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Radio and Electronic Engineer

Issue 2 • Date August 1967

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Displaying Results 1 - 7 of 7
  • Computers and the engineer

    Publication Year: 1967
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (130 KB)  

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  • Automatic recognition of low-quality printed characters using analogue techniques

    Publication Year: 1967 , Page(s): 67 - 80
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2510 KB)  

    After comment on the obvious disparity between the print quality accepted as normal for human reading and the much higher quality needed for machine reading, a system is proposed and results of a simulation study presented for reducing this gap. The system employs a modified form of auto-correlation to extract characteristic properties from which specimen unknown characters can be identified by a simple recognition logic. In order to avoid the problem of representing the continuous grey-tone density scale of low quality print as a two state (binary) variable, analogue techniques are proposed for use in the system. Using a computer simulation of the proposed system a limited number of printed samples of exaggerated quality distribution are used to explore the limits of performance of the system. Numerical results are given and factors effecting performance discussed. View full abstract»

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  • Letter to the Editor: A suggested prefix and symbol for the sub-multiple 10¿21

    Publication Year: 1967
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  • New thin-film resistive memory

    Publication Year: 1967 , Page(s): 81 - 89
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1313 KB)  

    A new thin-film metal-insulator-metal device is described. After the insulator has undergone a forming process, which consists of the electrolytic introduction of gold ions from one of the electrodes, its conductivity is observed to have increased quite markedly. In addition the sample displays negative-resistance and memory phenomena. It is shown that under the appropriate switching conditions the device can be used as a non-volatile analogue memory with non-destructive read-out. The theory of operation of the device is also presented. View full abstract»

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  • Low-pass active filters

    Publication Year: 1967 , Page(s): 90 - 96
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (969 KB)  

    Microminiature active filters have been constructed using a combination of thin film and integrated circuits. The advantages of such an approach are discussed. The filter required could be met by a fifth-order Chebyshev function and the method of realization was to split the transfer function into quadratic and linear factors with each factor then realized separately. The tolerances required have been examined using a Monte Carlo computer program and the results are discussed. A filter constructed for use in p.c.m. systems is described. View full abstract»

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  • Galvanomagnetic thin film devices

    Publication Year: 1967
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1822 KB)  

    Thin films of In As and InSb directly evaporated on to substrates, such as glass, ceramics or ferrite, have interesting properties which make them suitable for galvanomagnetic devices as Hall probes or magneto resistors. The reasons for this are as follows: the Hall-sensitivity increases with decreasing thickness of the semiconducting layer. The higher inner resistance of thin films facilitates matching of the device to a particular circuit. Directly evaporated layers have a better heat dissipation factor than thin slices cemented to a substrate. Suitable methods of producing stoichiometric thin films of InAs and InSb with mobilities comparable to bulk material values are the flash-evaporation techniques and the three-temperature method. As the mobility shows a strong dependance on the crystallite size of the polycrystalline films, recrystallization techniques were subsequently applied to InSb films. This treatment results in larger crystallite sizes and mobilities of up to 30,000¿40,000 cm2/Vs. The properties of thin film devices are discussed with special regard to Hall probes. The average values of mobility and Hall coefficient versus temperature and the resulting characteristics such as Hall-sensitivity, inner resistance, control current and temperature coefficient, are discussed with reference to several typical devices. View full abstract»

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  • Voltage stabilized sinusoidal inverters using transistors

    Publication Year: 1967 , Page(s): 109 - 128
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2026 KB)  

    A voltage stabilized, sinusoidal inverter system and an analysis of the operation is described. Design equations are derived for output voltage, distortion, stabilization and regulation, for loads of varying power factor. The particularly important transistor parameters are emphasized, and an inverter design example together with photographs of all relevant waveforms is included. View full abstract»

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