为什么联系人不能均匀地放置在SD卡上？
If you have ever looked at the contacts side of an SD card, you may have wondered why the contacts are not uniform in size or placement. Why is that? Today’s SuperUser Q&A post has the answers to a curious reader’s questions.
如果您曾经看过SD卡的触点一侧，您可能想知道为什么触点的大小或位置不一致。 这是为什么？ 今天的“超级用户问答”帖子回答了好奇的读者的问题。
Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites.
今天的“问答”环节由SuperUser提供，它是Stack Exchange的一个分支，该社区是由社区驱动的Q＆A网站分组。
Photo courtesy of CLF (Flickr).
照片由CLF(Flickr)提供 。
问题 (The Question)
SuperUser reader Rahul Basu wants to know why contacts not uniformly placed on SD cards:
超级用户阅读器Rahul Basu想知道为什么联系人未统一放置在SD卡上的原因：
As you can see below, some of the contacts seem to be longer than the others. Also, in the SD card section (second row from the top) the last contact (#8) seems to be thinner and closer to the seventh contact. Why not have all the contacts be the same size and place them at uniform distances from each other?
如下所示，某些联系人似乎比其他联系人更长。 同样，在SD卡部分(从顶部起第二行)中，最后一个触点(＃8)似乎更薄并且更接近第七个触点。 为什么所有触点的大小都不相同，并且彼此之间保持均匀的距离？
Why are contacts not uniformly placed on SD cards?
为什么联系人不能均匀地放置在SD卡上？
答案 (The Answer)
SuperUser contributor Ecnerwal has the answer for us:
超级用户贡献者Ecnerwal为我们提供了答案：
The power and ground contacts stick out farther so that power is applied or removed, before or after, the data contacts are connected or disconnected.
电源和接地触点伸出的距离更远，因此在连接或断开数据触点之前或之后接通或断开电源。
The eighth and ninth contacts were added to the MMC format when making the full-sized SD format. There was not room for eight full-sized contacts (maintaining backward compatibility) and perhaps they learned a thing or two about applying and removing power first between the implementation of the MMC and SD formats (or about making it cheaper without an extra switch if they extended the contacts).
制作全尺寸SD格式时，第八和第九联系人已添加到MMC格式。 没有足够的空间容纳八个标准尺寸的触点(保持向后兼容性)，也许他们学到了一两个关于在MMC和SD格式的实现之间首先施加和断开电源的知识(或者如果他们没有额外的开关就可以便宜一些)扩展联系人)。
Have something to add to the explanation? Sound off in the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.
有什么补充说明吗？ 在评论中听起来不错。 是否想从其他精通Stack Exchange的用户那里获得更多答案？ 在此处查看完整的讨论线程 。
翻译自: https://www.howtogeek.com/238195/why-are-contacts-not-uniformly-placed-on-sd-cards/