24V Passive Volume Control for Amplified Speakers UPC 765368450927 "The SLC is a continuously variable volume control that can remotely control the volume of up to 150 self-amplified speakers.The SLC fits into a single gang electrical box. - Remotely control the volume of up to 150 self-amplified speakers - Rugged and attractive stainless steel plate with engraved lettering - Mounts in a single gang electrical box - Easy and secure terminal strip connections - Passive (requires no DC power)"