The System 91 family includes Expansion and Extension modules that you can use directly on the N2 Bus. These arrays are typically used for simple input monitoring or commands.
Although the M4-XPM and IOM modules provide similar I/O capability, you cannot use M4-XPMs or IOMs on the N2 bus. You need to replace the XT Communication module with an N2-capable FEC or CGM and add M4-XPMs or IOMs to the FEC's or CGM's SA bus if more points are needed.
Consider the following:
- FEC1611, CGM04060, or CGM09090 controllers replace XTM-501 communication modules (XTM) and their associated point expansion modules (XP).
- Add M4-XPMs or IOMs as required to duplicate point count and type.