Showing papers on "Communications system published in 1968"

Communication Systems

Abstract: The major in communication systems combines the theoretical focus of communication studies with the practical skills of information technology, resulting in a program that prepares students to perform on the cutting edge of modern media systems. This program is flexible, emphasizing the interdisciplinary study and project work that are critical in a rapidly-changing field. With a communications systems background, students can enter the dynamic fields of the information industry, media and communication, management, public policy, and a variety of other corporate and non-profit areas.

A Method of Using Audio Signal-to-Noise Measurements to Obtain Criterion Contours for the Probability Scoring Model for Scoring Voice Communications Reception

Abstract: The Probability Scoring Model used for electromagnetic compatibility analysis considers the probability of correct information transfer, written as P(R+), to determine link quality. Experience has shown that the smallest value of articulation index (AI) which consistently provides correct information transfer in the presence of normal language configuration is 0.7 in a scale ranging from 0 to 1, and that the largest value of AI for a nonuseful link is 0.3. AI has been shown to be a function of the link description (receiver/transmitter type and frequency), the interferer description (type and frequency), and the strength of the desired and interfering signal, SRF and I, respectively; hence, for any given communications system of such configuration that the link and interferer descriptions and frequencies are known, AI can be established as a function of SRF and I. Determination of AI requires the use of the Voice Interference Analysis System (VIAS), test equipment which is costly and not readily available to all potential users of the Electromagnetic Environmental Test Facility (EMETF) Probability Scoring Model. However, receiver audio signal-to-noise ratio (S/N) can be shown to be a function of the same variables. A nonlinear regression analysis line has been established by relating empirical audio S/N values to AI for AM, FM, and SSB link and interferer modulation combinations. Typical military communications sets were used. As a result of this analysis, the criterion values of 0.3 and 0.

Elements of Detection and Signal Design

Abstract: Due to a steady flow of requests over several years, Springer-Verlag now provides a corrected reprint of this text. It is designed to serve as a text for a first semester graduate level course for students in digital communication systems. As a pre requisite, it is presumed that the reader has an understanding of basic probability and stochastic processes. The treatment of digital communications in this book is intended to serve as an introduction to the subject. Part one is a development of the elements of statistical communication theory and radar detection. The text begins with a general model of a communication system which is extensively developed and the performance analyses of various conventional systems. The first part also serves as introductory material for the second part of the text which is a comprehensive study of the theory of transmitter optimization for coherent and noncoherent digital commu nication systems, that is, the theory of signal design."

Terminals for a high-speed optical pulse code modulation communication system: II. Optical multiplexing and demultiplexing

Abstract: Techniques are described for optically multiplexing and demultiplexing individual pulse code modulation channels in order to develop the terminal capability for a high-capacity optical communication system. It is shown that, using these techniques, an information capacity in excess of 1010bit/s can be achieved on the output beam of a single laser.

Performance Monitor Techniques for Digital Receivers Based on Extrapolation of Error Rate

Abstract: There is a need in many digital communication systems to estimate the current digital error rate of the receiver without the use of special transmissions and without interrupting traffic flow. Devices for performing this function have been termed performance monitor units (PMU). As an element of an adaptive communication system, the PMU could be used to determine when adaptive change is needed and, by comparing the error rates which would result from the various available choices of adaptation, to select the best change to be made at any time. This paper describes a PMU technique which is applicable to a wide class of digital modulation methods. Details are given for the cases of noncoherent frequency shift keying (FSK), differentially coherent phase shift keying (PSK), and coherent PSK receivers operating over a fading channel.

Hospital communication system having provision for connecting patient with nearest nurse-occupied station

Abstract: A communication system adapted to find the closest available station to the calling station. The attempt to reach an available station out of a plurality of stations is accomplished by test means which test the availability of the plurality of stations so that they are selected in an order depending on the identity of the calling stations.

Communication multiplexer for online data transmission

Abstract: A communications system comprised of a multiplexer and a plurality of unit adapters for transferring data characters between a high speed digital computer and a plurality of relatively low speed data transmission devices operating online with the computer. A scanner circuit included in the multiplexer provides for sequential servicing, in turn, each of the unit adapters for transferring the data characters. The scanner circuit may be interrupted at any time such that the computer can transfer a function selector character to any of the unit adapters, the character determining whether the unit adapter will thereafter operate in an input or output mode. Monitor and control logic in each unit adapter has circuitry therein for detecting an overload condition resulting from online operation of the computer system during an input mode of operation, thereby detecting any loss of data in its real time operation and enabling the computer to monitor the circuits to correct the loss of data caused by the overload condition.

