The first interior power wiring systems used conductors that were bare or covered with cloth, which were secured by staples to the framing of the building or on running boards.Where conductors went through walls, they were protected with cloth tape. Splices were done similarly to telegraph connections, and soldered for security. Underground conductors were insulated with wrappings of cloth tape soaked in pitch, and laid in wooden troughs which were then buried.
The NEC is available as a bound book containing approximately 1000 pages.
Although the code is updated every three years, some jurisdictions do not immediately adopt the new edition. The NEC is also available as a restricted, digitized coding model that can be read online but not saved, copied and pasted, or printed, free of charge on certain computing platforms that support the restricted viewer software. In the United States, statutory law cannot be copyrighted and is freely accessible and copyable by anyone.When a standards organization develops a new coding model and it is not yet accepted by any jurisdiction as law, it is still the private property of the standards organization and the reader may be restricted from downloading or printing the text for offline viewing. For that privilege, the coding model must still be purchased as either printed media or a CD-ROM. Once the coding model has been accepted as law, it loses copyright protection and may be freely obtained at no cost. Archive.org and many state or local government sites allow download of the NEC without the registration that the NFPA requires. External links to both the restricted NEC online access and free public access sites are referenced at the end of this article.Źródło: https://en.wikipedia.org/wiki/National_Electrical_Code.