This mod improves the performance of the King Serial DME distance output. Units without this mod would sometimes incorrectly display distance, groundspeed, or time to go on KPI-553A, KDI-572, and KDI-574 DME indicators. This mod applies to KLN-900 units, P/N 066-04034-0101, -0201, -0102, and -0202 with S/N 2127 and below. Units with serial numbers above 2127 have Mod 1 incorporated during manufacturing.