Recovery of intertidal mussel beds in the Wadden Sea after large-scale destruction

Disclosed is a mechanism for controlling the relative positions of one or more rotating objects or local cams with respect to a master rotating object or cam. In addition, the mechanism also controls the rotating speed of the object or cams with respect to a master. Each local cam is normally driven by a motor which rotates the cam at the same speed as the master cam. A synchronization pulse is produced by the master cam and by each local cam, one pulse being produced for each revolution. When the synchronization pulses of the master and local cams are coincident in time, the cams are in their proper relative positions. When the synchronization pulses are not coincident, relay circuits are energized and, in turn, energize as second or third drive motor for the local cam. The second or third drive motor drives the cam at a greater or slower speed and overrides the normal local cam drive motor. The length of operation of the override motors is controlled by transfer cams which are also energized by the relay circuit. The mechanism may advantageously be incorporated in a traffic control system where the individual controllers are regulated from a master. The disclosed mechanism permits the smooth and rapid transistion from one control sequence to another depending on local traffic conditions.