Revision Standard - Active. The Standard Letter Designations for Radar-Frequency Bands was first issued in 1976 and was written to remove the confusion that developed from the misapplication to radar of letter band designations of other microwave frequency users. This standard relates the letter terms in common usage to the frequency ranges that they represent. The 1984 revision defined the application V and W to a portion of the millimeter wave region while retaining the previous letter designators for frequencies. The current (2002) revision keeps the same letter band designations, includes a change in the definition of millimeter wave frequencies to conform to the ITU designation, and revises the notes to Table 1. Table 1 has been modified for international applications by including Regions 1 and 3 in addition to Region 2.