The 4011 CVR is our most popular round damper with a synchronous, power open/spring closed, motor in conjunction with a constant volume regulator. This provides a low (or no flow) unoccupied position and a pressure-independent, regulator, higher flow when occupied. It has been designed for fresh-air intakes in compliance with ASHRAE Std. 62.1 and similar IAQ codes. The Constant Volume Regulator requires no power or input signals. The Aero-Gate floats up and down depending on the speed of the air through the part. It adjusts itself to provide the desired air volume to the space independent of pressure drop. The 4011CVR is an all-in-one package solution. Available in either 24vac or 120vac so it can run off the fan circuit on the equipment, an occupancy sensor, or interlocked with a light switch. The unit can also be fit with a Belimo brush-less motor for high pressure or larger diameter applications.