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shall 应 指满足本规范必须遵从的强制性要求' }# h8 e; W. u
should 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
% d- I* c: ]. s在否定证据当中不赞成某个措施但也不禁止
4 O. m6 a6 `) G5 ]) s7 P# G建议看一下:
( r3 X% l1 b4 [. M3 y5 ?- [* zhttp://bbs.angui.org/forum.php?m ... ghlight=shall%2Bmay
2 `- v( Y1 \* D- ^' f o8 J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
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& U6 {0 G9 l. o" h: x6 isingle-core cable: no preferred colour scheme;
8 v' j& A5 h7 P& C2 k* Qtwo-core cable: no preferred colour scheme;( i; Y2 l3 R8 c+ X* _. M) f8 A
three-core cable: either green-and-yellow, blue, brown,
: i9 d% s/ k& H! C% Lor brown, black, grey
2 c5 c$ e$ g2 Qfour-core cable: either green-and-yellow, brown, black, grey,4 m! U' x: @4 N1 p) @) E
or blue, brown, black, grey
0 i; c% h& o! Z" U( G b4 E- |; ]- Qfive-core cable: either green-and-yellow, blue, brown, black, grey,0 d! B T6 b2 }9 Y
or blue, brown, black, grey, black.
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