No need to replace existing telephone Powered by AC adapter (included) or optional 9-volt battery (not included) Separate volume and tone controls with a slider movement for easy adjustment and multiple levels of amplification Offers a 30dB max gain with the slider controls plus a 10dB ‘Boost’ button for occasional added amplification Universal telephone compatibility dial works with just about any phone with a modular connector UltraClear Sound-Clarifying Technology allows patient to “shape” sound to match hearing needs Compatible with digital office phones and VOIP phones Size: 3 7/8" x 2 1/2" x 1 1/3" Color: White (also available in white CS-IL95) 1-year warranty Please note: if you try to use the CS-IL95 to amplify an already amplified telephone you may experience feedback from the handset. Package contains: Base amplifier AC Power adapter Telephone line cord User manual