Behind the podiums, there will be two green lights which are a signal for the microphones. When the lights are off, the microphone is mute. When a candidate speaks, the microphone of the other remains off and at that time if the second one interrupts the first one, his voice will not reach the viewers -- he will only be seen miming. But as they are be standing at lecterns that are only 8 feet apart, they will hear each other, even if on mute.