Showing papers in "Bell System Technical Journal in 1933"
TL;DR: In this paper, a new method of computing modulation products by means of multiple Fourier series is described, which is used to obtain for the problem of modulation of a two-frequency wave by a rectifier a solution which is considerably simpler than any hitherto known.
Abstract: A new method of computing modulation products by means of multiple Fourier series is described. The method is used to obtain for the problem of modulation of a two-frequency wave by a rectifier a solution which is considerably simpler than any hitherto known.
141 citations
TL;DR: In this article, an empirical formula for calculating the loudness of any steady sound from an analysis of the intensity and frequency of its components is developed, based on fundamental properties of the hearing mechanism in such a way that a scale of loudness values results.
Abstract: An empirical formula for calculating the loudness of any steady sound from an analysis of the intensity and frequency of its components is developed in this article. The development is based on fundamental properties of the hearing mechanism in such a way that a scale of loudness values results. In order to determine the form of the function representing this loudness scale and of the other factors entering into the loudness formula, measurements were made of the loudness levels of many sounds, both of pure tones and of complex wave forms. These tests are described and the method of measuring loudness levels is discussed in detail. Definitions are given endeavoring to clarify the terms used and the measurement of the physical quantities which determine the characteristics of a sound wave stimulating the auditory mechanism.
116 citations
TL;DR: In this paper, a method of measuring attenuation and field strength in the ultra short wave range was described, and a resume of some of the quantitative experiments carried out in the range between 17 meters and 80 meters.
Abstract: Part I of this paper first describes a method of measuring attenuation and field strength in the ultra-short wave range. A resume of some of the quantitative experiments carried out in the range between 17 mc. (17 meters) and 80 mc. (3.75 m.) and with distances up to 100 km. is then given. Two cases are included: (1) “Optical” paths over sea-water and (2) “Non-optical” paths over level and hilly country. An outstanding result is that the absolute values of the fields measured were always less than the inverse distance value. Over sea-water, the fields decreased as the frequency increased from 34 mc. (8.7 m.) to 80 mc. (3.75 m.) while the opposite trend was found over land. As a rule, the signals received were very steady, but some evidence of slow fading was obtained for certain cases when the attenuation was much greater than that for free space.
33 citations
TL;DR: In this article, a general formula for the mutual impedance of wires embedded in a conducting medium and lying in one of two parallel planes of discontinuity in the conductivity is derived.
Abstract: A general formula is derived for the mutual impedance of wires embedded in a conducting medium and lying in one of two parallel planes of discontinuity in the conductivity. The general formula is quite complicated, but simplifies in a number of important cases, and summarizes the published mutual impedance formulas relating to two-layer earth and its special cases. The two most important cases are obtained by making the conductivity of one or the other of the outer regions zero. The special case in which the conductivity of the outer region adjoining the wires is zero gives the mutual impedance of any thin grounded wires lying on the surface of a horizontally stratified earth having conductivities λ 1 and λ 2 at depths less than or greater than b, respectively. When the conductivity of the other outer region is zero, the formula gives the mutual impedance of wires lying in the plane of separation, at the depth b. The formulas in both cases involve integrals which apparently cannot be evaluated in closed form: for practical application the use of curves of the kind given is suggested for approximate numerical results. The formulas for the special cases, of which there are 11, together with some of their limiting forms, are tabulated together for ready reference.
32 citations
TL;DR: In this paper, it was shown that transmission to regions beyond the optical range is determined by conditions which are not constant and which, in fact, can produce great signal strength changes, such as the variable percentage of water vapor normally present in the atmosphere.
Abstract: Earlier published work has shown that, while the chief features of ultra-short-wave transmission over “air line” ranges are calculable from optical theory, there are deviations from this theory at the greater distances where a bending around the earth occurs. In this paper the results of a further study of these phenomena are given. It is shown that transmission to regions beyond the optical range is determined by conditions which are not constant and which, in fact, can produce great signal strength changes. The variable percentage of water vapor normally present in the atmosphere is suggested as a possible cause. The explanation seems, therefore, to involve a combination of diffraction and refraction, this latter variable with time, and at times predominant.
15 citations
TL;DR: In this article, the mutual impedance of any insulated wires of negligible diameter lying in horizontal planes above the surface of the earth and grounded by vertical wires at their four end points was investigated.
Abstract: This paper presents a formula for the mutual impedance of any insulated wires of negligible diameter lying in horizontal planes above the surface of the earth and grounded by vertical wires at their four end-points. The formula holds for frequencies which are not too high to allow all displacement currents to be neglected. Tables and curves are given to facilitate numerical computation by means of the formula. In the expansion of this formula for low frequencies and for any heights the first two terms give the direct-current mutual impedance; the third term is independent of the heights, thus being identically the same as that previously found for wires on the surface. The mutual impedance for wires at any heights H and h, with separations large in comparison with these heights, is found to be approximately equal to the mutual impedance for wires on the surface multiplied by the complex factor [1 + Γ(H + h)], where Γ is the propagation constant in the earth.
