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Volume 126
Issue 12
Proceedings of the Institution of Electrical Engineers
Volume 126, Issue 12, December 1979
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Volume 126 (1979)
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Volume 123 (1976)
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Volume 122 (1975)
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Volume 126, Issue 12
December 1979
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- Author(s): R. Neri and T.S.M. MacLean
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1209 –1219
- DOI: 10.1049/piee.1979.0209
- Type: Article
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The receiving and transmitting properties of a grid paraboloidal reflector of aperture diameter 2.73λ and f/D ratio 0.395, operating at 410 MHz, are analysed using the moment method. For the receiving situation, with a normally-incident plane wave illuminating the reflector, the distributions of current, obtained in the inner grids only, show a close resemblance to those predicted by the physical optics approximation. It is shown that neither maximum scattered nor maximum total electric field on axis is received at the geometrical focus, but at a point between this focus and the vertex. This result is in agreement with that calculated by the physical optics method for small solid paraboloids of the same f/D ratio. Contours of scattered off-axis fields are also presented in the geometric and true focal planes of the paraboloid as well as in longitudinal planes of such a reflector. In the transmitting situation, the grid paraboloid is excited by a centrally driven couplet feed, positioned at different points along the axis. It is shown that the feed position affects considerably the distributions of current in the feed elements but not in the reflector grids, and confirms that defocusing the couplet feed results in an increased forward power gain. - Author(s): Liang C. Shen
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1220 –1222
- DOI: 10.1049/piee.1979.0210
- Type: Article
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The input impedance and the electromagnetic fields of a circular-disc printed-circuit antenna are found. The antenna is driven at an arbritrary point. The present analysis takes into account the radiation through the side wall and the fringe field at the edge of the printed-circuit antenna. - Author(s): M.S. Narasimhan and K. Sudhakar Rao
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1223 –1226
- DOI: 10.1049/piee.1979.0211
- Type: Article
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A technique of analysing the principal-plane near-field patterns of pyramidal horns excited in the dominant mode based on the uniform geometrical theory of diffraction (u.g.t.d.)1, 2 is presented in this paper. The geometrical-optics field is derived by approximating the horn as a quasipyramidal horn waveguide.9 Numerical computations of the near-field amplitude patterns of a typical pyramidal horn based on the g.t.d. technique detailed here well correlate with the measured patterns, justifying the validity of the analysis presented. Further, the analysis presented is valid for any arbitrary field point (located in the principal planes) so that pattern computation is possible in the near field or in the Fresnel zone or in the far field. - Author(s): T.C.K. Rao and M. Hamid
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1227 –1232
- DOI: 10.1049/piee.1979.0212
- Type: Article
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The problem of surface-wave propagation over the modified Goubau line, which consists of a Goubau line with an airgap between the conductor and dielectric, is formulated by the boundary-value method. The various modes which exist on the line as well as their cutoff conditions and the specific effects of the airgap are obtained from a solution of the characteristic equation. The mode spectrum for the symmetric and hybrid modes as well as the transverse field distributions for the E00 and H01 modes are also presented. The axial power flow and the attenuation constant are calculated for the dominant mode and the salient low-loss feature may be explained perhaps in terms of total internal reflection or duct propagation phenomena. - Author(s): K. Arora ; S. Prasad ; P.V. Indiresan
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1233 –1236
- DOI: 10.1049/piee.1979.0213
- Type: Article
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The problem of optimum design of an m.t.i. system for clutter rejection is considered in this paper. The procedure involves minimisation of the output clutter power subject to the constraint that the average output-signal power over the expected target Doppler range is to be kept constant. Another constraint in the minimisation problem is incorporated, according to which the transfer function of the system has a null at the dominant clutter Doppler frequency fm, which may often be zero. In this way, the distributed component of clutter is minimised at the filter output while the clutter component at a fixed mean relative velocity is completedly suppressed. With the two constraints specified above, the problem is mathematically formulated as a modified eigenvalue problem. Comprehensive results for the performance of the resulting filters are presented. - Author(s): Lennart Hansson
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1237 –1240
- DOI: 10.1049/piee.1979.0214
- Type: Article
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Five years of slant-path-attenuation and point-rain-rate measurements in Sweden have been used to estimate the prediction accuracy of a simple equivalent-distance model. Radiometer attenuation data at 11.4 and 14.0 GHz, obtained at 21° elevation and rain-rate data from a tipping-bucket-type rain gauge have been used. The long-term predication error is estimated to be within a few tenths of a dB, giving strong support to the usefulness of the method. The equivalent distance is found to be frequency independent over the range 11–14 GHz at least, and consequently frequency scaling of attenuation data, using the theoretical specific attenuation, is proposed. - Author(s): P.C.K. Kwok and P.S. Brandon
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1241 –1244
- DOI: 10.1049/piee.1979.0215
- Type: Article
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The problem of applying a set of constraints to antenna arrays is discussed. It is shown that when the noise between different elements is uncorrelated, the optimum radiation pattern can be expressed as a sum of the quiescent beam and the constraint-vector beams. To determine the excitations of the array, only the weighting coefficients of the constraint-vector beams need to be calculated. The method can be used to set pattern nulls as well as sidelobes at some specified positions.
