CO Line Expansion Board (4 CO lines)	Extension Expansion Board (8 Extensions)	Door Phone	Door Lock	Backup Battery

C.O. Lines 4 Expandable up to 8 C.O. lines Ext. line 16 Expandable up to 32 extensions Multiple communications lines Backup battery interface Billing software Power failure transfer External line caller id Transfer caller ID Intercom caller ID Auto – attendant(DISA-20s three paragraphs) Outgoing message recording Automatic C.O. line distinguishes External music input on hold Internal music on hold Day/night mode Door bell & door open function Key phone function Alarm clock Remote Programming Real time clock Memory Protection while power off Private Password Auto/Operator mode System Password Flexible Ext No. assignment Multiple Dial-out mode External line group Call duration control Call pickup Outgoing call transfer Call transfer Call forwarding Flexible coding (change Ext. No) Do not disturb Automatic ext. reporting Flash time choice Ringing restriction Three way conference C.O. Line transfer to C.O. Line Call extensions Specific C.O. line Ring identify dialing C.O. Line booking C.O. Line reservation Operator Setting C.O. Monitor