Norstar MICS expansion rules

You cannot mix and match 2 port and 6 port expansion cards.
You cannot install two 2 port expansion cards in one system.

XC software supports:
No expansion cards
OR
One 2 port expansion card in slot 2 (right)
OR
One 6 port expansion card in slot 2 (right)
OR
Two 6 port expansion cards; first in slot 2 (right, modules 3-8) and second in slot 1 (left, modules 9-14)
XC Software version prior to version 7 supports expansion modules 3-12 with modules 13,14 reserved for Companion base stations.
XC Software version 7 and higher supports expansion modules 3-14 and does not support Companion base stations (manufacture discontinued)
Trunk modules are only supported on modules 3-8 and will not function on modules 9-14 (only applies to XC software since XC is required to enable modules 9-14)

Non XC software supports:
No expansion cards
OR
One 2 port expansion card in slot 2 (right)
OR
One 6 port expansion card in slot 2 (right)

You cannot downgrade system size or software version without a **startup or coldstart