Abstract: An equipment for displaying a specification of behavior of a real time system includes a program memory for storing a plurality of program objects for simulating operations of objects indicative of an arrangement of the real time system and a plurality of graphical symbol objects for expressing operational states of the objects and relationships between the objects in the form of a graphical symbol representation on a display screen. In the equipment, the plurality of program objects are linked with the plurality of symbol objects through an inter-program communication control routine. Each of the program objects, when receiving a message from the communication control routine, is executed for simulation operation according to the received message to thereby generate a new message to be sent to the associated program routine and a new message indicative of an object state change to be sent to one of the symbol objects corresponding to the associated object.

Abstract: A method of telephone call, in which if a subscriber is unable to answer an expected call to this telephone due to a conference, business trip, vacation or temporary absence, the reason of not answering is registered with an electronic switching unit from the subscriber's telephone. When an incoming call arrives for the subscriber's telephone, the electronic switching unit decides whether the subscriber's telephone is advisable to call it on the basis of the registered subscriber status data. If the reason for no answer is registered, the calling subscriber is informed without calling the other subscriber by an audible signal or a recorded message.