C7 C7 Audio Visual & Communication Systems 2 — Questions and Answers
Question 1: Which protocol is the industry standard for controlling lighting and AV equipment in modern California commercial installations?
- DMX-512 (Correct answer)
- RS-232
- BACnet
- Modbus
Correct answer: DMX-512
DMX-512 is the standard digital protocol used by C7 contractors for controlling dimmers, LED fixtures, and theatrical lighting in commercial AV installations.
Question 2: What is the purpose of a balun in an audio/video distribution system?
- To amplify signal strength
- To convert between balanced and unbalanced signal formats or impedances (Correct answer)
- To split one signal into multiple outputs
- To filter out high-frequency noise
Correct answer: To convert between balanced and unbalanced signal formats or impedances
A balun (balanced-unbalanced transformer) converts between balanced and unbalanced signal types, allowing coaxial-to-twisted-pair runs over structured cabling.
Question 3: Per California electrical code, low-voltage wiring for AV systems run in a plenum space must use cable rated as:
- CL2
- CMR (riser rated)
- CMP (plenum rated) (Correct answer)
- Any listed cable with conduit
Correct answer: CMP (plenum rated)
CMP-rated (Communications Plenum) cable is required in plenum air-handling spaces because it has low smoke and flame-spread characteristics per NEC Article 800.
Question 4: What is the recommended separation distance between low-voltage AV cables and 120V power conductors when run in parallel without conduit?
- At least 2 inches
- At least 6 inches (Correct answer)
- At least 12 inches
- No separation required
Correct answer: At least 6 inches
NEC guidelines and industry best practice recommend at least 6 inches of separation between power and low-voltage signal cables to minimize inductive interference.
Question 5: Which fiber optic connector type is most commonly used for HDMI-over-fiber AV extender systems in California commercial installations?
- SC
- ST
- LC (Correct answer)
- FC
Correct answer: LC
LC connectors are the dominant choice for modern AV-over-fiber systems due to their small form factor and compatibility with SFP transceivers.
Question 6: An AV system integrator under a C7 license installs a ceiling speaker system. Which document must be provided to the building owner at project completion?
- Manufacturer's warranty card only
- As-built drawings showing speaker locations and cable routing (Correct answer)
- Only the permit inspection card
- A signed NDA
Correct answer: As-built drawings showing speaker locations and cable routing
California contractors are required to provide as-built documentation so building owners and future technicians can maintain, service, or modify the installed system.
C7 C7 Audio Visual & Communication Systems 2
Which protocol is the industry standard for controlling lighting and AV equipment in modern California commercial installations?