Microprocessor based analog gas transmitter with 4 – 2 mA output signal for monitoring the ambient air an detecting toxic gases and vapours by means of electrochemical cells or an infrared sensor. The calibration fo types without LCD display is possible via the handheld calibration keypad XT.S/CKD. The types with LC display have a non-intrusive magnetic calibration featur 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- protection for Ex zone 2.