This part of the IEC 61784-3 series explains some common principles than can be used in the transmission of safety-relevant messages among participants within a distributed network using fieldbus technology in accordance with the requirements of IEC 61508 series2 for functional safety. These principles can be used in various industrial applications such as process control, manufacturing automation and machinery. This part3 and the IEC 61784-3-x parts specify several functional safety communication profiles based on the communication profiles and protocol layers of the fieldbus technologies in IEC 61784-1, IEC 61784-2 and the IEC 61158 series. NOTE 1 Other safety-related communication systems meeting the requirements of IEC 61508 series may exist that are not included in this standard. NOTE 2 It does not cover electrical safety and intrinsic safety aspects. Electrical safety relates to hazards such as electrical shock. Intrinsic safety relates to hazards associated with potentially explosive atmospheres. All systems are exposed to unauthorized access at some point of their life cycle. Additional measures need to be considered in any safety-related application to protect fieldbus systems against unauthorized access. The IEC 62443 series will address many of these issues; the relationship with the IEC 62443 series is detailed in a dedicated subclause of this part. NOTE 3 Additional profile specific requirements for security may also be specified in IEC 61784-44 [10]. NOTE 4 Implementation of a functional safety communication profile according to this part in a device is not sufficient to qualify it as a safety device, as defined in IEC 61508 series. NOTE 5 The resulting SIL claim of a system depends on the implementation of the selected functional safety communication profile within this system.