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Volume 121
Issue 12
Proceedings of the Institution of Electrical Engineers
Volume 121, Issue 12, December 1974
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Volume 121, Issue 12
December 1974
Generationrecombination noise of junctiongate fieldeffect transistors
 Author(s): Waguih J. Boctor and Sheila Prasad
 Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1457 –1459
 DOI: 10.1049/piee.1974.0306
 Type: Article
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The generationrecombination noise of junctiongate fieldeffect transistors is calculated taking into account the variable mobility. The field dependence of mobility suggested by Trofimenkoff is used, and the resultant spectral intensity of the drainnoise fluctuations shows no signs of a logarithmic singularity at saturation. The need for any cutoff procedure to remove the logarithmic singularity at saturation is therefore removed, and it is thus an improvement over earlier methods.
Design of m.t.i. filters with staggered p.r.f.: a polezero approach
 Author(s): H.W. Thomas ; N.P. Lutte ; M.W. Jelffs
 Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1460 –1466
 DOI: 10.1049/piee.1974.0307
 Type: Article
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The paper presents a polezero diagram which is applicable to m.t.i. radar filters operated with a staggered p.r.f. Such a diagram is readily constructed from the pulse transfer function of the filter, and may also be used when timevarying coefficients are employed. It enables the potential performance of a given filter to be quickly assessed, and affords the designer a convenientmethod of obtaining optimum stopband performance from staggered p.r.f. filters without the use of computer optimisation techniques.
Analytic theory of the IMPATT diode and its application to calculations of oscillator locking characteristics
 Author(s): A.L. Cullen and J.R. Forrest
 Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1467 –1474
 DOI: 10.1049/piee.1974.0308
 Type: Article
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The paper describes an analytic theory of the IMPATT diode, based on the well known Read model. The inclusion of finite avalanche pulse width and spacecharge effects in the treatment yields a relatively simple theory that compares well with a computer simulation such as that of Scharfetter and Gummel, or the University College London fullsimulation program. The use of such diode admittance calculations in the prediction of oscillator locking characteristics is described. The circuit of a reflectiontype locked oscillator is analysed for steadystate conditions and stability limits. After allocation of practical parameter values to the theory, the resulting predicted variation of locked output power with frequency shows good agreement with experimental measurements on a lowpower X band IMPATT oscillator.
Analysis of skewing in amplitude distributions of filtered m sequences
 Author(s): G.H. Tomlinson and P. Galvin
 Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1475 –1479
 DOI: 10.1049/piee.1974.0309
 Type: Article
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The skewing that is found to occur in the amplitude distributions of m sequences subjected to lowpass filtering is discussed. An analysis is presented which establishes a systematic relationship between the extent of skewing and the characteristic polynomial. The results show that the extent of skewing varies considerably for different m sequences of the same length. It is shown howthe skewing can be minimised by the choice of a sequence having an appropriate characteristic polynomial.
New families of errorcorrecting codes generated by modification of other linear binary block codes
 Author(s): Abdullah A. Hashim
 Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1480 –1485
 DOI: 10.1049/piee.1974.0310
 Type: Article
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Two procedures for modifying linear block errorcorrection codes are proposed. The first is based on the deletion of x rows and y columns from the paritycheck matrix of a given (n, k) code, in such a way that the minimum Hamming distance of the resulting (n−y, k+x−y) code remains equal to that of the original. It is shown that if x is unity, then y may be as low asthe minimum Hamming distance of the (n, n−k) dual of the original (n, k) code. This procedure of deleting rows and columns when applied to the known linear binary block code yields a family of codes, some of which have better rates than those of the best previously known codes of identical Hamming distance and the same number of paritycheck digits. 17 examples of such new codes are derived and included in the paper. It is also shown that apart from appropriate slight modification, the coding and decoding algorithms for this family of modified codes are similar to those of the original code. The second proposed procedure of code modification entails lengthening the original (n, k) linear block code by annexing k′ message digits. If the original code is capable of correcting t random errors or less, then the resulting modified (n+k′,k+k′) code has a rate higher than that of the original (n, k) code. Moreover, its errorcorrecting capability is such that it will correct t random errors or less if at least one of these occurs in the block of k message digits and s random errors or less, where 1≤s<t, if none of the errors occur in any of the k message digits. Five examples of such codes are given.
