shall be permitted with approved flexible cords and cables as provided elsewhere in Article 520. Fastening such cables and cords by uninsulated staples or nailing shall not be permitted.

(C) Nonrated Construction. Nonmetallic-sheathed cable, Type AC cable, electrical nonmetallic tubing, and

rigid non-metallic conduit shall be permitted to be installed in those buildings or portions thereof that are not required to be of fire-rated construction by the applicable building code.

520.6 Number of Conductors in Raceway. The number of conductors permitted in any metal conduit, rigid nonmetallic conduit as permitted in this article, or electrical metallic tubing for border or stage pocket circuits or for remote-control conductors shall not exceed the percentage fill shown in Table 1 of Chapter

9. Where contained within an auxiliary gutter or a wire way, the sum of the cross-sectional areas of all contained conductors at any cross section shall not exceed 20 percent of the interior cross-sectional area of the auxiliary gutter or wireway. The 30-conductor limitation of 366.22 and 376.22 shall not apply.

520.7 Enclosing and Guarding Live Parts. Live parts shall be enclosed or guarded to prevent accidental contact by persons and objects. All switches shall be of the externally operable type. Dimmers, including rheostats, shall be placed in cases or cabinets that enclose all live parts.

520.8 Emergency Systems. Control of emergency systems shall comply with Article 700.

520.9 Branch Circuits. A branch circuit of any size sup- plying one or more receptacles shall be permitted to supply stage set lighting. The voltage rating of the receptacles shall be not less than the circuit voltage. Receptacle ampere ratings and branch-circuit conductor ampacity shall be not less than the branch- circuit overcurrent device ampere rating. Table

210.21(B)(2) shall not apply.

520.10 Portable Equipment. Portable stage and studio lighting equipment and portable power distribution equipment shall be permitted for temporary use outdoors, provided the equipment is supervised by qualified personnel while energized and barriered from the general public.

II. Fixed Stage Switchboards

520.21 Dead Front. Stage switchboards shall be of the dead-front type and shall comply with Part IV of Article

408 unless approved based on suitability as a stage switchboard as determined by a qualified testing laboratory and recognized test standards and principles.

520.22 Guarding Back of Switchboard. Stage switch- boards having exposed live parts on the back of such boards shall be enclosed by the building walls, wire mesh grilles, or by other approved methods. The entrance to this enclosure shall be by means of a self-

closing door.

520.23 Control and Overcurrent Protection of Recep- tacle Circuits. Means shall be provided at a stage- lighting switchboard to which load circuits are connected for over-current protection of stage-lighting branch circuits, including branch circuits supplying stage and auditorium receptacles used for cord-and- plug-connected stage equipment. Where the stage switchboard contains dimmers to control nonstage lighting, the locating of the overcurrent protective devices for these branch circuits at the stage switchboard shall be permitted.

520.24 Metal Hood. A stage switchboard that is not completely enclosed dead-front and dead-rear or recessed into a wall shall be