"The psychophone, an invention pursued by Thomas Edison in the late nineteenth century to convey communication from the dead to the living, is now studied mainly in paranormal and occultist societies. Its main principles however, were in line with most mainstream motivations behind early audio recording technology, whose initial goal was to preserve the voice of the speaker after death."
Edison himself wrote “If our personality survives then it is strictly logical or scientific to assume that it retains memory, intellect and other facilities and knowledge we acquire on Earth. Therefore, if we can evolve an instrument so delicate as to be affected by our personality as it survived in the next life, such an instrument, when made available, should record something”. – Thomas Alva Edison
"Unfortunately, Edison died before he could complete his final invention and contact was never made. Edison’s final dying words were, “it is very beautiful over there.” "
Even more info here: http://www.sdparanormal.com/page/page/265918.htm