Terminal Apparatus Research Articles

Cable Carrier-Telephone Terminals

This paper describes the circuits, performance, and equipment features of the terminals of a new 12-channel carrier system for application to existing toll cables. The 12-channel group of terminal apparatus has been designed also to form a basic part of the terminals of other carrier systems now under development, such as the type-J system for open wire and the coaxial system.

Cable Carrier Telephone Terminals*

This paper describes the circuits, performance and equipment features of the terminals of a new 12-channel carrier system for application to existing toll cables. The 12-channel group of terminal apparatus has been designed also to form a basic part of the terminals of other carrier systems now under development, such as the type J system for open wire and the coaxial system.

Wide Band Transmission Over Balanced Circuits*

In a recent paper 1 amplifiers capable of handling frequency band widths of the order of 1,000 kc. or more are described, together with terminal apparatus for effectively utilizing these wide bands for telephone, telegraph and television purposes. The paper confines itself to the coaxial line structure for transmitting these wide frequency ranges but points out that broad-band transmission is also applicable to balanced conductor systems. The present paper discusses briefly some of the possibilities of the more familiar balanced circuits, circuits more or less as they now exist in the present plant being first considered, following which are circuits obtained by new construction. Wide-band transmission over balanced circuits offers interesting possibilities both for circuits in the present plant and for new construction.

Seeing Sound at the Chicago Exhibition

THE exhibits of the Bell Telephone Co. at the Chicago Exhibition are of considerable interest. By means of a rotating mirror, beams of light are successively picked up from a small mirror on the receiver and flashed on a screen where they can be seen by a large audience. The speed of the mirror is regulated so as to give the best effect for sound and music. Typical speech sounds are listened to and at the same time their wave form is shown on the screen. High-pitched sounds show waves close together, and loud sounds result in waves of great height. Filters of various types are inserted and their effect in cutting out certain frequencies are both seen and heard. In the Bell Laboratories Record for August a full account is given by Mr. R. F. Mallina of these exhibits. A photograph is shown of the combined signal produced when twelve telegraph messages are transmitted simultaneously along a wire. Visitors to the exhibit can listen to the curious medley of musical sounds produced in the loud speaker. The combined sound gives no hint of what the messages are. When the complex current goes into the terminal apparatus the twelve different messages are all duly sorted out. Of particular interest was the separation of the rectangular pulses of direct current which operate teletype instruments from the corresponding high-frequency impulses caused by the combination of the carrier wave with the signal wave. The apparatus should prove useful in lecture rooms when it is necessary to explain the characteristics of various vibratory phenomena.

Ultra-Short Wave Radio Link across Bristol Channel

ONE of the results of the study of the mode of propagation of ultra-short electric waves has been to show that for wave-lengths of from one to about nine metres, the effective range is limited to the horizon or the optical distance for ordinary vision. While this property prevents the application of such waves for long distance radio communication, it has for some time been recognised that this range of wave-lengths would be very suitable for providing a radio link in the ordinary telephone system. This application is of particular advantage in spanning short stretches of water, such as a channel or river estuary, where the present alternative is a submarine cable or a land-line following a circuitous route. According to recent reports in the Times and the Wireless World, tho Post Office Engineering Department has been investigating the possibilities of this application for some time past, and experiments have now successfully terminated in the setting-up of a radio link across the Bristol Channel. This link, which is twelve miles long, connects up the ordinary telephone land-lines at Lavernock, near Cardiff, on one side, with those at Hutton, near Weston-super-Maro, on the other. The wave-length employed is about five metres, and the transmitters and receivers are placed in separate huts at each site. The aerial system consists of horizontal dipoles connected to the terminal apparatus by special transmission lines, and the whole equipment has been designed to work unattended, apart from periodic maintenance operations.

Two-Way Radiotelephone Circuits

This paper deals with the problems of joining long-distance radiotelephone transmission paths to the ordinary telephone plant. It gives the possibilities and limitations of various methods of two-way operation of such circuits where the radio channels employ either long or short waves. It also describes the special terminal apparatus for switching the transmission paths under control of voice currents and lists the advantages of using voice-operated devices.

Two-Way Radio Telephone Circuits*

This paper deals with the problems of joining long-distance radio telephone transmission paths to the ordinary telephone plant. It gives the possibilities and limitations of various methods of two-way operation of such circuits where the radio channels employ either long or short waves. It also describes the special terminal apparatus for switching the transmission paths under control of voice currents and lists the advantages of using voice-operated devices.

