Why are there three gears for model L03 hand switch

Why are there three gears for model L03 hand switch?
Model L03 hand switch is an electrical control accessory. The hand switch can be used to control the on and off of electrical signals, photographic equipment and exposure of medical diagnostic X-ray machine. Generally, the hand switch is equipped with two gears such as L01, L02, L04, two-stage switch press the button to turn on the current, release or disconnect, press the button to the first step, I gear switch on, buttons are all pressed to the bottom of the button, II gear switch on, at this time I gear is still connected, 1-step is preparation, 2-step control exposure.
and L03 is added on the basis of the second gear a button. On the side, other devices can be connected to control the button, according to customer feedback, the currently connected device limited beam, control the LED lights in the beam limiter, turn on the film bed, control the movement of the bed and so on. L03 hand switch is also equipped with fixed support for convenient placement and equipment carrying.