IEC 61784 3-3:2007 specifies a safety communication layer (services and protocol) based on CPF 3 of IEC 61784-1, IEC 61784-2 (CP 3/1, CP 3/2, CP 3/4, CP 3/5 and CP 3/6) and IEC 61158 Types 3 and 10. It identifies the principles for functional safety communications defined in IEC 61784-3 that are relevant for this safety communication layer. It 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 for functional safety. These mechanisms may be used in various industrial applications such as process control, manufacturing automation and machinery. This bilingual version (2013-05) corresponds to the monolingual English version, published in 2007-12.