Rich, this is a very interesting discussion. I agree with most you are saying. I like to add that there is some pressure from ACOS (IEC Advisory Committee on Safety) to bring together IEC 65 and IEC 950 into one set of requirements. The problem arises in residential areas where you have cable-TV, your PC hooked to a telecommunication network, and other applications, e.g. you control your entrance with a TV camera, or you monitor your windows/doors in the home for burgler-protection. Assuming you have tied all together into one system,
>>>>what is the correct standard to be applied?<<<< With your following statement "Standards should not limit the acceptable constructions, but should specify ALL the alternative constructions that provide equivalent protection" I do not agree to 100 percent. It is not the correct approach to specify ALL possible alternative constructions. This may be required in some exceptional situations where you are not in the position to clearly specify the goal which hazard you need protection from. The discussions and interpretation problems with testhouses arise if you choose an alternative construction which was not described before in the standard, but which provides at least the same level of safety as the specified ones (see IEC 950, 1.3.1). The normal case in a standard should be to specify exactly what shall be or what shall not be. (BTW: I consider IEC 950 to be of the form "If .... , then .... .", again see 1.3.1 and also 1.4.1.) -- Kind regards/mit freundlichen Gruessen, Horst Dierich, Germany EMAIL: dier...@ibm.net
