A customer reports that in a CTS1300 room, a microphone switches to a segment that has no one talking. Which step is first in the troubleshooting process?

Replacing microphones is a last-resort hardware fix and is not warranted before simpler configuration-level steps have been attempted.

Reseating cables addresses physical connection problems and would not resolve incorrect zone-switching behavior caused by sensitivity miscalibration.

Phantom switching in the CTS1300 is most commonly caused by incorrect microphone sensitivity or zone calibration settings. Recalibrating the microphones adjusts these detection thresholds and zone boundaries, directly addressing the root cause without requiring hardware replacement or a full system reboot.

Rebooting the codec resets software state but does not correct microphone sensitivity thresholds or zone calibration data that cause phantom switching.

Replacing the audio expansion box is an invasive hardware replacement step that is not appropriate before calibration has been attempted first.