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shall 应 指满足本规范必须遵从的强制性要求
" Y& V$ U% ^/ j6 L; _' ashould 应该 指在多个可能性当中,认为特别合适,但不排斥其它的可能性.或是优选一套措施,但不是要求.或是
; U6 O1 O- {# F1 I. r t在否定证据当中不赞成某个措施但也不禁止
) A2 o2 `/ B* f/ a, y3 f" n4 t建议看一下:
& h7 e7 o8 {* O8 rhttp://bbs.angui.org/forum.php?m ... ghlight=shall%2Bmay
$ y) |0 `& {3 r7 |+ M$ l( G0 f如果可以用别的颜色作为地线,那么,不排除让写标准的人承认,“棕、蓝”都可以用来作地线6 f+ ~1 N4 Q( j, F
# `+ Q* i3 L4 q7 L b' Gsingle-core cable: no preferred colour scheme;! c4 m7 E& B6 w9 T
two-core cable: no preferred colour scheme;, i9 P7 H7 R+ a+ A, x1 S
three-core cable: either green-and-yellow, blue, brown,
' I9 S+ [ M- E* Z) ~" p+ \or brown, black, grey' b6 x' d/ C) S8 k1 n% }: p( A4 Z
four-core cable: either green-and-yellow, brown, black, grey,2 V9 \ o+ }2 ]" X @
or blue, brown, black, grey- |; M+ ~% a; a; {
five-core cable: either green-and-yellow, blue, brown, black, grey,5 x/ v t1 M) t- ~
or blue, brown, black, grey, black.
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