Safety and Code Fundamentals
Low voltage does not mean low hazard. A candidate must know the shock, arc-flash, and thermal hazards that persist at 12–70 V, plus the practical safety rules: lockout/tagout, PPE selection, confined-space and ladder discipline, and safe battery handling. On the code side, understand the hierarchy: California Electrical Code (based on NFPA 70) with California amendments, then Title 24 Parts 3 and 6, then local ordinances and utility requirements. Know the difference between Class 1, Class 2, and Class 3 circuits under NEC Article 725, because the class drives conductor sizing, separation, and overcurrent rules. Article 800 governs communications circuits, Article 820 community antenna and radio distribution, Article 760 fire alarm, and Article 770 optical fiber. Traps: assuming Class 2 means "no rules," confusing remote-control and signaling circuits with power circuits, and forgetting that Class 2 conductors still must be separated from power unless a recognized barrier or class-permitted mixing applies.
Rule of thumb: when a circuit's power source is listed as Class 2, the listed source itself limits energy; you may not substitute a larger transformer to "fix" voltage drop without reclassifying the circuit.
Worked example: a 24 V control run loses voltage over 200 ft. Rather than upsizing the transformer, verify the load current, compute drop with the actual conductor resistance, and if the drop is unacceptable, move to a Class 1 method or a local power source, then re-check separation and overcurrent protection.