Lead, ie one that is rated for much higher current (13Amp from memory) than the 5A that is normal for computer kit.
    – MikeB
    Commented May 20, 2019 at 14:55
  • 1
    @MikeBrockington, not current, just the temperature.
    – ilkkachu
    Commented May 20, 2019 at 17:15
  • 1
    From what I understand, Cisco (among other vendors) moved to a higher temperature rating cables because PoE is causing higher power draw (current) which produces more heat combined with many newer switching platforms (have the potential to) generate more heat than older platforms.
    – YLearn
    Commented May 20, 2019 at 21:01
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    It's not power draw by itself. Both C15 and C13 have the same maximum current and hence power draw. The issue is higher power draw plus high ambient temperatures (stuck by server exhaust) plus the tendency for the power cords to get buried in other cables which limits natural convective cooling.
    – user71659
    Commented May 20, 2019 at 22:29
  • Suggested, add that these can be used in "regular" power supplies, but not the other way around. IE the wiring is the same. And that trying to modify the plug or power socket is a really bad idea.
    – Criggie
    Commented May 21, 2019 at 9:56

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