Since the end of the 2000th century the cellular telephone industry has had enormous development in the world. The first commercially attractive cellular telephones or terminals were introduced in the market at the end of the 1980's. Since then, a lot of effort has been made in making smaller terminals, with much help from the miniaturisation of electronic components and the development of more efficient batteries. Today, numerous manufacturers offer pocket-sized terminals with a wide variety of capabilities and services, such as packet-oriented transmission and multiple radio band coverage.
The development in electronics has come to the point where a further miniaturisation of the terminals might cause some drawbacks—not the size itself but the capability to handle the keypad and reading the display. However, the display has in fact become larger and larger at the same time as the size of the total terminal has decreased. For several years it has been expected that the design of the terminals will become more alike the small pocket computers known as personal digital assistants (PDA), with only few buttons or keys and a large display substantially covering the entire front side of the terminal. In any case, the terminal display will still be quite small and therefore not suitable for presentation of large volumes of data. Still, already today the terminals are quite capable and have a lot of technical functions and can be used for many different services. In order to navigate through the different options and actions that are selectable, the terminals are generally devised with some form of menu information system. When browsing through such menus more text than fits the screen must generally still be viewed. Furthermore, in many cases the menu items themselves are sub-menus in which further browsing can be made. When the display is very small, which would still be the case even if the display would cover the entire front-side of the phone, it is not possible to expand menus horizontally more than maybe a few pixels. Most menus for portable terminals therefore expand vertically or open up into a whole new screen mode.
One problem with drop-down menus is that they cover what is beneath them when they unfold. Most times the menu-items of terminal menu are arranged in the order of expected frequency of use. This means that when the menu drops down to expand it covers items which are frequently used i.e. those immediately below the expanded menu item, but leaves the not so frequently used menu items further down the list still visible. Another problem with drop down menus is that there is no hierarchical feeling visualising the interdependence between the different menus, and no good way to present several drop-downs within each other.
U.S. Pat. No. 5,801,703 disclose a method and an apparatus for selectable expandable menus for computers. According to the proposed solution, expanded menu panels within a given master menu are expanded in place, leaving the relative order of menu items intact. However, the sub-menus or expanded menu items are simply presented on a larger space in the main menu without a clear identification of the hierarchical structure.