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Communication Technology, IEEE Transactions on

Issue 6 • Date December 1967

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Displaying Results 1 - 25 of 28
  • [Front cover and table of contents]

    Page(s): 0
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    Freely Available from IEEE
  • Reliability field experience in electronic switching systems

    Page(s): 729
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    Electronic switching systems have progressed through the experimental trial stages and a number of systems are now in regular commercial use. The reliability experienced in these field installations wiII be discussed by authors representing four different companies - one English, one German, and two American. Reliability and maintenance data from several operating systems will be used to demonstrate the system dependability currently achieved, and these achievements will be compared with the desired objectives. View full abstract»

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  • Field experience with quasi-electronic telephone switching systems

    Page(s): 730 - 735
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    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. View full abstract»

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  • Reliabilty and Field Experience of Electronic Switching Systems

    Page(s): 736 - 743
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    Field experience of electronic switching systems is compared with design objectives expressed in reliability and maintainability parameters, applied from the start of design, for the purpose of meeting stringent customer requirements. A feedback system of field performance was established, reliability analysis was performed, and the results were applied to a reliability model to determine to what degree the established objectives were met. View full abstract»

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  • Early No. 1 ESS Field Experiences: I--Two-Wire System for Commercial Applications

    Page(s): 744 - 750
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    The No. 1 Electronic Switching System (ESS) is the first electronic machine produced in quantity by the Bell System for central office switching. A 2-wire version is being used for Bell System commercial customers and a 4-wire version for a variety of government and military applications. The system is composed largely of solid-state devices and is controlled by a stored program. The nine No. 1 ESS's now in use have been giving good service to their commercial and government users. Judging from customer reaction and from various technical performance criteria, the No. 1 ESS has met its design objectives. View full abstract»

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  • Early No. 1 ESS Field Experiences: II - Four-Wire System for Government and Military Applications

    Page(s): 751 - 754
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    Late in 1962 Bell Telephone Laboratories began the development of a 4-wire version of the No.1 ESS for government and military applications. An electronic stored program system was requested by the government to meet the growing needs of defense communication. There are now thirteen 4-wire No.1 ESSs in the government's AUTOVON network, in addition to 23 No. 5 crossbar offices, most placed in service prior to 1966. By 1969 it is anticipated that more than 50 Bell System offices will be in operation throughout the United States. By this time the crossbar machines will have started to be replaced by ESSs, as shown in Fig. 2. Additional electronic offices, overseas as well as in the United States and Canada, are being planned for AUTOVON by non-Bell System companies. Before 1970 a global defense communication network of ESSs should be realized. Early field experience with the No. 1 ESS, both 2- and 4- wire, has been satisfactory. New offices endowed with new service features and improved maintenance capabilities are being introduced at a growing rate. About 100 No. 1 ESSs are now in various stages of manufacture and installation or in field operation. The ability of this design to provide continuous, high-quality service seems assured. View full abstract»

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  • Electronic Reliability in the Field

    Page(s): 755 - 767
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    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. View full abstract»

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  • Partitioned Switching Arrays

    Page(s): 768 - 777
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    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. View full abstract»

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  • Vulnerability of Communication Networks

    Page(s): 778 - 789
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    A communication system can often be represented as an interconnection of stations and links. The assumption is that the system is subject to enemy attack aimed at isolating stations from each other. Vulnerability criteria are defined, and asymptotic and recurrence relations are given for computing the vulnerability of several classes of networks with a large number of stations. Based on the analysis procedures, optimum synthesis procedures are suggested. A simple model is analyzed first, then the results of the analysis are extended to include systems with repair, memory, and to those whose interconnections depend on distance. The main objective of this paper is to show under what conditions asymptotic expression for vulnerability can be derived. View full abstract»

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  • Maximal-Ratio Diversity Combiners

    Page(s): 790 - 797
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    A diversity combiner with a structure which is common to many communication systems is described. When the combiner inputs are independent and identically distributed narrowband Gaussian random processes and the reference signals are timeinvariant, it is found that the combiner output can be conveniently represented as a function of a Gaussian random process, a chisquare variate, Gaussian variate, and known time functions. This representation clearly indicates the performance gain from diversity. In addition, it simplifies the evaluation of expectations of functions of the combiner output; recursion relations, with respect to the order of diversity, are found for these expectations. The results of this paper thus serve to unify and generalize many other results dealing with maximal-ratio diversity combiners; extensions of many well-known results can also be found by using the recursion relations. View full abstract»

