Low Voltage Systems: Communications, Signaling, and Control
This domain tests the system-specific articles for communications, signaling, control, fiber, and broadband. The exam expects you to choose the correct article before choosing cable or installation rules.
Core rules
- Communications, Article 800: cable markings CM, CMR, and CMP; separation per 800.133; abandoned cable must be removed per 800.25; grounding per 800.100.
- Fire alarm, Article 760: power-limited fire alarm circuits need a listed PLFA power source (760.121); cable is FPL, FPLR, or FPLP; separation per 760.136; plenum rules in 760.154.
- Control, Article 725: Class 1, 2, and 3 circuits; listed sources in 725.121; separation in 725.136; bundled cable ampacity in 725.144.
- Fiber, Article 770: conductive optical fiber cable must be grounded per 770.100; nonconductive cable does not require grounding.
- Audio, CATV, and broadband have separate articles: 640, 820, and 830.
Worked example
A fire alarm notification circuit runs through a plenum. The designer specifies FPLP cable, a listed PLFA power supply, and 2 in separation from power wiring. FPLP satisfies 760.154. A CL2P cable would not be acceptable even though it is plenum-rated, because Article 760 requires fire alarm cable for fire alarm circuits.
Traps
Using CL2 or CM cable for fire alarm; treating fire alarm as Article 725; ignoring abandoned cable; mixing Class 2 and Class 1 in one raceway; using an unlisted power supply; forgetting that CATV and broadband are separate articles.