Subcarrier Tracking Methods and Communication System Design

Abstract: It is advantageous from power considerations to allow suppressed-carrier coherently-detected communications. Two methods for generating a coherent reference for the demodulation of a suppressed-carrier signal, namely, the squaring loop and the mathematically equivalent Costas loop, are analyzed, including at some points the effects of VCO noise and initial frequency detuning. The steady-state phase error probability distribution is presented, as is the expected time to first loss of lock in the first-order loop. Probabilities of error in coded or uncoded telemetry systems which use a squaring loop to generate a coherent subcarrier reference are investigated, allowing appropriate values of system parameters to be chosen by system designers.

Taxonomy of Communications

Abstract: Communication is the vehicle of control. A communication system provides the means with which information, statements, views and instructions are transmitted through an organisation. Although we often speak of the ‘flow’ of communications, in fact this flow consists of a series of discrete messages of different length, form or content. These messages are transmitted through certain channels (or ‘lines of communication’), which comprise the communication network; some of these channels are heavily congested, others are not. Each message is generated by a transmitter (an individual, a group, a department, a computer) to a receiver or several receivers. It may induce action or provoke a reaction in the form of a counter-message, or both. Every individual or department in an organisation acts as a transmitter and a receiver (though not for the same messages). Some individuals transmit more than they receive, others receive more than they transmit, depending on their role and function in the organisation. Messages in a communication network, then, are a manifestation of interactions in the system and of the control mechanisms at work.

Facsimile system having incremental stepping paper drive assembly

Abstract: A facsimile communication system including an incremental stepping paper drive assembly for advancing a document or the like past a scanning station. In combination with a binary digit encoder and buffer storage unit, the incremental stepping paper drive assembly is activated and interrupted in accordance with the amount of information detected, encoded and stored in order to maintain maximum information transmission over a limited bandwidth transmission medium.

Emergency warning and identification apparatus for two-way radio communication system

Abstract: Apparatus for audio communications and other such systems are disclosed in which a plurality of portable transceivers each generate a signal having audio components and a unique combination of continuous wave frequency components, for transmission to a remote station. Manual operation of a multiposition switch in each transceiver permits indicating the existence of an emergency or nonemergency transmit condition by controlling the duration of one of the continuous wave frequency components. The transmitted signal is received at the remote station where circuitry filters and detects the unique combination of continuous wave frequency components to identify the transceiver and also determines the duration of the controllable duration component to indicate the particular transceiver''s condition. Other embodiments are also covered.

Audio visual information processing and communication system

Abstract: A visual communication system comprising a telephone switching system, a plurality of video telephone stations each connected to the system, and a data storage and computing machine also connected to the system via a data translator. A connection from any video telephone station may be established to any other station or to the data storage and computing machine by ''''dialing'''' or keying certain codes on a telephone set of the video station. After establishing a connection to the data storage and computing machine, instructions to the machine are keyed on the telephone set and transmitted via the system and data translator to the machine. In response thereto, the machine generates output signals which are applied to the data translator and there converted to video signals to be transmitted via the system to the originating station for display on the station''s video set.

The digital filter and speech communication

Abstract: The study of speech communication and speech processing systems by simulation on a digital computer, and the design and physical implementation of these systems with discrete components, require a detailed knowledge of the elements known as digital filters. Following a definition of the digital filter, the different areas in which digital filters have been used in speech research and communication are explored. The basic theory relating to the design and application of digital filters is reviewed. Attention is given not only to the use of a general purpose computer to mechanize the simulation but also to the design of special purpose hardware to realize the digital filter as either an actual communication system component or as a laboratory research element. Following a discussion of several of the numerical problems that can arise in the design and utilization of digital filters, the paper concludes with a cursory look at some of the advantages and disadvantages of the use of digital filters in speech processing systems.