Receiving and transmitting properties of small grid paraboloid by moment method
Analysis of a circular-disc printed-circuit antenna
G.T.D. analysis of the near-field patterns of pyramidal horns
Mode spectrum of the modified Goubau line
Class of optimum m.t.i. filters for clutter rejection
Rain attenuation measurements using the equivalent-distance model
Maximisation of signal/noise ratio in antenna arrays subject to constraints
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- Author(s): D.B. Watson ; J. Arrillaga ; T. Densem
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1245 –1248
- DOI: 10.1049/piee.1979.0216
- Type: Article
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A variable-speed generating system is described which uses a 3-phase squirrel-cage induction machine with self-excitation capacitors. The variable-frequency/variable-voltage generated is then fed through a 3-phase controlled rectifier to provide a d.c. supply at constant voltage. The proposed scheme is suitable for wind power sources as it allows wide changes in wind turbine speed and, at all speeds, optimum generating power can be set up by rectifier delay angle control. - Author(s): J.W. Finch and P.J. Lawrenson
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1249 –1254
- DOI: 10.1049/piee.1979.0217
- Type: Article
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The starting and pull-in behaviour of typical, single-phase reluctance machines, with and without capacitive excitation, is explored experimentally and by computation. A comprehensive study of the effects of impedance variations on the pull-in performace is presented. This study enables new designs to be produced which are shown to exhibit greatly improved pull-in behaviour. The experimental machines are of segmented type but the general results are applicable regardless of construction. - Author(s): W.F.J. Kersten
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1255 –1262
- DOI: 10.1049/piee.1979.0218
- Type: Article
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The paper presents results of digital computer calculations of the sheath overvoltages and the energies absorbed by sheath-protecting surge arresters in a crossbonded cable system. Especially, the energy loading of the arresters during energisation and discharge of an underground cable-overhead line configuration is considered. An analysis of the natural wave propagation characteristics of the cable system is given. Based upon this analysis a frequency-independent wave propagation of all modes has been adopted as a basis of the calculation method. The requirements concerning the choice of the arrester are discussed. - Author(s): K.J. Cornick and J.R. Lucas
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1263 –1268
- DOI: 10.1049/piee.1979.0219
- Type: Article
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In transmission systems operating at the higher voltage levels, increasing use is being made of surge diverters as the first line of defence against overvoltages. The determination of the interaction between the surge diverters and the system is therefore becoming of prime importance. When studies of this interaction are to be performed numerically, means have to be developed for representing the surge diverter in the system-network equations. The present paper will describe a technique whereby the surge diverter can be included in transient overvoltage calculations based upon the modified Fourier-transform method. In this technique it will be demonstrated how system elements with voltage-dependent characteristics can be considered together with system elements with frequency-dependent characteristics. The use of the technique derived will be illustrated by studies on a simple transmission system in which surge diverters operate under switching-surge conditions. - Author(s): L.M. Wedepohl and D.J. Wilcox
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1269 –1274
- DOI: 10.1049/piee.1979.0220
- Type: Article
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The paper considers transient induction from an undergound power circuit into an adjacent pilot cable. Results, in the form of transient waveshapes, are given for a number of representative cases in response to step-type energisation of one of the power cables. The results show that dangerous transient overvoltages may arise in the case of relatively long systems. The paper then compares various design measures aimed at reducing prospective overvoltages. The given analytical results were obtained by applying numerical Laplace transform methods, and multiconductor transmission line theory, to a mathematical model which takes realistic account of such factors as skin effect in the conductors and of mutual coupling between cables due to current penetration into the soil. - Author(s): B.J. Harker and J. Arrillaga
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1275 –1281
- DOI: 10.1049/piee.1979.0221
- Type: Article