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  • Error Probability for Multipath Fading--The "Slow and Flat" Idealization

    Page(s): 797 - 805
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    The ideal slow and flat fading model, consisting of any number of multipaths, is revisited. In this model the assignment of specular and scatter components is arbitrary. The additive disturbance need not be Gaussian noise, certain random distortions in the receiver are permitted, and the digital system and the modems are not restricted. Under these assumptions alternative error probability relations are given between the fading and nonfading signals. Their application to practical cases is straightforward. General performance bounds are also derived which are simple functions of the specular and scatter energy ratio in the multipath signal. View full abstract»

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  • Performance of an Efficient Parallel Data Transmission System

    Page(s): 805 - 811
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    A parallel quadrature AM data transmission system may be implemented with a number of overlapping channels, each carrying a signaling rate b , spaced b/2 apart in frequency. When a large number of channels are used, the system allows transmission speeds very close to the Nyquist rate, with little sensitivity to delay and amplitude distortion of the transmission medium. The receiver requires precise phasing of the demodulating carriers and sampling times in order to keep crosstalk between channels small. In the presence of delay and amplitude distortion, better results are obtained when half cosine roll-offs are used for shaping each channel than for full cosine roll-off. This transmission scheme appears to be a promising technique for achieving good performance at high information rates over bandlimited dispersive transmission media. View full abstract»

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  • The TOUCH-TONE® Telephone--Transmission of Digital Information ®

    Page(s): 812 - 824
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    A discussion of the Bell System TOUCH-TONE®dialing system when it is alternatively used in data applications is presented. The particular aspects of this service and the hardware involved which lend themselves to alternate data uses are discussed in detail. Among the points covered are coding, the keyboard, error possibilities, and the technical aspects of the receiving data set. View full abstract»

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  • Visual Sensor Systems in Space

    Page(s): 824 - 834
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    Slow-scan television cameras have been used as visual scanners in orbiting satellite programs. The sensor, as an input device, and the associated readout or output device are the terminal parts of an orbiting television satellite system. Some of the input-output elements will be described covering visual sensors, optics, kinescope recording, and facsimile. Sample systems, such as TIROS and Essa satellite systems, will show these elements as part of the system. Trade-off parameters of resolution, light level, electronic bandwidth, frame time, and storage time will be examined to show their effects on the video transmission system. View full abstract»

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  • Variable Redundancy Product Codes

    Page(s): 835 - 838
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    The tensor product codes, as either iterated codes or error-locating codes, possess the property of variable redundancy (allowing up to eight different levels of error control). It is shown that the implementation of an encoder for such codes can be decomposed into the implementation of the component codes. The selection of eight encoder modes yields four iterated codes and four error-locating codes that lend themselves to both adaptive coding and feedback transmission strategies. View full abstract»

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  • Design Concepts for Transportable Ionoscatter Systems and Experimental Results

    Page(s): 839 - 847
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    An experimental ionoscatter system carrying four 50-baud telegraph circuits has been designed and tested at 36 MHz over a distance of 1000 km between the Netherlands and Southern France. The object was to demonstrate the possibility of designing a system sufficiently compact to be made transportable. By using multiple-diversity reception and automatic request (ARQ) equipment, it has been possible to achieve a reliability of 99.9 percent with simple Yagi antennas and a transmitter power of 5 kW. The performance limits were an error rate of 1 to 3000 characters and a speed reduction of 10 percent. Frequency, horizontalspace, and vertical-space diversity reception have been tried. Signal strength measurements have also been made over paths shorter than 1000 km. It is shown that for a system with low-gain antennas the propagation loss at 400 km is 6 dB greater than at 1000 km. The use of error-correction codes is suggested for one-way connections where the ARQ technique is not applicable. It is shown that it is possible to obtain the same performance as with ARQ. View full abstract»

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  • The Raisting Satellite Earth Station and Its System Noise Temperature

