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shall 应 指满足本规范必须遵从的强制性要求
. s. m1 z: b" Y0 e! oshould 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
- c; W# G s( O在否定证据当中不赞成某个措施但也不禁止( r/ j& k- r, J/ C8 A
建议看一下:
; s/ a, A4 {2 Rhttp://bbs.angui.org/forum.php?m ... ghlight=shall%2Bmay
( c& V8 K* r: J) `: n, ?5 @! ~; T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; X) F& E2 k. t) o+ M+ r
: X D% [# k0 v! X; F7 P' h8 {single-core cable: no preferred colour scheme;
: I9 `$ @+ ?) c! x! v; k9 N6 ztwo-core cable: no preferred colour scheme;4 H, z$ J) I* a- {# A0 G' F4 K' E
three-core cable: either green-and-yellow, blue, brown,5 k; T0 M# p/ r$ g
or brown, black, grey
% X& V" _ ~6 y4 O# Kfour-core cable: either green-and-yellow, brown, black, grey,
+ g' ?- _! s0 For blue, brown, black, grey9 U$ r+ x d* L/ t9 i
five-core cable: either green-and-yellow, blue, brown, black, grey,
( s8 `: a$ c$ o5 V4 v) D4 Jor blue, brown, black, grey, black.
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