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A phase-co-ordinate model of h.v. d.c. transmission systems suitable for integration into 3-phase load-flow analysis is developed in the paper. The model is sufficiently general to allow representation of alternative control strategies, such as the predictive and symmetrical firing control. The integration of the model into the load-flow analysis described with particular reference to the 3-phase fast-decoupled algorithm. The results indicate the flexibility and powerful convergence of the proposed algorithm. - Author(s): E.de S. Saraiva and L.L. Freris
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1282 –1286
- DOI: 10.1049/piee.1979.0222
- Type: Article
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The characteristics of electromechanical filters for the suppression of harmonics and the supply of reactive power on the a.c. side of d.c.-link convertors are described. The problem in the design and construction of small-scale units are highlighted. Tests with the prototype filters on a model d.c. link show that stability margins are considerably improved when compared to operation with conventional static filters. - Author(s): L. Blahous
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1287 –1290
- DOI: 10.1049/piee.1979.0223
- Type: Article
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When testing high voltage circuit breakers synthetically the question arises as to how the test results can be compared with test results in direct tests. In the paper the thermal equivalence between direct testing and the method of voltage injection is investigated. The circuit breaker is modelled by the Urbanek equation. It is shown that the prospective voltage alone cannot define the test circuit to ascertain thermal equivalence. To lay out the synthetic test circuit to obtain results equivalent to direct testing requires the exact knowledge of all circuit elements including the auxiliary breaker and the test breaker. There is no problem, however, if this method is applied for tests in which the breaker is dielectrically stressed. - Author(s): L. Blahous
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1291 –1294
- DOI: 10.1049/piee.1979.0224
- Type: Article
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The present IEC requirements for testing high-voltage circuit breakers impose certain conditions on the prospective voltage of the test circuit. This approach seems justified by the fact that the prospective voltage in theory describes exactly the test circuit in its elements and its topology. As in practice the prospective voltage is known only with certain tolerances, this method needs to assume that slight variations in the test circuit mean only slight variations in the circuit-breaker behaviour. By using the Urbanek equation to describe the circuit breaker, it is shown that, in direct test circuits which yield undistinguishable prospective voltages, differences of 9.7% in the breaking capacity of an otherwise identical breaker are possible. An explanation of this phenomenon is given and the limits are shown. In more realistic circuits, the result is verified in its trend. - Author(s): E.E. Baràkat and D.E. Hirst
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1295 –1300
- DOI: 10.1049/piee.1979.0225
- Type: Article
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A numerical method is described for predicting the possibility of jump resonance or subharmonic oscillations being sustained by a given 3-phase circuit, based on the describing function and dual-input describing function concepts of control theory. The method can be applied to predict asymmetrical jump modes which have no equivalent in single-phase circuits. Results predicted by this method are compared with results obtained from laboratory experiments. - Author(s): M.M. El-Marsafawy ; R.W. Menzies ; R.M. Mathur
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1301 –1302
- DOI: 10.1049/piee.1979.0226
- Type: Article
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A new exact diakoptical technique for load-flow solution of very large power systems, using the bus admittance matrix, is developed. This method employs bifactorisation and other sparsity techniques. It produces the same final result, retains the convergence property of the original untorn system, and can be applied to systems of any voltage level. - Author(s): A.P. Russell and I.E.D. Pickup
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1303 –1304
- DOI: 10.1049/piee.1979.0227
- Type: Article
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- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, page: 1304 –1304
- DOI: 10.1049/piee.1979.0228
- Type: Article
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Controllable d.c. power supply from wind-driven self-excited induction machines
Asynchronous performance of single-phase reluctance motors
Surge arresters for sheath protection in crossbonded cable system
Inclusion of surge diverters in system overvoltage calculations
Transient pilot-cable induction from underground power-transmission systems
3-phase a.c./d.c. load flow
Development of electromechanical filter and performance evaluation in d.c. link
Problem of synthetic circuit-breaker testing with voltage injection
The problem of defining a test circuit for circuit breakers in terms of the prospective voltage
Susceptibility of 3-phase power systems to ferro-nonlinear oscillations
New diakoptic technique for load-flow solution of very large power systems using the bus admittance matrix
