I am on infinity (I think). I have 4 yellow ones. One of which takes the supply from the wall socket into the hub. The connector on that is a smaller one like what goes into a phone handset. Then there's a single red socket on the hub that has a larger ethernet connection that goes into the pc.
I tried using another yellow socket no luck. Christ alight.
The home hub 5 apparently doesn't need the open reach grey boxy thing. My hub does look like that yes. Sorry my supply from wall socket comes in to the little grey connector on the left of that picture.
My link to the WiFi extender goes into one of the yellow ones and the supply to the pc goes from that red one.