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Electrical Engineers, Proceedings of the Institution of

Issue 9 • Date September 1966

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Displaying Results 1 - 25 of 26
  • Problems in the specification and assessment of electronic-equipment reliability

    Publication Year: 1966 , Page(s): 1413 - 1419
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (754 KB)  

    This paper is concerned with some of the problems involved in the specification and assessment of electronic-equipment reliability. The emphasis is on mathematical and statistical aspects of reliability, in particular problems involving the use of the exponential reliability formula and its derivatives, and the development of cost/reliability models to estimate the optimum reliability for an equipment type. The related problems of definition and measurement of reliability, involving choice of time base, redundancy and reliability testing, are also discussed. View full abstract»

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  • Synchronisation of a p.c.m. network using digital techniques

    Publication Year: 1966 , Page(s): 1420 - 1428
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (881 KB)  

    In a network of interconnected digital p.c.m. telephone exchanges, all the signals should be virtually in synchronism to facilitate interconnections between channels on different routes. However, to maintain the security of the system, it is also desirable for each station to have an independent master oscillator. There are several possible methods for effectively synchronising the signals in such a system. Apart from the effect of frequency differences, synchronism is also affected by changes in the propagation delays of the interconnecting junctions, caused by temperature variations. A system is described in which the phase of an incoming signal is allowed to drift in relation to the signal generated locally, until a given limit is reached. The limit may conveniently be related to the amount of storage provided for temperature compensation of the junction delay. When the limit is reached, a digit is either added to, or omitted from, one of the signals during a part of the signal not carrying intelligence, such as a frame-synchronising period, so as to reduce the degree of asynchronism. This system adds some complexity to both the exchange master timing circuits and the received-signal timing circuits, and also complicates the switching of calls through the exchange. The time relationships between the various signals in the network can be deduced mathematically, allowing the behaviour of a network with a given set of initial conditions to be computed. Paralysis of the system can be avoided by a proper choice of the amount of storage. View full abstract»

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  • Introduction of p.c.m.-junction links and switching into a dispersed sectionalised switching system

    Publication Year: 1966 , Page(s): 1429 - 1436
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (929 KB)  

    The advantages are examined of a sectionalised main-/dependent-exchange complex for a local-exchange area, together with the particular suitability of a p.c.m. switching section in the main exchange. The dependent exchanges, which may be linked to the main exchange by audio or p.c.m. junctions, use a spatial system of concentration with reed-relay crosspoints, and operate as remote reed-electronic exchanges (REX) controlled by the main exchange. The dependent exchange therefore has all the advantages and facilities normally conferred on a REX type of main exchange. The progressive introduction of p.c.m. switching into the main exchange can be accommodated as p.c.m.-linked dependents are added; all share the main exchange control. Ultimately, a complete turnover to p.c.m. may be achieved at the central exchange. The general principles of p.c.m. switching are discussed, and the desirability of frame alignment is explained. A method of channel-slot changing is proposed, appropriate to small junction groups, and a variable-delay slot changer is described. The problems of time-slot alignment and area synchronisation are considered. A detailed description of the p.c.m. main-/dependent-exchange complex is given, with particular regard to various types of connection. The REX main/dependent arrangement is immediately suitable for exploitation, initially using audio junctions and, later, incorporating p.c.m. for junctions and switching at the main exchange. Codec equipment will be used at the interface between the audio and p.c.m. portions of the main exchange, and to replace links and junction relay sets at the dependent. View full abstract»

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  • Television standards convertors using a line store

    Publication Year: 1966 , Page(s): 1437 - 1456
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (3110 KB)  

    The paper describes the fundamental principles of design of a new type of standards convertor which has been developed specifically for conversions between the 625-line and 405-line television standards. The need for a new type of standards convertor and the basic principles of a line-store convertor are first discussed. A complete account of the new convertor is then given under four main divisions. First, the fundamental aspects of standards conversion are discussed in terms of time functions and spectra, and then the specifications of the various functions of the new convertor are derived by analytical and empirical means. The last two sections discuss aspects of the instrumentation which are either novel or of particular interest, and, finally, the design of two fundamentally similar but instrumentally different line-store convertors. An indication of the performance which has been obtained and the present and future operational use of these devices are discussed. View full abstract»

