Showing papers on "Communications system published in 1973"

Research toward optical-fiber transmission systems

Abstract: The fundementals of optical fiber transmission systems including the fiber transmission medium, sources suitable for use as a carrier, modulation and detection techniques, and some system design considerations are reviewed. The advent of low-loss optical fibers brings new dimensions to optical communication prospects. Fibers may soon be used much as wire pairs of coaxial cable are now used in communication systems. Transmission losses as low as 2 dB/km have been achieved. Experimental repeaters for fiber systems with 10-9error rate at about 300-Mb/s pulse rate have been reported. Fiber cabling and splicing are among the problems requiring new ideas in order to make feasible an operable system.

Digital communications system

Abstract: A time division multiple access communications system which provides communication linkages between remote subscriber terminals. The communications system comprises a plurality of remote terminals interconnected by a common wideband signal path and a central control terminal. A repetitive framed message signal format is maintained by the control terminal to provide a predetermined average time required for access to the signal path for each remote terminal. Communication links over the channel between remote terminals are further provided, wherein the links comprise adaptively allocated portions of the channel spectrum in response to request signals from the various remote terminals.

Electronic bilateral communication system for commercial and supplementary video and digital signaling

Abstract: A bilateral cable communications system - as for a lodging facility, distributes commercial and supplementary video programs from common equipment to spaced subscriber stations located, for example, in each hotel-motel room. Heterodyne converter apparatus is included at each station for viewing the supplementary programing on a standard television receiver.

Bilateral communications system for distributing commerical and premium video signaling on an accountable basis

Abstract: A bilateral communications system, as for CATV application, distributes commercially available and premium video programming on a subscriber demand--directly accountable basis. At least the premium video programming is impressed on the cable in a frequency band and/or format not recoverable by a standard television receiver, absent receipt at a particular subscriber location of a reception-authorizing message from the system head end. A central processor at the system head end sequentially polls cable subscribers under stored program control, permitting bilateral digital communications between the subscriber and the head end.

System for communication and navigation

Abstract: A radio navigation and digital communication system is used for the transmission of navigation modulation and digital data. A modulation locked loop, which may be constructed with three channels, is used to develop synchronization signals for the digital data signals and to ensure a high level of communication reliability and accuracy of navigation measurement using pseudo random navigation code.

Emergency communication system

Abstract: An emergency communication system used by stranded motorists to summon help when travelling on toll roads or other limited access highways The emergency communication system comprises a portable, self-powered, hand-held transceiver set which transmits coded distress signals and directional signals, when activated, and cycles until reception of an answer back signal The signals or messages from the portable transceiver are transmitted at incrementally increasing power levels to a single or a plurality of roadside relay stations spaced strategically along a limited access highway or toll road The relay stations retransmit the signals to a terminal station which has means to decode the signals and determine the location of the repeater station nearest to the stranded motorist The terminal station also has means for displaying the location of the relay station with the information derived from the decoded signal, and means for generating an answer back signal which is transmitted via the roadside relay station to the portable handset

Facsimile communication system

Abstract: A facsimile communication system is described wherein the transmission of data between a transmitting and receiving apparatus over a voice quality transmission medium is accomplished by providing spectrum compressing encoding of a video signal and by frequency modulation and vestigial sideband transmission of the frequency modulated video signal. In a principal mode of operation, the transmission of video data is preceded by receiver alerting, equalizing, synchronizing and scan pitch signals for respectively shifting the receiver from a standby to an operating status, for connecting distortions in the transmission medium, for causing line by line synchronization between sending and receiving units and for establishing the scanning pitch at the printing unit. A transceiving unit of the system when operating as a receiver in the principal mode generates reverse signalling information for acknowledging a ready to receive status at the initiation of communication and a printer ready status for enabling the transmission of video information. A high degree of reliability in interaction between the sending and receiving units is thereby imparted to the system and facilitates scanning and electrostatographic printing techniques. The transceiving system of the invention is further adapted for operating in optional modes including an automatic document feeding mode, an unattended sending mode and a printer polling mode. The communication system is further adapted to operate with existing facsimile systems which transmit at relatively lower document transmission rates, exhibit different signal formats and have different internal controlling.

