This "In-Skin" Voice Mail Card is compatible with the KX-TDA50 and KX-TA848 Key systems with the Ver. 3.0 or higher operating system. This is a 2 channel, 60 minute, 125 message per card voice mail system. Standard features include: Personal Greeting for every Time Mode used, Day-Mode, Nighe Mode and caller ID Mailbox logging. Number of mailboxes will match the number of extensions. Floating number 591 & 592.