RCA ViSys 25424RE1 4-Line Expandable System Speakerphone with Call Waiting/Caller ID/Intercom 4-Line Expandable Corded System System Expandable up to 16 Base Stations Each Base Station Can Expand to Include One DECT 6.0 Accessory Cordless Handset - Handset Sold Separately 3 Party Call Conferencing/Two Way Conference Recording/Intercom Compatible with the following: GE 29487 and GE 29488 Series, RCA 25403 and 25404 Series, RCA 25413, 25414, and 25415 Series, RCA 25423 and 25425 Series.