C7 C7 Audio Visual & Communication Systems

Question 1

What is the minimum impedance typically required for speakers in a distributed audio system installed under a C7 license in California?

Accepted Answer

8 ohms

Answer

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?

Accepted Answer

Shielded twisted pair (STP)

Answer

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?

Accepted Answer

Nurse call systems in healthcare occupancies

Answer

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?

Accepted Answer

4,000 feet

Answer

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?

Accepted Answer

Bonding to the building's main grounding electrode system

Answer

NEC Article 820 requires CATV systems to be bonded to the building's main grounding electrode system to equalize potentials and prevent surge damage.

(C7) California C7 Low Voltage Systems Contractor Certification Practice Test