Showing papers on "Communications system published in 1974"

Power line access data system

Abstract: A two-way communication system is disclosed utilizing power transmission lines as the transmission medium. The system is a multilevel repeater system in which each repeater has a unique address. The lowest level repeaters poll the terminal stations connected thereto in time multiplex. Transmission over the system is in the form of tone codes, each level preferably utilizing a different set of tones from the next higher or lower level.

Signal repeater for power line access data system

Abstract: A signal repeater is described for relaying information in a two-way communication system superimposed on a power distribution network. The repeater senses signals passing in either direction in the system, translates the received signal to a different band or group frequencies, and transmits the frequency translated information. Provision is made for address-coding the repeaters so that, when connected in several levels, a particular path can be selected through the various levels. Provision is also made for a signal having priority in a system of such repeaters.

Integrated source and channel encoded digital communication system design study

Abstract: The results of several studies Space Shuttle communication system are summarized These tasks can be divided into the following categories: (1) phase multiplexing for two- and three-channel data transmission, (2) effects of phase noise on the performance of coherent communication links, (3) analysis of command system performance, (4) error correcting code tradeoffs, (5) signal detection and angular search procedure for the shuttle Ku-band communication system, and (6) false lock performance of Costas loop receivers

Multiple zone communications system and method

Abstract: A method and system for more efficiently utilizing presently available and prospectively available two-way communication channels for communication between mobile telephones and either fixed telephones or mobile telephones. A large mobile telephone service area is divided into a plurality of smaller zones, and channels are assigned to the zones in a manner which permits the reuse of channels in zones on a non-interfering basis. A control signal is broadcast over a designated one of the channels assigned to each zone by equipment at a fixed station in each zone under the control of a central control unit. Each mobile telephone monitors one of the designated control channels in accordance with the signal reception characteristics thereof. When a call is placed over the designated control channel, a service or talking channel is assigned to serve the call and the mobile unit is remotely tuned to the assigned talking channel. Provision is made for using the designated control channel as a talking channel if necessary, for assigning additional channels to a fixed station on the basis of user density, and for maintaining communications between two parties as a mobile unit moves from one zone to another. A novel mobile telephone unit operable in accordance with the techniques of the present invention and providing simplified call placement and control is also disclosed.

Station for power line access data system

Abstract: A central station is described which acts as an interface between a two-way communication system superimposed on a power distribution network and a data processing computer. Information from the computer is converted into control signals for activating various sequences of sub-tasks by the communication system. Information from communication system is temporarily stored, converted into a suitable code, and transferred to the data processing computer by way of a teletypewriter terminal. Provision is also made for receiving and responding to priority signals from the system.

Premium interactive communication system

Abstract: A cable television and communication system is disclosed which is suitable for community antenna television (CATV) closed circuit television (CCTV) and other types of signal distribution systems with service function applications such as for use in hotel, motel, apartment complexes, and the like. The system has the capability of distribution and subscriber reception of unencoded and encoded or limited access video and audio programs with simultaneous two way digital data communication. The subscriber units are interconnected by a tree-organized wideband communication link such as co-axial cable system with a network central unit. Subscriber unit identification control and data exchange is accomplished by the use of a high speed time-slot organized format with each subscriber being assigned a predetermined unique television synchronization related time-slot. The central unit utilizes a small digital computer which functions to provide network supervision and management of subscriber requests, accounting, billing and other processing such as viewing analysis. The system utilizes a modular configuration which allows for a low cost and simple initial installation capable of being later expanded to a more sophisticated version.

A Digital Loop Communication System

Abstract: In this concise paper, we describe the concept of a local loop communication system with distributed control. Digital signals offered by the subscribers are parceled and transmitted in blocks to their destination using address-coding. Access of the terminals to the loop is gained by switching a delay network (shift register, containing the message block to be transmitted) into the loop line. This strategy guarantees that every station is able to transmit a message at any time regardless of the traffic conditions in the loop. A quantitative analysis of the loop traffic capabilities as a fnnction of the loop parameters is given. A laboratory model for line frequencies of about 10 Mb/s is presently being built. It allows data and telephone connections including such features as call back, call transfer and forwarding. Loop transmission is realized by means of a three-core symmetrical cable which carries the data sequences and the timing information separately. This allows the use of an extremely simple regenerator. Possible applications include integrated in-house communication systems and control and supervisory systems for manufacturing processes, railway stations and trains.

