Note: Most OTDRs have an “auto test” function, but these functions are not foolproof. Most problems with OTDR tests occur when untrained users use the autotest function without having an understanding of how the instrument works, what a good trace looks like and, most inportantly, what are the characteristics of the cable plant they are testing (length, number and locations of splices and connectors). Refer to the next section on reading OTDR traces. Once you are confident that the autotest function is giving valid results, it is a major timesaver in OTDR testing