There are a couple of short "informational" films that were produced in the 1930's-40's that do a better job of explaining (and more importantly for me, showing) the actual wire photo process. The original "Type 1" news photo is the one you see them attaching to the apparatus on the sending end. The "Type 3" wire photo is what is produced on the receiving end and typically exhibits some slight loss of clarity (though I have seen some very nice ones that you would never have known just from looking at the image) and have the caption embedded in the front image of the photo.
Spot News (1937)
http://www.youtube.com/watch?v=LetlcmqZFyA
Good Neighbors (1944)
http://www.youtube.com/watch?v=k0aXF0JQWEo