Abstract: A modularly-structured integrated services digital network (ISDN) communication system comprises a system processor that should be available for a real-time operating system and for a timesharing operating system. In order to enable continuous transitions of the system processor from one operating system into the other operating system, the task having the lowest priority (idle task) and a program subsystem having comparatively high priority in the real-time operating system (multitasking operating system) are fashioned as branch subsystems in which an assignment change from the addressing tables of the real-time operating system onto that of the timesharing operating system occur. The program subsystem with comparatively high priority which is fashioned as a branch subsystem assures that a certain minimum portion of the calculating capacity of the system processor is assigned to the timesharing operating system independently of the traffic load of the real-time operating system.

Abstract: A modularly structured ISDN communication system has a system processor that is administered by a multi-tasking real-time operating system. Since this operating system can only assign system-internal function programs to the system processor (on-line system), a software application module having a time-sharing operating system is provided, so that the same processor can be administered by both operating systems. In order to effect this, one task of the real-time operating system is fashioned as a sluice sub-system SUB in which an allocation switch from the addressing tables of the real-time operating system onto those of the time-sharing operating system occurs. An interrupt transition routine that leads back into the sluice sub-system SUB in which the allocation switch is in turn cancelled is present in the time-sharing operating system for a processing of interrupt requests.

Abstract: In a process for transmitting items of information between devices of an indirectly controlled exchange system via time division multiplex (TDM) channels, with multiple repetition of the items of information, the items of information comprise a plurality of bytes including a number byte which numbers the relevant item of information. The items of information are transmitted by means of buffer stores and multiplexers. The item of information also include a acknowledgment bytes which acknowledge the correct reception of previously transmitted items of information. The reception of acknowledgement bytes is also evaluated as a signal that the TDM channel previously used to transmit the acknowledged information has been released for the transmission of a further item of information.