Showing papers on "Communications system published in 1970"

THE ALOHA SYSTEM: another alternative for computer communications

Abstract: In September 1968 the University of Hawaii began work on a research program to investigate the use of radio communications for computer-computer and console-computer links. In this report we describe a remote-access computer system---THE ALOHA SYSTEM---under development as part of that research program and discuss some advantages of radio communications over conventional wire communications for interactive users of a large computer system. Although THE ALOHA SYSTEM research program is composed of a large number of research projects, in this report we shall be concerned primarily with a novel form of random-access radio communications developed for use within THE ALOHA SYSTEM.

Principles of communication systems

Abstract: From the Publisher: Here is a text for the introduction to principles of communications,the introduction to digital communications,and the introduction to data communications. A clear and readable tutorial style is combined with thorough coverage of both basic and advanced concepts. And the second edition acquaints students with the state of the art,including treatment of topics that have only recently become important and which many available texts ignore. This edition features improved treatment of signal analysis,including representations in signal space,as well as a more complete and modern presentation of random variables and random processes,with illustrative examples to teach detection of signals in noise. There is also a complete discussion of modulation techniques and synchronization and error rate calculation.

Vehicle command and control system

Abstract: A dual frequency ranging and communication system for communicating with and locating mobile vehicles in a multipath environment such as an urban center. This system functions in urban areas for both communication and ranging where line of sight radiation techniques may not properly function. A plurality of remote relay stations are located at points throughout the urban area, each station receiving and transmitting coded digital data and tone signals, the tone signals being used for phase ranging. Each of the vehicles is equipped with a transponder responsive only to the radio signal having a formatted message including the vehicle identification code with a ranging tone suitably impressed thereon. The formatted signal is transmitted from one of the relay stations at a first frequency and picked up by a preselected number of other relay stations as well as by the vehicle transponder. The vehicle transponder in turn generates a reply signal at a second frequency containing message data and a tone signal modulated on the second frequency for use in ranging, all of which signals are processed at a central location.

Mass Communication Systems and Communication Accuracy in Science News Reporting

Abstract: 1 Percy H. Tannenbaum, “Communication of Science Information,” Science, Vol. 140, No. 3567, May 10, 1963, pp. 579-83. Bruce H. Westley and Malcolm S. MacLean Jr.. “A Conceptual Model for Communications Research,” JOURNALISM QUARTERLY, 34:31-8 (Winter 1957). 3 This definition is comparable to the one offered by Mehrabian and Reed: “Communication accuracy is defined as the degree of correspondence between the referents decoded, or inferred, from a set of communication behaviors by an addressee and the referents encoded, or represented, in those communication behaviors by the communicator.” Albert Mehrabian and Henry Reed, “Some Determinants of Communication Accuracy,” Psychology Bulletin, Vol. 70, No. 5, 1968, pp. 365-81. * Hillier Krieghbaum, ed., When Doctors Meet Reporters (New York: New York University Press, 1957), Hillier Krieghbaum, Science and the Mass Media (New York: New York University Press, 1967). p. 162ff.; David Warren Burkett, Writing Science News for the Mass Media (Houston: Gulf Publishing Co., 1965). subsystem, a channel or gatekeeper subsystem, and an audience subsystem.2 Our intent is to study the extent to which certain specified characteristics of the source and channel subsystems are associated with one criterion of communicative performance. The criterion under study is communication accuracy, defined as the extent to which a message produces agreement between source and recei~er .~ Communication accuracy is studied here in the context of science news reporting. Scientists have criticized mass media sharply for inaccuracies, which are assumed by them to result from sensationalism, from quoting out of context and from media practices that sometimes take editing and display treatment out of the reporter’s hands.4 A systems perspective of mass communication is fruitful in that it moves away from the idea of a message forcing its way through from event to final audience. Instead, it conceives of a disseminated message as an outcome, or

Traffic Capacity of Three Types of Common-User Mobile Radio Communication Systems

Abstract: The traffic-carrying capability of three types of common-user mobile radio systems are derived and compared; they are also compared with a private-user system. The systems considered make use of multichannel capability for mobile units or a dispersed array of base stations, or both.

