机械行程限位失效后的电子行程限位保护功能；
Limitation protection of electronic process after failure of mechanical process limitation .
可以在电子邮件上附上可执行程序文件。
It is possible to attach executable program files to e-mail.
例如，旅游者计划行程，代理商选择行程路线而航空公司签发电子机票。
For example, the Traveler plans the trip, the Agent selects the legs of the trip and the Airline issues the electronic ticket.
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