Parametric oscillatory motion in electromechanical device
Erratum: Synthetic testing: the present state
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- Author(s): D.P. Atherton and S. Shankar
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1305 –1306
- DOI: 10.1049/piee.1979.0229
- Type: Article
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This paper shows that a pole transformation on a nonlinear autonomous feedback system can alter the frequency response of the linear element and eliminate those characteristics which have previously been suggested as indicators of counterexamples to the Aizerman conjecture. The root locus, however, is invariant under this transformation and examination of counterexamples has revealed common properties in their root loci. - Author(s): J. Fenton ; D.N.L. Horton ; K.F. Gill
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1307 –1310
- DOI: 10.1049/piee.1979.0230
- Type: Article
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A method is presented for the design of a discrete, state-vector feedback controller operating on an open-loop unstable process. Kalman filtering is used for state estimation and the effectiveness of this technique is evaluated for high levels of noise. - Author(s): C.S. Berger
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1311 –1315
- DOI: 10.1049/piee.1979.0231
- Type: Article
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A moving-average filter is used to generate input signals for system identification. This has enabled the development of an efficient numeric algorithm and also some sufficiency results for a stationary point of the filter parameters. These sufficiency results give simple design equations for the design of identification experiments with an output-power constraint. A theoretical result for autoregressive systems is also given and used to interpret the numeric examples. - Author(s): M.P. Ford and K.C. Daly
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1316 –1320
- DOI: 10.1049/piee.1979.0232
- Type: Article
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Pseudodecoupling enables the design of frequency-dependent precompensators (postcompensators) to improve the column (row) dominance of the compensated plant over an extended range of frequencies. This allows diagonal dominance to be achieved for a wider range of plants than was previously possible. The procedure arises from generalising Hawkins's pseudodiagonalisation procedure in a number of directions; in particular, stability of the compensator is guaranteed. Log σ plots are introduced as a means of determining the degree of dominance over a wide frequency range. - Author(s): H. El-Sherief and N.K. Sinha
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1321 –1325
- DOI: 10.1049/piee.1979.0233
- Type: Article
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A unified recursive algorithm is presented for identifying linear discrete-time multivariable systems from the input/output data which may be contaminated with noise. The system is represented in the form of a transfer-function matrix, and decomposed into subsystems corresponding to each row. The proposed algorithm is based on determining the order of each subsystem utilising the residual-error technique. This is followed by estimation of parameters using a recursive adaptive least-squares algorithm. Results of simulation are included. - Author(s): H. El-Sherief and N.K. Sinha
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1326 –1330
- DOI: 10.1049/piee.1979.0234
- Type: Article
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A critical study is presented of the relative effectiveness of four types of models which have been used in the area of linear multivariable discrete-time systems identification. Each model's features and their effect on the complexity of the identification algorithm are studied. The structural parameters required to characterise each model and the number of parameters to be estimated are examined and compared. The characteristics of the parameter estimates of each model when using the least-squares method are also investigated. Results of a simulated example are given which show the advantages and disadvantages of each model when used for identification. - Author(s): B. Rammohan Rao and S. Ganapathy
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1331 –1335
- DOI: 10.1049/piee.1979.0235
- Type: Article
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The state transition matrix of a linear time-varying system cannot, in general, be expressed in a closed form and has, therefore, to be evaluated numerically. For the commutative class of linear time-varying systems, the state-transition matrix is the exponential matrix. A numerical procedure is developed for the evaluation of this matrix to any desired degree of accuracy by the method of series expansion. For linear time-varying systems, which are not restricted to belonging to the commutative class, an efficient computational algorithm is developed for the evaluation of the state-transition matrix. This is based on the minimum m.s.e. approximation of a time function in terms of a set of block-pulse functions, which are orthogonal in the speficied interval. The algorithms developed in the paper are illustrated by appropriate examples. - Author(s): D.H. Owens
