C7 C7 Audio Visual & Communication Systems 1 — Questions and Answers
Question 1: What is the minimum impedance typically required for speakers in a distributed audio system installed under a C7 license in California?
- 4 ohms
- 8 ohms (Correct answer)
- 16 ohms
- 32 ohms
Correct answer: 8 ohms
Most distributed audio systems use 8-ohm speakers as the standard minimum impedance to match amplifier output ratings.
Question 2: Which cable type is most commonly used for analog audio signal transmission in a commercial intercom system?
- Cat6 UTP
- RG-6 coaxial
- Shielded twisted pair (STP) (Correct answer)
- Fiber optic
Correct answer: Shielded twisted pair (STP)
Shielded twisted pair cable is preferred for analog audio because the shield reduces electromagnetic interference that degrades signal quality.
Question 3: Under California Title 24, which low-voltage communication system requires a dedicated conduit pathway separate from power wiring?
- Doorbell wiring
- Telephone wiring
- Nurse call systems in healthcare occupancies (Correct answer)
- Residential intercom
Correct answer: Nurse call systems in healthcare occupancies
Nurse call systems in healthcare occupancies are life-safety systems that require dedicated, protected pathways per California Title 24 and NFPA 99.
Question 4: What is the maximum recommended cable run length for a standard RS-485 communication bus used in an AV control system?
- 100 feet
- 500 feet
- 4,000 feet (Correct answer)
- 10,000 feet
Correct answer: 4,000 feet
RS-485 supports cable runs up to approximately 4,000 feet (1,200 meters) at lower baud rates, making it suitable for distributed AV control.
Question 5: Which grounding method is required for CATV/antenna systems installed by a C7 contractor to protect against lightning surges?
- Floating ground
- Bonding to the building's main grounding electrode system (Correct answer)
- Separate ground rod only
- No grounding required for low-voltage systems
Correct answer: Bonding to the building's main grounding electrode system
NEC Article 820 requires CATV systems to be bonded to the building's main grounding electrode system to equalize potentials and prevent surge damage.
Question 6: In a video distribution system, what device is used to split a single coaxial signal to multiple TV outputs while maintaining signal level?
- Balun
- Passive splitter
- Signal amplifier/distribution amplifier (Correct answer)
- Attenuator
Correct answer: Signal amplifier/distribution amplifier
A distribution amplifier actively compensates for signal loss when splitting to multiple outputs, unlike passive splitters which reduce signal strength.
C7 C7 Audio Visual & Communication Systems 1
What is the minimum impedance typically required for speakers in a distributed audio system installed under a C7 license in California?