1.1 Software Classes

Annex H of the IEC 60730 safety standard defines three classes of control software for appliances:

• Class A – Control functions which are not intended to be relied upon for the safety of the equipment (H.2.21.1).
• Class B – Software that includes code intended to prevent hazards if a Fault, other than a software Fault, occurs in the appliance (H.2.21.2).
• Class C – Software that includes code intended to prevent hazards without the use of other protective devices (H.2.21.3).

Software used in protective control functions are either Class B or Class C. This application note deals with Class B controls, which applies to most household appliances.