... Gas Monitor's features:1.Small sized, proper structured, light weighted,and easy to install;2.Low cost, high accuracy;3.Program ... 485, GPRS/CDMA/ADSL (optional);5.Anti-static, anti-lightning, and anti-electromagnetic interference;6.Dual channel -- 4-20 mA current ... -5 V voltage output;7.Large-screened LCD, intelligent keyboard, and LED indicator can satisfy all the requirements for expansive control ...