HSI Spot On Leverless Limit-Switches are designed to handle the most extreme operating environments. The four different Spot On models can sense farther, faster and last longer than the competition.
*SPOT ON WIRE COLOR DESIGNATIONS:
Black Wire = Common / Red Wire = Normally Closed / Blue Wire = Normally Open / Green Wire = Ground (steel housing only)
From 'Making Sense' Blog
I have been designing reed switches and proximity sensors to meet the needs of the multitude of applications that are out there for 40 years. The primary purpose of our sensors is to convert a mechanical motion to an electrical signal. The designs of these sensors can be very simple or really critical and complicated.