This is a 3 line, 8 station PBX designed for smaller business operations that need a system for optimal functioning, but do not need the expandability that comes with bigger systems. These businesses usually need phone system features such as paging and transfer but do not need something too large. The 308 Compact DR5.1 KSU supports all Norstar and Business Series telephones, including fully featured digital functions with LCD and soft keys. It's also easy to add the options that your business needs, including Norstar applications, automated attendant, analog terminal adapters, and station message detail recording (SMDR). Can be purchased without the power supply for replacement sales.