Principles of a permanentmagnet axialfield d.c. machine
 Author(s): P. Campbell
 Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1489 –1494
 DOI: 10.1049/piee.1974.0311
 Type: Article
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The theory of a permanentmagnet d.c. machine that has an axial field and a discshaped armature is discussed. Consideration is given to the effect that the distribution of magnetic field inthe airgap will have on the generation of e.m.f. The machine parameters in the angular and radialdirections are related to this distribution, so that a pole shape may be chosen that maximises the output power.
Sources of harmonic currents in slipring induction motors
 Author(s): A.K. Wallace ; E.S. Ward ; A. Wright
 Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1495 –1500
 DOI: 10.1049/piee.1974.0312
 Type: Article
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Several features which could cause an unsaturated 3phase induction motor to draw nonsinusoidal currents from a supply of negligible harmonic content are examined. An analysis is developed which provides a simple method for the prediction of the harmoniccurrent magnitudes and frequencies. A comparison of predicted and measured current harmonics is presented to substantiate the theory.
Determination of synchronousmachine parameters allowing for unequal mutual inductances
 Author(s): Y. Takeda and B. Adkins
 Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1501 –1504
 DOI: 10.1049/piee.1974.0313
 Type: Article
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The conventional theory of the synchronous machine is based on the assumption that the mutual inductances between the three directaxis windings are all equal. The method is satisfactory for a calculation of the armature current, but the value of field current is considerably in error. Better results are obtained if another reactance is included in the equations to allow for additional coupling between the field and damper windings. The paper shows how the value of the additional reactance can be deduced from the shortcircuit oscillograms.
Invertorfed synchronous motors with induced excitation
 Author(s): B.J. Chalmers ; A.L. Mohamadein ; A.C. Williamson
 Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1505 –1512
 DOI: 10.1049/piee.1974.0314
 Type: Article
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Invertorfed brushless synchronous motors are described, in which the harmonic content of typical invertorsupply waveforms is utilised to produce rotor excitation in wound rotors with shaftmounted diodes. Particular attention is paid to a 3phase starconnected rotor, connected to two diodes, and a salientpole rotor with a single diode. Approximate analyses of synchronous performance are presented which provide a clear understanding of the special modes of operation of these systems, and results of full digital simulations are shown to be in excellent agreement with measured performance characteristics. Practical developments are reported which demonstrate the influence of design features, including saturation and skew, and which typify the high levels of performance attained with these motors.
Simulation of a synchronous generator connected via a delta—star transformer
 Author(s): M.D. Barber and M. Giannini
 Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1513 –1521
 DOI: 10.1049/piee.1974.0315
 Type: Article
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A mathematical model of a 3phase synchronous machine, connected to the infinite bus through a delta—star transformer and a transmission line, is given. Symmetric and asymmetric faults on the lowvoltage side and on the highvoltage side of the transformer are analysed by using 3phase variables. Since the simulation is in terms of the directphase quantities, the digitalprogram solution can very easily simulate simultaneous fault conditions as well as sequential faults on either side of the power transformer. By applying proper constraint conditions, the model can be readily used to include symmetric and asymmetric faults for an unloaded alternator, and powerfrequency transients following the closure of the generator circuit breaker. The validity of the analysis developed is examined by comparing the digital results with the theoretical results for 3phase faults on a generator on open circuit, and with a number of experimental results. Versatility is demonstrated by the range of experimental results considered and by further studies.
Dynamic performance of fieldregulated synchronous machines
 Author(s): E. Fishwick ; B.W. Hogg ; D.P. Sen Gupta
 Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1522 –1528
 DOI: 10.1049/piee.1974.0316
 Type: Article
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The paper analyses the influence of various types of field regulators on the dynamic performance of synchronous generators. Both conventional and dualexcitation generators are considered, with basic controls provided by voltage and angle regulators, which may have proportionate and derivative feedback. In the case of dualexcitation machines, both busrotorangle and terminalrotorangle signals are employed in the quadratureaxis regulator.Stability is initially defined by computed regulation curves, and additional information is then obtained by calculating the variations of the synchronising and dampingtorque coefficients (T_{s} and T_{D}) with regulator gain. These graphs are superimposed on the regulation curves, to show how T_{s} and T_{D} determine the dynamic stability of the machine, and to illustrate the underlying reasons for stability.
