What is EMC?

I’m sure that some folks who have stumbled on this web site are confused.  There’s a company called EMC and they’re wondering what this site has to do with them?  The answer is – nothing.

EMC stands for Electromagnetic Compatibility.  EMC is defined in MIL-STD-463A (in 1977) as “The condition which prevails when telecommunications (communication-electronic) equipment is collectively performing its individual defined functions in a common electromagnetic environment without causing or suffering unacceptable degradation due to electromagnetic interference to or from other equipments/systems in the same environment.”

What does this mean?  In simple language, it means being quiet and ignoring the noisy neighbors upstairs.

Various regulatory bodies around the world mandate compliance with EMC standards in order to sell a product in their country.  A few countries (or groups of countries like the European Union) mandate that the product be tested for immunity to a set of electromagnetic phenomena, but most simply place limits of the levels of emissions from the product in order to protect radio and television communications from potential interference.  The need for protection of radio services from interference was driven home in the mid to late 1970s when home computers first appeared.  EMC was not a consideration in the design of these early computers and interference to radio communications services was common and widespread.  The immediate result was the FCC’s adoption of Part 15, Subpart J to their rules in 1979 and the publication of CISPR 22 (ITE Emissions) in 1985.  The FCC re-wrote Part 15 of their rules a number of years ago and the limits that appeared in Subpart J in 1979 are now incorporated in Subpart B of the re-written Part 15.  CISPR 22 has been amended a number of times over the years and forms the basis for most national regulations for emissions from computer systems.

I hope this helps reduce some of the confusion you may have had when you came to this site.  If you have questions about EMC, please feel free to contact me at Ghery@PettitEMCConsulting.com or (360) 790-9672.