Bizfon 680 Telephone System Connects up to 6 external phone lines to a total of 8 physical extensions. May connect 3 additional units to expand number of lines and extensions handled. Includes built-in voice mail with private mailboxes for all extensions. Automated attendant answers multiple calls at one time. Transfers calls to any extension, and forwards calls to any phone, in or out of the office. Includes One Year Warranty and 30 days Help Desk.