"PREFACE Almost fifty years have passed since the advent of formalized military specifications requiring EMI qualification of electrical/electronic equipment. From a few specialized emissions measurements an entire industry has grown up. In the nature of such an evolution the limits and procedures have become codified and passed on from program to program. The form has been kept@ but in many cases the functionality has been lost. Some of the most basic limits and methods are largely proof of compliance requirements@ with a sometimes questionable relationship to system level EMC concerns. This was recognized as long ago as 1967. The top level EMC specification@ MIL-E-6051D@ EMC Requirements. Systems (still current at this writing) stated. ""3.2.4.1 Subsystragetunornerus@ Unless otherwise specified in the contract sub-systems/equipments shall be designed to meet the requirements of MII-STD-461 and MIL-STD-462. Since some of the limits in these standardsare very severe@ the impact of these limits on system effectiveness@ cost@ and weight shall be considered Proposed modifications to the limits shall be included in the EMC plans for the system and subsystems/equipments..."" (Author's italics) (I) The purpose of this document is to foster an engineering issues oriented understanding of military EMI requirements. There are several reasons that this is important. The MIL-STD-461D and MIL-STD-462A revision process is currently nearing completion. There is little understanding of how the current (MIL-STD-461C) requirementsCa= about. MIL-STD-461D promises to be in some cases a radical departure from the past@ but in others cases quite traditional. The MIL-PRIME philosophy being incorporated into a new system level electromagnetics effects standard will place a premium on the understanding of engineering issues behind EMI/EMC requirements. Imposition of MIL-STD-461 requirements in the past has placed the responsibility for EMC design on the Procuring Activity. Suppose a weapon system were to have a system level incompatibility due to MIL-STD-461 compliant equipment interaction. Given a reasonable configuration equipment installation@ the contractor could make a case requiring the Procuring Activity to pay for the fix. Under MI-Prime philosophy@ the contractor will achieve system level EMC in pan by system opplicarionspecific tailoringof MIL-STD-461 requirements. Such tailoring will become a more visible responsibility of the contractor. PI There is thus a need for a broader understanding of the engineering issues behind EMI requirements. Rationale for the limits and test procedures are unknown to the majority of industry's EMC engineers. Reviewof specifications and papers written in the formative years of the discipline reveals strong interest in the design of limits and procedures. There has been a shift away from this aspect of EMI control towards a design to specification compliance emphasis. Optimum techniques for designing to compli-ance are very important. However@ if the EMI limits/procedures are themselves not optimized@ then the but the cleverest designer can hope to achieve is to minimize the cost@ space@ and weight impact of the improper requirement. The EMC discipline is extremely empirical in nature. In general. the control of"