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This paper describes a study of transmission control procedure for computer-to-computer and computer-computer-to-terminal communication through a public packet-switched network. Four types of basic data link are defined over a packet travel path in the network, and the functions required for the data link are discussed. A process number and its associated control method are proposed as a method of packet-interleaved communication. By applying the result of the discussion and introducing the concept of a data link and a process number, a transmission control method and a call control method between packet-switched network and computers are proposed for the packet-interleaved communication on the basis of the HDLC procedure (high-level data link control procedure).

A new system has been designed to provide protection switching capability for the L5 repeatered line. This line-protection switching system, called lpss−3, provides one standby line for protection of as many as 10 service carrying lines. Switching equipment is located in terminal, terminal main, and switching power-feed stations. Economic and reliability considerations allow switching spans of up to 150 miles. Either temperature pilot deviations or excessive total signal energy initiates automatic switching. Manual control of all switching functions is provided locally and via telemetry. A dedicated pcm signaling system maintains interstation switching system coordination. Identical information is transmitted in complem entary form over two adjacent L5 channels. Parity and complementary checking as well as automatic retransmission of failed codes enhances error immunity.

Increasing success of computer networks performed the necessity of the packet switching machine more and more powerful. But for a widely use such a machine must be cost and throughput adaptable. High degree of reliability and easy maintenance may also be provided. As packet switching functions become more and well known, using the feature of ARPA network of Cyclades network, the emphasis is put on the way of implementing these functions on a special packet switching oriented computer structure. The designed structure, as a packet switching node, handles packets working on bit sequences. The functions are decentralized over a multi-processor structure in order to increase the parallel processing. Data link procedure management is performed by two processors, the receive and send processors, who act for only one link. There are as many couples of these processors as links. To each link a switching processor is assigned performing the switching function. A packet oriented memory is provided which allows simultaneous accesses for all the receive and send processors. A core processor manages the communications between the receive, send and switch processors, the processor also deals with memory allocation, sending packet who have not been acknowledged and links failures. Furthermore a software system implemented on a micro-processor processes background functions principaly flow control function and routing table management. For that structure correctness and recovery capabilities are provided using peculiar features concerning either internal packet manipulation, or duplicated modules. As a result the cost-performance ratio is acceptable and the modularity allows to fit the node configuration to the requirements of a large scale of packet switching networks, having different characteristics related to the number of links connected to each node and to the transmission data rates on these links.

The congestion in broad-band communications networks resulting from the increased demand for interactive services is considered. It is shown that services such as a video library could not be provided to the majority of subscribers in a conventional CATV network. A design is developed for a space division multiplex broad-band network which can be expanded at minimum cost to meet an increasing demand for interactive services. The network contains two signal distribution networks: a cablecast system similar to the Rediffusion system, and a switched communication network providing point-to-point circuits for both one-way and two-way services. All broad-band signals are transmitted to the subscribers in the 1- to 10-MHz spectrum, permitting the use of twisted pair video cables and a minimum number of cable amplifiers. The broad-band cable network (BCN) is organized around 15 local switching exchanges and one central exchange. Multipoint switches in local exchanges under wired-logic circuit control connect individual subscriber communication lines to any channel. Crosspoint matrix switching groups in the local and central exchanges connect communication circuits in the broad-band communication network under programmed computer control. This network is accessed via links terminating on one channel of the multiposition switches. Per-subscriber costs are estimated to be 190 dollars for a cablecast system serving 3800 subscribers. Additional expenditures per subscriber of 40 dollars for fixed costs and 40 dollars for variable costs would provide interactive services. The range of interactive services provided would be extremely flexible, including both one-way video library service and point-to-point two-way communications.

A new packet-switching network technique is described which, while utilizing certain aspects of the ARPANET technology, introduces a substantially different technique for handling traffic which is longer than a single packet in length. The technique is keyed to a common-user network environment, where a wide variety of subscriber types, ranging from computers to simple terminals, are to be serviced. Subscribers in most cases would be remotely located from the network switching nodes. By splitting the buffering between the originating and destination nodes and by essentially eliminating the segment reassembly process, substantial reductions in on-line buffering can be achieved, while still maintaining short response times for interactive messages and large bandwidths for long data exchanges. In this paper we describe the network operational concepts and traffic flow for various subscriber types, show specific examples and timing diagrams for message flows, and present a comparative analysis of the buffer sizing, throughput, and delay for this new technique compared to the well-known ARPANET technique of packet switching.