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1335 –1337
- DOI: 10.1049/piee.1979.0236
- Type: Article
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Some observations on the Aizerman conjecture
Attitude control of a flexible satellite in noisy environment
Synthesis of input signals for parameter identification using moving-average filter
Dominance improvement by pseudodecoupling
Online identification of linear discrete-time multivariable systems
Choice of models for the identification of linear multivariable discrete-time systems
Linear time-varying systems—state transition matrix
Computation and characterisation of the zeros of linear multivariable systems
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- Author(s): M.H.S. El-Markabi and E.M. Freeman
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1338 –1343
- DOI: 10.1049/piee.1979.0237
- Type: Article
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A nonuniform-transmission-line analogy is employed to simplify the calculation of the axisymmetric electromagnetic field in, and hence the screening effect of, a set of concentric spherical shells excited by a coil carrying current in a circumferential direction only. The use of spherical Bessel functions is shown to be unnecessary. Various special cases are described together with experimental results to support the theory. - Author(s): A. Tslaf
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1344 –1348
- DOI: 10.1049/piee.1979.0238
- Type: Article
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The depth of penetration of phase transition (i.e. solid-liquid) is analysed and taken as a measure of the destruction of insulation due to a high-current arc discharge. Analytical equations are obtained by replacing the actual physical situation with an equivalent analytical model. This is done at each of the two main steps in the thermal response of insulation: (a) the temperature rise, and (b) the equalisation of temperature in an adjacent surface layer. Both steps are related by the equation of energy balance and by the temperature conditions at the boundary. Satisfactory agreement has been obtained between analytical results and existing experimental data. It is concluded that the energy density of the discharge (in J/m2) has a decisive effect upon the degree of destruction of insulation. The specific heat capacity and the specific energy associated with phase transition are also shown to be of significance in the process under study. - Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, page: 1348 –1348
- DOI: 10.1049/piee.1979.0239
- Type: Article
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Electromagnetic shielding effect of a set of concentric spheres in an alternating magnetic field
Electric insulation at phase transition caused by arc discharge
Erratum: Dielectric breakdown of supercritical helium
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- Author(s): P.L. Mothersole
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, page: 1349 –1349
- DOI: 10.1049/piee.1979.0240
- Type: Article
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- Author(s): Peter L. Mothersole
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1350 –1354
- DOI: 10.1049/piee.1979.0241
- Type: Article
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Viable teletext and viewdata systems have been evolved in the UK over the last few years and public services established. The major system parameters are discussed together with descriptions of typical signal originating equipment. - Author(s): K.E. Clarke
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1355 –1361
- DOI: 10.1049/piee.1979.0242
- Type: Article
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This paper explains, in terms readily understandable by general communication engineers, the principles and techniques of the various coding systems being proposed for videotex, and summarises the arguments for and against each proposal. - Author(s): W.R. Betts
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1362 –1366
- DOI: 10.1049/piee.1979.0243
- Type: Article
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The paper briefly considers the background to viewdata development during the 1970s. It goes on to discuss a number of aspects of a full terminal which affect, or are affected by, the viewdata system: the display, display control, data controller, user interface, terminating unit, autodialler and auto-identifier, keypage, home terminals and business terminals. The paper continues with possible developments to the basic system such as editing station, foreign languages, security, and high-resolution graphics. Finally, the paper looks to the future and how the viewdata concept can be extended, not only in the home and in the office but in many other fields. - Author(s): K. Pandey
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1367 –1373
- DOI: 10.1049/piee.1979.0244
- Type: Article
