Motorola MD451sys 2.4 GHz Digital Expandable Cordless Phone with Caller ID (Silver) 2.4 GHz digital signal; expandable to 4 model MD41 handsets, 1 included Call waiting/caller ID ready, 50-name-and-number memory Handset speakerphone, 3-way conferencing, walkie-talkie function Desk or wall mountable, headset compatible, belt clip 12 selectable ring tones; voicemail message-waiting indicator