新人请教，call trace是什么？

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常听别人说call trace，但是不明白call trace的真正意义，请高人解释一下，非常感谢！

刚才google到如下信息：
What is Call Trace?If you receive harassing, obscene or threatening calls, you can use Call Trace to record the caller’s number.
Note: This service should only be used in serious situations. The details of the trace will only be released to the police and you will not be advised of the caller's number. May not be available in certain areas.

按这个的意思call trace就是纪录拨入的号码，现在有来电显示的电话不可以记录拨入的号码吗？call trace跟来电显示有什么联系/区别？ call trace 保存在哪？RNC? nodeB?