There is some confusion in the avionics industry relating to the various terms used for terrain awareness, terrain advisory, and terrain alerting systems. Not all terrain systems are certified to Class A or B TAWS standards specified in FAA TSO C147b. If a terrain system is certified and approved to FAA TAWS standards, then the manufacturer will specifically use the term "TAWS" and/or "Class A/B TAWS". In most if not all cases, the term "terrain advisory" should not be understood to indicate "TAWS" or imply the product meets TSO C147b.