Explanation
A toner is a tool that generates an audible signal that can be traced by a probe. A network technician can use a toner to identify the appropriate patch panel port by connecting the toner to one end of the patch cord and using the probe to scan the patch panel until the signal is detected. A toner is the easiest way to identify the patch panel port when the patch panel is not labeled, as it does not require a laptop, a cable tester, or a visual fault locator. A toner can also be used to locate breaks or shorts in a cable, or to verify continuity.
References:
Using a Toner and Probe - CompTIA Network+ Certification (N10-008): The Total Course Video CompTIA Network+ Certification Exam Objectives, page 141