A method for automatically executing a navigation software is provided. The engagement assembly comprises a locking device that is responsive to an MDA position indicator in automatically locking and unlocking the module in the cabinet. The magnetometer is characterised in that the reactor is a metal tube having a length which permits its ends to remain external of the signal pickup device during the relative movement. The output form is provided from a set of Forms Definition Language forms. A guide washer is provided for each connecting pin. A processor determines a pipe length based on the detected signal and a signal generator generates the signal to be sent through the pipe.