Digital communications system with immunity to frequency selective fading

Abstract: A digital communications system with increased resistance to frequency selective fading. Digital signals to be transmitted are phase shift modulated upon a spectrum spreaded carrier. The carrier is generated by mixing the output of a band spread oscillator with a locally generated IF oscillator signal. The signal thus obtained is divided into transmission periods, each of which is longer than the maximum spreading time of the nonlinear transmission medium. The increased bandwidth occupancy thus obtained increases the immunity of the transmitted signals to frequency selective fades moving across the allocated bandwidth. The signals are received by a differentially adaptive receiver which automatically adjusts its response to the envelope of received signals.

The star coupler: a unique interconnection component for multimode optical waveguide communications systems.

Abstract: The use of optical waveguides in communications systems may require the interconnection of many interactive terminals. The preferred configuration for passive interconnection in optical waveguide systems is shown to be a configuration termed the Star system. The central interconnecting component, the Star coupler, is described, and the performance of a system incorporating it is compared to that of an equivalent system using a common optical bus and Tee couplers. The Star system is shown to have lower terminal-to-terminal loss, easier upgradability, enhanced reliability and survivability, inherent bidirectionality, and inherent equivalence of all terminals. Construction of two Star couplers is described, and measurements of their performance characteristics are reported.

Satellite communications system incorporating ground relay station through which messages between terminal stations are routed

Abstract: A satellite relay communications system includes a ground relay station arranged so that each message from one subscriber to another is relayed by the satellite relay to the ground relay, processed by the ground relay and then transmitted to the second subscriber by way of the satellite relay. Processing at the ground relay station includes a switching function in which the carrier frequency of each message is changed from the frequency used for transmitting by the subscriber sending each message to the frequency used for reception by the subscriber to whom the message is addressed. This permits each subscriber to use a single transmitting frequency and a minimum number of receiving frequencies.

Chirp communication system

Abstract: A communication system that is difficult to jam has a transmitter transmitting successive chirp signals, which start at different initial frequencies and all have the same frequency - time slope. At the transmitter successive selections are made from among the different available chirp signal frequencies in accordance with a predetermined pseudorandom program that is known at the receiving station. The receiver has a chirp matched filter capable of receiving all of the different chirps but, being a distributed filter, it delays the different received chirps by differing amounts depending upon the initial frequency of each chirp. The output of the chirp filter is envelope-detected, and the resulting pulse signal is passed through a time gate that is gated on at a time that is selected in accordance with the predetermined program. The system has advantages for anti-jam communications, multiple-access communications, frequency diversity radio, and coding using multiple frequencies, as examples. The chirp matched filter is conveniently a surface wave device.

Portable telephone system having a battery saver feature

Abstract: A battery saving system for a portable duplex communications system such as a portable telephone system includes a voice operated transmitter within each portable unit which automatically transmits radio signals upon application of audio signals thereto and discontinues transmission upon termination of the audio signals to conserve battery power. A companion receiver includes a fast acting squelch system to substantially eliminate the noise bursts occurring between transmissions by said portable unit.

Channel switching device for mobile radio communication equipment

Abstract: A channel switching device for use in a mobile radio communication system is disclosed. The device is intended for use in systems wherein the service area is divided into a plurality of zones each having a fixed base station and each accommodating a plurality of mobile stations. The base stations have a plurality of frequency-divided communication channels exclusively assigned to them. The mobile stations are provided with a detector and a switching circuit which are responsive to the received signal to controllably switch between channels. When the received signal exceeds a predetermined threshold, only the channels assigned to the zone in which the mobile station is located are selectively switched or scanned. On the other hand, when the received signal falls below the threshold, all the channels in the service area are scanned.

Data processor for a loop data communications system

Abstract: A data processor for a time division multiplexed communications system. A plurality of such data processors are connected in series in a loop configuration, each having a data terminal associated therewith, for establishing a connection between data processors in a time division multiplexed channel. Each data processor demodulates the signal on the loop, extracts timing information from the loop signal and locates the channel to be used for establishing the connection between itself and another data processor. Each data processor in addition, regenerates and passes on data not intended for that data processor. Data found in the correct or selected channel is provided to the data terminal which may be a synchronous or an asynchronous device. Data from the terminal is inserted into the selected channel, modulated in accordance with a particular rule and transmitted onto the loop to another data processor operating in the selected channel.

Error-rate monitoring unit in a communication system

Abstract: A method and apparatus are disclosed for monitoring the accuracy of electronic data transmitted over a communication channel or telemetry link. An error code is generated for a unit of data transmitted and one for a unit of data received. The error code for a unit of data received is transmitted to the data transmitting station and then compared with the error code representing the unit of data transmitted. Means are provided to synchronize the comparison of error codes so that the two error codes compared represent the same data. After synchronization the bit error rate (BER) is calculated based on the number of miscompares that result for a given quantity of data transmitted. When the system exceeds a predetermined level corrective action is taken.