Optimal Reliability of a Complex System

Abstract: In a complex system where the redundant units cannot be reduced to a purely parallel or series configuration, the reliability is obtained by using Bayes' theorem. A mathematical model is formulated for the reliability of a system with nonlinear constraints. The system reliability is optimized based on the model and the solution is obtained by using the sequential unconstrained minimization technique (SUMT). This method is an efficient method for solving this type of problem. Two life support systems, one is the communication system of a two-man space capsule and another is a high-pressure oxygen supply system in a space capsule, have been identified to have the complex system configuration treated in this work.

Organizational Communications Systems and the Decision Process

Abstract: The emergence and solution of organizational problems are examined from the framework of the communications system. A general model is developed based on the information-processing activities of the individual members of a communications network. The model describes the problem-solving process as a sequence of five stages: problem recognition, identification procedures, information acquisition and integration, definition of constraint set, and comparison and adaptation. The relations among the critical variables of the model are then specified in a series of propositions. The main purpose of the model, as exemplified in the propositions, is to provide a testable framework for the empirical analysis of the decision process in organizations.

Communications system for alphanumeric information employing audio tone signalling

Abstract: A communications system for exchanging alphanumeric information between remote stations, employing station apparatus (e.g., modified typewriters) capable of generating and responding to an audio tone code. The system is compatible with use of a push-button telephone instrument as an alternative sending station.

Demand access digital-communications system

Abstract: This disclosure relates to a multiparty data-transmission system in which a central location controls the communication traffic in a transmission loop while at the same time permitting remote locations to independently request transmission privileges or ''''demand access'''' to the communications loop without interference or message overlap either with demand access requests originating at other remote locations or with other data which may be present on the transmission line, whether destined to or from the central location.

Information transmission, modulation, and noise : a unified approach to communication systems

Abstract: Information transmission, modulation, and noise: a unified approach to communication systems , Information transmission, modulation, and noise: a unified approach to communication systems , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Portable traffic control system with television monitoring

Abstract: A portable, electronic, vehicular traffic control system consisting of a central control console, telemetry links and numerous, remote flagging units. The remote flagging units are located at the traffic thresholds to a restricted zone and relay traffic entrance orders from the central control console thereby allowing the remote control of the ingress and egress of vehicles into that zone. The remote flagging units contain remotely operated traffic signal lights, a communications system, mechanical and electrical traffic passage sensors and a closed circuit television camera. The system is primarily adapted for the control of vehicular traffic within a control zone where portions are visually obscured.

Reliability of quantum-mechanical communication systems

Abstract: We are concerned with the detection of a set of M messages that are transmitted over a channel disturbed by chaotic thermal noise when quantum effects in the communication systems are taken into account. Our attention is restricted to the special case in which the density operators specifying the state of the received field are commutative. In particular, the performance of two special communication systems is evaluated. For a system in which orthogonal signals with known amplitudes and random phases are transmitted over an additive white Gaussian channel, the structure of an optimum receiver is found. Expressions for the system reliability function and channel capacity are derived. For a system in which orthogonal signals are transmitted over a Rayleigh fading channel, the optimum performance is obtained. The optimum degree of diversity for an equal-strength diversity system is found numerically as a function of the average thermal-noise energy and information rate.

Use of control words to change configuration and operating mode of a data communication system

Abstract: A data communication system comprising a processor, a memory, a communications controller and a plurality of terminal devices utilizes control words to select the configuration and to select the operating mode of the communication system. This system uses peripheral control words stored in memory to select the number of bits in message characters which may be used in the data communication system, to select the baud rate of the message which is received and to select a synchronous or asynchronous mode of transmission.

