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shall 应 指满足本规范必须遵从的强制性要求
% s; k3 F! p, `* A; i P P) 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6 Q i5 l( Q: e" Y2 K8 K E
在否定证据当中不赞成某个措施但也不禁止
: T! k( u- J _5 S$ s( o建议看一下:6 s, v7 |% q/ X0 q' q2 u
http://bbs.angui.org/forum.php?m ... ghlight=shall%2Bmay& e6 O! N0 e6 C9 U5 J( X
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 p7 P9 A7 l W+ T3 R
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single-core cable: no preferred colour scheme;/ @% d/ n5 H, I# ~; M
two-core cable: no preferred colour scheme;
& S! D: o$ T* F! }7 Jthree-core cable: either green-and-yellow, blue, brown,9 V, S& i0 ^" r Q9 d0 u
or brown, black, grey
- Y+ ^7 I9 j: Ifour-core cable: either green-and-yellow, brown, black, grey,
" z1 h4 L% K% m0 kor blue, brown, black, grey
* Y# r& {/ B, G( Kfive-core cable: either green-and-yellow, blue, brown, black, grey,
3 ]+ d- s2 v* X( ^or blue, brown, black, grey, black.
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