Abstract: A light pen for use in data imput to data processing equipment, has an adjustable tip assembly wherein the tip switch sensitivity and tactile feel or feedback to the user can be varied according to user preferences and particular applications. In one mode, the pen can be set for a normal, longer throw of the switch, so as to provide and require a definite touch or push action on the part of the user in order to actuate the switch. In another mode, the tip switch characteristics can be adjusted for a very light feel, so as to permit delicate input such as handwriting or drawing. The tip assembly includes an adjustable stop member provided within the tip housing, to provide a variable limit for the travel of the tip structure.