Each control box fitted acts as a Stereo Amplifier thus delivering sufficient power output to drive the Headphones. Built in Microphone provided in each control Box for Students. plug-in type Control Boxes. This system is available for any number of student say 4, 6, 8, 10 or 12 and so on and warranted for one year. The Teacher is provided with Teacher Control unit / Power Supply System. Student Microphone can be controlled by the Teacher.