Control Unit or KSU (Key Service Unit)

In small business phone systems the control unit is commonly referred to as the "brain" or "phone box". The size of the control unit determines the maximum configuration. Most business phone systems have a number in the name such as

"Meridian Norstar 616" or " Norstar 824 Meridian phone system or the MICS 0x32". These numbers usually refer to the maximum configuration of the system although not always. The "616" would mean 6 incoming lines and 16 telephones (extensions). The "8x24", 8 incoming lines and 24 telephones (extensions). The 8x24 Meridian phone system is expandable to 56 incoming lines and 56 telephones (extensions) by adding expansion modules. The Modular design for the Norstar business phone systems allows companies to start small and then grow into their phone systems. The Norstar MICS 0x32 is the largest of all the Norstar key phone systems. It is initially configured 0 lines by 32 digital stations. It can be expanded to 272 total ports, ports being lines and phones. If a company wanted to have the ability to accept 9 lines from the telephone company and have 35 telephones available you would need the base ksu plus additional modules. The benefit of the modular design can be seen here. The Norstar business telephone systems are like building blocks. You start out with the foundation and work your way up until you get the desired result. Note: All key business phone systems have music on hold.