Showing papers in "Bell System Technical Journal in 1945"
Journal Article•
807 citations
TL;DR: In this article, the causes of failures are generally inadequate protective cushioning, lack of ruggedness of the outer packing container, or occasional abnormal weakness of the packaged article, and the first of these difficulties is the subject of this paper.
Abstract: Mechanical damage is a common occurrence in the transportation of packaged articles. The causes of failures are generally inadequate protective cushioning, lack of ruggedness of the outer packing container, or occasional abnormal weakness of the packaged article. The first of these difficulties is the subject of this paper.
91 citations
TL;DR: A theoretical study of lightning voltages in buried telephone cable, of the liability of such cable to damage by lightning and of remedial measures, together with the results of simulative surge tests, oscillographic observations of lightning voltage and lightning trouble experience, is presented in this paper.
Abstract: A theoretical study of lightning voltages in buried telephone cable, of the liability of such cable to damage by lightning and of remedial measures, together with the results of simulative surge tests, oscillographic observations of lightning voltages and lightning trouble experience.
11 citations
TL;DR: Nicolson as discussed by the authors showed that when the electrodes of a quartz crystal are connected in certain ways to an electric oscillator circuit, the frequency is held very constant at a value which coincides with the period of the vibrating crystal.
Abstract: A Study or an explanation of the performance of a piezoelectric crystal in an oscillator circuit involves a study or explanation of oscillator circuits in general and a study of the crystal as a circuit element. Nicolson1 appears to have been the first to discover that a piezoelectric crystal had sufficient coupling between electrical electrodes and mechanical vibratory movement so that when the electrodes were suitably connected to a vacuum tube circuit, sustained oscillations were produced. In such an oscillator the mechanical oscillatory movement of the crystal functions as does the electrical oscillatory circuit of the usual vacuum tube oscillator. His circuit is shown in Fig. 12.1. Cady2 independently though later made the same discovery, but he utilized it somewhat differently and expressed it differently. He found that when the electrodes of a quartz crystal are connected in certain ways to an electric oscillator circuit, the frequency is held very constant at a value which coincides with the period of the vibrating crystal. He made the further discovery that due to the very sharp resonance properties of the quartz crystal, the constancy in frequency to be secured was far greater than could be obtained by any purely electric oscillator.
8 citations
TL;DR: The theory of the general behavior of crystals in oscillator circuits has been described by I. E. Fair as discussed by the authors, and it has been pointed out that in the neighborhood of the operating frequency a crystal is equivalent to the circuit shown in Fig. 15.
Abstract: The theory of the general behavior of crystals in oscillator circuits has been described by I. E. Fair1. In Fair's paper as well as in others2, it has been pointed out that in the neighborhood of the operating frequency a crystal is equivalent to the circuit shown in Fig. 15.1A. The crystal possesses two resonant frequencies, a series resonant frequency determined by the effective inductance, L 1 , and effective capacitance, C 1 , and an anti-resonant frequency determined by these same elements plus the paralleling capacitance, C 0 . This paralleling capacitance is the static capacitance between electrodes of the crystal and any capacitance connected thereto by the crystal holder and lead wires within the holder. The dotted resistor, Rl, shunting the equivalent crystal circuit represents the effective shunt loss of the holder. In the ideal case and in many practical instances this loss is negligible.
7 citations
TL;DR: In this paper, the intentional generation of a modulated wave by control of the low frequency behavior of an oscillator is also considered, and the circuit modifications are required to promote stability.
Abstract: Oscillators of all sorts may, for certain values of the parameters, show law-frequency disturbances. Usually the disturbance takes the form of a low-frequency interruption of the desired oscillation. By the method here presented it is possible to determine whether or not such intermittent behavior will occur in a given oscillator and what circuit modifications are required to promote stability. The intentional generation of a modulated wave by control of the low frequency behavior of an oscillator is also considered. Oscillators of the negative resistance type are not considered.
4 citations
TL;DR: Physical limitations in electron ballistics are discussed in this paper, where it is pleasant to have a chance to talk about such physical limitations, because there is so little we can do about them, and although these limitations are apt to be discouraging, a knowledge of them is very valuable, for it keeps us from spending time trying, like the inventors of perpetual motion machines, to do the impossible.
Abstract: The subject of this talk is “Physical limitations in electron ballistics”. It is pleasant to have a chance to talk about such physical limitations, because there is so little we can do about them. And, although these limitations are apt to be discouraging, a knowledge of them is very valuable, for it keeps us from spending time trying, like the inventors of perpetual motion machines, to do the impossible.
4 citations
TL;DR: The final lecture of a series on Electron Ballistics as mentioned in this paper is a summary of the material which has been previously presented but rather it is an attempt to show how the ballistic approach can be extended to the analysis of high-frequency devices.
Abstract: This, the final lecture of a series on Electron Ballistics, is not a summary of the material which has been previously presented but rather it is an attempt to show how the ballistic approach can be extended to the analysis of high-frequency devices. Much that might otherwise be said about ultrahigh frequencies cannot be said because of secrecy requirements. However, there is considerable material which can be presented, within the limits of the necessary security regulations, which may be of interest to those who are not already well acquainted with the subject. I will, perforce, not be able to say anything specific about actual devices utilizing the principles to be discussed.