Many central applications in production require full redundancy in accordance with SIL 2 to IEC 61508 so that critical systems remain functional even if the primary CPU unit fails or is accidentally damaged. The Melsec iQ-R PLC redundancy pair from Mitsubishi Electric has been certified by TÜV Rheinland as meeting the requirements of this functional safety standard for the international market. The guidelines require a fully duplicated PLC housing with all modules, which can be switched over to immediately if the primary system fails. The 'GX Works3' programming platform provides a common environment for programming both process and safety control. This enables the execution of integrated process and safety control programs with a single CPU module, eliminating the time and cost of purchasing and installing a separate safety controller. The basic redundancy architecture of the 'iQ-R' has been extended by a further layer of protection: In addition to the power supply module, the base unit and the network module, the safety version of the PLC includes a set consisting of a SIL 2 process CPU module and a separate SIL 2 function module. This ensures continuous operation by switching to standby mode in the event of a fault in the control system.