A line finder is a telecommunications device that tracks down the source of a telephone call. It can be useful in both troubleshooting and investigating telephone calls. A line finder hunts for the calling line by tracing the path of the call and identifying the location of the originating telephone number. There are several synonyms for the term "line finder," including "call tracer," "caller identification system," "caller location identification," "telephone line locator," and "phone line tracker." Each of these terms describes the same basic function of tracing a call to its origin and identifying the calling line. No matter what it's called, a line finder is an essential tool for anyone working in telecommunications.