You have to appreciate how many times the name of the Wizard of Menlo Park comes up with so many inventions - the incandescent light bulb, the motion picture, the telephone. Having found a means of supplying people with electricity, Edison also invented the meter so he could charge people for the supply thereof.
In 1920s, he said he was working on an apparatus to communicate with the people In the spirit world.
Just as we can communicate with our friends with the aid of a mobile phone, is it not possible to communicate with God or with the spirit world through something that is beyond such technology - the human spirit. I would suggest a finely tuned human being is a spirit phone.