EMC is defined as 'the ability for equipment to carry out normal functions within operational distances of each other, without any electro magnetic coupling which causes malfunction or undesirable response'.
Sources of problematical interference can be any electronic system which radiates high frequency signals into the ambient area. This includes communications equipment such as mobile phones, navigation, radar and many microprocessor based systems. These products can run at speeds of 300MHz or more and with harmonics, this interference can reach very high frequencies.
The shielding requirement is especially sensitive where a rogue signal could adversely affect the operation of for instance, navigational guidance systems or engine controls. Normally the offending radiating or susceptible circuit would be surrounded by a shield. With the move towards digital systems and smaller hand-held devices, incompatibility of adjacent circuits causes major problems. In a mobile phone for example, a variety of conflicting areas must be isolated from each other within a small total enclosure.
The EMC Directive 89/336/EEC became law on 1 January 1996. It is designed to ensure that a base level of EMC is established within electrical and electronic products moving throughout the EC, to produce goods which comply with the regulations.