Configuration control circuit for control and maintenance complex of digital communications system

Abstract: A digital communications system includes duplicate copies of a central processor, instruction storage, process storage and peripheral controllers, together with duplicate copies of buses communicating the central processors with each of the other units. Each central processor includes a configuration control circuit which generates internal signals for determining the various bus configurations.

Satellite communications link monitor

Abstract: In satellite relay communication systems, apparatus for automatically measuring and indicating in real time, the absolute bit error rate introduced in a transmitted bit stream by the data link. In an exclusive test mode, a selectively predetermined random or fixed code sequence is transmitted over the link. At a receiver site, the identical, reference code sequence is generated for comparison, on a bit-by-bit basis, with the transmitted sequence after bit and code synchronization are completed.

Mobile computer terminal and system

Abstract: The disclosed two-way mobile digital communications system includes a plurality of remote terminal units, a programmable terminal controller operable to manipulate stored data from a plurality of local or remote computer files on command from any or all of the mobile terminal units in operational locations, and a network for communication between the central data processing station and the mobile terminal units. A high speed audio phase shift keyed transmission method has absolute phase referencing. Each of the remote terminals include a low-voltage solid state plasma screen which displays dot matrix characters. The buffer memory therein allows uninterrupted message composition and incoming message storage which the terminal controller insures the compatability of the remote terminal units with existing data bases and controls data transfer between the terminal units and for between the units and the computer data base.

Data communication system

Abstract: A data communication system is disclosed which is particularly suited for ''''in-house'''' or localized on-line data transactions. The system includes a central communication processing unit, such as a digital computer, coupled to a plurality of remotely located units through a single, wide bandwidth, bidirectional communication line, such as a coaxial cable. The system includes interface logic for coupling a large number of remote units to the communication line in a ''''daisy chain'''' configuration, thereby permitting all remote units to have simultaneous access to the single communication line. An addressing scheme is provided to allow selective data transactions to be carried between the central communication processing unit and individual remote units.

Application of Acoustic Surface-Wave Technology to Spread Spectrum Communications

Abstract: Spread spectrum transmission is being proposed for an increasing number of digital communication, navigation, and RADAR systems. One of the reasons is the simplicity and availability of surface-wave devices (SWD) for performing the necessary signal generation and processing. The properties of spread spectrum signals, the operation of SWD's, and their advantages and limitations when used in communication systems are discussed. Spread spectrum terminology and basic concepts are defined in terms common to both systems engineers and device designers.

Time division multiple access communication system for status monitoring

Abstract: A communication system wherein data at a plurality of different zones is transmitted to a control panel at a central location over a common communication line including an address pulse generator at the central location which transmits a programmed number of address pulses over the communication line to effect sequential enabling of zone status monitors at each of the zones, each of which obtains power from the address pulses, and provides frequency signals representing a normal or off-normal condition for a variable for transmission over the communication line to the central location, and a receiver at the central location which decodes and processes the responses. A number of zone status monitors may be divided into groups with each group transmitting data to a central location over an area address pulse generator which is connected to the communication line, or multiple communication lines may be monitored from a master control panel through the use of slave control panels.

Time division multiplex exchange

Abstract: A decentralized time division multiplex communication system having independent exchange modules arranged to individually set up connections without the need of central control. Commonality of hardware is limited to a simple interconnection unit, and a clock allowing synchronization of all modules. Each exchange module, with its associated group of terminals, is arranged to form a time division multiplex system of first order. The exchange modules, together with the interconnection unit, are arranged to form a super-multiplex system, i.e., a time division multiplex system of second order. All bus line time division multiplex channels of all exchange modules are interspersed on the interconnection unit. To each of these bus line channels, a time slot is permanently assigned in the super-multiplex time frame.