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The architecture of second generation hardware for teletext and viewdata decoding, System 12, is shown as an evolutionary progression of industry's experience and needs. The new architecture is described with emphasis on its application to data sources other than teletext, e.g. viewdata and cassette text. The (AI2L) technology strength which allowed such a system is also described, together with some commercial and technical reasons for its choice. Speed-power products in the order of 0.5 pJ, and delays of about 15 ns for a 5-collector gate, are achieved in production at a circuit density, and process complexity comparable to the most up-to-date m.o.s. processes in industry without the complexity of iterative design. Two of the newer devices that greatly increase system capability are described in greater detail. The remote control interface chip, SN76926, integrates System 12 to Texas Instruments Ltd.'s Mistic family of t.v. peripherals, which includes a low cost, 64-channel remote control. The bus system used also allows communication with Texas Instruments microprocessors. The other circuit described in detail is the system controller, i.e. SN76924, which allows microprocessors handling data to delegate to it a large proportion of the total task of communicating with System 12. Two-way interchange of information with System 12 is so far eased as to allow very low cost, 4-bit microcomputers to cope with major data handling functions. The technical and commercial maturity of product reached by this system gives UK teletext and Prestel services a substantial leadership which should be difficult to ignore if other factors do not retard the speedy development of the market - Author(s): D.J. Beakhust and M.C. Gander
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1374 –1396
- DOI: 10.1049/piee.1979.0245
- Type: Article
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An efficient and low-cost teletext decoder based on l.s.i. i.c.s is essential for the success of broadcast teletext and viewdata. However, other vital peripheral areas, such as teletext remote control, interface with the video circuits, low-cost modem functions, surface acoustic wave (s.a.w.) i.f. filters and so on, are not ignored in a comprehensive component solution from Mullard. Remote control for teletext must have up to 32 commands available together with a very fast action to allow rapid keying of page numbers and must also control all the normal t.v. functions. A system employing infra-red serial data transmission, and which interfaces directly with the teletext decoder, is realised in two low-cost l.s.i. i.c.s. Four l.s.i. i.c.s together with appropriate page memory i.c.s comprise the teletext decoder; three, in m.o.s. technology, carry out the digital functions of data acquisition, display timing and character video generation; the other, a linear bipolar i.c., provides a very efficient data slicer and data clock system which is vital to good off-air teletext performance. The decoder is designed for easy extension for viewdata use. A viewdata extension system based upon the MP8048 microcomputer includes a data-recording facility, optional full-keyboard operation, automatic dialling of several alternative numbers and a comprehensive set of on-screen legends to aid the viewer. A modem unit, designed to meet the British Post Office performance and safety requirements for installation in a t.v. reciever or v.d.u. forms part of the system. The performance of the i.f. amplifier in a t.v. receiver is more critical for the reception of data than t.v. signals and the use of a s.a.w. i.f. filter with excellent amplitude and group-delay response is beneficial to teletext. Feeding decoded data video into the RGB channels of a receiver is greatly simplified by colour decoder i.c.s designed for data insertion, particularly if text inlay into the t.v. picture is required as an option. - Author(s): P.R. Hutt and G.A. McKenzie
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1397 –1403
- DOI: 10.1049/piee.1979.0246
- Type: Article
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The parameters defining the UK teletext transmission standard were set in 1974 after some two years of intensive theoretical and practical investigations. There were available a multitude of possible combinations of binary signalling schemes, screen formats, character coding and control-coding methods. Many possibilities were assessed before a final choice was made in favour of the 40character × 24row fixed-format synchronous transmission system of the UK teletext specification. The paper discusses the reasons behind the selection of the many parameters defining the UK teletext standard, and why in particular a free-format composite character coding scheme is rejected as quite unsuitable for a broadcast data service. Teletext has been available as a public service in the UK for several years. The soundness of the UK teletext standard is being affirmed by the increasing thousands of viewers who, with a teletext receiver bought at low additional teletext cost, are now enjoying a reliable, error-free, efficient and effective domestic information service. - Author(s): B.J. Rogers
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1404 –1407
- DOI: 10.1049/piee.1979.0247
- Type: Article
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p.
