Control device

A phonograph including a pick-up arm, a first carrier member, the pick-up arm being mounted on the first carrier member, a second carrier member, the second carrier member being mounted for movement along a predetermined straight path, resilient means mounting the first carrier member upon the second carrier member for movement of the first carrier member relative to the second carrier member in directions parallel to the said path, electric motor means for moving the second carrier member along the path, electro-magnetic coupling means between the first and second carrier members, the electro-magnetic coupling means being constituted by a magnet attached to one of the carrier members and a coil attached to the other carrier member, and sensor means for detecting any displacement of the arm from a desired position, a control circuit coupled to the output of the sensor means and means to couple from the control circuit a first electric signal in a first higher frequency band to the coil and a second electric signal in a second lower frequency band to the motor means to move the first and second carrier members in such a way as to tend to compensate for any displacement of the arm from the desired position.