This highly versatile system may be installed anywhere along the door frame thanks to our adjustable proprietary reader module. The reed switch is an electrical switch operated by an applied magnetic field originally invented by Bell Telephone Laboratories. The reed module is paired with a magnet which can be installed in an instantly recognizable red slat shoe or alternatively within a sealed enclosure in the bottom panel end cap. This NFPA-compliant system has been tested to one million cycles under load and works seamlessly with Luma Bar® Integral light installations. Each module features dual 15 amp circuits capable of powering a wide range of compartment accessories, in addition to the cab warning system. The magnetic door ajar switch is available with a positive or negative ground for either new or retrofit installations.