The basic key service unit (KSU) comes equipped to operate four telephone lines and eight electronic keysets. Stations 7 and 8 have strapping options that will allow them to be used with single line telephones or keysets. System capacity is increased in two line by four station increments. By adding any one of three different expansion cards, the system capacity is increased to six telephone lines and twelve stations. By installing a second expansion card of any type, the PROSTAR 816 PLUS system is increased to its maximum capacity.of eight lines and sixteen stations.

By combining the various strapping options and different expansion card selections, the configuration of the PROSTAR 81 6 PLUS is extremely flexible. All the possible configurations are too many to list; however, the maximum numbers of each circuit type available in a fully configured PROSTAR 81 6 PLUS are listed below.

Electronic Keyset 16

Single Line Telephone 10

C.O. Line (Loop Start) 8

E & M Tie Line 4