PCM transmission and PCM switching cooperate economically in so-called integrated networks (integrated switching and transmission (IST)). Economical and technical aspects are ruling the introduction of IST. Possibilities of introduction were investigated for the various network levels in the Federal Republic of Germany. It was proved that first of all PCM tandem exchanges are required to which up to 5 000 speech circuits can be connected. A PCM switching network of T-S-S-T structure is being developed for such application within the scope of the EWS 1 system.

Stored-program control is at the heart of the Deutsche Bundespost's electronic telephone switching system.

When messages are transmitted as a series of possibly noncontiguous packets, an effective priority is introduced which favors short messages. The strength of this effect upon transmission time is investigated and compared with schemes where an additional priority scheme is imposed. It is found that imposing a real priority structure can markedly influence delays when: first, the trunks are relatively heavily loaded, and second, the nodes' incoming traffic arrives over high-speed channels.

Current studies are being undertaken by the United Kingdom Post Office to exploit more fully, in the shorter term future, and to rationalize, in the longer term, the local system of telecommunications distribution in the United Kingdom in order to offer a wider range of services to the customer. One proposal for a future integrated system utilizes a single wide-band medium to provide, in a cabinet area, groups of topological ring distribution highways on which all local traffic is assembled and switched. A laboratory model has successfully demonstrated engineering feasibility. Further studies are currently aimed at the determination of a viable technological progression toward an ultimately fully comprehensive telecommunition service.

This paper deals with current research aimed toward increasing circuit switching speed and logical complexity over that which is presently available on a given surface area of a silicon die. The relationship between circuit speed and power consumption is discussed for current mode logic circuitry. The technological tools available for pushing forward the barriers limiting speed and efficiency are presented. In addition, experimental data is shown comparing performance “of buried layer” devices to conventional devices in a ring oscillator configuration. Means for increasing logic complexity on a silicon die are discussed. A two phase shift bit example, developed and fabricated over a year ago, utilizing silicon interconnection cross-overs, is compared to a recent attempt utilizing film cross-overs. Also, results of integrating a 2×2 scratchpad memory device utilizing 101 elements are discussed. The paper concludes with some remarks pertaining to possible future technological approaches and their limitations for increasing logic complexity and circuit performance on a single chip of silicon.

The 100a protection switching system is intended to ensure continuity of service in TD Microwave Radio Relay Systems by transferring service from a failed working channel to a standby protection channel. Switching is done at IF on a switching section basis. A switching section may contain up to ten radio repeater stations, with the average section containing three to four repeaters. A fully equipped 100A system provides means to replace any one of ten regular channels with either of two protection channels. Two regular channels may be switched simultaneously to the two protection channels. The circuit interruption due to a fade initiated or a maintenance switch is less than 10 microseconds. The interruption due to an equipment failure is less than 35 milliseconds, a time short enough to prevent false operations in the telephone switching plant. The control information necessary to sequence the operation of the switches at the transmitting and receiving ends of the switching section consists of coded voice-frequency tones. These may be transmitted over any reliable voice-frequency facility having suitable transmission and delay characteristics. All of the active devices in the system are solid state. The system requires sources of both +24 and −24 volt power.

The switching is an important part of the telecommunication networks over the years for transferring and handling voice and data through the traditional switching nodes existing in the telecommunication networks. Various developments were seen in the recent years which resulted in increasing data transfer capabilities of the transmission networks all over the world, however the switching speed and techniques are still remained unchanged in most of the cases that neither match the data transfer capacities nor the expanding demand of the networks in the near future. Some switching technologies are still in the developing stage, of them two are more obvious: Optical Packet Switching (OPS) and Optical Burst Switching (OBS). In this paper, I tried to compare different paradigm of these two main developments, keeping in mind that the OPS would see rapid development in the near future than the OBS, though OBS would the ultimate solution of switching for the bulk volume of telephone and data traffic Keywords: Optical Packet Switching; Optical Burst Switching; Bulk Volume; Data Traffic; Wavedivision Multiplexing DOI: http://dx.doi.org/10.3329/diujst.v6i2.9342 DIUJST 2011; 6(2): 22-32

Developments in the plans for providing a comprehensive set of dedicated and switched digital services are reviewed. Descriptions are given of the considerations which influence the decisions on the technical solutions to be used to modernize the transmission plant. The description covers long-distance transmission, local distribution, multipoint systems, store-and-forward switching, access from unequipped customers, and circuit switching.