Brushless cascade alternator
 Author(s): A.R.W. Broadway ; B.J. Cook ; P.W. Neal
 Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1529 –1535
 DOI: 10.1049/piee.1974.0317
 Type: Article
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A brushless a.c. generator is described which has a mode of operation similar to two woundrotor induction machines connected in cascade. This cascade machine, which has previously been considered for application as a motor, has single stator and rotor windings in a conventional inductionmachine frame. The machine is one of inherently high pole number. As an alternator, therefore, it is suitable for the generation of medium to highfrequency supplies. The direct excitation current and the alternating output current flow in its one stator winding. Its cylindrical rotor iswound with an extremely simple shortcircuited polyphase winding. Since no brushes, slip rings or rotating diodes are needed, the machine may be driven reliably at high speeds.A theoretical treatment is developed which takes account of magnetic saturation both in the steady state and in the transient state. Design and performance details of a prototype 400 Hz, 3000 rev/min., 3phase machine are also included.
Examination of the axial flux in stator cores with particular reference to turbogenerators
 Author(s): D. Howe and P. Hammond
 Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1536 –1542
 DOI: 10.1049/piee.1974.0318
 Type: Article
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The distribution of axial flux in stator cores has been examined by numerical and experimental techniques. It has been found possible to consider separately the tooth region and the core back. In the tooth region, the axial flux is caused by the airgap fringing flux. In the core back, it is caused by the main core flux and the magnetomotive force of the winding overhang. The effect of slits in the teeth has been studied and also the effect of radial cooling ducts. The effect of butted joints between the core segments has also been considered. It has been found that axial flux is a very local phenomenon which cannot be eliminated, but which can be reduced by careful design of those regions where it is likely to be troublesome.
Phasevariable primarysystem modelling and solution methods in dynamicresponse assessments of highspeed protection
 Author(s): W.D. Humpage ; K.P. Wong ; L.Y.S. Au ; H.E. Zollezi
 Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1543 –1550
 DOI: 10.1049/piee.1974.0319
 Type: Article
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Dynamicresponse evaluations of highspeed primaryprotection systems are assuming an increasing importance as protection measuring times are progressively reduced, and these require very considerable detail of representation, not only for protection systems, but for the primary transducers from which they operate, and for the section of the primary system protected. Within this composite simulation, it is the latter area, that of the primary system for which the protection system under investigation provides coverage, to which the paper is devoted. In particular, the paper develops a phasevariable analysis scheme for synchronous generation in a form that allows it to be used directly in conjunction with electromagnetic transient analysis for the network system interconnecting generation. This provides a rational and unified scheme of analysis which combines fastsolution properties with considerable flexibility in application.
Probabilistic analysis of power flows
 Author(s): R.N. Allan ; B. Borkowska ; C.H. Grigg
 Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1551 –1556
 DOI: 10.1049/piee.1974.0320
 Type: Article
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The paper describes and examines a technique which permits the powerflow problem in a power system to be analysed probabilistically instead of using normal deterministic methods. All the nodal loads and generation are defined as random variables and the power flow in each line is computed in terms of a probability density function. The expected values and standard deviation of each power flow are also calculated, and, in addition, the overall balance of power in the system is determined in terms of a density function. The purpose of this analysis is to account for the errors and statistical variations known to exist in the operation and planning of systems within one solution. This enables the powerflow problem to be treated objectively and allows quantitative assessment of reliability and security. The paper compares the results obtained probabilistically with those that would be obtained deterministically, and shows the much wider range of information gained in this type of analysis.
Distance relay performance as affected by capacitor voltage transformers
 Author(s): M.A. Hughes
 Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1557 –1566
 DOI: 10.1049/piee.1974.0321
 Type: Article
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A 3phase capacitorvoltagetransformer simulation is described which, when used in conjunction with a conventional artificial transmission line, allows complete relaying schemes to be tested. The accuracy of the simulation is confirmed by comparison of its response with that of a fullscale capacitor voltage transformer. Conjunctive distancerelay/capacitorvoltagetransformer tests are reported showing that transient errors degrade relay performance in speed and stability. Various methods for providing a more faithful voltage signal to supply the relay circuits are discussed.
