Panasonic KX-TDA0174 16-Port Single Line Telephone Extension Card SLC1616-Port Single Line Card (SLC16)Supports single line telephones (SLTs)4 Ports are equipped with power failure transfer and 16 DTMF receiversRequires 1 free slotUse with KX-TDA100, KX-TDA200, KX-TDE100, KX-TDE200 AND KX-TDE600 sys..