The All Call button appears at the bottom of the screen on every screen. Press it to route signal from your mic to every headphone set connected in the studio or classroom. This is the quickest way to establish communication with the students, and it is convenient when you are in any mode other than Lecture mode.
By pressing the All Call button, you turn off all student instruments and student will hear you (the teacher) and your instrument only. All other audio present in the system is disabled Ð students can only hear you.