摘要:

The paper traces the development of satellite communication for commercial purposes up to the present day, and looks at the prospects for the next decade. A review of experimental programmes and of the institutions set up to provide satellite facilities is followed by an examination of the external constraints that mould system development, principally traffic demand, orbital geometry, choice of radio frequency and cost of launching. Next come Sections dealing with transmission, satellite design and earth-station design, with particular emphasis on systems serving large, high-performance, fixed earth stations such as are in use today. Finally, the prospects of development for these existing services are reviewed, and also those for new ones serving smaller fixed earth stations, ships and aircraft, and brief consideration is given to ways in which congestion in orbit, which will eventually result from expansion in the use made of satellite communication, can be minimised.

DOI:10.1049/piee.1972.0198

出版商:IEE    

年代:1972

数据来源: IET

摘要:

Peripheral data-storage units based on magnetic recording play a major role in computer systems. They have access times ranging from tens of milliseconds to seconds, contrasting with the microsecond or submicrosecond performance of core or semiconductor main-frame stores, but provide an online storage capacity of millions of characters at costs of ‘millipence’ per bit. The major components are the magnetic-recording or storage medium, the recording head, the transport mechanism and the electronics. The transport mechanism moves the heads and medium accurately with respect to each other; the control electronics control the mechanism in response to computer command; and the data-channel electronics, acting through the recording heads, write and read data to and from the storage medium. In the paper, the functions and general performance parameters of these units are reviewed, and the basic magnetic-recording principles are explained, with emphasis on the design of the recording medium and heads. Exchangeable-disc stores and magnetic-tape transports are then described in some detail, and attention is drawn to the level of development in many closely related branches of engineering that makes the present overall performance possible. Other magnetic peripheral stores such as drum and magnetic-card files are briefly reviewed, and the paper concludes by considering the limits of this technology and briefly discussing possible future technologies in this area.

DOI:10.1049/piee.1972.0199

出版商:IEE    

年代:1972

数据来源: IET

摘要:

The paper is divided into two parts. The first part deals in broad terms with the principles and acceptable levels of safety in relation to standards and certification leading up to the formation in this country of the British Electrotechnical Approvals Board for Household Equipment (BEAB). Particularly with regard to BS3456 (the Standard covering the testing and approving of household electrical appliances), the contents of which are analysed, the conclusion reached is that the safety levels contained therein have been determined largely through subjective judgement rather than technical appraisal. The second part of the paper is concerned with the objectives and procedures, and the organisation to implement them, of the BEAB. The BEAB's relationship with the electrical industry, the British Government, particularly with regard to legislation, and the general public are outlined together with an analysis of the present effectiveness of the BEAB and its importance in the future when the UK joins the EEC.

DOI:10.1049/piee.1972.0200

出版商:IEE    

年代:1972

数据来源: IET

摘要:

The review paper traces the history of superconductivity from its discovery in 1911 to the more recent developments of superconductors that are potentially useful in practical applications. The present state of knowledge of the theory of superconduction is presented in sufficient detail to gain an understanding of the phenomenon and the characteristics that will be important to the engineer. This leads to a summary of the exploitable properties of superconductors. The need for a low-temperature environment itself brings technological problems and the need for auxiliary equipment of reliability higher than at present exists, and hence the evolution of specialised design practices and solutions. The state of development of a range of actual and potential applications of superconductors is assessed in terms of research magnets, electrical machines, cables, transformers, magnetic suspension, energy storage and others. The authors conclude that, while the range of applications likely to be realised in commercial practice is perhaps less than that being advocated a few years ago, certain areas of development of large-scale electrical-engineering equipment employing superconductors will attract increasing interest and effort in the future.

DOI:10.1049/piee.1972.0201

出版商:IEE    

年代:1972

数据来源: IET

摘要:

In recent years, the study of the reliability of equipment has been put on a more clearly defined statistical basis. This demands the precise definition of the terms used and the development of specialised mathematics. Particularly when considering the availability of systems incorporating redundancy and facilities for repairs, there have been advances that allow sophisticated calculations to be made. The reliability of process-control equipment can usefully be considered at three levels: components, assemblies and systems, and features of each of these should be taken into account. The practical value of reliability studies is shown when they enable predictions of performances to be made, and this has happened in several industrial fields. When the predictions have been based on valid data, they have commonly been found to agree—within the broad limits set by statistics—with subsequent observations.

DOI:10.1049/piee.1972.0202

出版商:IEE    

年代:1972

数据来源: IET

摘要:

After a brief account of the reasons for introducing computers into power stations, the extent of the applications of computers in the UK and abroad and the economic factors involved are discussed. The differing conditions for nuclear and thermal stations are identified. These lead to different reliability specifications and scopes of requirements. The role of the computer in alarm and data display, logging and control is outlined, and the available hardware and software techniques are reviewed, with special reference to cathode-ray-tube displays for alarms and data, the latter being in the form of alphanumeric tables, graphs or pictorial representations. The systems engineering and planning of projects are considered in relation to the specifications of hardware and software and their production, system testing and installation at the site. The relationship of these activities to the main power-station-erection programme is summarised. A method of specifying the system reliability is given, and the requirements are interpreted in terms of the system configuration with the use of redundancy. Schemes employing multiple central processor units and interconnecting highways are described, and some availability figures are reported for systems in service. The safety implications of using computers and the problems of operator-computer communication are summarised. Details are tabulated of the duties and hardware of some UK power-station computer systems, and an indication is given of the directions that may be taken by future developments.

DOI:10.1049/piee.1972.0203

出版商:IEE    

年代:1972

数据来源: IET