MTL 7787+ Zener diode barrier 

Safety barrier to prevent the ignitability of circuits within an explosive area

Two stages of pulse-tested zener/on-state diodes per channel, for limiting voltage and current in hazardous areas

All models have 'ia' certification for all zones and 'IIC' for all explosive atmospheres

tival-sensors.com/productdetails/zenerbarriere-mtl-7787