Abstract: An interface unit for a telephone receives data from an external source, such as an ISDN switch. Some of the data from the external source can be displayed on a display of the telephone. The interface unit also receives user inputs from various keys on the telephone, including a set of dialog keys. The interface unit includes a user interface that generates menu messages for displaying and operating a set of menus on the telephone display. A user of the telephone can use the dialog keys to navigate through the menus and perform a variety of actions, including executing telephone functions and changing the configuration of the telephone. A display data selector within the interface unit receives the data from the external source and from the interface unit and selects particular data items to be displayed on the telephone display. The selection of data to be displayed is based in part on the operational state of the telephone. The telephone has an active state, a configuration state and an idle state.