Microprocessor based analog gas transmitter with 4 – 2 mA output signal for monitoring the ambient air an detecting flammable gases and vapours in the lower explosion level (LEL) by means of an infrared sensor. The calibration for types without LCD display is possible via the handheld calibration keypad XT.S/CKD. The types with LCD display have a non-intrusive magnetic calibration feature for easy calibration without opening the instrument and declassifying the area.. The gas transmitter is available with EEx-d protection for Ex zone 1 and 2, or with EEx-n protection for Ex zone 2.