RCA 25423RE1 ViSys 4-Line Expandable System Phone with Intercom No Caller ID 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 Compatible with the following: GE 29487 and GE 29488 Series, RCA 25403 4-Line corded telephone Expandable to 16 base stations Compatible with the RCA-25424RE1and RCA-25425RE1, and also the GE-29487/88, GE-25403/404/405, RCA-25413/414/415, and the 25424/425 series Speakerphone Intercom (station to station)