Q-See QSDB8209C - Manual (Page 7)

Sound Alarm Setup:
To set up the sound alarm slide the alarm switch to the VOX position. The
system will enter standby mode until a sound triggers the alarm. When sound is
detected the alarm sounds for two minutes or until the Eliminate Alarm button is
pressed, which will put the system into snooze mode for 35 seconds. After the
35 seconds is up the alarm will go back into standby mode until triggered by the
next sound alarm event.
Turn Off Alarm:
To turn off the alarm slide the alarm setting switch to the Off position. The alarm
function will be disabled.
Note:
The Sound alarm will be turned off automatically if the Eliminate Alarm button
is not pressed within 2 minutes after the alarm sounds. If both the battery and
A/C adapter are in use and the alarm setup failed to trigger, turn the camera and
the receiver off and then back on to re-activate the alarm.
4-2. Setting Up the Receiver
1. Connect the receiver to the adapter and then slide the power switch to the ON
position.