The SMP4000 series high-density matrix modules allow the user to connect any row to any column. The smallest building block is a (4x4) 2-wire matrix, and rows and columns can easily be expanded to form larger matrices. A (4x216) 2-wire matrix can be accommodated in a double-slot VXIbus card (SM1200). Various configurations are shipped from the factory, and the user also has the capability to define a custom configuration using the available 9 (4x4) building blocks. Complete block diagrams for each configuration can be found in the SMIPII™ manual.