Call detail records (CDR) are an important part of the accounting process of any phone system. They are also an invaluable resource for troubleshooting. FreeSWITCH provides several different methods for the generation of CDRs. The most common method is to create plain-text comma-separated values (CSV) files. Each line in a CSV file represents one phone call or, more accurately, one call leg. (A call is often made by two "legs": one leg, called leg A, is incoming from the caller to FreeSWITCH; the other leg, called leg B, is outbound from FreeSWITCH to the callee. FreeSWITCH "bridges" the audio of the two call legs so that the caller and callee can talk to each other.) There are other options for processing CDRs, most notably using mod_xml_cdr to store more detailed information about calls, as well as using the event socket to process CDR information.