BX is a common type of armored building wire that consists of insulated conductors enclosed in a flexible metallic sheath, typically rated for 600 volts.
BX, also known as armored cable (AC), is widely used in commercial and industrial electrical systems. Its flexible steel or aluminum armor surrounds the conductors, providing strong mechanical protection against impact, abrasion, and stress. This armored design not only shields the inner wires but also helps reduce electromagnetic interference (EMI), making BX a good choice for environments with heavy equipment or sensitive electronics. BX cables are available in various configurations, often including two or more insulated conductors and a bonding strip or grounding conductor. With a voltage rating up to 600 volts, BX is suitable for lighting, branch circuits, and power distribution in commercial facilities. Its flexibility makes it practical where conduit is less efficient, while still offering the strength of a metallic shield.
BX is regulated under the National Electrical Code (NEC) and certified by organizations such as UL (Underwriters Laboratories) for safety and performance.
BX cable was introduced in the late 19th and early 20th centuries as a safer alternative to open wiring. The name “BX” is believed to have originated as a product designation by General Electric and Sprague Electric. Its armored construction quickly became a standard in the electrical trade and remains widely used today.