Thomas Edison's Frequency Harmonizer in the film is based off the rumor that he actually made such a device to communicate with ghosts.
The fictional town of Chesapequa, New York is taken from the novel "Second Sight" by David Williams, as well as it's 1979 film adaptation The Two Worlds of Jennie Logan (1979).
The woods, canyon, and caves, are all shot on the popular Mullerthal hiking trail in Luxembourg, leading to the Hohllay Cave, which is man-made and was used for mining in the medieval times. It is a national landmark and major tourist attraction.
Actor Claudette Roche is married to the film's Director, Jeff Woolnough.
The movie takes place in Ulster County, New York; but in the fictional town of Chesapequa.