Original sentence: Although these rules were developed specifically for international competitions, they have become the de facto standard used as the basis for all competitions worldwide.Competitors in the other categories may skip only a specified transmitter or transmitters.Current IARU rules divide entrants into nine categories based on their age and gender.Only the M21 category must locate all five transmitters
Edited sentence: Although these rules were developed specifically for international competitions, they have become the de facto standard used as the basis for all international competitions worldwide.Current IARU rules divide entrants into different categories based on their age and gender.Note: IARU Region I ARDF rules are to be revised in September 2009 with proposed changes to transmitters and classes.Only the M21 category must locate all five transmitters, while the other categories may skip only a specified transmitter or transmitters