摘要:

In the telecommunication transmission field the word ‘system’ has been widely used for many years when referring in a collective sense to the equipment forming a communication path, usually of multichannel type. The purpose of the paper is to present a broad survey of the systems commonly used in trunk and junction networks, in particular, those in use and being developed in the United Kingdom. Transmission paths, or links, and terminal translating equipment, together with its associated carrier-generation equipment, are treated in separate sections of the paper for convenience of description.Trunk and junction networks, however, rarely consist of multichannel systems alone. For example, in the United Kingdom, as in most other countries, individual audio circuits form a large part of the network; programme and television channels have also to be accommodated. Information regarding equipment for the provision of these facilities is therefore included in the paper.

DOI:10.1049/piee.1964.0122

出版商:IEE    

年代:1964

数据来源: IET

摘要:

The local network is briefly described and three problems are posed: establishing an acceptable standard of performance, providing local planning engineers with a sound basis for economic calculation, and determining the quantity of plant to be provided. The standard local telephone circuit is described, and methods of assessment of the transmission performance are referred to. This leads to the methods of determination of line planning limits for design purposes in the local network. The basic principles of engineering economic cost comparisons at present used in the Post Office are described. Methods of forecasting growth and of providing a flexible system to meet fluctuations in the demand for telephones are described.A brief section on the more efficient use of the network at audio frequencies is included, and the paper concludes with consideration of the use of the network at carrier frequencies. Various uses, e.g. subscribers' carrier, wired-broadcast services, data collection and alarm concentration, are mentioned. The transmission properties of the existing local network at carrier frequencies are given and conclusions drawn as to the limitations on its use for various methods of working. A final Section deals with the possible future use of the network at carrier frequencies.

DOI:10.1049/piee.1964.0123

出版商:IEE    

年代:1964

数据来源: IET

摘要:

Communication-network planning is a complex process involving a number of interrelated factors among which transmission performance is of major importance. In the paper, detailed consideration is given to the various aspects of transmission performance in relation to speech, telegraph, programme and television channels.Under the auspices of the international consultative organisations (CCITT and CCIR) much study has been devoted to the subject of performance planning. The rapidly increasing length and complexity of modern communication channels have intensified this study in recent years. Several of the major recommendations of the CCITT and CCIR are enumerated and discussed in the paper.Transmission-performance assessment, particularly of speech channels, is a fundamental factor in determining transmission performance limits. The paper includes brief information on assessment studies.The provisions of the new United Kingdom national transmission plan and of the proposed new CCITT switching and transmission plan for worldwide telephony circuits are defined and discussed in some detail.

DOI:10.1049/piee.1964.0124

出版商:IEE    

年代:1964

数据来源: IET

摘要:

The paper surveys some of the technical problems involved in the design of communication-satellite systems providing substantially worldwide coverage for the transmission of multichannel telephony and television signals.Factors affecting the choice of orbit and type of satellite are discussed, and it is concluded that attitude-stabilised, station-keeping satellites in medium-altitude circular orbits represent a desirable design objective.The operational and performance requirements for multichannel telephony and television are considered in the light of the findings of the international Radio Consultative Committee at its Xth Plenary Assembly (Geneva, 1963).Technical factors, such as the choice of frequency and modulation method, are discussed, with particular reference to the problem of providing multistation access to satellites. The limitations on satellite and terrestrial radio-relay system transmitter power imposed by the need to share the same frequency bands are examined, and the advantages of using preferred radio-frequency channelling arrangements by both systems are discussed.Finally, an outline is given of one possible approach to the design of a worldwide system using twelve station-keeping, attitude-stabilised satellites in a subsynchronous (8h) orbit at 14000km height in the equatorial plane of the Earth.

DOI:10.1049/piee.1964.0125

出版商:IEE    

年代:1964

数据来源: IET

摘要:

The general equations of a synchronous machine, with continuous regulation and connected by tieline to a large system, are reduced by small-departure methods to linear relationships from which is derived the characteristic equation for a particular situation.An examination of the coefficients of this equation over a range of operating levels shows that the results obtained for one operating point would be valid over a considerable range.Stability and dynamic response depend on the roots of the equation, and root-locus diagrams are introduced to demonstrate their value in displaying variations in performance of several parameters of the regulator circuit, such as gain, exciter time constant and the constants of certain derivative circuits used for stabilising.

DOI:10.1049/piee.1964.0129

出版商:IEE    

年代:1964

数据来源: IET

摘要:

The paper develops expressions for the self- and mutual-inductance coefficients of machine windings for the general case of nonsinusoidal winding distributions and nonuniform air gap. These expressions involve the harmonics of the winding distribution and the air-gap permeability. For some sample cases, numerical values are given and the departures from the ideal sinusoidal case assessed.The coefficients evaluated in the paper are those which form the starting point of the generalised mathematical theory of machines. The results are of significance in showing how, and to what extent, departures from the ideal machine modify the coefficients and introduce new terms not amenable to the usual mathematical treatment.

DOI:10.1049/piee.1964.0130

出版商:IEE    

年代:1964

数据来源: IET

摘要:

The paper presents a numerical method for the solution of transient-stability problems utilising the number-series approach. Significant generator characteristics which are normally neglected, such as transient saliency, field decrement and damping, are included in the transient-stability study. The swing equation is arranged in a block-schematic form separating the linear and nonlinear parts. Data for the swing curve are obtained from convolution of the impulse response of the linear block with its input; the convolution integral is evaluated by standard numerical methods such as the trapezoidal and Simpson's rules.Rational bases are presented for the selection of a suitable time increment for a specified accuracy. The results obtained by the number-series method are compared with those of the fourth-order Runge-Kutta method. Finally, general hints and suggestions are given for programming the number-series method on a digital computer.

DOI:10.1049/piee.1964.0131

出版商:IEE    

年代:1964

数据来源: IET

摘要:

The paper defines the problem of calculating the transient terminal-voltage rise due to self-excitation of a synchronous generator when a capacitive load is switched, and a typical case neglecting magnetic saturation is computed, first by an analytical method and then by use of analogue computer. The advantage of computational aid is indicated.Established indirect analytical methods of including the effects of magnetic saturation are described. The analogue-computer method is then extended to evaluate the problem of the effects of magnetic saturation on the terminal-voltage transient, produced by self-excitation, by a direct method.

DOI:10.1049/piee.1964.0132

出版商:IEE    

年代:1964

数据来源: IET

DOI:10.1049/piee.1964.0133

出版商:IEE    

年代:1964

数据来源: IET

摘要:

The paper deals with the electrical installation of the Shell Centre, the central office of the Royal Dutch/Shell group of companies in London and the largest fully air-conditioned building in Europe. A brief description of the buildings is given, followed by an account of the progress of the design from the provision of electrical supplies and a description of the high-voltage and low-voltage distribution.Electrical supplies from two separate sources enable half the lighting to be connected to each supply and all power plants to be switched to either supply. Most floors above ground level are laid out on the same general lines as standard office floors and divided into offices by demountable partitions. Switching of the lights can be adjusted, according to the partition layout, without any modification to the permanent wiring, and this system is described together with an extensive and intensive underfloor duct system with permanently wired floor socket outlets.The paper deals also with the electrical supplies to lifts and escalators, air-conditioning-plant rooms and special departments. Information is given on the clock system, various sound systems, alarms and security control and amenity and recreation areas such as restaurants, kitchens, underground garages, swimming pool and cinema/theatre etc. A brief description is given of the heating and air-conditioning plant, owing to the considerable quantity of electrical services employed.

DOI:10.1049/piee.1964.0134

出版商:IEE    

年代:1964

数据来源: IET