摘要:

This paper contains a review of the improvements and growth of colonial telecommunication services during the last 30 years or so, combined with a study of the measures that have been found necessary to overcome the special problems in telecommunication engineering that result from tropical conditions. It is based on experience in British colonial, protected and mandated territories, which lie mainly within the tropical zone. There has been previous mention of these problems in papers by the late Mr. Llewellyn Preece1and by the late Mr. R. W. Weightman.2Mr. Weightman was for many years associated with colonial telecommunication services, and it is appropriate that tribute be paid here to the large share he had in solving many of the problems discussed herein. He described in his paper the services in Canada, Australia, South Africa and New Zealand. Since then there has been much progress, and the telecommunication engineers of the Dominions must now be left to speak for themselves. The present paper is therefore concerned only with the colonial, protected and mandated territories under the direct control of the Mother Country. The paper is divided into four main sections as follows:(1) General requirements for telecommunications in colonial territories.(2) Characteristics of tropical climates.(3) General design of external plant.(4) Design of apparatus and components for tropical conditions.

DOI:10.1049/ji-3-2.1947.0046

出版商:IEE    

年代:1947

数据来源: IET

摘要:

This paper, which has been prepared in association with a paper on the development and design of colonial telecommunication services, discusses the planning and organization of the necessary systems. As in the associated paper, the countries considered are the colonial, protected and mandated territories under the control of the British Government, which lie mostly in the tropics.The subjects discussed include the factors governing the general planning of a telecommunication system so that it shall meet requirements and operate efficiently at minimum costs. The organization needed for such systems is outlined, with observations on the performance of work for other Government Services, staff selection and training requirements, arrangements for purchase of materials, the control of expenditure by the costing of works and the desirability of keeping cost accounts.

DOI:10.1049/ji-3-2.1947.0047

出版商:IEE    

年代:1947

数据来源: IET

摘要:

It is suggested that the rating of small-and medium-power thermionic rectifier valves in capacitance-input circuits requires amending, so that the full-load conditions may be deduced from the basic properties of the valves in a more general manner, and the usual family of regulation curves, supplied to show the performance at loads less than maximum, may be replaced by curves more suited to the design of rectifying equipment.It is further suggested that these improvements may be obtained by including, as part of the rating, recommended values for two parameters, namely the ratio of the source to the load resistance (R5/R0), and the product of the load resistance and the admittance of the input condenser (ωCR0)This parameter specification controls the circuit conditions under which the valves are operated and ensures that, independent of the type of valve, full-load operation is always accompanied by a particular set of waveforms. The ratios, such as peak/mean value, etc., that characterize these waveforms have been measured and are compiled into a Table which permits the full-load performance of a valve to be evaluated from its basic properties. In addition, an investigation has been made upon the parameter values in equipments employing valves at less than their maximum output. This investigation has led to the preparation of fractional-load performance curves, on which every point gives the full-load performance of an equipment designed to make the best use of the valve at the particular fraction of its maximum output.

DOI:10.1049/ji-3-2.1947.0050

出版商:IEE    

年代:1947

数据来源: IET

摘要:

Section 1 of this paper outlines the present technique of disc recording and indicates briefly its principal advantages and disadvantages as compared with other systems of sound recording. Present practice and the existing degree of standardization are discussed as regards cutting speed, turntable speed, groove shape, groove spacing and disc dimensions. The magnitudes of the stylus amplitudes, velocities and accelerations normally involved are shown, and the considerations which govern the use of radius compensation and the choice of the optimum recording characteristic are discussed.Section 2 deals in a little more detail with some of the technical problems which were encountered in developing a high-fidelity disc recording equipment. The turntable drive and the various considerations which arise in mounting the cutter head are discussed. The design of a robust, high-fidelity cutter head is described and methods of making cue marks and of removing swarf while recording are outlined. A practical method of obtaining the required radius compensation is also discussed.Section 3 describes a high-fidelity disc recording equipment, and indicates the performance that may be obtained from it.

DOI:10.1049/ji-3-2.1947.0051

出版商:IEE    

年代:1947

数据来源: IET