摘要:

This paper gives details of many of the engineering developments which have taken place in the inland telegraph service of the British Isles during the past few years. Some account is also given of the theory and nomenclature of modern telegraphy and of the application of alternating currents to telegraph transmission.Chief among the developments is the conversion of the main telegraph system of the British Isles to multi-channel voice-frequency working, which has resulted in the unification of the telephone and telegraph line plant. The introduction and rapid expansion of the private-wire services have also contributed to a renewal of interest in telegraph matters, and engineers have seized the opportunity to adapt for telegraph purposes many of the technical developments of other branches of the telecommunications art.

DOI:10.1049/jiee-1.1937.0040

出版商:IEE    

年代:1937

数据来源: IET

摘要:

The work of G. N. Watson on the propagation of electric waves over a spherical earth has been extended by the author to take account of the finite resistivity of the earth, the effect of which is of great importance in ultra-short-wave transmission.The work is in such a form that the field intensities above the earth can be computed numerically. The effect of refraction in the earth's atmosphere can also be taken into account. The results for a range of wavelength between 2 and 10 m and for heights up to 4 000 m and distances up to 400 km, are published in the paper in a set of curves, the general properties of which are discussed.The effect of atmospheric refraction is considered, and a comparison between observation and theory is made, in which good agreement is obtained, on the average, when neglecting refraction. Major changes may, however, be produced occasionally by refraction.

DOI:10.1049/jiee-1.1937.0047

出版商:IEE    

年代:1937

数据来源: IET

摘要:

After a brief description of Berlin and its chief electric supply company, the Berliner Kraft und Licht (Bewag) A.G., the existing distribution system in Berlin is described in detail.. Special reference is made to the introduction of low-voltage grids and to experiments in feeding them direct from 30-kV cables, the protective systems employed being also discussed. The paper concludes with a reference to the work done by the company's research departments.

DOI:10.1049/jiee-1.1937.0048

出版商:IEE    

年代:1937

数据来源: IET

摘要:

The paper deals with experimental results obtained on a modern coil ignition system operated by a double contact breaker with a small angle of open circuit. At high speeds the contact breaker closes before the spark discharge ceases. Measurements of the effect of the persistence of the spark dicharge upon the coil performance for various secondary loading conditions are described. It is shown that the increase in the just-regularly-sparking output which is obtained is approximately independent of secondary loading due to normal values of shunted capacitance and/or resistance. A theoretical investigation, based on the results, is carried out to determine the approximate increase in sparking frequency with a given output, due to the effect of the persistence of the spark dischafge, for various periods of open circuit. Under certafa conditions, the estimated increase is 35 per cent for 0–4 millisecond and 63 per cent for 0-1 millisecond. The maximum sparking frequency of 12-volt coil systems, capable of meeting the output requirements of the Service specification for ignition apparatus, is estimated for various values of the open-circuit period. It is shown that the probable limit for reliable operation with a double contactbreaker is about 300 sparks per sec. per coil.

DOI:10.1049/jiee-1.1937.0051

出版商:IEE    

年代:1937

数据来源: IET