n process is IEC 335 Safety of household currently nearly two years behind, but the mandatory requirements (mod) and similar 60335 in Europe refer to EN60950, which may be faulty and out of date electrical appliances compared with IEC 950. Designs of hardware cannot change over- IEC 348 Safety of electronic night and there must be room to accommodate these timing prob- measuring apparatus 401 S1 lems SO that they do not cause unnecessary denial of 'permission to connect' and delays in the market-place. IEC 479 The effects of Periods of overlap must be allowed between the old and new current passing through versions of a standard, during which either version can be used. the human body There must also be room for 'grandfathered' equipment that has Medical electrical already been accepted under an earlier regime and is still being sold. 601-1 equipment 60601-1 Where problems of this kind arise, designers should consult with IEC 950 Safety of information their approval authority to see what can be accepted, and perhaps (mod) technology equipment 60950 persuade them to modify their rules to meet practical needs. The including electrically objectives of compliance with a safety standard should be safety, not operated business the tidy adherence to bureaucratic rules and dates which may not machines have been fully thought out. Designers may also find that some test houses and approval authorities are more flexible than others, and Principles concerning they should act accordingly. Guide the safety of equipment For new designs, designers are advised to use EN 41003 or IEC electrically connected 950, second edition, including (or allowing for) amendments or proposed amendments to those standards for as far ahead as there is telecommunications visibility. Visibility can be improved by designers becoming in- network volved in the standards writing process through national standards 1991/2 ISDN Primary Rate institutes or trade associations. These organisations can quite likely 300 046 Access Safety and benefit from such in