The Model CMT200 Carbon Monoxide Transmitter provides a field selectable current or voltage output that is proportional to the gas concentration in underground parking garages, vehicle maintenance facilities, or mechanical rooms. A field replaceable, electrochemical sensor provides accurate readings for up to 4 years with proper calibration. Field calibration can be done by using Model GCK-200CO-2000CO2 calibration gas, Model A-507A calibration adapter, and the on board span and zero potentiometers.