摘要:

The paper describes a new type of non-register two-stage rural exchange for a maximum of 1000 subscribers. The control circuits are all-electronic, while the speech network is composed of crossbar switches. Further characteristics are as follows:The control circuits (electronic marker) are built up of transistors, cold-cathode tubes and diodes.For an outgoing call, subscriber-dialled digits are received in a register at the main exchange.Establishment of all other calls (incoming and local) is controlled by the main exchange via a separate control line.The control line may serve several rural exchanges.Trunk line connections of incoming and outgoing trunk calls are established in the direction from the rural to the main exchange.The first of the two stages of the rural exchange may work separately as a line connector with remote control over the control line.The exchange is suitable for centralized subscriber metering at the main exchange. However, subscriber meters located at the rural exchange may also be used.The exchange is now in the shape of a few line connectors in actual service at various locations in the Jutland network.Within a year about 25 line connectors will be installed as part of the automation of the present manual exchanges.The first complete rural exchanges are expected to be in service in 1962.

DOI:10.1049/pi-b-2.1962.0163

出版商:IEE    

年代:1962

数据来源: IET

摘要:

Published information concerning the mean speech volume and likely range of volumes in a telephone circuit is summarized, and curves are reproduced for the variation in instantaneous amplitude of an individual talker. It is concluded that, to be able to handle both types of variation, a p.c.m. system should have its smallest quantization step at least 62dB below the peak limiting level. This range can be handled by a 7-digit binary code using non-linear encoding (companding). Two main types of non-linear characteristic, namely logarithmic and hyperbolic, are compared, first on the basis of signal/quantizing-noise ratio and secondly in terms of theoretical information content. It is shown that, provided that the non-linearity parameter is chosen to give an adequate dynamic range, there is little to choose between the two characteristics.The possibility of using automatic volume regulators to reduce the dynamic range is also considered, but it is concluded that they give little advantage.

DOI:10.1049/pi-b-2.1962.0164

出版商:IEE    

年代:1962

数据来源: IET

摘要:

A detailed consideration is given of certain specialized units by means of which an analogue machine, normally used for simulation of continuous systems, may be adapted to allow also simulation of sampled-data systems. Emphasis is mainly on those circuits and methods which achieve best accuracy, the order of 0.1% being possible when valve circuits are employed.

DOI:10.1049/pi-b-2.1962.0165

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The authors describe a procedure for the empirical determination of system dynamic characteristics in which the time of measurement may be exchanged for test signal/noise ratio. The technique hinges on the well-known result that, if white noise is applied to a linear system, the cross-correlation of input and output gives the system impulse response.The authors point out that, in practice, it is much more convenient to use a periodic ‘random’ test input rather than a true stochastic input. Furthermore, by employing binary test inputs, the multiplica tion of output and input (in the cross-correlation) becomes simply a switching process. In describing some preliminary experimental work, the authors discuss the problems of mechanization supported by analytical considerations. The errors of such measurements are examined (including the interesting case when the test signal is com parable with system noise), and some illustrative results are presented.

DOI:10.1049/pi-b-2.1962.0166

出版商:IEE    

年代:1962

数据来源: IET

摘要:

Magnetic cores having approximately rectangular hysteresis loops and bistable properties have been used as logic and switching elements for several years. They offer exceptional reliability, flexibility and cheapness for systems not required to operate at extremely high speeds.The principle of current-steering circuits based on ferrite-core and semiconductor-diode combinations has been discussed in previous papers. This paper describes current-steering commutators which steer well-defined current pulses sequentially along a number of paths. Expressions are included which, although simplified, are sufficient to allow reliable systems to be designed, and a practical example is included in the Appendix.There is no general rule to be followed when designing a core device; the choice of core material and size should be decided individually for a particular application. It is always advisable to study manufacturers' published data and to design adequate circuits in view of the inexactness of the assumption that the spread of switching characteristics from core to core is negligible.

DOI:10.1049/pi-b-2.1962.0167

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The field strength produced by curtain arrays—typical of those used for a high-frequency broadcasting service—has been calculated and plotted as a function of distance from the receiving site. This form of presentation is more suitable for operational use than the aerial power-distribution diagrams commonly employed, since it gives an immediate indication of the most suitable type of array for a specified range of distances.

DOI:10.1049/pi-b-2.1962.0168

出版商:IEE    

年代:1962

数据来源: IET

DOI:10.1049/pi-b-2.1962.0169

出版商:IEE    

年代:1962

数据来源: IET

摘要:

A common-base equivalent circuit of alloy-type transistors containing a multi-element representation of collector capacitance and base resistance has been verified by a variety of measurements. As a consequence it is shown why different methods of measuringrbb', the single-element representation of base resistance, do not lead to consistent results. However, provided that suitable values are chosen forrbb'and forcc, the total collector capacitance, a simpler equivalent circuit containing these two elements is acceptable over the usable frequency range.

DOI:10.1049/pi-b-2.1962.0171

出版商:IEE    

年代:1962

数据来源: IET