Add V-1094A'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: 4.44" H x 2.75" W x 2.88" D (11.28 cm x 6.98 cm x 7.32 cm)