Head office of detection of carbon monoxide (CO) and dioxide of nitrogen (NO2) of 4 zones, with two levels of alarm for zone. 3 exits of relay for zone (two of control extraction / ventilation and one of general alarm). Designed for applications where CO'S concentrations could be accumulated and / or NO2 and need to be controlled, to protect the persons. Certificate according to norm JOINS 23300. Indicator by means of display of CO'S concentration in ppm (Sensibility from 0 to 300 ppm) showing him the reading of the detector with the level of detection mas highly and the number corresponding to the above mentioned detector.