If even higher system availability and fault tolerance is required, ProSafe-RS can be configured for dual redundancy while maintaining SIL3 by simply plugging in the appropriate additional card. Because the I/O or processing functions of ProSafe-RS have a modularity that extends down to the function level, redundancy can be applied exactly where it is needed - to input, output, or processor modules - providing a combination of safety and economy that is unprecedented in the SIS market. This flexibility allows any mix of dual redundancy to be configured such as a single input and redundant output or a redundant input and single output.