In a communications network, a network access point address is determined that is currently associated with at least one of a plurality of subscriber mobile devices associated with a subscription to an information service. The methods include a point-focus procedure that works by moving the slide to the desired measurement location, moving the objective lens through a predefined set of height values, acquiring imagery data at each height, and determining the height of maximum contrast. The recording-reproducing opening 21 is provided on the cartridge body 6 for externally exposing part of a recording area of the optical disc 5 ranging from an inner periphery to an outer periphery.