The present invention relates to an interlocking coupling system (1) for overhead aligned rails (4, 5) of which at least one rail (4) is displaceably arranged and comprises a first coupling part (2) and a second coupling part (3), each of said coupling parts (2, 3) is arranged at end parts of said rails (4, 5) and arranged for interlocking, when said rails (4, 5) are in aligned position, wherein each of said coupling parts (2, 3) comprises a pivotal gate member (23, 33), and said first coupling part (23) comprises a locking bolt member (21) with a tapered end part (214) adapted to engage with a pin (334) projecting from said gate member (33) of said second coupling part (3) and said locking bolt member (21) is adapted to engage with a recess (234) in said pivotal gate member (23), and both said gate members (23, 33) are activated by displacing said locking bolt member (21).

A method for intelligent control includes an exchange of historical parameters of events for operating a system and operating a hoist where an electric motor, preferably a DC-motor, is used for lifting and lowering a lifting belt. It can take place at different speeds by registering amperage through the motor and to perform a switching between fast and slow speed when a given current level is reached. The change in hoisting/lowering speed is achieved when a control unit changes the voltage supplied by the battery unit to the DC-motor or changes the frequency of power supply to an AC-motor. The method makes it possible to control the system and to optimize the hoisting/lowering speed for the lifting belt depending on the load thereon.