... wire connection 5)Unit:ppm, mA, %,%LEL,%VOL Programmable alarm operation value 4-20mA Smart Toxic Gas DetectorTechnical features * 4 ... -20mA, 2 wire connection ,compatible with existing alarm control unit or DCS (Distributed Control System) * Flameproof body ... for O2,CO and combustible gas. Stainless steel for others. * IP rating: Ip66 Smart Toxic Gas Detector with alarm operation value 4 ...