(A) A flexible glass fiber, sputter coated with gold to enhance its contrast, deflects the tip of a kinocilium. The magnified image of the tip of the fiber is projected onto a dual array of photodiodes, positioned at the camera port of the microscope. Movement of the glass fiber changes the distribution of light on the photodiodes. (B) As the fiber passes between the two diodes, the diode output voltage is linearly related to fiber position, the plot is an illustration.