A switching phenomenon has been reported in certain lateral geometry transistors in silicon integrated circuits. These devices switch between conducting and nonconducting states at a critical value of V CE . A hypothesis for the mechanism has been proposed. In this paper an equivalent circuit is developed for the switching lateral transistor and is used to predict transistor behavior. The effect of manufacturing tolerances on the device switching voltage is investigated and a technique of production control is proposed. Circuits using the device are described in which the circuit switching voltage may be varied over a wide range. Some applications of the switching lateral transistor, as an overvoltage protection circuit and a relaxation oscillator, are described.

In order to hasten the development of electronic switching in the Bell System, the first two No. 1 Electronic Switching Systems (No. 1 ESS) were placed into service without benefit of a field trial. Based upon experience gained in these early offices, hardware and program modifications were made prior to placing subsequent offices into service. This paper describes the program, hardware, and translation changes that were retrofitted into the first two No. 1 ESS offices in order to bring them up-to-date. The retrofit of these changes were successfully made on an in-service basis.

By the very nature of telephone traffic, any telephone subscriber may wish to be connected to any other subscriber in a continental area or possibly anywhere in the world. This implies switching of connections. It also implies switching these connections at more than one point since it would be economically impracticable to concentrate all switching operations at one point for even a single metropolitan area. With subscriber line switching on a decentralized basis, it naturally follows that switching centers themselves must be switched in order to accomplish economical interconnection of any two telephone subscribers.

Suitability of a switching system to solve wide and diverse application problems as well as the general case, is largely determined by its switching plan. In No. 1 EAX, the strategy of the plan is to establish a flexibility in internal network trunking that allows separation of traffic by type, directional flow, and intensity. The three major network divisions-line, selector, and trunk registerare sectionalized accordingly and are positioned relative to each other so as to avoid wasted motion in setting a call to completion. Control, supervision, and maintenance of the network are arranged to better utilize machine capacity by relieving the processor of high volume routine jobs.

A high-speed telephone switching network with electronic controls is described. The high speed allows one-at-a-time operation, reducing both the number and complexity of control circuits. Germanium diodes, transistors, cold-cathode tubes and fast relays perform the control functions; glass-sealed relay contacts provide paths for speech. A laboratory model of the network has performed reliably for over three years.

The general features of the 10-C toll and transit switching system have been briefly described in two earlier publications [1], [2]. More detailed information on the switching matrix configurations and interconnecting arrangements used in this system and on the calculation and simulation methods employed to ascertain its traffic load handling performance is provided.

General predictions are made about the development of the state of the art by shortly reviewing the latest findings of theoretical investigations as well as hardware developments. A few examples are given to illustrate recent attempts to reorganize, standardize and integrate present day digital data processing and transmission systems for future use. Concepts of "data moving" and "dynamic matching" within a transmission network are introduced. It is believed that tele-data processing (TDP) systems, i.e., electronic data processing (EDP) systems with input/output devices at remote locations, will experience a growth that will warrant the specialization of a number of manufacturers and organizations on data moving only. Dynamic matching may be considered as the basic principle of a new organization of digital data-transmission networks. It will ultimately load every available communication channel to its practical peak capacity and will therefore optimize the efficiency of systems. This principle is discussed in detail at four different levels of a network. Demand matching of input devices, branch matching, link matching, and finally network matching will be a common feature of many systems in the 1970's. For the user of TDP facilities, data movers will incorporate these principles in "general services" networks, which will operate on a message switched basis and in completely digital form. "Private facilities" will also be provided on a circuit switched basis for special purposes.

