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That was before high-quality wire insulation was invented. Each subscriber's telephone line had to be physically separate from all the others, because they wer
by chronomex 13y ago
That was before high-quality wire insulation was invented. Each subscriber's telephone line had to be physically separate from all the others, because they weren't coated in anything.
http://scienceray.com/technology/information/open-wire-telephone-lines/ http://scienceray.com/technology/information/open-wire-telep...
- darkmighty 13y agoI guess the great shift were low cost polymers for insulation. In the early 20th century rubber was very expensive, extracted from trees (in a process much like maple syroup extraction I guess). http://en.wikipedia.org/wiki/File:Latex-production.jpg http://en.wikipedia.org/wiki/File:Latex-production.jpg
- chronomex 13y agoActually before that came paper insulated cable: http://www3.alcatel-lucent.com/bstj/vol12-1933/articles/bstj12-1-1.pdf http://www3.alcatel-lucent.com/bstj/vol12-1933/articles/bstj... These cables had paper pulp insulation around the wires, and a jacket of soft lead around the whole cable. The cable is pressurized with dry air at the central office to drive out water, though flooded lines can still be a problem sometimes. If you see any dirty-light-grey aerial cable (usually 2-5 cm diameter) in a city, that's probably pulp-insulated lead cable still in service.
- Aardwolf 13y agoSo that's how Nokia, the rubber company, started in the telephone cable business! Anyway, the tower looks awesome, like 19th century science fiction...