Thomas K: It looks like it would have pins, since the input from a flatcap has pins. But i'm not sure, and don't know what difference it could make....
I was talking about the Aux 2 blanking plug!! That does not have pins, and you do NOT need it for the unit to operate.
The link plug (the one that goes in the "Upgrade" socket) has to have pins, and if you're not using an external power supply unit this plug needs to be plugged into the "Upgrade" socket.