[Gurthang]

Thanks Olorin, I hadn't thought of that. You're saying the signal was unneccesary, and was just for show. That is quite a good thought.

I don't think that the mini-palantir theory is credible at all(but who knows). But Tuor is correct in the idea that Sauron did copy after the elves. His making of the Ring was completely founded on the knowledge of the elves, who made the first magical rings.

Here's a new thought: the books say that Frodo could hear Galandriel's voice inside his head. Perhaps distance is somewhat compressed in the spirit world, so that Sauron could use this thought-speak method with the Nazgul.

P.S. I might be getting mixed up with book and movie about Galandriel, but the theory is still credible. Oh, and thank you, Willow, for fully answering the question(although I disagree).