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  • Second-order ring modulator. Calculations of losses and some design considerations

    Publication Year: 1966 , Page(s): 1457 - 1462
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (687 KB)  

    The second-order ring modulator takes its output at a second-order sideband frequency from the input terminals of a lattice switch (or ring connection of rectifiers); the normal output terminals of the lattice are terminated in a reactive `idler¿ circuit. This arrangement has practical attractions, and uses fewer transformers than other modulators. With ideal switches and ideal selective circuits, the conversion power loss is zero. The effects of resistance in the switches or rectifiers, of changes in the idler arrangements, and of not tuning the input and output circuits, are examined in the paper, and the results are compared with those of the conventional types of modulator. View full abstract»

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  • Noise parameters for metal-oxide-semiconductor transistors

    Publication Year: 1966 , Page(s): 1463 - 1467
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (478 KB)  

    The noise performance of a metal-oxide-semiconductor transistor is represented by a voltage source and a current source at the input to the device. A relationship is established for the noise factor in terms of the magnitudes of these sources, the complex correlation coefficient between them and the input-impedance termination. The conditions for minimum noise factor and the corresponding optimum source impedance are studied. By measuring the variations of noise with source impedance, the noise contributions of the equivalent generators are separated, and results are given for a low-frequency metal-oxide-semiconductor transistor, at frequencies within the band of low noise factor. Measurements are also made showing the variation of the noise factor with source resistance, and with frequency in the range 3¿300kc/s. View full abstract»

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  • Current/voltage characteristics of p-n Ge-Si and Ge-GaAs heterojunctions

    Publication Year: 1966 , Page(s): 1468 - 1476
    Cited by:  Papers (9)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1083 KB)  

    The current characteristics of solution-grown and vapour-grown p-n Ge-Si and Ge-GaAs heterojunctions have been studied as functions of voltage and temperature. All the junctions studied exhibit a range over which the forward-current characteristics are proportional to exp (AV)×exp (Br), where A and B are constants essentially independent of voltage and temperature. Although this is the only type of behaviour observed in nGe-pGaAs junctions, the other heterojunction pairs often exhibit this type of characteristic only above a certain temperature-dependent forward bias. Below this bias, the forward current is proportional to exp (eV/¿kT) The forward characteristics of nGe-pGaAs devices have been successfully explained by a multistep recombination-tunnelling model, in which tunnelling is the predominant current-transport mechanism across the entire junction. This model, however, cannot explain the thermal-current type of characteristic often observed at low forward bias in pGe-nGaAs, nGe-pSi and pGe-nSi heterojunctions. In these junctions, it appears that a tunnelling current flows in the germanium, while a diffusion current, which recombines at the interface, flows in the wide-gap material. These currents flow in series, and are related by interface-state parameters. A model based on this type of current flow is developed and is shown to agree with the observed characteristics. View full abstract»

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  • Experimental investigation into radio propagation at 11.0ߝ11.5 Gc/s

    Publication Year: 1966 , Page(s): 1477 - 1489
    Cited by:  Papers (8)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1575 KB)  

    Fading caused by precipitation, multipath transmission and other causes has been measured in experimental microwave paths operating in the 10.7ߝ11.7Gc/s frequency band. Multipath signals have been analysed and used to compute the intermodulation distortion likely to occur on various-capacity systems. Diurnal and monthly variations of fading equal to or greater than an arbitrary level are given, together with the association between activity on paths taken in pairs. For the month of August 1964 the hourly mean noise powers have been calculated. Over the period for which observations were carried out, it is concluded that neither precipitation nor intermodulation arising from multipath transmission would have significantly restricted the use of the 10.7ߝ11.7Gc/s band for multichannel telephony. View full abstract»

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  • Operational experience with a tropospheric-scatter radio-relay link

    Publication Year: 1966 , Page(s): 1490 - 1494
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (656 KB)  

    In July 1961 the first tropospheric-scatter radio-relay system within the British Commonwealth was installed over the 195 mile path between Trinidad and Barbados in the West Indies. The system was initially engineered to carry 12 telephone channels, and employs 30ft-diameter antennas, 1 kW transmitters, and operates at 900 Mc/s. It has proved operationally satisfactory in every way. To accommodate increasing traffic demands, the capacity will ultimately be extended to 64 telephone channels. View full abstract»

