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This paper deals with some important practical applications of teletraffic theory to field engineering problems. It is shown that the following tasks concerning line switching telephone networks can be mastered by means of a few handy tables: loss calculation and dimensioning of trunk groups for full or limited access; very accurate loss approximation of link systems with an arbitrary number of stages, operating as group selection or traffic concentrating arrays with point-to-group selection mode (regarding this, and also optimal link structures, wiring, etc., see [7] in this issue); dimensioning groups with limited or full access for offered peaked overflow traffic; cost minimizing partition of the traffic in local or toll networks with alternate routing to the various trunk groups; and computerized dimensioning is of course also possible.

A brief review of Swiss PTT history shows that a number of switching systems have been introduced over the years. This problem of inhomogeneity shall be overcome in the future by a unique all digital PCM telephone network currently being developed which will be introduced gradually in the 1980's. Transmission systems will use more minicoaxial cables for carrier-as well as PCM-systems. A special PCM transmission system network which will reach the major cities will provide data transmission service for channels up to 48/64 kbit/s. This early data network shall be combined later with the PCM telephone network.

(1974). The Automatic Telephone Exchange. Transactions of the Newcomen Society: Vol. 47, No. 1, pp. 35-46.

This paper is a sequel to previous papers which considered the characteristics of a proposed synchronization control system for an integrated telephone network. In those papers, delay of the paths of each junction, one for transmission and the other for control signal, were assumed to have the same value. Though the analysis produced exact expressions for the static and dynamic characteristics of the control system, this assumption is not likely to be found realistic, in many cases. The present work extends that condition into a case where the above-mentioned delays of the paths are not equal. The conclusion is reached that the stability limit of the network is chiefly defined by the path that has the shorter delay. The stability of a synchronization control system in sampled-data control mode is also discussed. It was clarified that the reduction of the sampling rate results in higher stability of the network.

The design and construction of a modem for a remote hybrid computer terminal is described. This modem utilizes both existing and newly developed equipment to provide true remote access through the switched telephone network to a hybrid computer facility. The unit is used in conjunction with an on-campus, hard wired, remote terminal system. Together, these terminals permit both on- and off-campus students to participate in a new set of simulation laboratories.

The problems set by the development of the Italian telephone network and particularly by the scheduled introduction of new services (also of a nontelephone type) are surveyed in this paper. The solution of these problems employing analog techniques presents many difficulties and, also, creates obstacles for future developments; therefore Italy is at present oriented towards the extensive use of digital techniques. In this paper the scheduled developmental stages are described for the evolution of the present telephone network, which is founded on an analog basis, towards a telecommunication network set on a digital basis and with an accentuated integration of services.

This paper presents function facilities for suppression of telephone lines and associated subscriber equipment. A setup of test combinations can be arranged by technical clerks at the centralized antiinterference station as well as by a field engineer. The present telephone technique is checked directly from the test desk via direct through-connected lines of the supervisory network. In special cases, remote-controlled measuring equipment and test devices are installed. In the new computerized local electronic telephone exchange system (EWSO 1), remote-controlled test circuits are used primarily, but only by means of trunk circuits of the telephone network. The ac voltages, the frequency of which is analog to the measured value, flow to the test desk via a speech channel and digital information via a data channel. Both facts are visual on the test desks panel The tester can use a service computer via a video data terminal and so be enabled to call from a subscriber index important data for testing a telephone connection. A special test unit can be called from subscriber's plant. This line is then partly checked by automatic steps and partly by dialing of recallable steps. Results are sent to a suppressor as a voicefrequency signal.

In this article the significance and requirements of monitoring outdoor noise pollution in urban environments are discussed. Potentialities and limitations of using the regular telephone network for this purpose are identified. A system of noise monitoring is described which uses single telephone lines and existing electronic and data processing components. This system provides a technically and economically feasible means of enforcing local legislation controlling noise from aircraft overhead and from other outdoor sources, and of analyzing needs and trends with respect to such sounds over time.

An integrated telephone network requires synchronization of digital signal streams arriving at each switching system with its switching points. A new synchronization control system for this purpose was already proposed by one of the authors and the final clock rate and stability criterion were discussed in the preceding material. Continuing with this discussion, impulse responses of the proposed control system applied to mesh networks are mathematically analyzed under the condition that all of the clock pulse generators have respective clock rate derivations from their nominal value. The conclusion was arrived at that the more stations included in a network, the shorter the time elapsed before the frame pulse phase disturbances are settled down to a steady state, although this tendency is rather gradual. The dynamic response of the synchronization control system applied to mesh networks, a ring network, a chain network, and an assumed worldwide network are computer simulated in linear and three-value clock rate control modes and the characteristic of the control system is clarified.

