detail records provide a wealth of information that can help to identify suspects, in that they can reveal details as to an individual's relationships with associates, communication and behavior patterns, and even location data that can establish the whereabouts of an individual during the entirety of the call. For companies with PBX telephone systems, call detail records provide a means of tracking long-distance access, can monitor telephone usage by department or office, and can create listing of incoming and outgoing calls. Privacy The U.S. Supreme Court has held the records of numbers called are not protected by the Fourth Amendment to the Constitution of the United States because the caller "voluntarily conveyed numerical information to the telephone company." But there is limited protection under the Electronic Communications Privacy Act. The revelation that call metadata records are being universally collected and stored in the U.S. and elsewhere has generated considerable controversy. In June 2013, a top secret order of the United States Foreign Intelligence Surveillance Court was leaked to the public. That order referenced and defined call detail records as follows: Usage in research CDRs have found various uses in academic research, with topics ranging from social networks to human mobility. See also Charging data record Customer proprietary network information NSA call database Telecommunications data retention Pen register Internet Protocol Detail Record Communications data Datacom Average call duration Answer/seizure ratio Telecommunication transaction processing systems References External links Visualize/playback 6-months' Call Detail Records – records of German politician Malte Spitz (ZeitOnline) Telephony Telecommunications economics