AIO-220 provides 2 Analog Input ports. Each port can detect 0 ~ 20 mA or 4 ~ 20mA currents. AIO-220 is used to interface with 3rd party detectors: (1) Temperature/Humidity, (2) Flame proof H2 gas detector, (3) Flame proof O2 gas detector, (4) Flame proof CO gas detector, etc.