Electrical Engineers, Proceedings of the Institution of

A dynamical-coupling algorithm for the implementation of a random-walk process in the gain adjustment of an adaptive echo canceller is described. The idea of dynamically coupling adaptive subsystems in this manner was first proposed by Mark in conjunction with predictive coding. An essential component in the dynamical coupling technique is an adaptive quantiser first proposed by Jayant. Computer s... View full abstract»

Two simple branch synchronisation schemes for a class of single-generator binary convolutional codes are presented in this paper. The first scheme is based on the selection of the generator sequences from a set of codes defined to have self-synchronisation property. This scheme is very useful for low rate codes with long constraint length, and its complexity is independent of the encoder/decoder c... View full abstract»

The paper presents a detailed study of a common-control delay system with non-pre-emptive priority service. The system considered in the paper has a single server and r priority classes of customers, each with a distinct independent Poisson input, but all customers have the same exponential service time. The operating time of the common control is assumed to have an exponential distribution. The s... View full abstract»

Two circuit models developed recently for two operational-amplifier gyrators are modified to include the case of nonidentical amplifiers and unequal gyrator resistances. These are then used to derive formulas for the sensitivities and temperature coefficient of the simulated inductance, and also to minimise the variations due to the gain-bandwidth products of the amplifiers. In addition, a filter-... View full abstract»

In analysing sequential gate networks one must take into account the propagation delay of each gate. In conventional methods, state variables are associated with feedback loops, and a flow table based on these variables is constructed. This flow table may be incorrect if hazards are present, and an additional complex analysis is required to obtain the correct behaviour. In this paper, we describe ... View full abstract»

Vibrational mode structure, resonance-frequency constants and temperature coefficients of resonance frequency are calculated for lithium-niobate and lithium-tantalate thin-plate resonators as a general function of plate orientation. Using selected plate orientations resonators with desirable properties have been fabricated and assessed for applications in wideband crystal filters. View full abstract»

The paper suggests a method of investigating from a unitary point of view the operational characteristics of charge-transfer devices. The equations of the model, as well as the voltage-dependent elements of the equivalent circuits, are derived. Solutions for the transfer inefficiency, the distribution of charge in the discharging potential well and for the currents along the channel, obtained by a... View full abstract»

A new method for treating the interconnections of arbitrarily located straight thin wires irradiated by a linearlypolarised plane wave is presented. The resulting Pocklington's integral equation is solved by the Bubnov-Galerkin projective method. The current distribution along the wires is approximated by polynomials with complex coefficients. This formulation is valid for wires forming any angle,... View full abstract»

A systematic procedure to locate a faulty cell in a column (row) of the main array (rotated array) in cutpoint cellular arrays is presented. It is assumed that a cell failure may be due to stuck-at faults at the input/output leads of the cell or due to stuck-at faults within the cell. View full abstract»

A 2-element static balancer, which enables 3-phase induction motors to operate more satisfactorily from singlephase supplies, is described. It is demonstrated that balanced phase voltages and currents are possible, no matter what the machine speed or phase angle, and the economic and operational advantages are briefly discussed. View full abstract»

The paper covers the practical measurements made, by London Transport, on the levels of induced current in track circuits produced by conventional and thyristor-(chopper-) type traction equipment on their 4th-rail traction supply system. The method of measurement, the subsequent method of analysis and the implications of the results are described and discussed. View full abstract»

The paper extends the presently available techniques for evaluating the load flow problem probabilistically. It presents two possible formulations of the problem that permit the probability-density curves of the angles, voltages, injected reactive powers and active and reactive power flows to be computed. Owing to the complexity of the problem, the load-flow equations were linearised. The errors i... View full abstract»

In this paper, a mathematical analysis of a transient due to initiation of a single line-earth fault at any intermediate point on a double-circuit transmission line, using the modified Fourier-transform method, is presented. The double-circuit line has been modelled, taking into account the mutual coupling between the two circuits. A typical 400kV double-circuit line is considered and the fault tr... View full abstract»

Two synthetic-temperature tests for use both on induction and synchronous machines have recently been described. The tests can be performed on free-standing machines with only their losses supplied from external electrical sources. The original test is simple to perform, particularly for induction machines, but it can result in abnormal secondary losses when applied to machines which employ skin-e... View full abstract»

The application of recent techniques of identification and adaptive control to the speed control of a steam turbine is investigated. A minicomputer was used for data acquisition, off-line and online identification and adaptive control. The turbine was modelled under different loading conditions using a recursive linear least-squares method. Although such a system is complex, second-order models we... View full abstract»

The sources of a magnetic field can be regarded as either electric currents or magnetic poles. This makes it possible to describe the field energy as kinetic or potential and to write the field equations in terms of two alternative Lagrangian densities. These two Lagrangians have the property that they provide lower and upper bounds to the field energy. The existence of dual bounds enables accurat... View full abstract»

After the invention of the telephone in 1876, telephony developed rapidly, and a public telephone service grew up in most countries. Growth was much more rapid in the USA than elsewhere. Telephone exchanges were introduced from 1878, and interurban links came into use as the density of exchanges grew. Technical difficulties, commercial rivalries, and, outside the USA, governmental policies, held b... View full abstract»

The homogeneous chemical vapour-deposition technique, developed for the preparation of phosphosilicate glass fibres, is described. The properties of the binary phosphosilicate glass are outlined and details of preform fabrication and fibre drawing are given. Multimode graded-index fibres have been produced in lengths up to 4km, with numerical apertures up to 0.25, attenuations as low as 2 dB/km an... View full abstract»

A light-focusing fibre guide named Selfoc was developed in 1968 by the joint research work of the Nippon Sheet Glass Co. Ltd. and the Nippon Electric Co. Ltd. During the past seven years of research work, the losses of Selfoc fibres have been reduced to 6 dB/km at a wavelength of 830nm. The optimum glass composition for low-loss Selfoc fibres and the purification methods of raw materials for them ... View full abstract»

The manufacture and performance of high-silica fibres made by the doped-deposited-silica technique are briefly reviewed. A general picture of the present degree of development is attempted, including examples of exceptional and typical transmission and mechanical properties. View full abstract»

Properties of doubly-clad optical fibres with a low-index inner cladding (W-type fibres) as single-mode or multimode transmission lines are discussed both from theoretical and experimental viewpoints. Such fibres are characterised by the tight confinement of the modal power in the core. A small bending loss is one of its consequences. A single-mode W-type fibre can be used at a v-value significant... View full abstract»

Sodium borosilicate glasses have been prepared from high-purity materials, with absorption losses between 5 and 6 dB/km. Continuous production of fibre from these glasses using the double-crucible technique has given fibre with losses as low as 10.5 dB/km at 800 nm. The loss mechanisms in the fibre have been investigated and the reproducibility of the process studied. View full abstract»