The solution of circuits subjected to traveling waves

THE EFFECT of traveling waves upon terminal apparatus usually is most easily solved by means of Heaviside's operational calculus. Solutions have been given previously for various combinations of impedances that may be encountered in service, by considering such impedances to be contained in simple circuits. These are intended to approximate the general conditions of a transmission system. However, a purely mathematical analysis of such an involved nature often is looked upon skeptically and experimental variation of such calculation therefore is valuable.

Lightning Discharges and Line Protective Measures

This paper describes the mechanics of the development of a lightning stroke in a cloud and the formation of a surge on a line. It shows that the energy of a stroke can vary between wide limits so that the actual surge on the line may be of practically any magnitude. Fundamental types of high-tension line construction are analyzed to show the performance that would be obtained with them. Experience obtained on the 220-kv. lines of the Public Service Electric and Gas Company is offered to substantiate the belief that induced surges are of relatively small importance and that the direct stroke is the criterion for good design. The effects of line construction on the character of surges impressed on the terminal substation apparatus is discussed to indicate the degree of protection that would be required.

Certain Topics in Telegraph Transmission Theory

The most obvious method for determining the distortion of telegraph signals is to calculate the transients of the telegraph system. This method has been treated by various writers, and solutions are available for telegraph lines with simple terminal conditions. It is well known that the extension of the same methods to more complicated terminal conditions, which represent the usual terminal apparatus, leads to great difficulties. The present paper attacks the same problem from the alternative standpoint of the steady-state characteristics of the system. This method has the advantage over the method of transients that the complication of the circuit which results from the use of terminal apparatus does not complicate the calculations materially. This method of treatment necessitates expressing the criteria of distortionless transmission in terms of the steady-state characteristics. Accordingly, a considerable portion of the paper describes and illustrates a method for making this translation. A discussion is given of the minimum frequency range required for transmission at a given speed of signaling. In the case of carrier telegraphy, this discussion includes a comparison of single-sideband and double-sideband transmission. A number of incidental topics is also discussed.

Abridgment of certain topics in telegraph transmission theory

The most obvious method for determining the distortion of telegraph signals is to calculate the transients of the telegraph system. This method has been treated by various writers, and solutions are available for telegraph lines with simple terminal conditions. It is well known that the extension of the same methods to more complicated terminal conditions, which represent the usual terminal apparatus, leads to great difficulties. The present paper attacks the same problem from the alternative standpoint of the steady-state characteristics of the system. This method has the advantage over the method of transients that the complication of the circuit which results from the use of terminal apparatus does not complicate the calculations materially. This method of treatment necessitates expressing the criteria of distortionless transmission in terms of the steady-state characteristics. Accordingly, a considerable portion of the paper describes and illustrates a method for making this translation. A discussion is given of the minimum frequency range required for transmission at a given speed of signaling. In the case of carrier telegraphy, this discussion includes a comparison of single-sideband and double-sideband transmission. A number of incidental topics are also discussed.

Automatic Printing Equipment For Long Loaded Submarine Telegraph Cables

The introduction of the permalloy loaded submarine cable has presented the possibility of telegraph transmission at speeds several times those obtainable on non-loaded cables and has made practicable the operation of printer telegraph equipment. The present paper presents the various factors which affect the design of operating equipment and describes the apparatus which has been developed and used for a considerable period of time under service conditions. The transmission speed attained may exceed 2,400 letters per minute. To a certain extent, the detailed design of the terminal apparatus is controlled by the electrical characteristics of the particular cable to which it is to be applied and this type of equipment cannot, therefore, be completely standardized.

Fundamental considerations of power limits of transmission systems

P. H. Thomas: The paper by Doherty and Dewey emphasizes even more than those of previous date the part played by the terminal apparatus in stability of operation. Of course, it matters not what the electrical equations show as to the theoretical capacity of a long line if when terminal apparatus be applied to supply power and receive load the combination is unstable to operate, as might easily be the case with loads anywhere nearly approaching the theoretical capacity of the line should the usual present designs of synchronous apparatus be used.