The optimal control of a single-stage multi-server time-varying queuing system is considered. A mathematical model and an index of performance for the queuing system are formulated, and the optimal arrival rate of the input process to the service mechanism is then determined. Some of the physical implications of the optimal control policy relative to the dynamic overload control system presently adopted in the toll telephone network are discussed.

THE communication problems of rural areas offer an unique opportunity for the application of automatic switching methods. In no other situation is the combination of factors so favorable. Automatic exchanges are particularly suited to rural needs, especially when they are installed as unattended units in connection with nearby attended exchanges. The principal benefit springs from the fact that in a small manual exchange the number of operators cannot be adjusted to take care efficiently of the maximum traffic, because too often there is not enough traffic to occupy the time of even one operator. The low traffic factor in rural areas therefore results in a twofold handicap — a handicap which only automatic equipment has been able to remedy. Experience has shown first that it is the infrequency of calls in an exchange, rather than high traffic, that makes the operator inattentive, and often causes delay in putting through calls. Service being the essence of all telephone facilities, this is a condition which cries aloud for a remedy.

The principles of new switched data networks planned in France are explained together with a short survey of the present state of the art. Basic techniques, offered services, compatibility with telephone, envelope concept, synchronization, and international compatibility are covered. The general ideas underlying the outline of its implementation are given but many technical details are still under study both in the French Post, Telegraph, and Telephone (PTT) Administration and in international bodies such as the International Telegraph and Telephone Consultative Committee (CCITT). Such studies, made by various administrations in Europe, should lead to new possibilities by sharing many features which are presently afforded within private networks, but interchange of information between potential users and administrations should throw light on the extent with which many services should be offered.

Most of the mobile radio telephone systems now in use depend upon operator call-handling and require the mobile subscriber to work push-to-talk. In addition, although the mobile set may be equipped to operate on several channels, it can be selectively called on only one. If that one channel is busy, base-to-car calls are blocked even if other idle channels are available. All of these features have combined to make mobile telephone service less convenient and useful than wire-line telephone service, and this has seriously hampered its growth.

The transatlantic telephone cable system was designed as a connecting link between continent-wide communication networks on the two sides of the Atlantic. The technical planning of the system and the objectives set up so that this role would be fulfilled are the principal subjects of this paper. Typical performance characteristics illustrate the high degree with which the objectives have been realized. Optimum application of the experience of the British Post Office with rigid repeaters and the Bell System with flexible repeaters, together with close co-operation among the administrations, has played a large part in achieving the objectives.

The potential application of electronic data processing and data transmission techniques to voting and election processes is described; its implication and outlook for the future of democratically organized societies are discussed. The state of the technical art is considered as well as some of the economical, political, psychological and organizational factors necessary for a successful implementation. Various methods are taalyzed, including the transmission of votes through the telephone network. The automated tallying of votes allows speedy and frequent polling and voting on all significant issues affecting the community both on local and national levels.

A low-speed data transmission system that permits communication from machine to machine over the telephone network is described. This data set, as part of the general DATA-PHONE service, provides economical data transmission well-suited to data collection of relatively short messages from many transmitters to a single receiver. It transmits alphabetic and numeric characters, asynchronously, using parallel multifrequency signaling techniques. The system has been field tested over a wide variety of telephone facilities with very satisfactory results.

This paper is an attempt to place before engineers general information in regard to automatic telephone switching. The subscriber's requirements are independent of the means used to satisfy them. Automatic switching is uniformly fast and involves reduced mental stress to the user because the passing of the number is positive and waiting time is reduced to the minimum. Viewed by the owner the apparatus has longer life, the service is very acceptable to the public, and but a tithe of the female employees are used. Automatic switching apparatus has increased greatly in margin of safety. Much progress has been made toward standardization of form and toward best methods of maintenance. A few changes in structure are described and data given to show margins of safety in operation. Present practise regarding party lines and measured service (cash and credit) is stated briefly. The durability of automatic equipment is illustrated by the fact that plants have not yet worn out. Maintenance routines are essential to successful operation. Girls do routing testing with marked success. Rural telephone lines present problems which have been solved in several ways, influenced by the greater number of telephones per line, the conditions of signalling subscribers, and the inferior insulation often encountered. Code ringing can be retained. Rural automatic service is only a little inferior to city automatic service. The community automatic exchange serves a small group of subscribers, either isolated or part of a telephone network.

The engineering of a data system for use on the switched message network is reviewed. First, the conditions imposed by this specific application are shown to influence the selection of signal characteristics, and the choice of raised-cosine pulse shaping is given support by a brief treatment of some pulse transmission fundamentals. Finally, the results of a field trial are summarized to show that, while the system objectives were met, factors such as delay distortion, attenuation distortion, and transmission loss limited the performance obtained.

