Applies to fibrous insulated cables and flexible cords intended for use in ambient temperatures above 60 degrees Celsius (140 degrees F) and in electrical installations at working voltages not exceeding 250 voltolts. It applies to both protected and unprotected types. The unprotected types are intended for the internal wiring of equipment where they can be installed without damage, will not be subjected to undue bending and abrasion, and are protected from mechanical damage and other deleterious effects by virtue of their location and the general design of the equipment in which they are incorporated.