The Matrix Module for SwitchBlock is for use with the PXI Carrier Module for SwitchBlock and can operate as an individual relay card, can combine with other Matrix Modules for SwitchBlock in the same PXI Carrier Module for SwitchBlock, and can combine with other Matrix Modules for SwitchBlock in other PXI Carrier Modules for SwitchBlock in the same PXI chassis. Each Matrix Module for SwitchBlock comes in an A-type version, which serves as the first matrix building block and offers row and column access through the front connector, and a B-type version, which serves as an expansion module and only provides column access through the front connector. Typically, SwitchBlock systems contain one A-type module and numerous B-type modules.