A Speech Predictive Encoding Communication System for Multichannel Telephony

Abstract: This paper describes a speech predictive encoding communications (SPEC) system that is designed to accommodate the traffic of N PCM telephone trunks in the capacity of N/2 PCM telephone channels. The system exploits the statistics of multichannel voice communication in a manner significantly different from the technique employed in the well-known time-assignment speech interpolation (TASI) system. Specifically, the SPEC system operates at the transmitter by removing redundant speech samples during talk bursts as well as during silence intervals. The receiver remembers the most recent sample transmitted through each channel. As long as a new sample is not transmitted, the receiver simply repeats the sample value stored in its memory. Each sample from each incoming trunk is examined every 125 μs to determine which samples must be transmitted and which are redundant. Because the SPEC system operates at this high speed and predicts redundant or missing samples at the receiver, it does not produce the speech clipping effects typical of TASI-like systems. Any voice-quality degradation due to increased call load and/or speech activity is manifested as an increase in noise power. The subjective result is a graceful degradation that is virtually imperceptible to the listener.

Electronic communications system for supplementary video program distribution

Abstract: A one-way cable communications system -- as for a lodging facility, distributes commercial and supplementary video programming from common equipment to spaced subscriber stations located, for example, in each hotel-motel room. Heterodyne converter apparatus is included at each station for viewing the supplementary programming on a standard television receiver. The system includes common address and command transmitting, and room terminal receiving equipment to control the video reception mode for the several room terminals.

Method of ultrasonic data communication and apparatus for carrying out the method

Abstract: In an ultrasonic data communication system, each datum is represented by a specific ultrasonic wave signal composed of plural frequency components arranged according to a specific one of predetermined frequency permutations so that the data transmission time can be considerably reduced without the influence of reverberation.

Broadband cable communications system

Abstract: Continuously operating injection and carrier oscillators attached to a broadband cable with means for data modulating the carrier oscillator and a transmitter/receiver attached to the cable remotely from the carrier oscillator and including means for picking off the carrier frequency and means for picking off the injection frequency and mixing the two to provide an IF signal which may be demodulated to retrieve the data or modulated by data and transmitted back along the cable for two-way communications.

Pseudo-noise test set for communication system evaluation

Abstract: A test set for communications systems includes a pseudo-noise sequence generator providing a test signal which is fed to a pair of signal channels The first channel includes a spectrum shaping filter and a conditioning amplifier The second channel includes a variable delay circuit, a spectrum shaping filter matched to the first filter, and an amplifier The output of the first channel is applied to the system under test The output of the system and the output of the second channel are compared to determine the degree of distortion suffered by the test signal due to the communications system

Automatic line transfer system and method for a communications system

Abstract: In a communications system such as a telephone system, an automatic line transfer system for a failed line includes a method and apparatus for looping around the failed line by a protection line and locating a remote failure by cross connecting the failed line to the preceding protection line and thereafter interrogating from the command office. The equipment determines whether a failed line is good again and will accept a remote manual reset.

Fascimile communication system

Abstract: A facsimile communication system is described wherein the transmission of data between a transmitting and receiving apparatus over a voice quality transmission medium is accomplished by providing spectrum compressing encoding of a video signal and by frequency modulation and vestigial sideband transmission of the frequency modulated video signal. In a principal mode of operation, the transmission of video data is preceded by receiver alerting, equalizing, synchronizing and scan pitch signals for respectively shifting the receiver from a standby to an operating status, for correcting distortions in the transmission medium, for causing line by line synchronization between sending and receiving units and for establishing the scanning pitch at the printing unit. A transceiving unit of the system when operating as a receiver in the principal mode generates reverse signalling information for acknowledging a ready to receive status at the initiation of communication and a printer ready status for enabling the transmission of video information. A high degree of reliability in interaction between the sending and receiving units is thereby imparted to the system and facilitates scanning and electrostatographic printing techniques. The transceiving system of the invention is further adapted for operating in optional modes including an automatic document feeding mode, an unattended sending mode and a printer polling mode. The communication system is further adapted to operate with existing facsimile systems which transmit at relatively lower document transmission rates, exhibit different signal formats and have different internal controlling.

A Novel TV Add-On Data Communication System

Abstract: This paper presents a description of the theory and operation of a new television add-on data communication system which does not utilize the vertical interval. The basic add-on signalling technique allows more efficient utilization of the television spectrum. Added information, producing no perceptible interference with either the picture, or ancillary and test signals, is sent through a television channel along with the standard video signal. Novel techniques to significantly reduce errors in the data channel will be described. Several interesting systems utilizing this new signalling method have been built and will be described in this paper.