Direct digital closedloop control of h.v. d.c. convertors
 Author(s): J. Arrillaga and D.G. Baldwin
 Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1567 –1571
 DOI: 10.1049/piee.1974.0322
 Type: Article
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As an alternative to present analoguebased control schemes, the basic design characteristics and dynamic performance of a newly proposed direct digital control are described. Tests are carried out in a specially designed scaleddown model provided with the necessary monitoring facilities for direct digital control. Special emphasis is given to the performance of relatively weak a.c. systems, and therefore the model includes suitable representation of the system parameters and of the filters normally used. It is shown that the implementation of equidistantfiring control by means of digital feedback loops provides fast recoveries from convertor and line disturbances.
Numerical technique for computing surges in multiphase power systems with nonlinear lumped elements
 Author(s): S.C. Tripathy and M. Yusuf Khan
 Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1572 –1574
 DOI: 10.1049/piee.1974.0323
 Type: Article
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A numerical technique for computing switching transients in multiphase nonlinear systems is presented. The nonlinear terminal characteristics of the lumped parameters have been considered in totality without approximating them as piecewise linear characteristics It has been shown that a fast, stable and accurate algorithm results from using Bergeron's method of characteristics for distributed parameter lines and a semiimplicit Runge—Kutta method for solution of the differential equations which describe the dynamics of linear/nonlinear lumped parameters.
Costs of electricitysupply interruptions to industrial consumers
 Author(s): A.F. Jackson and B. Salvage
 Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1575 –1576
 DOI: 10.1049/piee.1974.0324
 Type: Article
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The results of a survey into the effects and costs of electricitysupply interruptìons to 23 large industrial consumers are described. Detailed costs have been obtained for 12 companies and it is shown that they can be expressed in terms of a fixed cost, varying with the frequency of interruption, and a variable cost, varying with the duration of interruption.
Digital simulation of distancerelay comparators and their response to primarysystem d.c. transients
 Author(s): D.A. Bradley ; C.B. Gray ; D. O'Kelly
 Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1577 –1578
 DOI: 10.1049/piee.1974.0325
 Type: Article
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Digital computer models of a selection of 2input phaseand amplitudecomparator distance relays, generating mho and offsetmho characteristics in the steady state, are described and evaluated under transient conditions, necessitating interpretation of the criteria of operation in instantaneous terms. The primary system is simply represented by sinusoidalvoltage source and lumped impedances, comparator representation includes consideration of finite sensitivity and the provision of self polarisation. Dynamic performance is presented in the form of contoured distancetofault/systemimpedanceratio curves.
Analysis of circuits containing components with cores of ferromagnetic material
 Author(s): A. Wright and S. Carneiro
 Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1579 –1581
 DOI: 10.1049/piee.1974.0326
 Type: Article
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Examinations of ferromagnetic behaviour under conditions likely on power systems show that eddy currents may be allowed for by including an appropriate linear resistor in mathematical models. They also show that hysteresis paths depend on the previous history of a core but are hardly affected by the time derivative of the flux. Currenttransformer studies are described to illustrate a computational method in which discrete points on a number of hysteresis paths are specified. An extrapolation technique is used, and consideration is given to points at which flux reversals occur. It is shown that highlyaccurate representation may be achieved.
Variablecharacteristic generalised techniques for distance protection: Doublecircuitapplication studies
 Author(s): A.T. Johns and A.A. ElAlaily
 Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1582 –1584
 DOI: 10.1049/piee.1974.0327
 Type: Article
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A previous paper outlined the principles of a new method for dynamically varying the shape of polarised quadrilateral relay characteristics for the protection of e.h.v. transmission lines. The present paper extends these methods to the protection of doublecircuit lines. Consideration is given to the compensation of earthfault relays, and it is shown that compensation schemes which ignore the effect of mutual coupling between circuits are desirable. Digitalcomputer application studies of a typical doublecircuit 400kV transmission line of earthed construction indicate that, from the point of view of accuracy and fault coverage, there is little advantage in the use of variable devices in zone 1. However, they enable a greater proportion of the protected feeder to be covered with minimum faultdetection time. Emphasis is placed on the response of relays connected to healthy conductors, and the possibility of avoiding unwanted tripping emerges. A high degree of immunity to maloperation during heavycircuit loading and power swings is achieved.