13 citations
TL;DR: A system for presenting the transmission performance of telephone circuits on the basis of repetition observations in a form suitable for engineering use and the steps required for obtaining these data from the repetition observations are described.
Abstract: A previous paper1 introduced the idea of rating the transmission performance of telephone circuits on the basis of repetition observations and outlined briefly a method for expressing such ratings. The present paper describes in some detail a system for presenting these data in a form suitable for engineering use and the steps required for obtaining these data from the repetition observations.
13 citations
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TL;DR: In this paper, a 25-mile loop of underground cable was used to test the performance of nine carrier telephone circuits 850 miles long and showed that the quality of transmission was satisfactory, while the methods and devices adopted to prevent interference between them were found to be adequate.
Abstract: In order to meet future demands for high-grade and economical circuits in cables, considerable carrier development work has been done which has included an extensive experimental installation on a 25-mile loop of underground cable. Sufficient pairs were provided in the cable and repeaters were installed to set up nine carrier telephone circuits 850 miles long. Tests on these circuits showed the quality of transmission to be satisfactory, while the methods and devices adopted to prevent interference between them were found to be adequate. The trial has, therefore, demonstrated that the obtaining of large numbers of carrier telephone circuits from cable is a practicable proposition.
12 citations
TL;DR: In this article, various types of musical and non-musical atmospherics occurring within the frequency range lying between 150 and 4000 c.p.s. have been studied.
Abstract: Various types of musical and non-musical atmospherics occurring within the frequency range lying between 150 and 4000 c.p.s. have been studied. Particular attention is directed to two types of the former, one a short damped oscillation, apparently a multiple reflection phenomenon, and the other a varying tone of comparatively long duration, probably related to magnetic disturbances. Several quasimusical atmospherics which appear to be associated with the two more distinct types are described. Dependence of atmospheric variations on diurnal, seasonal and meteorological effects is discussed. Characteristics of audio frequency atmospherics are shown in oscillograms and graphs.
10 citations
TL;DR: An analysis is made of the requirements for satisfactory operation of the simple four-arm bridge when used for impedance measurements and several methods of operation are described which show their flexibility in the measurement of impedance.
Abstract: An analysis is made of the requirements for satisfactory operation of the simple four-arm bridge when used for impedance measurements. The various forms of bridge are classified into two major types called the ratio-arm type and the product-arm type, based on the location of the fixed impedance arms in the bridge. These two types are subdivided further, based on the phase relation which exists between the fixed arm impedances. Eight practical forms of bridges are given, three of them being duplicate forms from the standpoint of the method of measuring impedance. These bridges together allow the measurement of any type of impedance in terms of practically any type of adjustable standard. The use of partial substitution methods and of resonance methods with these bridges is discussed and several methods of operation are described which show their flexibility in the measurement of impedance.
8 citations
TL;DR: This paper describes a transmission measuring system which automatically records the results of many of these measurements made on telephone circuits to determine their transmission performance.
Abstract: A number of types of measurement are made on telephone circuits to determine their transmission performance, these measurements being made with manually operated devices. This paper describes a transmission measuring system which automatically records the results of many of these measurements.
TL;DR: In this paper, a galvanometer element has been developed for the rapid record oscillograph which uses strings stretched to a natural frequency of 4500 c.p.s., and equalized to from ten to twelve thousand cycles.
Abstract: Efforts to extend the frequency range of oscillographs have, for the most part, been directed toward increasing the natural frequency of the vibrating element, which has formed the upper limit of the useful range. This paper describes a new method of attack which consists in employing a vibrator strung to only a moderately high natural frequency, and in equalizing the response of the string by electrical circuits both up to and beyond the fundamental resonance frequency. Employing this method of equalization, a galvanometer element has been developed for the rapid record oscillograph which uses strings stretched to a natural frequency of 4500 c.p.s., and equalized to from ten to twelve thousand cycles. The paper concludes with a description of such a modified rapid record oscillograph and with an oscillogram illustrating its use.
TL;DR: In this paper, the authors describe the fundamental structure and properties of the nucleus of an atom as a geometrical point endowed with mass and charge, which is the case for all nuclei.
Abstract: This article, like its forerunners on radioactivity and transmutation, is devoted to the beginnings of the oncoming stage of atomic physics: the study of the nucleus. The nucleus or kernel of an atom is in ultimate control of all its properties and features, for such of these as do not depend directly on it depend upon the number and arrangement of the orbital electrons, both of which are decided by the nuclear charge; further, the atomic weight is decided almost exclusively by the nuclear mass. Though in dealing with most of these properties it is usual to imagine the nucleus as a geometrical point endowed with mass and charge, the truth is far less simple and more interesting. Nuclei are structures built of elementary particles — some and maybe all of which are independently known to us — bound tightly together. It is of great importance to ascertain these structures, not only for their own sake, but because through understanding them we may become able to control and extend the transformations of nuclei from one kind to another — the processes of transmutation, some of which are already feasible. Several fields of research are apt to contribute to such an understanding. Accurate measurement of the masses of atoms, and of the masses and charges and other properties of the elementary particles, are the first two of these, and form the subject of the present article.
