4-line expansion handset compatible with RCA Unison phone systems. Will not function as a stand-alone phone. Features 10-number speed dial, Do Not Disturb function, caller ID, incoming/outgoing call logs, custom ring tones, DECT 6.0 wireless connection, intercom, voicemail, 99-name & number phonebook, handset speakerphone, digital receptionist, transfer a call from desk phone to handset, and 3-way conferencing. Includes high capacity battery with 8 hour talk time. 2-year warranty.