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  • Coverage and overlap of satellites in circular equatorial orbits. With applications to multiple-access communication-satellite systems

    Publication Year: 1966 , Page(s): 1495 - 1503
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1140 KB)  

    This paper considers the earth areas within which many stations, all using the same satellite, can have multiple-access intercommunication without interruptions. These areas are the effective earth coverage in the case of a stationary satellite, or the coverage overlap at handover in the case of single-earth-track medium-altitude circular-equatorial-orbit systems. An equation is derived for the overlap of the coverage areas of two satellites at equal heights, for given angular separation and given minimum angle above the Earth's horizon. Families of coverage and overlap curves are given. The relations between coverage and the earlier `mutual-visibility area¿ are explained. Diagrams of the boundaries of one-hop multiple-access systems, as viewed from above the pole, are shown and discussed, both for a six-satellite stationary-orbit system and for a 12-satellite 14000km phased circular-equatorial-orbit system; these are used and com pared in discussing routing principles. All such equatorial-orbit systems provide a flexibility of routing, via a choice of satellites, which decreases and disappears at higher latitudes. Specific illustrative long circuits using surface-communication `tails¿ are discussed using Mercator maps. It is shown that these longest circuits will probably be multihop systems, when using medium-altitude satellites, while single-hop use of stationary satellites (with surface tails when necessary) will be preferable and possible. The stationary-orbit system has the economic advantages that its earth stations do not require complex tracking facilities, fully steerable antennas or duplication of the installation for performing periodic handovers. Additionally, the use of relay stations and of more than one satellite hop does not appear to be necessary or probable, as with lower-orbit systems. View full abstract»

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  • Electromagnetic momentum associated with waveguide modes

    Publication Year: 1966
    Save to Project icon | PDF file iconPDF (167 KB)  
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  • RC-gyrator low-pass filter

    Publication Year: 1966 , Page(s): 1504 - 1506
    Cited by:  Papers (1)
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  • Stability and instability of active networks

    Publication Year: 1966 , Page(s): 1506 - 1508
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  • Prospect of employing conductors at low temperature in power cables and in power transformers

    Publication Year: 1966 , Page(s): 1509 - 1521
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1515 KB)  

    An estimate is made in economic terms of power that could be saved if the conductor in a 760MVA, 275kV a.c. cable were alternatively: niobium at 4°K aluminium at 20° K beryllium at 77° K The first of these metals is a soft superconductor, and the others, if sufficiently pure, are assumed to exhibit resistivities of 3×10¿9 and 2×10¿8¿cm, respectively. The analysis takes into account the effects of eddy currents at these resistivities, and considers the spacing of refrigerating units along the cable and the distribution of refrigerants in order to minimise that part of the cost that stems from refrigeration. The study turns next to a 570 MVA generator transformer with aluminium at 20°K and resistivity 3×10¿9¿cm, or, alternatively, a hypothetical metal at 77°K and resistivity 2×10¿8¿cm, as the winding conductor. The paper finds that these metals would both have to be used in the form of foil, and derives expressions for three components of foil loss. It then compares the possible saving in conductor loss with the drive power used by the refrigerators, and with the cost of refrigeration plant. It finds that neither in power transmission by cable, nor in power-transformer windings, is there any promise of a net saving over conventional costs that would warrant the constructional and operational complexities entailed in deep refrigeration. View full abstract»

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  • Discussion on "Method of predicting the thermal loading of an oil circuit breaker"

    Publication Year: 1966 , Page(s): 1521 - 1522
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  • Discussion on ¿Generalised computer program for power-system analysis¿

    Publication Year: 1966
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  • High-voltage switchgear. A review of progress

    Publication Year: 1966 , Page(s): 1523 - 1539
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2451 KB)  

    After describing the development of the ratings of switchgear for voltages above 100kV during the last few years and indicating the current trends, the paper considers the more important special conditions for which modern switchgear has to be designed. A brief account is given of the present state of the theory of circuit breaking and of the research now being conducted, together with a review of the switchgear testing methods and stations now in operation. The principles of the more recent developments in the design of circuit breakers, isolators, switches, instrument transformers, surge diverters, fuses, insulators and the layout of substations are illustrated by examples from British and foreign practice. An indication of possible developments in totally enclosed switchgear for high voltages and in the switching of high-voltage direct current is given. View full abstract»

