External hard drive -- you must want the external power adapter specifications, not the one for the drive that is inside the case.
My fault. That's not what I meant.
I haven't got this external drive yet, I need those specifications to decide whether to buy it or not. I have to connect it to a TV digital terrestrial decoder (I'm in Italy) whose USB port has these features: USB 2.0, 5V, 500mA max.