Communication processes message generation

AAC system outputs in common use are speech, displays, printers, beeps, data, infrared, and other control formats. Outputs are used to facilitate the interactive nature of real time communication. Users may rely on auditory and visual feedback to enhance vocabulary selection and the construction of messages. The speech and display outputs may be directed toward the communication partner to support the exchange of information. Auditory feedback such as beeps and key clicks, while useful to the individual using the system, also provide the communication partner with the pragmatic information that a user is in the process of generating a message. Finally, outputs may be used to control other items or devices such as printers. 

The Context model is the most abstract level which interconnects the on-board and trackside interfaces through the air gap. The Process level specifies the general communication setup. The Scenario level is used to as a message generator. It sends messages both to the track and to the train. The function models are illustrated on the Movement Authority (MA) example. 

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