These filters have been designed to be fitted externally to existing Military systems in order to reduce the effects of imported transients. In particular those due to the Differential tests of Def Stan 59-41 DCS11, and 12 and the Common mode tests of DCS 05. The filters therefore have greater than 15dB Differential mode attenuation at 10kHz and greater than 30dB Common mode attenuation at 100kHz -50MHz to imported signals. The output impedance has been kept low in order to minimize the risk of any interaction with any filters/power supplies fitted into the system load. The filters have little impact on EMC exported from the system load, and little impact on the Power Factor of any system load.