It is self checking but when additional security is required, a check character is an option.

这是自我检查，但需要额外的安全性时，检查字符是一个选项。

youdao

It is self checking but when additional security is required, a check character is an option.

这是自我检查，但需要额外的安全性时，检查字符是一个选项。

youdao