Uniden LRD 6199SWS - Manual (Page 14)

Visual Alert Only Operation
You can operate the LRD 6199SWS in Visual Alert Only by setting the
Volume control at the minimum position in Full Alert Mode. At this
setting you can barely hear the audio alert in a quiet environment. Be sure
that the Audio Alert Only indicator is off.
Auto Mute Operation
Press the Mute button to activate the Auto Mute feature.
When the Mute indicator is selected, the unit is in Auto Mute Mode. In
this mode you hear the full audio alert when a signal is first received. The
audio alert automatically reduces to half volume for the duration of the
warning.
14
MUTE AUDIO
CITY