An Investigation of Transmission-System Power Limits

Results of theoretical analysis, verified by miniature-system tests of the power limits of transmission systems, are discussed, among the major conclusions being the following: The criterion for stability under all conditions is the steady-state power limit. The charging kv-a. exercises marked detrimental effects on stability. The characteristics of synchronous terminal apparatus are of great importance. Improvements can be made by modifying present apparatus design. Automatic voltage regulators, suitable exciters and fast relays are essential. The mercury-arc rectifier, as an adjunct in excitation circuits, shows real advantages.

Some artificial lines and networks associated with the uniform telephone transmission line

In Part 1, it is shown that the problem of constructing a network the impedance of which shall be equal to the impedance of an infinite uniform telephone line, can be solved exactly by the use of a number of sections of simple artificial lines. The artificial lines described are intended entirely for use in this way, and since their propagation constants are widely different from that of the uniform line, they cannot be used as “artificial transmission lines” to which any terminal apparatus might be added.Some of the artificial lines can be used for attenuation correction.In Part 2, it is shown that related networks can be obtained such that when placed in series or in parallel with the infinite uniform line, the impedance of the combination is a pure resistance

Key West-Havana submarine telephone cable system

The system discussed in this paper includes three single-core continuously loaded submarine cables, each of which provides, in addition to a telephone channel, direct-current and carrier-current duplex telegraph channels. A description is given of the design and construction of the cables, of the method of superposing the various channels on each cable and of the terminal apparatus used for their operation.

Key West-Havana Submarine Telephone Cable System

The system discussed in this paper includes three single-core continuously loaded submarine cables, each of which provides, in addition to a telephone channel, direct-current and carrier-current duplex telegraph channels. A description is given of the design and construction of the cables, of the method of superposing the various channels on each cable and of the terminal apparatus used for their operation.

Practical application of telephone transmission calculations

I. General :?General transmission equation ; standards ; graphical construction ; description of vector scale ; accuracy of graphical construction. II. Applications :?Effect of terminal apparatus ; equivalents of various lines under different conditions ; reflection losses ; proposed new standard ; composite lines ; effect of direction of speaking ; allowances for apparatus in circuit. III. Experimental results :?Predominant frequency of voice ; equivalent wave-form of voice ; speech tests on composite lines ; use of a single frequency for general testing ; tests on loaded lines ; tests on unloaded cable. IV. General conclusions. V. Appendix :?Constants of telephone lines and apparatus.

The influence of terminal apparatus on telephonic transmission

The influence of terminal apparatus on telephonic transmission

On the Peripheral Distribution of Non-Medullated Nerve-Fibres

ABSTRACT Safter the terminations of non-medullated nerve-fibres had been discovered in the tactile corpuscles of the skin and in the Pacinian bodies; after Max Schultze had come forward with his surprising and stirring doctrine as to the special terminations of some of the nerves of the higher senses, and Krause had described what were named by him the “clubshaped extremities “in many nerves of common sensibility, as well as in those of the conjunctiva, oral mucous membrane, and genital organs; and after special terminal-apparatus had been found out in the striated muscles,—the doctrine of a terminal network of nerves in general seemed to be finally set aside, especially in the case of the nerves of common sensibility, which, according to it, break up into a network in the most superficial layers of the skin and mucous membranes, consisting sometimes of thin fibres partly medullated, partly non-medullated, or bending round to form a loop. Indeed, within the last ten years a great number of treatises have appeared on the modes of termination of the peripheral non-medullated nerves, showing in general that special terminal apparatus are to be found in the most various organs and in the most various nerves. Here I can call to mind only the termination of the nerves of common sensibility in the branching corpuscles lying between the epithelial cells of the rete Mal-piffhii of the skin (1); the so-called terminal corpuscles of the genital nerves (2); the termination of nerves in the nucleolus of the smooth muscular fibre (3); the knob-shaped termination of the corneal nerves in the precorneal fluid (4); the ending of nerves in the corneal corpuscles (5); the nervetermination in the nucleoli of the epithelium of the tail of the tadpole (6); and in the branched cells (7) of the same organ; the terminations of nerves in the pear-shaped structures of the tissue of the epiglottis (8); in the nuclei of capillary bloodvessels (9); in special bodies in the mucous membrane of the urinary bladder (10); and in structures which lie between the epithelial cells of the mucous membrane of the stomach of the frog (11); the freely outrunning nerve-fibres in the tissue of certain serous membranes (12); the termination of nerve-fibres in the cells of the alveoli and of the ducts of the salivary glands (13); in the cells of the liver (14); and so on.