This part of the IEC 61784-3 series specifies a safety communication layer (services and protocol) based on CPF 17 of IEC 61784-2 (CP 17/1) and IEC 61158 Type 21. It identifies the principles for functional safety communications defined in IEC 61784-3 that are relevant for this safety communication layer. This safety communication layer is intended for implementation in safety devices only. NOTE 1 It does not cover electrical safety and intrinsic safety aspects. Electrical safety is related to hazards such as electrical shock.Intrinsic safety is related to hazards associated with potentially explosive atmospheres. This part 1 defines mechanisms for 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 mechanisms may be used in various industrial applications such as process control@ manufacturing automation@ and machinery. This part provides guidelines for both developers and assessors of compliant devices and systems. NOTE 2 The resulting SIL claim of a system depends on implementation of the selected functional safety communication profile within this system; implementation of a functional safety communication profile according to this part in a standard device is not sufficient for it to qualify as a safety device. 1 In the following pages of this standard@ ??this part?? will be used for ??this part of the IEC 61784-3 series.?? 2 In the following pages of this standard@ ??IEC 61508?? will be used for ??IEC 61508 series.??