2.4 GHz Frequency Hopping Spread Spectrum (FHSS) Technology, FHSS technology provides clear sound over longer ranges, as well as digital security to prevent eavesdropping. Digital Speakerphone (Handset)You can answer the phone without interrupting what you are doing . Light-Up Indicator with Ringer Alert (Handset)The indicator on the handset lights up in amber when there is an incoming call for visual confirmation. Convenient AAA (R03) Ni-MH Rechargeable Battery (Handset)Since AAA-type rechargeable batteries are used, you can replace them with two commercially available AAA batteries for added convenience. (Rechargeable Battery: HHR-4MRT)Illuminated Display (Handset).Whenever you get a call or touch a key, the LCD&s backlight lights up, so even in the dark you&ll be able to see who&s calling and easily operate the phone. 50-Name & Number PhonebookUp to 50 station names and numbers can be stored in the built-in phonebook for fast, easy recall.