摘要:

The paper is concerned with the teaching of the fundamentals of electromagnetism; it is divided into three parts.Part 1 deals with a method of presenting electromagnetic concepts to the student which takes the inverse square law of force between magnetic poles or electric charges as its starting points. This method is considered to result in a more satisfying sequence of thought than that usually adopted, because the symmetry of magnetic and electrical relations is stressed.Part 2 is a detailed discussion of the teaching of Faraday's laws of electromagnetic induction.Part 3 is a presentation of Maxwell's equations in terms of electric and magnetic flux density.

DOI:10.1049/pi-1.1954.0054

出版商:IEE    

年代:1954

数据来源: IET

摘要:

In 1943 the British Post Office laid the first submerged repeater in a working cable system, and since that date the technique has been developed so that such units are now being used freely in the shallow waters of the Continental Shelf.Shallow-water repeaters are of particular interest to the Post Office, with its extensive system of submarine cables to the Continent. While the interest in repeaters suitable for transoceanic routes in deep water remains and increases, independent solution of the lesser problem has been well worth while and has provided valuable background and data for the solution of the greater problem.The Post Office has standardized one system which provides 60 telephone circuits of C.C.I.F. standard over a single cable with up to at least 10 repeaters in tandem. Systems transmitting 36 circuits have also been designed by a British contractor, and other arrangements are practicable if required. However, the advantages of standardization of repeaters and terminal equipment are obvious.The paper discusses the problems involved and the methods adopted or proposed for their solution. At present, 18 cables have been equipped with repeaters or will be so equipped in the near future; 47 repeaters are involved, the maximum number in one cable being seven.

DOI:10.1049/pi-1.1954.0057

出版商:IEE    

年代:1954

数据来源: IET

摘要:

The paper describes the equipment used to provide 36 telephone channels on each of two submarine cables laid between Oostmahorn in the Netherlands and the island of Rømø on the west coast of Denmark, a distance of some 142 nautical miles. Details are given of the construction and performance of the submerged repeaters used, together with the special terminal equipment associated with them.

DOI:10.1049/pi-1.1954.0058

出版商:IEE    

年代:1954

数据来源: IET

摘要:

The paper describes the design of submerged repeaters for use in tandem on shallow-water cables, together with the special terminal equipment required. This has become a standard system in the British Post Office, and provides 60 speech circuits on a single-cable both-way basis. It was first applied to the England-Netherlands route, where each of two cables has been equipped with four repeaters.

DOI:10.1049/pi-1.1954.0059

出版商:IEE    

年代:1954

数据来源: IET

DOI:10.1049/pi-1.1954.0062

出版商:IEE    

年代:1954

数据来源: IET

摘要:

The paper gives a general account of a 4-year research and development programme which has resulted in the installation at Hammersmith Hospital of a new type of super-voltage therapy equipment. This machine produces 8-MV X-rays, and stabilized outputs of up to 200 r/min at 1 m are available after filtration. Acceleration of the electrons is obtained by a 3-m length of corrugated waveguide energized by a magnetron giving a pulsed output of approximately 2 MW peak power at a free-space wavelength of 10 cm. Since the accelerating unit is fixed with its axis horizontal, the electron beam is deflected through a right angle before reaching the target, and the deflector system is made rotatable, to give variable direction of the X-ray beam. Many clinical facilities are available, and, in addition, the electron beam may easily be extracted.Early Sections of the paper deal with the background to the programme, the underlying principles and the basic design. These are followed by a description of the equipment and some details of its construction. The investigation of the performance is covered in some detail, and certain improvements in the understanding of the properties of the accelerating waveguide are discussed. Finally, a comparison is made between measured and calculated performance and the agreement is shown to be satisfactory.

DOI:10.1049/pi-1.1954.0063

出版商:IEE    

年代:1954

数据来源: IET

DOI:10.1049/pi-1.1954.0067

出版商:IEE    

年代:1954

数据来源: IET