The high and low states can be represented as true and false statements, which are used in Boolean logic. In most cases, high = true and low = false. However, this does not have to be the case-You could make high = false and low = true. The decision to use one convention over the other is a matter left ultimately to the designer. In digital lingo, to avoid people getting confused over which convention is in use, the term positive true logic is used when high = true, while the term negative true logic is used when high = false.