Panasonic KX-TGA550M Accessory Handset for KX-TG5500 Series Cordless Phones Requires Panasonic KX-TG5500-series expandable cordless base system for operation 5.8 GHz frequency-hopping digital spread spectrum signal Supports call waiting/caller ID; 50-station phone book Headset jack and belt clip; long lasting NiMH battery Speakerphone; lighted keypad; adjustable volume controls