A chair includes a backrest and a support frame. The rotary valve avoids redundant control edge pairs by having exactly one first supply edge pair for controlling a first fluid supply path, exactly one second supply edge pair for controlling a second fluid supply path, exactly one first return edge pair for controlling a first fluid return path, and exactly one second return edge pair for controlling a second fluid return path. The first path data transmission block transmits a first path data in response to the test enable signal, the edge detection signal, a clock signal, normal data and a second path data.