The Siemens DDC 540-865EN TEC VAV Controller is a direct digital control device designed for pressure-independent variable air volume (VAV) terminal units. It regulates airflow and room temperature by processing sensor inputs and controlling VAV dampers and heating equipment. Its 0–10 V analog output provides precise modulation of reheat, while CO₂ monitoring helps adjust ventilation ... https://www.partshnc.com/siemens-ddc-540-865en-tec-variable-air-volume-w-0-10v-ao-heat-modulation-co2