2.4 GHz frequency-hopping digital spread spectrum signal.For use with Uniden DMX7 (DMX776, DMX778, and others) systems.Also works with DCT6/DCT7 systems.Supports caller ID/call waiting, 100-number caller ID memory.Recordable ringer tones, handset speakerphone, 10-number speed dial The Uniden DCX770 2.4 GHz digital expansion handset and charger for DMX700 series is also compatible with the DCT600 series. It has a slide-open handset and recordable ringer tones. It features 7 display backlight colors, a 100-name phonebook with 4 numbers per name, and a 100-No. caller ID memory. There are distinctive ringer tones, and backlight color, and picture display. There is a handset speakerphone. The belt clip is included. It is headset compatible for hands free conversations. There is handset-to-handset text messaging, intercom, and phonebook transfer. There is a battery, clock, & banner displays. It features a calendar with programmable reminders. It uses the DirectLink™ 2-way radio feature. There is trilingual menus. This phone system has 20 ring tone options, last 3 number redial, and a mute/hold function, There is also a voicemail waiting indicator.