Does anyone know how this little device works?

There's a little device that you can plug into a computer USB slot and then it will allow high-current devices like an iPad to charge from your computer (they normally won't since they require 5V@2A). I've read the reviews and the device gives up the ability to sync, but it's still a nifty little device and I was just wondering if anyone knew how it worked. Here is a link to it:
https://www.amazon.com/Charging-Charger-Adapter-Apple-iPAD/dp/B0042LF23I/ref=pd_rhf_p_img_4

There's an image that tries to explain it, but says things like "700mAh" where I'm pretty sure it should be "mA" and "increase your voltage to 2.1V" when I think they were going for "current to 2.1A", so I don't really trust it to explain how it works...

(There's actually quite a few out there)
https://www.amazon.com/BoxWave-Corporation-iPad-Charging-Adapter/dp/B000FFV1VW/ref=pd_cp_e_1
https://www.amazon.com/XMultiple-iPad-USB-Charging-Adapter/dp/B004DE2MKU/ref=pd_cp_cps_2


Anyway, if anyone could shed some light on the circuit, that would be great. I'm very curious!

Apple starting with the 3GS, Apple started checking the D+ and D- voltages on USB chargers. This may just be a USB passthrough with resistors to ensure proper voltage on the data line. See this for more info.

Hmm, interesting. So the iPad is able to charge with only 500mA if you put a specific voltage across the data lines? I wouldn't mind having one of these and I have plenty of parts around to build myself, but I certainly do not want to fry my iPad. So I guess it's not unsafe to hook it up as shown in the last picture on the page you sent? (The voltage divider giving 2.0V to each data line)

interesting, with the appropriate resistors they achieved a 1Amp charging rate !!

cool

cheers
Dav e