I have a couple of mediums I've worked with in the past. I'm working on a case with one now, who at times was able to tell me what voices I would capture on my voice recorder and she was right! I did lend her a ghost box . She hasn't reported anything note worthy at this point.

A ghost box is a modified radio, it continues to scan through the radio stations. With that said, you can see what some of the problem could be with one, as far as creating false-positives. For example. If we ask a question like. "How many of you are here?"  We could and will get a number from a radio station broadcasting the time, temp, phone number, or address. Keep in mind, most often you only capture part of what is being said from any one broadcasting station. So, I desigened a set of ptotocols to reduce the what appears to be a spirit responding.

What I do is ask them questions to where they have to repeat words back to me as part of the answer. Or I ask for them to repeat a word. One of my favorite words to use is, "peanutbutter." It's not a common word one would hear over the radio. If I want to ask about how many disembodied presences are in a location.  I would ask in this matter.

"How many of you are there here?" "Can you respond by saying, There are, and give a number please?" This way you can be sure there is interaction. I do the same thing in recording EVP. The fact is, EVP can be captured anywhere. The mistake made by a large number of folks, is. They are not aware of the fact most EVP research was conducted in labs in a non haunted location.