Can I expand the number of inputs/outputs of the PR200?

The main and the simplest way to do it is to use the PRM Extension Modules from akYtec. With these modules, you can extend the PR200 by up to 16 additional digital inputs and up to 16 digital outputs. Alternatively, if your system requires more I/O-points, you can use Modbus RTU/ASCII and connect up to 32 expansion modules over the RS485 interface. We recommend using our I/O-Modules of the Mx110 series for this purpose.