A type of microphone system consisting of three cardioid microphone elements and a special phase correction equalization circuit. By varying the position of a control knob, the microphone outputs are combined in such a way that the directivity of the array changes from omnidirectional through cardioid to super-cardioid. These are sometimes used in film (or video) making because the control can be synchronized with the control of a zoom lens on a camera so that the auditory perspective changes with the visual perspective.
