The FX-400 series of high power digital fiber sensors is a simple, easy to use sensor that does not compromise functionality. Much work has been done to provide a sensor that beginners can operate out of the box that has some of the useful functions found in high-end units. The user interface of the sensor has been enhanced to provide a dual digital display and a large adjuster. The display shows the incident light intensity and the threshold value simultaneously, which improves configuration and maintenance procedures. Quick modifications of the threshold value have never been easier. It is also simple to make small changes because one digit on the display corresponds to a 30-degree turn of the sensitivity adjuster. The adjuster has no starting or end position, so it is impossible to cause any damage by overturning.