This portable unit ulitizes the latest available voice changing "chip" for the truest sound quality possible with a digital voice changing product. Simply place the Velcro attached "speaker" over the mouthpiece of any telephone and select from 16 levels of high or low voice change. NOTE: Even though this product offers the best available voice changing circuitry, most peoples voices are limited as to the number of positions on the unit that still maintain a somewhat "natural" sound. Usually, there are one or two positions that adequately disguise your voice and still sound as natural as possible with digital technology. 9 Volt battery powered.