Application of fuzzy algorithms for control of simple dynamic plant
 Author(s): E.H. Mamdani
 Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1585 –1588
 DOI: 10.1049/piee.1974.0328
 Type: Article
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The paper describes a scheme in which a fuzzy algorithm is used to control plant, in this case, a laboratorybuilt steam engine. The algorithm is implemented as an interpreter of a set of rules expressed as fuzzy conditional statements. This implementation on a digital computer is used online, to control the plant. The merit of such a controller is discussed in the light of the results obtained.
Gapped solenoid as a means of producing a highly uniform magnetic field over an extended volume
 Author(s): W. Gosling and M.J. Cunningham
 Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1589 –1593
 DOI: 10.1049/piee.1974.0329
 Type: Article
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Part of the winding near its middle is often omitted when the volume about the centre of a solenoid over which the magnetic field is relatively uniform is to be extended. Field distributions are considered, and optimum gap lengths computed. The volume of specified field uniformity is compared with hat of uniform solenoids. The use of solenoids with a gap makes certain precautions essential.
Model of emitting sites and erosion on nonrefractory arc cathodes with relatively thick oxide films
 Author(s): A.E. Guile
 Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1594 –1598
 DOI: 10.1049/piee.1974.0330
 Type: Article
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A model is proposed for the mechanisms by which multiple emitting sites are formed and material is lost from a nonrefractory arc cathode with an oxide layer more than about 10^{−8} m thick, when an arc is rotated magnetically over its surface for long times. Using measured copper cathode erosion rates and scanningelectronmicroscope photographs of the size and number of craters on cathode arcing surfaces, results have been obtained which seem to support the model. Average lifetimes of emitting sites have been estimated to be considerably greater than those on cathodes with very thin oxide films. The model suggests that it is important to keep the oxide layer from becoming too thick, to obtain low cathod erosion rates.
Time dependence of loss tangent in impregnated polypropylene capacitors
 Author(s): K.W. Plessner ; R. McNicholl ; T.E. Shen
 Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1599 –1602
 DOI: 10.1049/piee.1974.0331
 Type: Article
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Measurements are presented of the decrease of loss tangent with time of application of a high alternating stress and its return on removal of the stress. Measurements were made at an elevated temperature, as well as at ambient conditions. An explanation of the phenomena in terms of the movement of charge carriers into the polymer and their recombination within the polymer is attempted.
Phonopore and phonoplex F.D.M.telegraph systems used on railways in the late 19th century
 Author(s): D.G. Tucker
 Source: Proceedings of the Institution of Electrical Engineers, Volume 121, Issue 12, p. 1603 –1608
 DOI: 10.1049/piee.1974.0332
 Type: Article
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The phonopore and the phonoplex were both systems introduced in 1885 for providing additional telegraph channels (or, alternatively, in the phonopore system, a telephone channel) in the frequency range above that of the ordinary d.c. or Morse channels. The phonopore, developed by Charles LangdonDavies in England, used a special kind of coupling transformer/condenser, which is here analysed but shown to have had few useful special properties, and used a ‘harmonic’ telegraph channel, i.e. a keyed oscillatory signal. Edison's phonoplex used, for the highpass channel, signals derived from the transients produced by an induction coil. Both systems were made commercially, and had a certain success on railways. The Phonopore Syndicate (later Company) had an interesting but not successful history, here partially unravelled; from 1893, its managing director was C.E. Spagnoletti, F.R.S., PastPresident of the Society of Telegraph Engineers, and newlyretired telegraph superintendent of the Great Western Railway. Although the company had, by 1895, raised around £100 000 of capital, it was in that year effectively purchased by the New Phonopore Telephone Co. for £2000. The new company continued in existence, with an issued capital reaching no more than about £8000, until it was purchased for £175 in 1916 by the Phonopore Construction Co., which finally ceased operations soon after 1920.
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