    Page(s): 848 - 854
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    Features of the German satellite earth station at Raisting are cited in this paper. One essential criterion, the noise performance, is discussed in particular. The 25-meter Cassegrain antenna with horn reflector feed (covered by a radome) has been subjected to extended measurements of the system noise temperature. The results show the relation between the system noise temperature and the antenna elevation and azimuth angles under different weather conditions. In fair weather the system noise temperature is 53/\deg K with an elevation of 5° giving a ratio of antenna gain and system noise temperature of 40.7 dB. The curve of the system noise temperature at low elevation angles corresponds well to the optical horizon. During rain an increase of the system noise temperature has been noted. After rain, however, normal conditions are soon restored. View full abstract»

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  • Designing an Automated Oceanographic Buoy Interrogation System Using HF Radio

    Page(s): 855 - 860
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    Automatic interrogation and readout of a worldwide system of over 300 meteorological/oceanographic buoys requires careful attention to system control and communication interfaces. This paper describes the design of a system in which operation is executed by a medium-size digital computer which serves to control interrogation of the buoys, format the received digital transmissions, and put them on line for transmission over cable to a separate central data-processing center for analysis. To exercise system control, a number of functions must be performed. These are interrogation of buoys, data checking, data conversion, retransmission, control, and housekeeping. View full abstract»

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  • Correction - "Data communication through the atmospheric burst error channel"

    Page(s): 860
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    Summary form only given, as follows. The author of the above-named paper (19TP67-933), which appeared on pp. 383-389 of the June, 1967, issue of this Transactions, has called the following to the attention of the Editor: The factor 2/3 should not appear in expressions (11) and (28). View full abstract»

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  • Performance of Random Error Correcting Codes on the Switched Telephone Network

    Page(s): 861 - 864
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    The performance of perfect codes on the switched telephone network is evaluated in terms of output block error and output bit error probability. By evaluating these codes against experimental data describing the switched telephone network, it is shown that significant improvement in the block error rate is possible, but that only negligible improvement in the bit error rate is obtained even with block lengths as long as 230 bits and with redundancies approaching unity. View full abstract»

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  • Experimental Verification of a Model of the Oscillating Limiter

    Page(s): 865 - 867
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    Work done to verify the results of an analysis of the oscillating limiter published previously is reported upon in this paper. To this purpose experiments were made with an oscillating limiter, the characteristics of which are given, to check the nonlinear distortion produced on the baseband signals. The baseband equivalent circuit and nonlocking behavior of the oscillating limiter were also tested. Finally, a network for compensating the linear distortion produced in the message modulation by the oscillating limiter is shown, as well as experimental results. View full abstract»

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  • The Quatrix--A Proposed Electrooptical Position or Angle Sensor

    Page(s): 867 - 868
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    This technique, called quatrix (for quasi-matrix), has potential application in numerous communication and datahandling areas, since it provides high-density matrix-photocell capability at much lower cost. The method uses a few photographically-produced precision coding masks fitted over an equal number ( N ) of photocells. Thus, ten ( N ) typical high-detectivity photocells and ten coding masks will produce 210(2N) binary combinations, behaving like a 32 by 32 matrix photodetector and using only 10 preamps. Twenty larger cells and preamps promise a million element matrix. Limitations are discussed. View full abstract»

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  • Transposed Sideband Modulation for Data Transmission

    Page(s): 868 - 870
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    Transposed sideband modulation is a method for frequency multiplex transmission of digital voice band signals. Its significant feature is that no sharp cutoffs are required for the single sideband filters so that amplitude and phase distortions can be kept very low. Since transposed sideband modulation retains the CCITT channel subdivision, it is compatible with existing single sideband voice carrier equipment. View full abstract»

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  • Experimental Optical Links

    Page(s): 870 - 871
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    The design and performance of two experimental, optical links, tailored specifically to interconnect two high-speed tape units, are described. Both links, a full duplex digital link and a full duplex AM/FSK link, are presented in necessary detail. Laboratory experiments have shown that 33-Mbaud operation is feasible. View full abstract»

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  • A Least Squares Procedure for Aligning Antennas

    Page(s): 872 - 874
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    A procedure is described for aligning transmitting and receiving antennas in a communications link with a minimum number of positionings of the antennas. A statistical formalization of the interpretation of the received signal levels permits that combination of receiving and transmitting antenna orientations to be chosen which most probably represents the aligned combination. A criterion is also developed for estimating the goodness of the alignment. View full abstract»

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Aims & Scope

This Transactions ceased publication in 1971. The current retitled publication is  IEEE Transactions on Communications.

Full Aims & Scope