<p>This invention relates to improvements in interfaces between modules for use in an Industrial Process Control System. The invention provides an apparatus for industrial process control comprising a plurality of assemblies in communication with one another via a backplane portion, each assembly having a physical module interface comprising a plurality of input/output pins for connecting to the backplane portion and in which the assemblies use one or more differential signals to communicate with one another and in which the backplane portion is arranged to connect an input signal to two input pins on a physical module interface connecting to an assembly to provide a first and second copy of the input signal to said assembly.</p>
