Re: cell phone..
Um... sorry, but I don't think you can. Unless you physically went into the phone, and you had some electronics degree, you might be able to touch the cpu of the phone and change the voltage setting. But, even if you did that, you would probably screw up the phone. Can I ask why you are asking this question? Just curious?
Macbook Pro and Logitech z5500s. All you really need.