I recall the Greek equivalent to the spirit telephone was more or less a spirit video system. It has been replicated using mirrors. In its modern form, the basic idea is to use a darkened room, and to look into a mirror for some period of time. Eventually visions appear, and we presumably can see whomever we have sought after. I've been told that this also allows conversation, but I don't know how this would work. The original idea used a shallow pan of water into which one would look, whcih seems like a more reasonable idea, since it presents a "live" surface.
I've had very limited experience using water, mirrors and shiny metallic surfaces, and have noticed that there often seems to be a layer of particles of some kind lying just above the surface, through which it seemed possible to see something. Since my psychic abilities are roughly similar to those of your left shoe, I'm probably a poor example, but there seems to be some ability to enhance normal abilities to the point where something can be seen.
There are a few devices available that try to "trick the mind" into a psychic trance with blinking lights and hypnotic sounds. But to my knowledge, all of them actually send us into an alpha state, after which we're on our own. Otherwise, all that happens is lots of blinking lights and sounds.
Monroe and various workers using a combination of mechanisms plus appropriate suggestions have done much better. These combinations seem to operate by mechanisms similar to formal regression hypnosis, although there is rarely more than superficial guidance once we finally arrve in trance.
I suspect that in an actual trance state it would be possible to conjur up a Cosmic Telephone Exchange capable of connecting to anyone.Whether this could be packaged is another question. However, practice with hypnotic regression indicates that a person can be easily trained to go into a trance state and into the spirit world to access some of the resources there. This suggests that the simplest approach might be through CDs that are frankly hypnotic, suggestive and specificaly focussed on that task. Then any machine that would provide further stimulii by which incoming events might be decoded would be adequate. As an example, a shallow pan of water in a darkened room - perhaps reflected in a wall mirror, so that leaning over it isn't necessary.
The theory behind that approach would be that the live water surface would somehow express the state of the universe, and the hypnotic state, however induced, would allow regenerative detection of the images desired in the same way that listening to a babbling brook (or similar sound) eventually seems to produce words.
I've had very poor luck with Monroe's binaural recordings, but well crafted hypnotic material should be successful for this kind of gizmo. Unfortunately, it seems unlikely that we could get it to print out each of the 19 trillion personal addresses of the dwellers in psychic space. hat's where ther Cosmic Phone Exchange is used - Just call up Directory Assistance with the name and some identifying data, and the connection should be easily made. - The next problem is what to do if we get an Astral Answering Machine.
dave