Data Communication Equipment Research Articles

Specifying communications DACs

The explosion in the market for digital communications equipment has fostered unprecedented interest in high performance DACs and highlighted the shortcomings in the way in which these devices are described. The authors discuss the architectures and features of DACs together with specifications (dynamic and static) and signal distortion. Comparisons of DACs are also mentioned.

A powerful personal computer-based plant transient recording and analysis system

A personal-computer-based plant transient recording and analysis (PTRA) system has been developed under a joint effort between the system planning department of Taiwan Power Company (TPC) and A-D Technology, Inc. The PTRA system is an integrated hardware and software computer system to collect the high resolution data of a power plant's transient conditions. The hardware of the PTRA system consists of Intel 80386-based personal computers, an intelligent data acquisition system, resistor boards, and data communication equipment. Special software modules were developed for the hardware to perform data monitoring, trigger detection, data collection, data transmission, and data analysis. The PTRA system has proved to be effective, accurate, flexible, and easy-to-use. It reveals high potential for various applications on electrical generation and transmission systems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

ATM technology: a backbone for high speed computer networking

The use of data communication equipment in local environments is increasing rapidly. Applications such as electronic mail, file transfer, CAD/CAM, etc., currently result in the installation of more and more LANS in offices. Since the industry becomes more and more located at different places worldwide, the interconnection of these LANs becomes more and more a requirement. With the increasing number of applications, higher and higher bit rates are required at those interconnections. Different solutions exist to connect these LANs. Most of them are based on B-ISDN tecniques, using the ATM (Asynchronous Transfer Mode) cell relay principle. The first solution, which is initially applicable in a metropolitan area is based on the MAN (Metropolitan Area Network) technology as standardized by IEEE 802.6. It is based on the DQDB (Distributed Queue Dual Bus) principle, and offers to the customer both high speed data interconnectivity and isochronous services. To cover larger areas than metropolitan ones, MANs can be connected by high speed leased lines, or by an ATM backbone network. An alternative solution, but with some complementarity to MANs, is called an ATM crossconnect network. This solution offers to the customers semi-permanent high speed connectivity. This solution can also be used as an enhancement to MANs, to provide a backbone to connect multiple MANs. Such an ATM crossconnect network can be enhanced with a connectionless server, to offer to the customers full international high speed data connectivity. Both solutions use the ATM transfer mode of B-ISDN and thus allow a gradual evolution to the full B-ISDN, in which each service can demand dynamically its virtual connection (or multiple virtual circuits for multimedia services). To ensure a worldwide connectivity, all involved telecommunication operators have to plan the necessary coordination.

Knowledge-based techniques for fault detection in digital microwave radio communication equipment

The application of two distinct approaches to the diagnosis of faults in digital communication equipment is examined. The selected artificial-intelligence approaches use either rule-based or machine-learning techniques. Faults up to 8-dB TWT (traveling-wave tube) overdrive, 10% spacing error in the signal constellation, and 5 degrees nonorthogonality in the modulating carriers are introduced on an 11-GHz radio. Each approach shown is capable of diagnosing both the type and magnitude of the introduced faults, subject to certain constraints for each system. Results indicate that the machine learning system is more appropriate than the rule-based system for providing optimal adjustment of the radio, where the underlying mechanisms are too complex to allow simple rules of thumb to be applied. However, the rule-based technique has been shown to be suitable for areas with large nonlinearities. A combination of the two techniques would solve some of the problems caused by the suitability of each method to a specific problem type, the rule-based approach covering the areas with large nonlinearities and the machine learning system the more linear regions. This would help in simplifying the implementation as it would minimize the number of rules required for each different radio type. >

Design and implementation of a control system for a deuterium pellet injector

The Oak Ridge National Laboratory is currently developing a deuterium pellet injector for installation on the tokamak fusion test reactor (TFTR). This paper describes the design and development of a stand-alone data acquisition and control system for that device. Major elements of the hardware are an Allen–Bradley PLC 2/30 programmable logic controller, a MicroVAX-II computer using the VMS operating system, CAMAC data acquisition and communication equipment, and special-purpose controllers for temperature and for the sequencing of pellet firing valves. The PLC performs all actual control actions and acquires data pertinent to those actions. The MicroVAX receives the data acquired by the PLC, displays it for the operator, prompts for and processes requests for action from the operator, and informs the PLC of those requests. The primary purpose of this paper is to describe the software operating in the MicroVAX, including the system architecture, major tasks, and ancillary and background tasks.

Universal RS232C cable

Manufacturers of peripherals are inconsistent in their use of male or female connectors on their equipment. Combined with the increasingly common practice of producing data terminal equipment that in some respects is like data communication equipment (to cut the costs of extra null modem cables), this means that it can be very difficult to make two devices communicate over an RS232C serial link. The paper addresses the problems of incompatible male-female D-type connectors and reversed transmit-receive lines for three-wire communication. These ideas could be expanded for the problems associated with incompatible handshake lines.

Computers in data communication

The applications of computers in data-communication equipment and systems are put in the perspective of the evolution, over the past 15 years or so, of data-communication technology. A structural model of device functionality helps define the position of computerised equipment in relation to data-network requirements

Transmultiplexers: Current Trends

With the increasing introduction of digital communication equipment within the existing analogue communication network and the consequent requirement of interconnecting the two, the need for conversion or translation between TDM/FDM and vice-versa is growing.Transmultiplexing (TMX) or the process of translation between FDM and TDM offers interesting application possibilities. The paper defines the Transmultiplex problem, describes the basic methods of Transmultiplexing and the details of design considerations of a 120-channeI TMX system.The paper concludes with a review of the present trends in TMX, like the use of multistage structure of digital filters, development of LSI circuits with single chip arithmetic processor with multiplier capability, the NEC made VLSI (16 bit pipe-line multiplier (MPL)) which can realise any digital signal processor etc.

