u/augurmaton

I'm trying to research the history of ghost hunting equipment for a project of mine.

I'm specifically looking for information on the "spirit box" or "Ovillus" type equipment that is supposed to pick up on words or sounds by ghosts.

Does anyone have a history or a resource that I could research on my own containing the history of such equipment? I'd love to start from it's beginning of audio capturing of ghosts and work up to where the technology is at now.

Hope that makes sense, I do not have a lot of knowledge in this field. Thanks!