A call detail record (CDR) is a data record produced by a telephone exchange or other telecommunications equipment that documents the details of a

telephone call A telephone call is a connection over a telephone network between the called party and the calling party. First telephone call The first telephone call was made on March 10, 1876, by Alexander Graham Bell. Bell demonstrated his ability to "ta ...

or other telecommunications transactions (e.g.,

text message Text messaging, or texting, is the act of composing and sending electronic messages, typically consisting of alphabetic and numeric characters, between two or more users of mobile devices, desktops/laptops, or another type of compatible comput ...

) that passes through that facility or device. The record contains various attributes of the call, such as time, duration, completion status, source number, and destination number. It is the

automate Automation describes a wide range of technologies that reduce human intervention in processes, namely by predetermining decision criteria, subprocess relationships, and related actions, as well as embodying those predeterminations in machines ...

d equivalent of the paper toll tickets that were written and timed by operators for long-distance calls in a manual telephone exchange.

CDR contents

A call detail record contains data fields that describe a specific instance of a telecommunication transaction, but does not include the content of that transaction. By way of simplistic example, a call detail record describing a particular phone call might include the phone numbers of both the calling and receiving parties, the start time, and duration of that call. In actual modern practice, call detail records are much more detailed, and contain attributes such as: * the

phone number A telephone number is a sequence of digits assigned to a landline telephone subscriber station connected to a telephone line or to a wireless electronic telephony device, such as a radio telephone or a mobile telephone, or to other devices f ...

of the subscriber originating the call (

calling party The calling party (in some contexts called the "A-Number") is a person who (or device that) initiates a telephone call. The person who, or device that, receives a telephone call is the called party (or callee or B-party). In some countries, it ...

, A-party) * the phone number receiving the call (

called party The called party (in some contexts called the "B-Number") is a person who (or device that) answers a telephone call. The person who (or device that) initiates a telephone call is the calling party. In some situations, the called party may number m ...

, B-party) * the starting time of the call (date and time) * the call duration * the billing phone number that is charged for the call * the identification of the telephone exchange or equipment writing the record * a unique sequence number identifying the record * additional digits on the called number used to route or charge the call * the disposition or the results of the call, indicating, for example, whether or not the call was connected * the route by which the call entered the exchange * the route by which the call left the exchange * call type (voice, SMS, etc.) * voice call type (call setup, call continue, call operation, call end, call idle, call busy, out of service call) * any fault condition encountered Each exchange manufacturer decides which information is emitted on the tickets and how it is formatted. Examples: * Send the

timestamp A timestamp is a sequence of characters or encoded information identifying when a certain event occurred, usually giving date and time of day, sometimes accurate to a small fraction of a second. Timestamps do not have to be based on some absolut ...

of the end of call instead of duration * Voice-only machines may not send call type * Some small PBX does not send the calling party In some corporate private branch exchange (PBX) systems, a call detail record is termed a station messaging detail record (SMDR).

Uses

Call detail records serve a variety of functions. For

telephone service provider A telephone company, also known as a telco, telephone service provider, or telecommunications operator, is a kind of communications service provider (CSP), more precisely a telecommunications service provider (TSP), that provides telecommunicat ...

s, they are critical to the production of revenue, in that they provide the basis for the generation of telephone bills. For

law enforcement Law enforcement is the activity of some members of government who act in an organized manner to enforce the law by discovering, deterring, rehabilitating, or punishing people who violate the rules Rule or ruling may refer to: Education ...

, call 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 Geographic data and information is defined in the ISO/TC 211 series of standards as data and information having an implicit or explicit association with a location relative to Earth (a geographic location or geographic position). It is also call ...

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 Fourth or the fourth may refer to: * the ordinal form of the number 4 * ''Fourth'' (album), by Soft Machine, 1971 * Fourth (angle), an ancient astronomical subdivision * Fourth (music), a musical interval * ''The Fourth'' (1972 film), a Sovie ...

because the caller "voluntarily conveyed numerical information to the telephone company." But there is limited protection under the

Electronic Communications Privacy Act Electronic Communications Privacy Act of 1986 (ECPA) was enacted by the United States Congress to extend restrictions on government wire taps of telephone calls to include transmissions of electronic data by computer ( ''et seq.''), added new pr ...

. 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 Classified information is material that a government body deems to be sensitive information that must be protected. Access is restricted by law or regulation to particular groups of people with the necessary security clearance and need to kn ...

order of the

United States Foreign Intelligence Surveillance Court The United States Foreign Intelligence Surveillance Court (FISC), also called the FISA Court, is a U.S. federal court established under the Foreign Intelligence Surveillance Act of 1978 (FISA) to oversee requests for surveillance warrants a ...

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.Blondel, V.D., Decuyper, A. & Krings G
"A survey of results on mobile phone datasets analysis"
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References

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External links