The SLC Signal Level Control from Bogen is designed to control up to 150 self amplified speakers. This device mounts in a single gang electrical box with secure terminal strip connections. Continuously variable volume control. Mounts in a single gang electrical box with secure terminal strip connections to speakers. 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.