I hope it's ok to suggest an idea here, otherwise please let me know if I can do it elsewhere.

I recently bought my first TPLink PoE switch. It's powered by 53 V PSU.

In the same distribution board closet, I have also the TP-Link router powered by a 12 V PSU.

To my surprise, I discovered that the power connectors (those low voltage cyclindrical plugs) are exactly the same on both devices. 

I expect I would fry the router if I plugged the switch PSU into it. But they are just next to each other, with exactly the same power cables!

Idea: 

- either make the plugs different (use bigger-diameter plug for PoE PSU, to make sure it doesn't fit and make it poka-yoke)

- or at least put a flag label on the cable next to the connector. The socket side (device back wall) is already labeled clearly.

Illustrations

The boxes and cables look exactly the same, easy to get confused.

The sockets are labeled, but the cables are not. Easy to plug a 53 V cable into a 12 V box.