Wednesday, March 29, 2006

Oh, there be wires

In radio we use wires. The microphone is connected to the XLR cable, the XLR cable connects to the volume pot. the volume pot plugs into the mixer slot etc. here I discuss a couple very early wires. remember them the next time a crappy headphone cable shorts out.

Wires connect anything to everything to everyone. In this most recent stage of our technological evolution we have outgrown what copper can do and are moving toward fiber. I hate fiber, because I can't solder it, can't crimp it and in general I am trying not to be a Luddite. In the end you cant plug fiber into an antenna, so I get my way as well.

The very first interior power wiring systems used conductors that were bare or covered with cloth. This was not tractable outdoors or over long distances so we began to experiment with the first real cables. The above slotted block of wood is an early cable. They were called deal tongues. Into those slots early engineers pounded lengths of metal. Metallurgy was uncertain in the era so alloys were impure and irregular in gauge. All the more important that they slathered it in tar to keep out the water. This one is circa 1065 or so from London.

Another early cable was the first underground wire and was a gutta-percha-covered wire. The brown gutta-percha is cracked like crushed amber or resin. Gutta-percha is a resin from the Isonandra Gutta tree that has some properties as an insulating material. it originates in Malaya and was discovered by Samuel Canning. (who later was involved in laying transatlantic cables) More here.

In India, probably with help from the British, half-pipe (or tile) conduits were used. These were much like the terra cotta tiles we see on roof tops but cupped together to make a pipe. the wires ran through them like conduit. These tiles are filled with what looks like a mortar that appears in some examples to be tarry. Tar or pitch seems to have been used in some pieces for joining a collar into the larger end of the next half-pipe. Some pipes are liberally painted with tar inside and out. More info here and here.