Analysis of a System of Mutually Synchronized Oscillators

Abstract: An analysis of the performance of a synchronous digital communications system in which the clock rate of each station is established as the average of the clock rates of all incoming signals to each station is presented. Using both-end control, the system frequency is the average of the free-running frequencies of the phase locked oscillators, weighted by the number of inputs to each station. In single-end control, the frequency is a similar average plus a term, which is a function of changes in transmission path delay. Rules are derived defining how a transmision path delay change will be reflected in changes of total phase difference at each transmission path terminal. These phase changes reflect requirements for elastic storage of data at each transmission path termination. The dynamic stability of a simple two station network is analyzed mathematically. A subsequent technical paper [7] will report on the extensive analysis of the dynamic behavior of various system configurations using a computer simulation of the time history response to various perturbations.

Multichannel communication system

Abstract: Method of communicating in a multichannel communication system especially useful with high speed and low speed devices included in the system. One or more channels or subchannels are provided and controlled for addressing devices and transmitting commands, other channels and subchannels are assigned for the transmission of volumes of data. A poll-bid-grant routine is employed in facilitating the address and command channels, and queuing means is provided in assigning the working channels.

Terminal message monitor

Abstract: A monitoring system to permit a first terminal computer on line with a central processor to monitor message traffic from the central processor to other terminals concatenated or in a multidrop mode with the first. When messages are sent through a modem to a plurality of terminal computers in a concatenated configuration a verification of message traffic is provided. Logic circuitry is provided for monitoring both transmitted and received information and providing a printout of the communication line information. The monitoring terminal, regardless of the address of the message, will store the communication line information in its memory and print out the stored information to provide a positive communication system check.

Radio control and repeater communication system

Abstract: A communications system particularly adapted for use by police officers and including a portable transceiver, first and second mobile transceivers, and a recording unit. Code generator means is provided which is operatively associated with the portable transceiver. Decoding and switching means is also provided which is controlled by the code generator means and which selectively controls the first and second mobile transceivers and the recording unit. Additional auxiliary safety units may also be provided which are controlled by the code generator means and the decoding and switching means.

Pulse laser communication system

Abstract: A wide band tactical pulsed laser communication system capable of operating at high bit rates wherein an incoming digital data stream, as for example, a multi-channel time division multiplexed pulse code modulated signal, first is converted into a pulse position modulated signal and the corresponding pulse position modulated pulses of each channel are applied by way of appropriate gating circuitry in sequence to an array of injection lasers, each capable of generating optical signals at relatively high peak power.

Multiplex communication system for transmitting television and facsimile signals

Abstract: A multiplex communications system is described in which a continuous signal having a relatively narrow frequency band such as a facsimile signal, may be superimposed on a signal having periodic idle intervals such as a television signal.

Switching voice and data communications simultaneously over a common path

Abstract: An integrated voice-and-data communication system is disclosed wherein voice-and-data channels are frequency multiplexed and switched through a wideband switching network on a common fourwire path. When the switching connection is being established, coupler-and-detector circuits couple the voice channel, demultiplexed to baseband, to the network so that network control signals in the voice channel can be employed to establish the connection. The control signals, however, are isolated by the coupler-and-detector circuits from the outgoing data channel. When the switching connection has been established, the couplerand-detector circuits disconnect the baseband voice channel and connect frequency multiplexed voice and data signals to the common four-wire path through the network.

