jections of practical experience. Protection, 1991/2 ISDN Basic Access 300 047 Safety and 23.8 Documentation Protection ETR 12 1991/2 Safety categories and IEC Publications and corresponding European publications are protection given in Table 23.2. When the IEC Publication has been modified levels at various by CENELEC common modifications, indicated by (mod), the interfaces for relevant EN/HD applies. telecommunications International (and national) standards can be obtained from na- equipments in tional standards organisations or direct from IEC, 3 Rue de Va- customer premises rembe, 1211 Geneva 20, Switzerland. 23/10 Safety and EMC Electromagnetic compatibility Table 23.3 Electromagnetic compatibility phenomena All electrical and electronic devices generate electromagnetic inter- ference, and are susceptible to it. With the increasing penetration of Immunity Emissions solid state electronics into all areas of activity, acceptable levels of Mains voltage drop-outs, Mains distortion, transients or interference have become progressively tighter as physical separ- dips, surges and distortion RFI generated within the ation between devices has reduced and reliance on their operation equipment and conducted out has increased. Solid state, particularly integrated circuit technology, via the mains supply is more susceptible than the vacuum tube devices of years ago, and the popularity of plastic cases with their lack of screening is a Transients and radio Transient or RFI, generated further factor. The ability of a device to operate within the limits of frequency interference (RFI) within the equipment and interference immunity and suppression is known as electromagnetic conducted into the equipment conducted out via signal leads compatibility (EMC). via the mains supply In some areas of electronics EMC has been a product requirement Radiated transient or RFI RFI radiated directly from the for a long time. Military electronics has severe limitations imposed picked up and conducted into equipment circuitry, on it, often 