This clause of Part 1 is applicable except as follows: This standard applies to PT systems which are intended to be mounted on, or under the floor level and floor service units which are mounted on the floor, under the floor or flush with the floor. NOTE 1 Types and applications are shown in Figures AA.1a, AA.1b and AA.2 NOTE 2 Flush floor PT systems, with the exception of flush floor service units, are not covered by this standard.