The article analyses a stochastically bounded the GI/G/m//N circuit switched network model with packet losses, with stochastic input network traffic, stochastic served network node, and deterministic and finite network node buffer capacity. Max-plus algebra instrumentality is used for the network processes analysis. FIFO tail drop or LIFO tail drop buffer is used. We have established that the average waiting time in the queue had increased when the queue service discipline was FIFO as compared with LIFO, while the offered traffic was Poisson and the served in the node traffic was self-similar. The network traffic is served faster in the network node with the buffer queue discipline LIFO, while the offered traffic is Poisson and its intensity exceeds the served in the node traffic 10 times. Ill. 2, bibl. 24 (in English; abstracts in English and Lithuanian).http://dx.doi.org/10.5755/j01.eee.111.5.350

This paper discusses a local PCM switching network. The characteristics of this network are demonstrated with a model of three local exchanges. All subscribers are connected with the exchange via concentrators. An exchange is controlled by a central processor with a stored program. This processor interacts with the peripheral switching units, represented by the central switching network and two types of control circuits, located within the exchange. These control circuits control either the concentrators or they communicate with counterparts, situated in other local exchanges. All control functions that are not executed by programs of the central processor are realized by microprograms in a wired read-only storage (ROS) in these peripheral control circuits.

This paper presents a short general survey of the integrated network problems. How digital techniques can provide new capabilities of transmission and switching of the information that could allow the progressive realization of a single universal network of telecommunications is examined.

THE NUMBER 5 crossbar switching system was described by Korn and by Ferguson1 in 1950, just a year and a half after the first installation was placed in service at Media, Pa. These authors mentioned the growing need ? ? for a dial system which would better meet the telephone switching requirements for areas on the outskirts of metropolitan cities and at the same time care for medium-to-large sized offices in other areas.? Since that time, the basic switching plan of this system has proved to be so flexible and adaptable that it is finding an ever-expanding application in many new combinations of switching requirements. After a brief review of the basic switching plan described in more detail in the previous article, this paper will cover some of the new features since added to the system.

Federal Communication Commission Docket 18 262 allocated a 75-MHz band to the common carriers to implement high capacity mobile telephone systems. The Bell System has proposed a cellular arrangement of low-power transmitters/receivers that permits frequency reuse in a coverage area. This method of achieving spectrum efficiency will require extensive centralized coordination and control to properly administer channel assignments and to interconnect the mobiles with each other and with the direct distance dialing (DDD) network. This can be accomplished by means of an electronic switching system (ESS) with special data terminals and trunking arrangements, and a unique program. In the proposed plan the radio sites (base stations) act effectively as remote concentrators in the frequency domain under the control of ESS, which in turn acts primarily as a trunk-to-trunk switcher. In addition to the usual switching, signaling, and supervising functions, the switching office must also perform numerous special functions including paging of mobiles, location of mobiles (signal strength and ranging data analysis), channel reassignment of mobiles, and reswitching of mobiles to various base stations-these last three occurring while customers ate talking.

The successful planning, installation, and operation of a nation-wide switching plan to interconnect more than 62 million telephones in the United States requires a high degree of teamwork between various groups of people. This involves the development, design, transmission, equipment, and building engineers to provide the system and the operating and maintenance people to keep it going. This paper deals primarily with transmission phases of switching telephone trunks in the United States. Brief mention is made of the interconnection with the Canadian switching plan involving approximately 5 million additional telephones.

Known switching arrays service subscribers in either a blocking or a totally nonblocking manner. The first part of this paper describes a method of modifying totally nonblocking arrays to service a group of subscribers, some of which will be given nonblocking service while the rest will be given service at a prescribed blocking probability. It is shown that the resultant crosspoint saving compared with the totally nonblocking case is significant when the subgroup receiving nonblocking service is limited. The method used is illustrated for 3- and 5-stage symmetrical arrays and may be extended to arrays having a greater number of stages. It is then demonstrated how any number of subscriber groups can be serviced with different specified blocking probabilities by such arrays, which are called partitioned switching arrays. An example is included for a partitioned array affording three grades of service.

