This is the Norstar Compact 616 control unit for Nortel business phone systems. This cabinet has the capability of 6 lines and 16 extensions, and supports Disconnect Supervision (DS) which allows the addition of voicemail to these business phone systems. This cabinet does not include software - in order to use the DS capability you must use a DS enabled software such as 616 DS DR5 Software. The following Norstar phones will operate on this control unit: Nortel Meridian M7100, Norstar M7208, Nortel M7310, Meridian M7324, Nortel T7100 Phone Charcoal, Nortel Norstar T7208, Nortel T7316, NST7406CHN.