- The AT&T ML17929 2-Line Corded Office Phone System with Caller ID/Call Waiting features speakerphone capabilities for up to two separate phone lines. - This easy-to-use corded speakerphone allows you to program up to 18 of your most-phoned contacts into the built-in memory for easy speed dialing. - 3-party conferencing lets you chat with two friends at once and selectable ringtones let you choose the sound of your ring. - This 2-line corded phone also features a line status indicator and automatic line selection. - 2.5mm headset port - Inaudible mute