Background Music Input Optional Alert Tone and Repeated Alert Tone Transmit And Receive Volume Controls Screw Terminal Connections; ACCESS: 600 ohm Two-Way Page Port on Selected Telephone Systems Electronic Key System C. O. Line Key PBX Loop Start Trunk Port Or Dedicated Single Line Phone Set; Specifications: Input Impedance: 600 ohm; Music Source Impedance: 8 ohm; Music Input Level: 1 to 3 W; Power Requirements: -24 Vdc 300 mA; Shipping Weight: 1.5 lbs (0.86 kg) Dimensions: 7.25in.