All MTL7000 Series barriers are based on the same simple principle. Each channel contains three stages of Zener or forward-connected diodes and an ‘infallible’ terminating resistor. In the event of an electrical fault in the safe area, the diodes limit the voltage that can reach the hazardous area and the resistor limits the current: active output-current limiting circuits are not used. An internal fuse protects the diodes, and the three stages of voltage limitation ensure continued safety if the first or second stage should fail. MTL7100 barriers have an additional replaceable fuse which protects the internal fuse. The MTL7000 Series includes seven key barrier types which cover the majority of applications, simplifying barrier selection and the maintenance of spares stocks.