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7 l. l% ~! N. [# t4 wshall 应 指满足本规范必须遵从的强制性要求
/ y4 B; C I3 `- }* y Fshould 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 ]8 v M/ @, @1 j* ^ H
在否定证据当中不赞成某个措施但也不禁止
6 R1 V5 I; H6 [; b建议看一下:; O5 \ A3 |' z9 \
http://bbs.angui.org/forum.php?m ... ghlight=shall%2Bmay5 G$ a+ J) U" n% \
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+ |0 K4 `7 j+ G# ^
9 J ~4 a" J/ D4 ?# k1 Xsingle-core cable: no preferred colour scheme;5 R, a, V( z0 r# b8 O0 o, M# I
two-core cable: no preferred colour scheme;4 d4 ~ \( n& Z
three-core cable: either green-and-yellow, blue, brown,7 X1 i+ h+ _ w6 {8 l$ F- B/ I4 \
or brown, black, grey
2 S# I+ ~6 U/ A! H3 Hfour-core cable: either green-and-yellow, brown, black, grey,/ X6 K. E! E9 }6 d! C) Q3 V2 A
or blue, brown, black, grey6 O, H7 k0 @9 G* A9 X* Y
five-core cable: either green-and-yellow, blue, brown, black, grey,. k1 L+ S% F+ V8 j
or blue, brown, black, grey, black. o! K: }: I! c# A3 ? A6 c
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