Reliabile software for SPC systems

World Abstracts on Microelectronics and Reliability characteristic concepts of software is introduced. This paper discusses the latter approach and deals with such important problems as reliability prediction and designing. Reliability analysis of a 2-disslmilar units redundant system with Erlang-faflure and general repair distributions. MASANORI KODAMA. Microelectron. & Reliab. 13, 523 (1974). This paper considers the case of two dissimilar unit redundant system with Erlang-failure and general repair distributions. Three cases are considered. (1) warm standby redundancy; (2) warm stand-by redundancy with priority; and (3) parallel redundancy in which case the failures of the units are not statistically independent. In models (1) and (2), the failure of each unit is independent of the other. The Laplace transforms of the reliability and the explicit formula for the mean time to system failure are derived. Reliability considerations in the design and fabrication of polysilieon fusable link PROM's. G. H. PARKER, J. C. CORNETand W. S. PINTER. Proc. IEEE Reliab. Phys. Syrup. 88 (1974). This paper describes some of the design and fabrication considerations in a 1024 bit programmable read only memory. The memory element in the PROM is a fusible link consisting of a notched stripe of polycrystalline silicon. Some thoughts on the reliability of telecommunication networks. H. BACZKO. Telecommunication J. 14, 729 (1974). The definition of reliability and the concept of failure in telecommunication networks are analysed from the standpoint of the subscriber and the administration. The main reliability characteristic in telecommunication networks is defined. The difficulties encountered by maintenance staff, manufacturers of equipment and the CCITT in their work on reliability are discussed. Fault dearance in the periphery of stored-program controlled telephone switching systems with the aid of a central service computer (SC). W. Pucr~s and G. RmBECK. Proc. N.T.G. International Switching Syrup. Munich, p. 434/1 (1974). An example in the field of fault elimination in the periphery of the electronic switching system (EWS) serves to illustrate how automatic fault treatment in telephone maintenance is implemented with the aid of a central service computer (SC). The peripheral area is defined and the maintenance concept of the electronic switching system (EWS) is explained. In the following chapters the interplay between central processor (ZST), service computer (SC), and telephone maintenance office (FEUST) as well as the attained level of automation is described with the aid of a sequence of operations occuring during fault elimination in the peripheral circuits as initiated by the routine test program based on a failure indication (STOEME). Automation applied to repair and maintenance of electronic systems. G. HATTON and R. K. HAYWARD. Proc. N.T.G. International Switching Syrup. Munich p. 422/1 (1974). Maintenance of TXE 4 exchanges is based on corrective action following analysis of printed out information of equipment in use when call setting-up processes fail to establish a path at the first attempt. The maintenance activity is limited to determining the faulty unit and replacing this by a spare. Faulty units are repaired at a centre equipped with a logic card tester with software control. Diagnostic procedures are outlined and future improvements discussed. Method of predicting the reliability during the development of a switching system. J. DUTr and L. D. NICHOLS. Proc. N.T.G. Int. Switching Syrup. Munich, p. 131/1

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(1974). The vital service provided by a telephOne exchange to the community makes it essential that its availability to the subscriber be high, that is its reliability and maintainability be high. This paper discusses the use of reliability prediction in the design of systems to meet the necessary objectives and the place of reliability prediction in the overall reliability program for the system development. Reliabile software for SPC systems. S. H. CHISMANand M. BENNETt. Proc. N.T.G. International Switching Syrup. Munich, p. 144/1 (1974). Software seems to be at least the equal of hardware in producing errors leading to system breakdown. A survey of the techniques whose use is designed to result in reliable software is presented and work within the Research Department, UK Post Office on certain of these, more particularly high level programming languages, is described. An attempt has been made to incorporate a balanced bibliography. Reliability achievement in the IBM 3750. R. LEBLANC. N.T.G. International Switching Syrup. Munich, p. 145/1 (1974). For switching applications, the overall reliability objective of the IBM 3750 is several orders of magnitude better than current data processing systems figures. The techniques used to reach this objective are many and varied: some concern the system architecture, others the hardware and the software design, some the manufacturing process, others the maintenance strategy. This paper describes only that combination of techniques which appears to be most original in switching system technology. A program system for saleguarding the availability Of the Siemens system EDS. B. LAMPE,U. LENZ and G. MOSCmTZ. Proc. N.T.G. International Switching Syrup. Munich, p. 141/1 (1974). To complete efforts for safeguarding the availability of the Siemens system EDS by a modular structure and duplication of units a program system has been developed which controls the systems reaction to faults. Faults are mostly recognized by monitoring circuits within the units. These circuits then interrupt the running program and initiate a location program which traces a fault down as far as necessary for the system to be reconfigured for continuing its normal operation. Diagnostic programs indicate printed cffcnit boards to be replaced for repairing the faulty unit. Fault recognition, location, configuration and diagnosis, and the necessary programs are discussed in this paper for the central units as well as for the units of the network periphery. Availibility as a criterion of system perlormance. J. F. BAMPTON. Proc. N.T.G. International Switching Syrup. Munich, p. 132/1 (1974). Reliability is of major importance in the production of a new telephone system where reliability requirements must be specified, reliability predictions made during design and finally reliability observations made on the installed system. Maintainability and specifically the time to repair equipment, is of increasing importance as it affects design, it determines the maintenance policy and directly affects customer service. Availability--the probability that the system will meet the demands of the customer when he needs to use it--is important at three levels, the individual call, the customer's access to the system (telephone, local line, etc.) and the local exchange. Recognising the importance of availability as a criterion reflecting the customer's view of the system, the paper suggests that the customer uses a subjective scale of availability which takes into account the frequency and duration of the failures experienced and the way in which the failures affect his service. The paper extends the discussion to very large systems