Secondary phase modulated communications service via am broadcast stations

Abstract: A SECONDARY COMMUNICATIONS SYSTEM FOR USE WITH AM BROADCAST STATIONS EMPLOYS ENCODING PREDEFINED MESAAGE WHICH MAY BE INITIATED BY DIALING PREDETERMINED DECIMAL DIGITS OR INITIATNG TOUCH-TONE SEQUENCES IN THE TELEPHONE SYSEM, CONVERTING THESE DIGITS TO A PREDETERMINED BINARY VOFR SEQUENCE OR BINARY "WORD," AND TRANSMITTING THE CODE WORD BY A NON-INTERFERING PHASE MODULATION OF THE AM BROADCAST STATION CARRIER WAYS. SUBSCRIBER RECEIVERS, FIXED-TURNED TO THE BROADCAST STATION CARRIER, ARE EQUIPPED WITH SIMPLE CODE RECOGNITION MEANS WHICH IN RESPONSE TO RECEPTION OF ONE OR MORE PREASSIGNED CODED "WORDS," ACTIVATE ASSOCIATED INDICATORS TO VISUALLY OR AUDIBLY ANNUNCIATE PREDETERMINED MESSAGES TO THE SUBSCRIBER.

System for the transmission of information to a vehicle on rails

Abstract: A system for transmitting additional information throughout a railroad communication system that uses unmodulated signals representing signalling information transmitted through the rails by superimposing pulses having pulse repetition periods representing additional information on the unmodulated signals. A vehicle is provided with means for picking up the signals from the rails, decoding the pulse signals and displaying the additional information.

Satellite communications system

Abstract: A ground-air communications system is disclosed that includes ground station processors, aircraft, and satellite borne repeaters. Satellite weight and power economies are achieved by scanning with repeater antennas. The preferred embodiment utilizes a phased array antenna having its antenna elements and amplifiers disposed in the satellite borne repeater and its phase shifting and modulating components disposed in the ground station processor. Phase shifted modulated carrier waves are translated in frequency prior to transmission from the ground station processor and are retranslated to their original frequencies by the repeater. Means are provided to lock transmitted and received carrier waves in phase and frequency.

The Effect of Loop Stress on the Performance of Phase-Coherent Communication Systems

Abstract: In phase-coherent communication systems which use phase-locked loops to provide synchronization of the data detector, the communications engineer is frequently faced with the problem of determining the effects which noisy timing has upon detection efficiency. This paper is concerned with determining these effects when second-order phase-locked loops, operating in the presence of frequency detuning, are used as a means of providing phase synchronization. The results are also applicable to the problem of establishing noisy reference losses in a broad class of coherent PCM telemetry systems, e.g., PCM/PSK/PM. Also presented are results which can be used to determine steady-state statistical dynamics of second-order loops.

Filtered pulse width modulation communication system

Abstract: A communications system provides a practical means for transmitting a plurality of input information signals, such as television signals, over a single transmitter. The signals are combined or multiplexed to form a composite signal which serves to modulate an initial carrier signal. That modulated signal in turn pulse modulates a transmitter carrier to produce a pulse width modulated signal that contains all the essential information of the input signals.

Instrumentation Problems Encountered Making Man-Made Electromagnetic Noise Measurements for Predicting Communication System Performance

Abstract: One of the factors involved in communication system performance is the electromagnetic interference environment (broad-band radiated electronic noise). Attempts are often made to use commercially available radio-frequency interference field intensity meters for these measurements. Measurements made with these instruments are of limited use since detector functions like peak and quasi-peak are not useful parameters in statistical communication theory. It is recommended, instead, that rms voltage be measured simultaneously with average voltage and average logarithm of the voltage. These latter three parameters may be used to infer the amplitude probability distribution, which is a required statistic for predicting the performance of communication systems. Data are given on dynamic range requirements for accurate measurement of these statistical parameters for a given man-made noise sample. An Appendix contains several hardware solutions to the problems posed in this paper.

A one-gigabit-per-second optical PCM communications system

Abstract: An optical communications system is described which is capable of transmission and detection of 1-Gbċs-1pulse-code modulation (PCM) word patterns. Modulation of an argon laser beam is obtained with a lithium tantalate (LiTaO 3 ) modulator rod using a traveling-wave interaction. The high-speed electrical modulation signal is obtained by a multiplexing of four separate information channels.