Outside wiring consists of the installation of all outdoor lines, such as general electrical power transmission lines, street lighting, telephone, telegraph, and signal lines. There are two general types of outside wiring: aerial, in which the wires or cables are supported high in the air on poles or other suitable devices; and underground, in which the wires or cables are laid in conduits.
Inside wiring consists of the installation of electric wires, appliances, and fixtures for all purposes within the confines of some structure. It includes such work as lighting, heating, power, bell, telephone, and signal installation.
There are four general types of inside wiring: (1) open work, in which the wires are exposed to view, and are mounted on cleats or knobs; (2) molding work, in which the wires are run in a special molding, made either of wood or metal; (3) concealed work, in which the wires are run in partitions and other places not exposed to view, and are insulated by means of knobs and tubes; and (4) conduit and armored cable work, in which the wires are run in metal pipes called conduits or are protected by an integral metal coating or armor. The above classification does not include all forms of electrical work, as there are some specialized occupations, such as power house work, which have been omitted.