The flexible cord used for drop lights, connectors, portable lamps, extensions, etc., is made of two cords twisted together or two cords laid parallel and covered with braided silk or cotton. The conductors consist of a number of No. 30 B. & S. gage, unannealed copper wires twisted into a cable of required capacity. The conductor is wound with fine cotton thread over which is a layer of seamless rubber, and the whole is covered with braided cotton or silk. Lamp cord is sold in three grades, old code, new code, and commercial, which vary only in the thickness and quality of rubber which encloses the conductor.
The new code lamp cord is identical with the old code form except that it is required by the National Board of Fire Underwriters to be covered with a higher quality of rubber insulation than was used in the old form. The commercial cord is not recognized by the National Board of Underwriters. It is practically the same as that described but does not conform to the tests prescribed for the new code cord.
The sizes of the conductors enclosed in the lamp cord are made equal in carrying capacity to the standard wire gage numbers. The sizes ordinarily used are No. 18 and 20 gage but they are made in sizes from No. 10 to No. 22 of the Brown & Sharp gage.
This is a term used to designate reinforced lamp cord. The wires are laid parallel and are covered as with a supplementary insulation of rubber. The additional insulation and the braided covering assumes a cylindrical form. The covering is saturated with weatherproof compound, waxed and polished.
This wire is made in the usual sizes and covered with two layers of cotton thread saturated with a. special wax and highly polished. As the name implies it is used for annunciators, door bells and other purposes of like importance.