An operator chair comprises: a connection portion; a first parallel arm linkage to which an adjustable seat module is connected, the first parallel arm linkage being rotatably connected to the connection portion and to an armrest; a first actuator for driving the first parallel arm linkage between a first position and a second position, and thereby regulating a seat portion of the seat module between a first, substantially horizontal position corresponding to a sitting position of a user, and a second, at least partially vertical position corresponding to an at least partially standing position of the user, respectively; a second parallel arm linkage rotatably connected to the static fundament and to the connection portion; and a second actuator for driving the second parallel arm linkage so as to regulate at least the vertical position of the connection portion relative to the fundament.