Over nearly a decade the British Post Office has been operating normal production electronic equipment for the control and routing of calls through the long distance switching network. More recently the first normal production installation of a fully electronically controlled exchange has been cut into service and is the beginning of a regular program for the installation of such exchanges throughout Britain. It is appropriate at this time to review the performance record of the various types of electronic switching equipment, first to confirm that the direction of development is leading toward greater reliability in service, and second to determine whether changes in maintenance organization may be necessary to take advantage of the greater penetration of the more reliable electronic equipment. This paper deals mainly with the lessons to be learned from the performance of the various types of register-transistor equipment used in the long-distance switching network, but also gives some reference to the performance of the TXE 2 electronic exchange.

In the sectionalized electronic switching system under consideration, serial combinations of connections established through a general purpose switching network are used to associate any required combination of peripheral equipments with a call. The implementation of this process, known as serial trunking, is described with emphasis on the functions of registers which act as an interface between the switching network and the common control. The combination of serial trunking stored program control and sectionalization provides security and flexibility for the incorporation of new facilities.

SINCE the introduction of symbolic methods1,2 into the field of digital control, much has been written on the application of Boolean algebra to the analysis and synthesis of 2-terminal electromagnetic (relay and magnetic core) and electronic switching networks. In general, a switching network involves not only the network configuration and the switching elements but also the states of transmission through the network. A survey of the literature will show however, that it is generally (tacitly) assumed that the states of transmission through a switching network are limited to two values. For relays the two states are usually the establishment and the opening of a d-c path through the network; for electronic gate circuits these two states are usually the presence and absence of a pulse. An essentially similar situation prevails on the states of the switching elements in a network. For relays, a relay contact is either open or closed; for electronic gates, an input or output lead either carries a pulse or does not carry one.

This paper describes a nonblocking processor-controlled digital time-division multiplex (TDM) switching system for six 24-channel digital TDM trunk groups and 48 analog lines. This system uses integrated circuit technology throughout and is capable of handling combined voice-data trunk groups required in military systems of the future. A stored program processor provides a flexible control unit whose control functions can be readily modified. Communication channel interfaces among the common control processor, TDM switch, and signaling units permit line scanning by the digital switching unit under stored program control, and remote control of the switching center by a processor located at another switching center within the network.

The combination of electronic components and dryreed contacts for use in switching systems has proved its high reliability standard. For several years, various types of equipment, e. g., routing translators, switching arrangements for direct distance dialing plant and local telephone offices have been in continuous operation in the public network. Component reliability figures, gained from these devices, are given.

The transmission path of an electronic switching center utilizing time division multiplexing, its associated contact control circuits, and contact memory are discussed. Line, interhighway, signal injector and highway discharge switches are incorporated in this transmission network. The design of an accurate and flexible transmission measuring device was necessary so that some of the established transmission characteristics could be satisfactorily measured. The transmission characteristics were thus proven to be well within specified limits.

The U. S. army signal Corps required a basic telephone switching system which could fulfill the functions of a local central office and provide the basis for a long distance (LD) switching center. In addition, a complete switching network was required, built up of a series of local and LD switchboards.

Intercity transmission of television programs and telephone conversations is now provided via a network of TD-2 microwave radio relay equipment operating on a transcontinental basis. Whenever service interruption threatens because of equipment troubles or atmospheric disturbances in the transmission path, a switching system automatically and quickly substitutes a stand-by wide-band microwave radio channel for the defective channel. The circuits and operation of this switching equipment are described.

The Pentex System is designed for telephone exchanges in the range of 200 to 2000 lines. It uses reed-relay crosspoints in a 3-stage switching network; control operations are performed by semiconductor circuits and reed relays. The circuits are mounted on a new system of plug-in units. Easy growth in small increments, simple maintenance, low power consumption with standard exchange battery supplies, faulttolerance, and the ability to incorporate new features and services are main objectives achieved by the design.

This paper describes the 300A and the auxiliary channel protection switching systems which provide continuity of service on TH-3 medium-haul radio systems. Both protection switching systems operate on a one-by-one frequency diversity basis. The 300A is a baseband-to-baseband system and protects the message circuit load. The auxiliary channel switching system protects the order-wire and alarm circuits and operates at both IF and baseband frequencies. System design considerations and circuits of special interest, including solid state switches and integrated circuit modules, are discussed in some detail.

