AT&T 1070 4-Line Expandable Corded Phone System with Caller ID/Call Waiting and Speakerphone, 1 Handset, Black/Silver 4 line operation. Compatible with as few as 1, and as many as 4, telephone lines 32 Speed Dial and 16 Intercom;Chain Dialing 3-Party Conferencing Speakerphone; Product does not work on a digital line, Refer user manual below. Handset, Speakerphone, Headset and Ringer Control Volume DSL Subscribers may need to us a DSL Filter Compatible with AT&T 1040 and AT&T 1080 models