The local central limit theorem on the Ch?bli-Trim?che hypergroups and the Euclidiean hypergroup R

A rotational actuator including an electric motor and gear reduction means. The gear reduction is at least partly provided by a planetary arrangement which transmits the rotational motion or permits its output shaft to "free-wheel" as a function of engagement or disengagement of a solenoid operated device for restraining the rotation of the ring gear of a planetary subassembly or permitting its free rotation, respectively. The output shaft is thus readily manually overridden when the solenoid is not energized. An optional overcenter resilient means (compression spring) provides for return of the output shaft to a first or second extreme position when the solenoid is deenergized.