This paper describes a procedure for a suboptimal routing of simultaneous multiterminal multicommodity flows in circuit switched communication networks. The procedure is based on a concept of topological importance of a branch in a capacitated net with a given structure and relative to a given pattern of communication requirements. Once these importance weights have been attached to the branches of the net, the problem reduces to finding in a weighted network the shortest path between two nodes. The chosen objective here is to optimize the grade of service (GS) by satisfying (on a long-range traffic policy basis) the changing "call" demands presented to the network, as fully as possible.

A recently introduced large-size commercially available electronic switching system has versatility in application to different hierarchies of switching stages and is available not only in the telephone systems, but for forthcoming new telecommunication services such as video telecommunications, data applications, mobile radio telephones, etc. Successive developmental programs are now in progress for remote control switching systems, a small-medium-size electronic switching system and data-switching systems. In the international telecommunication field, an electronic telegraph switching system has been completed and electronic telex and telephone switching systems and a data-switching system are now under development. This paper describes some features of various electronic switching systems available in Japan for domestic and international telecommunications.

Tone operation of electronic switching centers is the natural outgrowth of 4-wire operation of communication systems using a radio link. The radio circuit may be anywhere between the subscriber and the switching center or between switching centers.

This paper reports an exact quantitative evaluation of the relative effectiveness of line-assigned and line-shared buffer storage in a message switch, or of a circuit switch that holds blocked calls for later connection. It is well known that shared storage is more efficient than line storage in the sense that fewer message storage units are required to provide the same level of protection against message rejection. However, a unit of common storage may be considerably more expensive than a unit of line storage because of differences in the storage media itself and the need for additional control circuitry. Thus, an exact quantitative analysis of the relative effectiveness of line assigned and line-shared buffer storage can provide a basis for trade-off studies between the two types of storage.

Customer distant dialing without operator intervention is predicated on rapid dependable switching and high-quality transmission with minimum contrast from call to call. It is, therefore, mandatory that each incremental unit in each built-up connection follow the best and latest design practice and be subjected to a rigid preventive maintenance program. This paper will discuss some recent changes in two-wire switching circuits to obtain improvements in transmission following the basic guidelines of the "Notes on Distance Dialing" ("Blue Book," AT&T) and bulletins released by the various United States Independent Telephone Association (USITA) committees.

Two types of markers were designed for the overseas AUTOVON (Automatic Voice Network). The switch marker and matrix (comprised of 6-element crosspoints) are used to interconnect the various switching circuits provided in the office. The DSA (Dial Service Assistance) marker and matrix are used to connect DSA trunk circuits to operator position circuits. Each marker is a sequentially operating device with self-checking circuitry to detect internal failures which are recorded by a separate maintenance monitor circuit. Two markers are always provided in each section (switch or DSA), one marker active or on-line, and the other used as a standby unit. When trouble is detected, an allotter circuit transfers the traffic load to the standby unit.

An ‘ideal* converter would accept the power flow of a 3-phase a.c. system operating with sinusoidal voltage and current, and, without energy storage and by a continuous process, convert to or from d.c. Present-day converters rely, however, on repetitive circuit switching operations, more than 12 per cycle being generally uneconomic despite the cost of the energy storage components required in damping circuits and in the filters to maintain acceptable waveforms. Analysis of the operation of such converters is based on the mathematics of repetitive transients (Laplace and Fourier) and on the use of a d.c. transmission simulator, an extensive model at 10 -7 scale in power, which is also necessary in the development of complex electronic control circuits. There exists a great background of experience contributing to the design of most components of the power circuit. In contrast, the development of the switching device, whether thyristor stack or mercury arc valve, calls for advances in the state of art, both in scientific appreciation and in technology, which must be supported by full scale tests. There is little immediate prospect of the theoretical ‘ ideal * converter, but this is unimportant, provided that development leads to enhanced overall reliability.

After an introductory discussion of the importance of electronic switching for certain functions in telephone and telegraph exchanges, the paper sets out the principles of switching with square-loop ferrite cores and the advantage of their use in combination with transistors. Various examples are given of the use of square-loop ferrite cores in telecommunication switching circuits. They refer particularly to electronically controlled telephone exchanges (register, impulse generators, counting circuits, code convertors), a multi-metering system for telephone exchanges, a memory circuit for the storage of telegraph characters and finally an automatic reservation system for airline companies.