TL;DR: The time required to carry out a program of tests has been materially reduced by the use of equipment which analyzes the articulation data automatically and provides the test results in typewritten form immediately after each list is called.
Abstract: The first part of this paper discusses the control and measurement of variable factors involved in testing telephone circuits by the articulation method and the simulation of the testing conditions in the laboratory to those of actual use; the second part describes the auxiliary apparatus by which these controls and measurements are effected. This apparatus includes a caller's control circuit, by which the caller's speech intensity may be measured and regulated independently of the circuit tested; a switching system which automatically reverses the direction of transmission between test sentences; devices for automatic and uniform agitation of carbon button transmitters; equipment for automatic measurement of the magnitude of the speech and noise waves on the circuits tested; phonographic sources of line and room noise; and a control board at which circuit elements and conditions can be changed and measured quickly. In addition, the time required to carry out a program of tests has been materially reduced by the use of equipment which analyzes the articulation data automatically and provides the test results in typewritten form immediately after each list is called.
TL;DR: Pulp insulation is a new type of insulation that has been developed to replace the well-known spirally wrapped ribbon paper insulation in certain kinds of telephone cables as discussed by the authors, which consists of a continuous pulp sleeving formed directly on the wire by a modified paper making process.
Abstract: Pulp insulation is a new type of insulation that has been developed to replace the well-known spirally wrapped ribbon paper insulation in certain kinds of telephone cables. It consists of a continuous pulp sleeving formed directly on the wire by a modified paper making process. The raw material for this insulation is commercial Kraft pulp and its preparatory treatment in the beaters corresponds to that given in the regular paper making process.
TL;DR: In this article, the authors provide a comprehensive set of graphs for the probability that a "normal" complex chance-variable deviates from its mean value by an amount whose magnitude (absolute value) exceeds any stated value.
Abstract: Part I of this paper contributes methods, theorems, formulas and graphs to meet a previously unfilled need in dealing with certain types of two-dimensional probability problems — especially those relating to alternating current transmission systems and networks, in which the variables occur naturally in complex form and thus are two-dimensional. The paper is concerned particularly with “normal” probability functions (distribution functions) in two dimensions, which are analogous to the familiar “ normal” probability functions in one-dimensional probability problems. It supplies a comprehensive set of graphs for the probability that a “normal” complex chance-variable deviates from its mean value by an amount whose magnitude (absolute value) exceeds any stated value; in other words, the probability that the chance-variable lies without any specified circle centered at the mean value in the plane of its “scatter-diagram,” that is, in the complex plane of the chance-variable. It gives a comprehensive treatment of the distribution-parameters of the “normal” complex chance-variable, and convenient formulas for the necessary evaluation of these parameters. For use in various portions of the paper, as well as for various possible outside uses, it supplies a considerable number of formulas and theorems on “mean values” (“expected values”) of complex chance-variables.
TL;DR: Vacuum tube amplifiers are now regularly built into long distance telephone circuits where they are required to maintain their volume efficiency as mentioned in this paper, and the overall volume efficiency of these circuits no longer depends to any important extent on the loss per unit length of the line wires.
Abstract: Vacuum tube amplifiers are now regularly built into long distance telephone circuits where required to maintain their volume efficiency. Consequently, the overall volume efficiency of these circuits no longer depends to any important extent on the loss per unit length of the line wires. Instead, the efficiency is controlled by certain factors which, before amplifiers were introduced, had negligible effect. Among these factors are echo, singing or “near singing,” and crosstalk. The stability of the lines and amplifiers also becomes very important.
TL;DR: In this paper, a discussion of the theories pertaining to the absorption of gases by metals and descriptions of actual work illustrating them are given, as well as an apparatus for the analysis and measurement of gases in metals and for melting metals in vacuum.
Abstract: In this paper there are included a discussion of the theories pertaining to the absorption of gases by metals and descriptions of actual work illustrating them. Apparatus for the analysis and measurement of gases in metals and for melting metals in vacuum are described. Information is included, also, on commercial vacuum melting methods and the results obtained.
TL;DR: In this article, the physical processes of induction between neighboring power and telephone lines are discussed and the means by which certain phenomena of interest in this connection have been qualitatively demonstrated to power and telecommunication employees.
Abstract: This article discusses the physical processes of induction between neighboring power and telephone lines and describes means by which certain phenomena of interest in this connection have been qualitatively demonstrated to power and telephone employees.