Q-See QSDB8209C - Manual (Page 6)

4-1-1. Camera Learning Setup
If there is interference from another wireless device the Learning Switch can
program the unit to avoid it. Push the Learning Switch on the back of the camera
from OFF to ON, then press the Eliminate button on the receiver for 3 seconds.
The picture will become clearer on the screen.
4-1-2. Camera Alarm Setup
1. The camera provides a Sound Detection alarm.