AT&T CLP990003 Accessory Cordless Handset, Silver/Black | Requires an AT&T CLP99383 Expandable Phone System to Operate DECT 6.0 Technology Accessory Handset Only. Requires TL92273 or TL96273 to Operate Caller ID Announce Push-to-Talk Make and Receive Landline and Cellular Phones Backlit Handset Keypad and Display DSL Subscribers may need to us a DSL Filter For optimal performance batteries should be charged for 16 hours prior to use