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  • Discussion on ¿The goodness of a machine¿

    Publication Year: 1966 , Page(s): 1539 - 1540
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  • Discussion on ¿Adjustable-frequency invertors and their application to variable-speed drives¿

    Publication Year: 1966
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  • Simulation of h.v.d.c. systems in a.c. load-flow analysis by digital computers

    Publication Year: 1966 , Page(s): 1541 - 1546
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (720 KB)  

    The paper presents a suitable method by which h.v.d.c. trunk lines may be simulated for the purpose of load-flow analysis by digital computer of a.c. power systems containing one or more d.c. transmission links. An explanation is given of the derivation of the relevant equations which comprise a small routine capable of being inserted into normal a.c. load-flow programs. The representation of the d.c. link in an a.c. system is best achieved by equivalent current generators at those a.c.-system nodes containing the convertor terminals. The relationship between the injected currents and the voltages at the nodes is defined by the proposed routine, which is accurate and fully equipped with h.v.d.c.-system controls. View full abstract»

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  • Discussion on extra-high-voltage power-cable systems and gas-pressurised dielectrics for use with them

    Publication Year: 1966 , Page(s): 1546 - 1547
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  • Wave propagation in multi-conductor overhead lines

    Publication Year: 1966
    Cited by:  Papers (3)
    Save to Project icon | PDF file iconPDF (167 KB)  
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  • New developments in high-pressure discharge lamps

    Publication Year: 1966 , Page(s): 1547 - 1548
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  • Low-inductance 100 kV switch (spark gap) for starting, diverting and clamping capacitor discharges

    Publication Year: 1966 , Page(s): 1549 - 1556
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (756 KB)  

    The development of an accurately triggered, pressurised spark gap of the field-distortion type operating in the cascade mode up to 100kV is described. The effects of variations in the air pressure and in the magnitude and polarity of the charging and trigger voltages have been determined. Designed initially as a switch for starting a high-frequency capacitor discharge (250kc/s), it has also been adapted for diverting and clamping such discharges at currents up to 200kA, passing up to 20C per discharge. View full abstract»

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  • Improved spark-gap voltmeter

    Publication Year: 1966 , Page(s): 1557 - 1561
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (616 KB)  

    The field in the conventional sphere gap is appreciably influenced by the surrounding earthed surfaces, and the expected accuracy of the sphere-gap voltmeter may be increased by modifying the configuration of the earthed electrode so as to make the field less dependent on the distance to these surfaces. Accordingly it is proposed that the conventional earthed sphere and supporting shank be replaced by a hemisphere placed on the ground plane, and that the upper sphere be made movable to vary gap length. Alternatively, the distance of the hemisphere above the ground can be varied if this is strongly preferred; for example, if difficulties arise in providing a motor driven high-voltage electrode. Use of the proposed electrode arrangements allows a considerable reduction in cost, especially when requirements of laboratory space are taken into account, and renders voltmeters using sphere diameters of 1 m and above very much simpler to use. Calculations of field factor and measurements of flashover voltage confirm that a sphere-hemisphere gap is affected very much less than a sphere gap by variations in the clearance to walls and large pieces of equipment near the spark gap. It is therefore possible to work with smaller clearances than are required by BS 358 and IEC52 without increasing the dependence of the voltmeter reading on the value of the clearance. Tests show that the sphere-hemisphere gap has a flashover voltage about 5% lower than the sphere gap when the gap length is equal to the sphere radius, and the difference is smaller as the gap length is reduced. A correction factor k is proposed to convert sphere-gap calibrations to sphere-hemisphere gap calibrations, where k = (1.015 ? 0.06g), g ? 0.25, and g is the ratio of gap length to sphere radius. Two quite different means of supporting the top sphere of the sphere-hemisphere gap have been proposed, and both give entirely satisfactory performance when used with alternating, direct or impulse voltages. View full abstract»

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Aims & Scope

The Proceedings of the Institution of Electrical Engineers was published by the IET between 1963 and 1979.

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