IR Pulses that are invisible light pulses. Ideally, the IR Sensors should be line-of-sight’ to the microphones. The microphones output very strong IR pulses that will reflect off wall, ceiling and hard floor surfaces and are then ‘seen’ by the sensors which enhances system performance when a microphone is moving around a class room. The IR Sensors should be installed on wall surfaces as high up the wall as possible (in a normal ceiling room) and one should be installed on each side of the room for best coverage.