Coarse and fine positioning device employing a single driving mechanism

A read-write head positioning device and method of operation that provide coarse and fine positioning using only one actuator. The read-write head is mounted on a carriage. The carriage is resiliently mounted to a moving frame. The moving frame is slidably mounted to a fixed frame. A detent mechanism disposed between the fixed frame and moving frame provides coarse positioning of the moving frame in several discrete positions relative to the fixed frame. An actuator disposed between the fixed frame and carriage provides for fine positioning of the transducer. To change coarse positions, the actuator drives the carriage in the desired direction to engage a mechanical stop on the carriage with a stop abutment on the moving frame. The actuator then continues to drive the carriage and the moving frame in the desired direction causing the detent mechanism to release from its current coarse position. When the detent mechanism captures the moving frame in the desired coarse position, the actuator backs the mechanical stop away from the stop abutment and resumes fine positioning operations.