The OSD Audio SVC205 is a self-impedance matching in-wall volume controller with an on/off switch. Volume controls do not add gain (volume) to your speakers; they simply attenuate the volume up or down. During setup, you'll set the source volume to its optimum level, then the volume control turns the sound down to almost inaudible levels. The SVC205 is unique in that it let's you turn sound off completely.