Research on rural communication and the microcomputer controlled modem and telephone

Rural areas have a high variance in quality of life attributes. Despite positive attributes such as quiet, clean air, woods, lakes, slower pace and other amenities, there are numerous negative attributes stemming from isolation, such as limited numbers of stimulating jobs, reduced access to educational, cultural and entertainment opportunities, reduced peer interaction, and other positive attributes of urban life. Modern communications media, such as telephone, mail, newspapers, magazines, radio and television, have helped, but there is still a lack of rapid, inexpensive, convenient, non-interruptive two-way communication facilities for rural use. Computer controlled telephones promise to remedy this situation in the near future. Microcomputer controlled data communication over telephone lines should produce a major improvement in quality of life in rural areas. This paper describes how this may come about, examines technical and economic problems in the way, and describes research being carried out at North Dakota State University to solve these problems. The work is part of a project called RAIN (Rural Agricultural Information Network) sponsored jointly by the North Dakota State University Agricultural Experiment Station and Cooperative Extension. The research centers on the development of adaptive software that allows a computer running UNIX (Thompson 1974 and Crowley 1978) to login on another computer and run programs there, as if the UNIX system were an ordinary time-sharing user. This capability allows the UNIX system to communicate with computers that are unprepared to communicate with it! In a rural environment where most computers will be owned by individuals, such capabilities are likely to be critical. In the course of the work it has become clear that some of the problems stem from the inadequacies of present data communications equipment, especially telephone interfaces and modems. These are outlined. A conceptual design is sketched for a highly adaptive computer controlled modem that would speed progress in rural data communication. The potential applications and value of such a modem are presented.

Extrapolation Technique for Long Term Bit Error Rate Determination

An extrapolation method is presented for determination of characteristic curves of long term bit error rate (BER) versus signal-to-noise ratio (SNR) for digital communication equipment. The method is to obtain a single reliable data point at a BER of 10-4 or 10-5 and then to draw a theoretically shaped curve through this reference. The technique is validated by both theoretically and experimentally demonstrating that variations of the internal anomalies that contribute to bit errors in digital communications receivers cause the BER curves to shift laterally, but that the curves retain their characteristic shape. Use of this extrapolation method can reduce test time by 3 to 4 orders of magnitude.

Jitter Effects on Bit Error Rate Reexamined

Standard references show the effects of carrier phase jitter on the performance of digital communications equipment as curves of bit error rate versus signal-to-noise ratio for constant values of jitter variance. In any real system, the variance consists of a relatively small constant component and a component which is inversely proportional to signal-to-noise ratio. This correspondence presents revised calculations of bit error rate for a number of values of the constant variance component and the proportionality constant. The resulting curves are shown to agree with experimental results, and are useful for predicting performance of real systems.

A new method for optimum alignment of digital communications equipment

The technique is to perform final adjustments on the equipment while monitoring the bit error rate at a very low signal-to-Gaussian noise ratio. Experimental verification of the method is presented.

Exploration techniques for the evaluation of digital communications equipment (Ph.D. Thesis abstr.)

Exploration techniques for the evaluation of digital communications equipment (Ph.D. Thesis abstr.)

Low-speed data communication and your micro

This paper is a simple introduction to asynchronous data communications with an emphasis on microcomputer applications. Fundamental data transmission concepts are explained and some criteria for selecting data communications equipment (modems, line drivers) are given.

Team Make-Up and Work Allocation at N.V. Kempense Steenkolenmijnen

The allocation of miners to teams, and of teams to production faces, is complicated by the high degree of absenteeism of miners in Belgium. Therefore, the exact knowledge of who is actually present at the beginning of a shift and of the exact skills of those present, enables the foremen and mine captains to constitute their teams before all men go down into the mine in the most effective way possible.This paper describes the system of attendance recording and of displays which the foremen use to constitute their teams and/or to interrogate the personnel data base in order to do so. It shows how the foremen dialogue with the computer, to change the function of a miner within a team, to another team, or the function of a team as a whole.The implementation of the system, data bases, and data communication equipment and procedures, is described. The benefits obtained are presented for each level of the company: foremen and team supervisors, engineers, mine management.

Digital Communications Equipment for Instructional Purposes

The design philosophy and implementation of a low-cost, modular digital communications system are presented. This system is suitable for laboratory experiments in sampling, time-division multiplexing (TDM), aliasing, pulse code modulation (PCM), quantization error, cross-talk, intersymbol interference, bandwidth requirements, noise performance, parity checking, and analog signal reconstruction. The system has been tested in an undergraduate laboratory with no failures and excellent student response. The entire system hardware costs under $500.00 and the system is expandable to include additional modules, both digital and analog.

Electrical Dispatching in France: Status and Trends

Electricité de France is operating for 10 years and continuonsly developing an automatic load dispatching system (one national and five regional centres) using data communication equipment and real time digital computers. At the same time a complete set of off-line predictive computer programmes has been developed.In 1972 - a new system of data processing equipment and software has been implemented to carry out the medium and short range predictive functions on a larger scale and in a more efficient and flexible way. The design of a future real time computer system for the national centre is now in progress.