When the snatch block of the crane reaches its top position the snatch block pushes a plate which is hanging from one end of the lever of the limit switch. Due to the weight placed on the other end of the lever this lever is pushed up. When the lever is pushed up the shaft to which this lever is connected rotates there by rotating the cams which eventually open the contacts and disconnect the motor. The electronic limit switch contacts are automatically reset when the lever returns to zero position due to gravitational force