When installed in the KX-TDA50 control cabinet this card will supports KX-T7700 (APT) Series Telephones, Single Line (SLT) and DSS Console. (KX-TDA0141)2-port cell station and voice mail. Maximum 1 per system. This card will also provide XDP on all ports. This card will NOT support 90-volt message waiting lamps on single line sets.