A general model for digitally linearizable companding laws for use in digital communication systems is presented. The model is utilized to compare a ternary code presented by Neu and Kundig with a binary code. The primary considerations are ratio of signal to quantization noise, companding improvement, and linearization.

In many circumstances a telephone call can be completed through a connecting network in several ways. Hence, there naturally arise problems of optimal routing, that is, of making the choices of routes so as to achieve extrema of one or more measures of system performance, such as the loss (probability of blocking) or the carried load. As is customary in traffic theory, a Markov process is used to describe network operation with complete information. The controlled system is described by linear differential equations with the control functions (expressing the routing method being used) among the coefficients. Restricting attention to asymptotic behavior leads to a problem of maximizing a bilinear form subject to a linear equality constraint whose matrix is itself constrained to lie in a given convex set. An alternative approach first shows that minimizing the loss, and maximizing the fraction of events that are successful attempts to place a call, are equivalent. This fact permits a dynamic programming formulation, which, in turn, leads to a very large linear programming problem. Two small examples are treated numerically by this method. It is particularly important to try to verbalize, and then mechanize, the optimal routing strategies. In this endeavor, the linear programming formulation is of limited usefulness. Therefore, in the latter half of the work we

THE NATION-WIDE telephone network is essentially composed of three distinct types or groups of facilities. Each is engineered and maintained on a different basis. Each, however, must be designed, engineered, and maintained in such a manner that when they are combined they will provide dependable and economical communication between all customers, regardless of their location.

This paper describes a study of a mathematical model of the impact of an equipment irregularity on trouble detection and the quality of customer service in a telephone network. The essence of the model is that the holding time of any piece of equipment may be altered if it develops a fault. Customer service is shown to be less sensitive to increases in holding time than decreases. Trunk and some types of other irregularities, characterized by holding times shorter than usual, are seen to affect service more severely than certain common control equipment irregularities, characterized by longer than usual holding times. Analytical and numerical techniques for studying the model are described. Results are presented for the various classes of equipment irregularities. The predicted effects are especially important in the area of recognizing and locating network faults and agree with practical experience.

There have been significant technological advancements in recent years in the automation of handling, switching, and accounting of telephone toll calls and other operator-assistance types of calls. The concept of the Traffic Service Position has been developed to speed and standardize human operations for all kinds of calls involving operators. Several features of the ADDDS system installed at Las Vegas, Nev., for the Central Telephone Company of Southern Nevada are described. A wide versatility of the operator position readily accommodates various difficult to handle categories of calls, such as time-and-charge, delayed, emergency, leave word, paystation calls, and others. An extremely effective system is used to monitor and control traffic to the operators under congestion conditions and to predict and adjust operator force size. A fully automatic scheme is used to deliver time-and-charge-information for calls made by guests of hotels, using teletypewriter techniques, within a few seconds of completion of the calls. A special solid-state and ferrite core computer serves the triple function of computing charges for: 1) Prepay coin telephone calls 2) Time-and-charge calls for hotel guests 3) All calls that are machine ticketed for preparation of billing. This system, cut into service in November 1964, serving approximately 80 000 subscribers and producing 15 to 20 thousand tickets a day, is equipped with 120 operator positions.

This paper presents the results of a nationwide data transmission field testing program on the telephone switched message network. Error performance using the FM digital subset is described and basic transmission characteristics such as net loss, bandwidth, envelope delay and noise are given.

In a recent paper a traffic assignment model has been constructed in which the cost on a link may depend not only on its load, but also on the loads on other links of the network. In this paper it is shown that this model is also capable of handling the case of several classes of users in the same transportation network each of which has an individual cost function and, at the same time, contributes to its own and other classes' cost functions in an individual way. Typical applications arise not only in street networks where vehicles of different types share the same roads (e.g., trucks and passenger cars) but also in other types of transportation networks (e.g., telephone networks). An algorithm is constructed for finding the system-optimizing flow pattern for such a multiclass-user transportation network.

The telephone transmission system described here is the Master Reference System of the Bell System for the expression of transmission standards and the ratings of the transmission performance of telephone circuits. The transmitter and receiver elements of this system are reference standards for the ratings of the transmitting and receiving performance of terminal station sets. A replica of this reference system, installed in Paris, has been adopted as the Master Reference System of the International Advisory Committee on Long Distance Telephone Communication in Europe. The establishment of these two master systems provides a common reference for the telephone transmission work of the Bell System and the telephone administrations which are members of this International Advisory Committee.

