Hi John:
> The subject here is regarding the words 'shall' vs. 'must' in various of
> product safety standards (including UL 1950 3rd Ed. and EN60950).
>
> Does anyone have any insight into the definitions of these as applicable to
> product safety? I have heard there are differences, but no one can seem to
> give me an answer.
The two words, "shall" and "must," are used interchangably.
Both words are verbs.
>From Webster's Collegiate Dictionary, 10th edition:
shall: used in laws, regulations, or directives to
express what is mandatory.
etymology: OE shal: ought to, must
must: be required by law, custom, or moral
conscience to.
etymology: OE moste: to be allowed to, to have to
Clearly, by definition and by etymology, the words are nearly
interchangable, at least insofar as usage in a standard.
The word "shall" is predominant in IEC 950 and UL 1950; it
appears throughout the standard.
The word "must" appears in the following sub-clauses:
1.2.7.3 Text
1.7.2 Notes
2.7.1 Note
5.2.2 Compliance
6.3.2 Text
Fig. 19 Notes
Annex NAA 3.4, Requirement
Annex NAA 6.4.4.2, Example
Annex NAA Annex NAB Example
Annex NAE Text
Annex NAE 2.5.9 Topic/Summary
Annex NAE 3.1.12 Topic/Summary
Annex NAE 3.2.1 Topic/Summary
Annex NAE 3.3 Topic/Summary
Annex NAE 3.3.5 Topic/Summary
Clearly, most of the "musts" are in UL 1950 addenda, not in
IEC 950. In context, it is very difficult to ascribe a meaning
to "must" that is different from "shall."
(Identifying the word in the text is an easy exercise with an
electronic copy of the standard and an application with a "find"
function.)
Best regards,
Rich
-------------------------------------------------------------
Richard Nute Product Safety Engineer
Hewlett-Packard Company Product Regulations Group
AiO Division Tel : +1 858 655 3329
16399 West Bernardo Drive FAX : +1 858 655 4979
San Diego, California 92127 e-mail: [email protected]
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