For functional safety, different consortia have developed different protocols for safety applications up to Safety Integrity Level 3 (SIL) according to IEC 61508 or Performance Level "e" (PL) according to ISO 13849. What most solutions have in common is that they are based on a "Black Channel" and can therefore be transmitted via different fieldbuses and networks. Depending on the actual profile the safety protocol does provide measures like counters, CRCs, echo, timeout, unique sender and receiver IDs or cross check.