Circuits over 600 volts: above-ground conductors in fixed installations run in rigid or intermediate metal conduit, cable tray, cablebus, other suitable raceway, or as metal-clad cable designed for the purpose run in the open; open non-metallic-sheathed cable runs, bare conductors or busbars are allowed only where accessible solely to qualified persons; metallic shielding is grounded; and open runs with bare lead sheaths or braided coverings are supported to avoid damage. Conductors emerging from the ground are in raceway, raceways on poles are rigid metal conduit, intermediate metal conduit, schedule 80 PVC or equivalent from the ground line up to 8 feet above finished grade, conductors entering buildings are enclosed from ground to entry point, and metal enclosures are grounded. Indoor circuit breakers are metal-enclosed units or cell-mounted units that are fire resistant (open mounting only where accessible to qualified personnel) and show open or closed; fused cutouts in buildings or vaults are identified for the purpose and readily reachable for fuse replacement; equipment has a means of complete isolation for inspection and repair, and isolating means not built to interrupt load current are interlocked with a circuit interrupter or carry a sign warning against opening under load. Mobile machines get a metal enclosure for power cable terminals with a solid ground connection for the frame, termination that keeps cable strain off connections, a lock so only authorized qualified persons open it, and a warning sign; energized switching and control parts are in grounded metal enclosures that are locked and signed, with breaker reset handles operable without opening them, and collector rings on revolving machines such as shovels and draglines are guarded. Portable or mobile high-voltage equipment associated with tunnels (substations, trailers, shovels, hoists, drills, pumps, conveyors, underground excavators and similar) uses metal raceway, Type MC or other suitable multiconductor cable protected from damage, with an equipment grounding conductor run with circuit conductors; bare terminals are enclosed, with drip-proof, weatherproof or submersible enclosures as conditions need; a disconnect opening all ungrounded conductors at once is at each transformer or motor location; and all non-energized metal parts, raceways and sheaths are grounded and bonded to all metal rails and pipes at the portal and then at least every 1000 feet through the tunnel. Class 1, 2 and 3 circuits (remote control, signaling and power-limited) are classified by voltage and power limits (for example Class 1 power-limited sources rated at 30 volts and 1000 volt-amperes or less; Class 2 inherently limited at 150 volts and Class 3 at 100 volts; when limited by overcurrent protection, Class 2 at 30 volts AC or 60 volts DC and Class 3 at 150 volts), and Class 2 or 3 power supplies may not be used unless durably and visibly marked with their class and rating. Communications systems (telephone, radio, outside fire and burglar alarm wiring) are exempt from 1926.403 to 1926.408(b), except that 1926.407 and 1926.404(c)(1)(ii) still apply, but need approved protectors on circuits exposed to power conductors over 300 volts, antenna discharge units on lead-ins, installation away from power conductors with at least 6 feet from lightning conductors and 2 inches indoors from power or Class 1 conductors, communication conductors below power conductors on poles where practicable and never on a crossarm carrying power, antennas sited so they cannot fall onto lines over 150 volts to ground, and grounding of sheaths, masts and transmitter enclosures.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.