Add V-1094Aft. s For Virtually Endless Expansion (150 One-Way Speakers Per Unit) Provides A Master Volume Control For Entire Systems Or Groups Of Remote Speakers Pre-Amplified Low Level Audio To Remote Sites Isolates Page Port From Speaker Lines; Specifications: Input Impedance: 600 ohm; Power Requirements: -24 Vdc 45 mA; Shipping Weight: 1.1 lbs (.50 kg) Dimensions: 4.44in.