Schools Headsets with In-Line Microphone are designed for use in education and Discover a quality selection of school headsets with an in-line microphone designed for use with devices that accept a single plug (TRRS), which controls both, the headphone and mic in one outlet. These are popular choices among teachers and technology coordinators for use with mobile devices, including tablets and other devices with a single 3.5mm (1/8") TRRS plug.