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The object of this standard is to standardise the conditions and methods of measurement to be used for the study of receivers and decoders for teletext broadcasting. Limiting values of the various quantities are specified but may need modification with increasing experience gained from equipment operating in the field. The standard constitutes a catalogue of selected measurements for assessing the essential properties of equipment of a given type. It is not limiting; if necessary additional measurements may be carried out. The recommended methods apply to a complete receivers or to decoding equipment. They also apply to that subunit of a complete receiver or decoder concerned with the acquisition and decoding of the data signal ignoring interface and power supply circuits. It should be realised that the measurements proposed and the limiting values quoted are subject to modification as mehods are refined and with the development of decoding techniques. - Author(s): N. Green
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1408 –1411
- DOI: 10.1049/piee.1979.0248
- Type: Article
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p.
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This paper describes both the technical implementation on the ITCA Oracle teletext system of a subtitling facility and also reviews the editorial constraints and research by various public and private bodies. - Author(s): J. Hedger and R. Eason
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1412 –1416
- DOI: 10.1049/piee.1979.0249
- Type: Article
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The authors seek to show how, by using a microprocessor, teletext may be extended to provide many new and useful facilities, while remaining compatible with existing teletext transmissions. The design and implementation of an experimental telesoftware terminal are described, and a summary of current thinking is given, indicating the probable future software and hardware constraints of the system and its potential applications. - Author(s): G.O. Crowther and D.S. Hobbs
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1417 –1424
- DOI: 10.1049/piee.1979.0250
- Type: Article
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p.
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The UK teletext and viewdata systems are analysed as a basis for discussion of their suitability for incorporating in the North American NTSC television system. Methods for adapting to the different band width and display format requirements are described which indicate the feasibility of immediate implementation in the USA. An interim teletext test transmission system to assist in the choice of a suitable data rate and general system parameters is outlined. The cost implications of adopting the basic UK systems, which are already well established, are reviewed in some depth. The flexibility of the present teletext system and its potential for future extensions is discussed and it is shown that initial decoder designs will not be made obsolescent when these are implemented. It is concluded that, with a suitable choice of data rate and page format, the UK teletext and viewdata systems form a sound basis for the establishment of these services on the NTSC system in USA. - Author(s): J.P. Chambers
- Source: Proceedings of the Institution of Electrical Engineers, Volume 126, Issue 12, p. 1425 –1428
- DOI: 10.1049/piee.1979.0251
- Type: Article
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p.
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The UK teletext system specification includes provision for future developments. This paper indicates how the addressing structure may be used to allow selection from a very large number of pages either individually or by classification. Up to 64 totally independent data channels can also be provided. Various techniques for extending the character repertoire are described, depending on whether the extra characters are predefined, postdefined or dynamically redefined. Methods of increasing the security against errors are presented. It is suggested that within the framework of the existing teletext standard it is possible to work towards a system capable of giving a short sequence of colour pictures, whose quality is limited only by the television display itself. Any other requirements for the broadcasting of information for display on the television screen can then be treated as suboptions of such a system.
Teletext and viewdata
Teletext and viewdata: new information systems using the domestic television receiver
International standards for videotex codes
Viewdata: the evolution of home and business terminals
Second generation teletext and viewdata decoders
Teletext and viewdata — a comprehensive component solution
Theoretical and practical ruggedness of UK teletext transmission
Methods of measurement on teletext receivers and decoders
Subtitling using teletext service — technical and editorial aspects
Telesoftware: adding intelligence to teletext
Teletext and viewdata systems and their possible extension to the USA
Teletext — enhancing the basic system
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