最近因个人原因回了一趟国，途经SFO返回美国的时候发生了一则有趣的事情。
当我过完海关，正拿着行李出去border control的时候，我路过的一个银色的门字形机器突然发出了滴的一声。随后把关在出关前电动门的CBP就找我要护照，看了一眼就放行，期间也没有扫描护照或者敲电脑查信息。
出关了以后赶着奔向下一站转机，到家以后现在想到那个滴滴声音，很好奇那到底是什么作用的。
google一下，换了好几个关键字都查不出sfo出关前的滴滴声音到底是查什么的。后来换了chatgpt，出来的答案是：
The beeping sound that you hear when you cross the exit gate at San Francisco International Airport (SFO) after passing through the border custom with your checked luggage is most likely a signal that indicates that the luggage tag on your checked bag has been successfully scanned and recorded as leaving the customs area. It’s a standard procedure at many airports to ensure that all passengers and their luggage are accounted for before exiting the customs area. The beep also indicates that you can continue on to the baggage claim area to pick up your checked luggage.
不知道有没有大佬知道chatGPT是一本正经说瞎话还是确实是这样？想不通这个gate是通过什么原理读取到我的护照跟baggage tag 