The advent of integrated digital communication systems will initiate a new period in speech communications research and development. The new and still adaptable systems environment together with the cost performance advantages of modern digital technologies will open up the way to practical utilization for many speech technology concepts and services that are not feasible within the framework of the present "classical" telephone networks.

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The Telephone, invented by Mr Graham Bell, is an instrument by means of which any sounds, musical notes or spoken sentences, sounded into an instrument at the sending end of a telegraphic wire may be reproduced at the receiving end. The theory of the Telephone is two-fold. First, the mechanical theory of the nature of sounds and of speech; and secondly, the theory of the action of the instrument. The first part is well known. All sounds consist of a succession of waves propagated through the air, the rate and intensity of their succession determining the nature of the sound, in pitch, loudness, and tone. If the same succession of waves as a speaker makes in using his voice can be reproduced in the air in contact with the ear of any other person, by any means whatever, the latter person will hear a fac-simile of the sound uttered by the former.

The rapid growth of computer communications in recent years has brought with it a number of difficult and controversial regulatory and economic problems. As the government agency responsible for the regulation of interstate common-carrier communications, the Federal Communications Commission (FCC) has been faced with many of these issues. This paper attempts to focus, in a tutorial fashion, upon four areas in the computer-communications field in which the influence of the FCC has been particularly significant. An overview of the regulatory process is given as background, after which we discuss the regulation of commercial computer-communications services, the interconnection of subscriber equipment to the telephone network, the creation of specialized communications carriers and of domestic satellite systems, and finally a number of data communications pricing problems which have arisen as a result of these developments.

When ``digital computer'' was an institutional rather than a household word, the machine required some very special personnel to cajole anything from its limited facilities. The operators came to the computer and spoon-fed it. And the computer's limited ``brainpower'' permitted only one operator at a time to tinker. Today, computers can be programmed so that almost anyone can be trained to access them?at least, in a limited way. Moreover, these electronic machines now have such massive central and peripheral memories that many people can use them simultaneously. Since it is impractical to have all of the computer users make a pilgrimage to the computer, the computer is made to come to the people that it serves. This is done via communication channels?predominantly in the telephone network. The various factors involved provide the substance for this primer article.

A description is given of the Italian Long Distance Network, which interconnects the 21 Transit Regional Centers of the Country and the international and intercontinental telephone networks. In particular, the characteristics of coaxial cables and radio links are detailed, as are the criteria to be adopted in order to guarantee a grade of service acceptable to subscribers. Fundamental outlines are also described for 1) functional and design standardization of equipments, 2) problems arising with interconnection on a full European and world basis.

Office balance, as applied to the toll telephone network, can be divided into two major divisions, those of through and terminal balance. Through balance concerns the connection of one 4-wire intertoll trunk with another, switched on a 2-wire basis. Terminal balance is required for the interconnection of an intertoll trunk with a toll connecting trunk to the subscriber's central office. Because of the extent of private networks presently being engineered, it is necessary to balance the interconnection of calls within these networks. This paper is concerned with the basic principles of through and terminal balance, but primarily centers on terminal balance in the private and DDD networks, because that is the area of the majority of engineering problems.

低速走査精細画像をハードコピーの形で受信する場合について検討する.まず可能な案について利害得失を論じ, 次にその中で有望と考えられるテレビ電話機の撮像管をファクシミリの送信に共用する方式に関し, 実験装置の構成と特性の測定結果を述べる.1インチビジコンを用いた実験装置の低速走査時 (水平走査周波数=500Hz, 走査線数=1024本) の特性は, 限界解像度=700TV本, SNR=20～30dB, 走査ひずみ=±3%, 階調=7～8段階であり, SNRを改善する必要がある.

To compose a telephone network with low transmission loss without cumulative increase of quantizing noise, it is desirable to accomplish both transmission and switching with PCM modulation. Such a system, called an integrated telephone network, requires synchronization of incoming signals arriving at each exchange to the local timing pulse generator controlling a time division switch of the exchange. In the synchronization method described in this paper-the equational timing system a local oscillator of controllable frequency that drives the local timing pulse generator in each exchange is controlled by making reference to the phase differences between incoming signals arriving at the exchange from the other exchanges and incoming signals arriving at the other exchanges from the exchange. This synchronization method permits the minimun storage capacity of the buffer memory indispensable for compensation of the junction-delay variation, indefinite enlargement of the network and multiplication of its complexity, and invulnerability to the consequence of failure of one or more junctions or timing pulse generators in the network. The phase differences between the local timing pulse generators of exchanges in the network, the stability of the network applied with this synchronization method, and an example of the equational timing system are discussed.