An ADSI telephone has a display and at least three softkeys with which the user can interact. It also has a virtual screen and a table of softkeys in its memory. The virtual versions usually represent a larger screen area and more keys than the real telephone. At any one time, the user sees a subset of the virtual data. The voice response system sets up the virtual display and key tables, and selected areas and keys are copied to the real telephone as required.
While the real telephone display and keys can vary in shape, size, and number, the virtual display size and number of keys are the same for all ADSI telephones. Six softkey definitions are always available for display at any one time, but the virtual display size depends on whether the telephone is operating in SDC or FDM mode.