A Y.1731 1DM or DMM frame (depending on type of test) is transmitted every so many milliseconds, in order to perform delay measurements (DM). The number should be selected so that at least three DM frames are transmitted during a trial in order to obtain delay variation results. After each trial the measured FTD and FDV is compared against the SAC's Acceptable FLR, FTD, and FDV. Valid range is from 100 to 10000 in steps of 100 milliseconds with a default of 500 milliseconds. A value of 0 effectively disables transmission of DM frames, which thereby indirectly disables the check against the SAC.