The CDMC-7 package includes the CDDS-2 Controller and the CDM-7001 Monitor. The Green Air Products CDM-7001 CO2 monitor is a breakthrough in CO2 detection and control. It is a sensing device which measures the level of CO2 in the air. It employs a revolutionary passive infrared element which samples the air once every second and interprets a value instantly. The passive infrared sensor precisely determines and displays the CO2 values in parts per million (ppm) on a large LCD screen. This enables you to maintain precise CO2 enrichment levels without guesswork. The monitor plugs directly into Green Air Products Carbon Dioxide Digital Sequencer (CDDS-2), which enables the user to adjust the desired CO2 level and span. All you do is plug the CO2 Monitor and your CO2 generator or bottled CO2 Enrichment System into the CDDS-2, set the values you want, and it will maintain your desired CO2 level perfectly and constantly all day. CO2 values are adjustable in 10 ppm increments from 0 to 5000 ppm. The span between CO2 "on" and CO2 "off" (hysteresis) is also adjustable in 10 ppm steps up to 300 ppm differential. The LED changes color to indicate CO2 function status. The CDDS-2 also provides a switchable photo sensor to disable CO2 production during periods of darkness. The CDM-6 sacrifices the digital display and portability for a more economical price (you still have the digital readout on the CDDS-2 controller, so you will still be able to see the ppm of CO2 in the room).