DOI:10.1049/pi-b-1.1958.0317

出版商:IEE    

年代:1958

数据来源: IET

DOI:10.1049/pi-b-1.1958.0318

出版商:IEE    

年代:1958

数据来源: IET

DOI:10.1049/pi-b-1.1958.0319

出版商:IEE    

年代:1958

数据来源: IET

摘要:

The paper describes experiments to determine the preferred viewing distance for a number of different types and sizes of picture, including 405-line and 625-line monochrome television and a 405-line colour television picture, all with varying bandwidths. The criterion ‘preferred viewing distance’ proved to be surprisingly consistent and repeatable, and the results obtained indicate that, unless some new development such as receiver picture storage improves matters, the present European standards of television are wasteful of bandwidth. Various methods of using this surplus bandwidth are discussed. The investigation also covered the use of spot-wobble on the 405-line television picture and two television scanning innovations—‘synchronous spot-wobble’ and ‘sampled synchronous spot-wobble’.

DOI:10.1049/pi-b-1.1958.0320

出版商:IEE    

年代:1958

数据来源: IET

摘要:

Among the test signals used for measuring the transmission performance of television links are ‘sine-squared’ and ‘smoothed-bar’ pulses. The paper gives details of the design of a test-signal generator which, at the line-frequency repetition rate, produces a composite waveform consisting of a sine-squared pulse, a smoothed-bar pulse and a normal line-synchronizing pulse. The sine-squared pulse may have a half-amplitude duration of eitherTor 2T, as selected by a switch, where 1/2Tis the nominal upper frequency of interest in the television system (e.g. 3Mc/s in the British 405-line system). The bar pulse has a duration of approximately one-half of the line period and has transitions of ‘integrated sine-squared’ shape.To facilitate precise measurements the generator has been designed with particular emphasis on stability of waveform shape and freedom from jitter.Consideration is also given to analogous test signals for colour-television systems.

DOI:10.1049/pi-b-1.1958.0323

出版商:IEE    

年代:1958

数据来源: IET

摘要:

The paper forms the first part of two papers on efficiency and reciprocity in pulse-amplitude modulation. A method of converting a low-frequency signal into a modulated pulse train and back again, with low power loss, provides multiplex communication on a 2-wire basis, without amplifiers. In principle, lossless 2-way channels with a bandwidth of half the sampling rate are feasible. The paper furnishes a theoretical study of the transmission properties of such channels.

DOI:10.1049/pi-b-1.1958.0324

出版商:IEE    

年代:1958

数据来源: IET

摘要:

The paper is the second of two papers on efficiency and reciprocity in pulse-amplitude modulation, and experimental and practical aspects are discussed. Transmission with an overall loss of about 2 dB is achievable in practice and should be capable of improvement. Response is level up to about 4 kc/s using 10kc/s sampling, depending on the choice of filter. Subjective speech tests show that satisfactory transmission can be obtained with an economical filter network. Advantage is taken of the ‘transparency’ of the system to provide voice-frequency signalling. The potential applications for the technique of efficient and reciprocal pulse-amplitude modulation are reviewed briefly.

DOI:10.1049/pi-b-1.1958.0325

出版商:IEE    

年代:1958

数据来源: IET

摘要:

Point-contact transistor circuits to generate pulses in the microsecond range are described, together with means of frequency-dividing and interlacing pulse trains and their application to time-division operation of telephone transmission and switching systems.

DOI:10.1049/pi-b-1.1958.0326

出版商:IEE    

年代:1958

数据来源: IET

摘要:

An expression, based on the classical Poiseuille equation for gas flow through capillary tubes, has been obtained to describe the passage of gas through non-coaxial telephone cables under steady-state conditions, and, for cables in this category, the factor governing the flow has been shown to depend upon the number, gauge and arrangement of the conductors. An approximation of the pressure gradient associated with a small rate of gas flow has been derived from this expression, and consideration has been given to the degree to which this limits the successful location of sheath faults by methods involving the direct establishment of the pressure gradient, the installation of pressure-sensitive contactors, rate-of-flow measurements and the use of flow-direction indicators.

DOI:10.1049/pi-b-1.1958.0330

出版商:IEE    

年代:1958

数据来源: IET

摘要:

The paper considers the problem of finding the impedance and attenuation of a transmission line when measured through an arbitrary loss-free junction. Several possibilities for the exact determination of impedance in such a case are mentioned, and the results of tests carried out to determine the usefulness and accuracy of certain methods are presented. Some information is also given on the experimental accuracy of the well-known circle-diagram technique for determining transmission-line characteristics.

DOI:10.1049/pi-b-1.1958.0331

出版商:IEE    

年代:1958

数据来源: IET