Performance of Phase-Coherent Receivers Preceded by Bandpass Limiters

Abstract: In phase-coherent communication systems, where bandpass limiters precede the radio frequency (RF) carrier tracking loop, it is of interest to understand how the noisy RF carrier reference effects system performance. This paper characterizes a model probability distribution for the RF phase error and uses this to predict the performance of phase-shifted keyed and differentially coherent systems. The theory developed is directly applicable to the Mariner- and Pioneer-type communication systems. For these systems two physical situations are considered: 1) system performance when the phase error is constant over the duration of one bit, and 2) system performance when the phase error is allowed to vary over the duration of one bit.

Air-Ground, Ground-Air Communications Using Pseudo-Noise Through a Satellite

Abstract: An air-ground, ground-air communications system that utilizes a satellite and a central control facility is described. The double-hop pseudo-noise system advantages, including equal sharing of power, use of frequency translating repeaters, optimum multipath rejection, and acceptable power densities on the ground are discussed. The selection of code division is presented together with an analysis of signal-to-noise ratios with a varied input. Modulation schemes are discussed, pro and con, and the effective radiated power versus antenna sizes for several combinations are analyzed.

Asynchronous communications system

Abstract: An asynchronous communication system for mobile and fixed radio communications which includes a plurality of subscriber''s stations, a plurality of trunk stations and a central station, in which the subscriber''s speech and associated audible signals are first modulated into three-level delta modulation pulses, then coded into a frequency-time address assigned to those subscribers, transmitted by radio, received by one of the nearby trunk stations, address decoded first to identify the subscriber, then demodulated to voice band signals, transmitted to the central office having stored program control features, switched in accordance with the dialed information to establish connection to the other subscriber''s stations, transmitted to another of the trunk stations nearby the other subscriber''s stations, first modulated into three-level delta modulation, then coded into address codes assigned to the other subscriber''s stations, transmitted by radio, received by the other subscriber''s stations by means of address codes, then demodulated into speech and sent to other subscribers.

Information theory and Cybernetics

Abstract: Following a review of terms used in information theory, conventional communications systems are examined. Functional models that lead to a statistical impulse generator are developed for a neuron and a fish. The problems of information generation, reduction, and storage in man are considered. The concept of bidirectional communication is advanced where the receiver as well as the transmitter is active and the theory of bidirectional communication is shown to be a generalization of Shannon's information theory.

Sampled-data control of high-speed trains,

Abstract: The report deals with the control of the positions and velocities of high-speed vehicles in a single guideway. It is assumed that each and every train measures its position and velocity every T seconds. The appropriate accelerations or decelerations to be applied to each vehicle are constrained to be constant during the sampling interval. Through the use of a control costs functional, which penalizes the system for any deviations from the desired headway and velocity, the required control accelerations and decelerations are obtained by deriving the system equations in discrete-time and, through the use of available results in the theory of discrete optimal control, the optimal linear time-invariant sampled-data feedback control system is determined. The general results, as well as the general purpose digital computer programs, are presented and are used to study the effect of changing the sampling time T upon the control-system performance. Since, in general, the cost of the communication system (in terms of required channel capacity, bandwidth, etc.) decreases with increasing values of the sampling time, the system designer has the capability of conducting trade-off studies involving the deterioration of the control system performance vs. the decrease in the cost of communication as the sampling time is increased. (Author)

Jamming Susceptibility

Abstract: Generalized equations are developed to evaluate the effects of interference upon communications systems. Interference may be due to natural causes and accidental or sophisticated jamming. One- and two-way communication systems are considered. The equations are applicable to near and deep space communication links as well as radar in both friendly and unfriendly environments. Both mainlobe and sidelobe reception and collocated and diversely located interference and signal sources may be analyzed. A practical discussion for each of the variables, as well as a sample solution, is included.

Radiotelephone communication system

Abstract: This system provides for automatic communications between the subscribers of public telephone networks and mobile sets over a large land area (or along a highway) covered by a plurality of radiotelephone exchanges. A call from a network exchange for a mobile is first transmitted to all these radio exchanges by a service-bus line. When one of the radio exchanges reaches the mobile in its area, it signals itself to the calling exchange and only then the calling exchange proceeds with the extension of the telephone toll connection to that radio exchange.

Data set adapter

Abstract: A data set adapter for coupling a facsimile transmission unit to a data set for use in transmitting facsimile information between locations over a direct-distance-dialing common carrier telephone line. By the means of logic and timing circuits, interfacing is accomplished between a facsimile communication unit and a data set coupled to the transmission line terminal. With such a data set adapter the facsimile communication system can be operated in a manual or automatic mode for attended or unattended operation.