The effects of multiplexing on a computer-communications system

Abstract: A study is made of the way in which asynchronous time division multiplexing changes the stochastic nature of the arrival process from a user to the computer and, consequently, affects the performance of a time-shared computer-communications system. It is concluded that while, for certain values of system parameters, there is noticeable improvement in the performance of the computer (model), in the sense that time-shared scheduling delays are reduced, these improvements are offset by the transmission delays imposed by multiplexing so that there may be little or no change in the computer-communications system performance.Analytical and simulation results are based on the model of the computer-communications system being an M/D/1 queue (the multiplexor) in tandem with a single exponential server (the computer). Analytical results include a general description of the output process of an M/D/1 queue and the conditions under which this output process is approximately Poisson.

Block coded communication system

Abstract: A noisy forward communication channel is employed to transfer data which has been symbolically coded and also to transfer correction instructions; a noiseless feedback channel is used to return each symbol as it is received to the sending station. The apparatus transfers binary digital data without excessive redundancy, delay or complexity by correcting transmission errors by means of correction instructions as opposed to retransmitting the entire block of data.

Submarine communications system

Abstract: A low frequency submarine communication system which utilizes the submarineody as part of the antenna. The antenna is coiled around the submarine hull and utilizes the hull as the core for low frequency (below 1000 Hz) communication. The system allows communication with other vehicles below, on, or above the surface without impeding submarine operation (speed or depth) and the system greatly decreases chances of unwanted detection of the submarine.

Synchronous data channel for pulse code modulation communications system

Abstract: One voice channel of a T1 PCM terminal of an exchange carrier system is replaced with a synchronous channel unit which may be run at various data rates with a clock which is supplied internally utilizing the basic clock repetition rate of the PCM system. This internal clock is derived by removing selected bits and counting down digitally.

Communication Technology: A Societal Perspective

Abstract: Historically the communications industry has been dominated by technology. Concepts such as efficiency, size, and fidelity have been the controlling factors affecting product and system design. Now, however, a wide variety of devices and systems can be provided to the consumer of communication services, assuming limited development of the relevant technologies. This requires that choices be made about what is worthwhile pursuing. Since these decisions will shape communication systems for years to come, inputs to the choice process ought to reflect considerations other than just short-run economics and technological feasibility. In particular, these choices ought to reflect societal needs. To assist in evaluating the impact of alternative communication systems on society, we propose three dimensions along which “social” values might be measured. These are: 1) ease of access to stored information, 2) scope of the interaction space common to the communicants, 3) the extent to which provisions exist to take feedback into consideration. The meaning and measurement of each dimension is explored, and a suggestion is made on how they might be applied. An example of a proposed communication system is presented that would appear to have high values along each of the three dimensions.

Time division multiple access synchronization technique

Abstract: A transmitting station gains access to a time division multiple access communication system without interferring with existing system communications by transmitting frequency shift modulated narrow band accessing signals to the system relay station which may be ground-based or in an orbiting satellite. By transmitting the accessing signals at a frequency located within the spectral null of the information signals being transmitted by the other stations in the system, the accessing signals can be processed to cause the signal transmission from the new station to occur in the correct time slot within the system time frame without interferring with the transmission of the other stations in the system.

Transmission properties of wayside communication systems

Abstract: Some transmission properties of wayside communication systems are discussed. These properties are common to all the wayside communication systems proposed for use on the high-speed ground transportation (HSGT) system. This study considers the method of echo theory, relating the ripple of the phase and amplitude response to the noise which may be produced in the channels. The noise sensitivity suggests its use as a criterion of line performance.

Simulation of centralized computer communications systems

Abstract: In this paper we describe the simulation approach for a general centralized computer communication system with emphasis on efficiency and versatility. The simulation program consists of three modules representing different levels in a hierarchy. The lowest level models the polled multidrop line connecting remote terminals to the concentrator. The second level models the trunk lines and the concentrator which interfaces the multidrop lines of lower speed to one or more higher speed trunk lines connected to a central computer. The highest level models the central computer which communicates with remote terminals via the trunks.A hybrid simulation approach is used to ease program development and to shorten computer running time. When feasible, empirical distributions, analytical formulae or analytical models are used to eliminate simulation steps and simplify simulation procedures. The techniques developed are illustrated by application to the NASDAQ System.