HSI Sensing (Formerly Hermetic Switch Inc) began manufacturing reed switches and proximity sensors in 1968. These devices complete electrical circuit paths when magnetism is placed in close proximity to the switch or sensor. HSI Sensing specializes in the difficult to manufacture products. For example, pacemakers of the highest quality contain the world’s smallest reed switch, which is made in their Hi-Rel department. Additional applications include the International Space Station, Golf and Turf Equipment, Hearing Aids, Valve Controls, Aircraft, Hospital Defibrillators and many more unique applications where quality and reliability are required.