It looks as though it's powered from the USB hub, in which case it would be 5 Volts DC, if trying to power one separately the 5V supply must be stabilized, about 0.5Amps would be more than adequate, it's the hub what determines the amount of current drawn the power unit has to be able to provide it.
Be careful of unregulated 'wall warts' many aren't regulated and the voltage could easily be around 7 Volts or so.
On Mon, 26 Oct 2009 01:59:05 -0700 (PDT),
Bozothedeathmachine <bozothedeathmachine@gmail.com> wrote:
>Does anyone know if the DC power spec for a Kensington 7-port USB hub?
>I need a new adapter, but don't know what the spec is.
>
>Thanks.
It would be a 5V regulated (switching type) PSU, though the
current capability of the original doesn't need to be
matched exactly. What I mean is, USB spec allows up to
500mA per port, so in theory it is possible to use upwards
of 3.5A and you could aim for and buy that if it's
reasonably priced, but unless you plan on having all the
ports populated simultaneously with high current
peripherals, you could probably make due with a 2A, and a
different brand 7 port hub I have here has a 3A PSU.
Other issue is the size of the connector it needs,
presumably a typical DC barrel connector in 5.5mm OD or
smaller size, and variable possiblity for ID, inner
diameter. Considering it has 7 ports, I would guess it more
likely to be 5.5mm OD and 2.5mm ID.
DC power specs for Kensington USB hub? 
Linear Mode
