Key lines are enhanced to work with a key telephone system. Rollover (hunting) is included at no additional charge for most areas. Key lines offer unlimited local calling.
The criteria for determining whether a multifunctional telephone system is to be considered a Key system or a PBX system will be based upon the following: Where the station user must selectively access which line is to be connected to that station in order to make a call, the use will be considered Key system usage. All other usage will be considered PBX system usage.