The Belimo CQKB24-RR 24V Modulating Valve Actuator is an electronic control device designed to regulate fluid flow in HVAC systems by positioning control valves. It operates using a 24V AC/DC signal to modulate or switch valve positions, converting electrical input into precise mechanical movement. Featuring a fail-safe function, it automatically returns to a closed position during power loss for system protection. Commonly used in air handlers, fan coil units, and hydronic heating and cooling systems, it enhances efficiency. Benefits include accurate flow control, energy savings, reliable performance, and improved system safety.