The Machinery Directive standard EN ISO 13849-1 is the European safety regulation. This is a common standard that defines the requirements for the security-related parts of a control system. The Guardian complies with this instruction without the expense and complexity of redundant sensors and external relay modules. Guardian also complies with NFPA 79 clauses A.9.2, A.9.4.1, A.9.4.3.2 as A way of assessing security-related aspects of control functions.