C7 Troubleshooting & Maintenance Procedures 2

Question 1

A security camera system shows intermittent video loss only during afternoon hours. What is the MOST likely cause?

Accepted Answer

Thermal expansion causing loose coaxial connections

Answer

Intermittent faults that occur during the hottest part of the day are often caused by thermal expansion loosening coaxial or other connectors.

Question 2

When testing a fire alarm circuit, a technician measures 0 ohms resistance between the positive and negative conductors. This indicates:

Accepted Answer

A short circuit fault

Answer

Zero ohms between positive and negative conductors indicates a short circuit, where current bypasses the intended load path.

Question 3

Which tool is MOST appropriate for locating a break in a buried low-voltage cable without excavation?

Accepted Answer

Time-domain reflectometer (TDR)

Answer

A TDR sends a pulse down a cable and measures the time for the reflection to return, pinpointing the location of breaks or impedance changes.

Question 4

A nurse call system annunciator displays a fault for Room 312, but staff confirm no call was made. The FIRST diagnostic step should be:

Accepted Answer

Inspect the Room 312 call station for a stuck or shorted button

Answer

A phantom activation most commonly results from a mechanically stuck or electrically shorted call button at the originating station.

Question 5

During a CCTV system inspection, the technician notices the image on a PTZ camera has excessive noise in low-light conditions. The BEST corrective action is to:

Accepted Answer

Increase the camera's gain setting

Answer

Increasing the gain amplifies the sensor signal in low-light conditions, reducing apparent noise at the cost of some image quality.

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

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

C7 Troubleshooting & Maintenance Procedures 2