Performance Evaluation of Reliability Improvement Techniques for Single-Loop Communications Systems

Abstract: One of the basic terminal-attachment configurations is the loop. As such, it is receiving substantial attention. But it has been pointed out that loop communication networks are relatively vulnerable and unreliable. This paper considers the single-loop reliability problem. Three loop reliability (availability) improvement techniques are investigated in detail. All three techniques are based on using an auxilliary transmission path parallel to the main loop. A comparative study shows the best techniques.

Channel identification for high speed digital communications

Abstract: A channel identification problem arises in high speed digital communication systems that transmit information over time-dispersive channels such as telephone channels and radio channels. This paper deals with algorithms for performing the channel identification rapidly in conjunction with the signal detection to recover the information. The stability and convergence properties of the algorithms are demonstrated.

Harmonic communication system

Abstract: A communication system comprising a transmitter for radiating a carrier frequency signal, which may be modulated, to a data station. The station includes a rectifier for rectifying the received carrier signal to provide energy to the station elements. A data source at the station produces a data signal representative of the information to be transmitted. A harmonic generator produces harmonics of the carrier signal and the harmonic signal is modulated with the data or information signal. An antenna radiates the modulated harmonic signal to a receiver which demodulates the received signal to extract the information therefrom. Thus, a completely self-contained and economic system is provided, since the carrier signal per se supplies the energy to operate the data station. Additionally, the communication system may include a carrier signal having an address encoded therein and the station may comprise an address decoder so that only a selected addressed station will transmit the desired data at any one time.

Optimal Message Block Size for Computer Communications with Error Detection and Retransmission Strategies

Abstract: Error detection and retransmission are used as error control in many computer communication systems. In these systems, random length messages are partitioned into fixed size blocks for ease in data handling and memory management. A mathematical model is developed in this paper to determine the optimal message block size that minimizes the expected waiting time in retransmission and acknowledgment delay and thus maximizes channel efficiency. The model considers two classes of error detection and retransmission strategies: 1) stop-and-wait and 2) continuous transmissions. Using the relationships among acknowledgment time, channel transmission rate, channel error characteristics (random error or burst error), average message length, optimal block size are computed from the model and presented in graphs. The model and the graphs should be useful as a guide in the selection of the optimal fixed message block size for computer communication systems.

Star coupler for single mode fiber communication systems

Abstract: An optical coupler system in which optical communications from separate cers are transmitted over separate lines of a single optical fiber to a coupler which combines the information and transmits the combined information over different single fibers to other communication centers.

Emergency civil defense alarm and communications systems

Abstract: In a cable television distribution system, an emergency pre-empt system is located at a transmission station separate from the distribution station. This pre-empt system contains circuitry for interrupting the normal distribution of cable television signals and for enabling an emergency operator to present desired audio and video information to the viewers of the receivers serviced by the distribution system irrespective of the channel to which a receiver may be tuned.

Superconducting Extremely Low Frequency (ELF) Magnetic Field Sensors for Submarine Communications

Abstract: The ferromagnetic-core type of solenoid that is used as a trailed antenna for communications reception by submarines has not demonstrated adquate sensitivity to satisfy the performance requirements for deeply submerged submarines receiving extremely low frequency (ELF) transmissions from the planned Sanguine communications system. It is possible, however, that a superconducting quantum interference device (SQUID) can be adapted to this role successfully and can permit all requirements of platform depth, speed, and maneuverability to be met. The present status of SQUID's is described, and some laboratory measurements that prove the potential of these devices for the ELF communications reception capability are presented. The engineering development that must be pursued in the areas of 1) sensor and electronics dynamic range, 2) sensor orthogonality, and 3) refrigeration systems to make SQUID ELF sensors available as operational receiving antennas is also discussed.

Power line communication system having a protective terminating impedance arrangement

Abstract: A terminating impedance network is disclosed for communication signals transmitted by a power line carrier communication system to the premises of residential customers of an electric utility Corrective impedance values suitable for communication signal terminations are established in the power line conductors serving the customer loads from a distribution network Frequency sensitive low impedance values are established across the service conductors adjacent the customer loads to protect the communication system from interfering signals and high frequency noise originating in the customer loads

Feedback Communications over Fading Channels

Abstract: A communication system using noiseless feedback for Rayleigh fading channels is proposed. Pilot tone signaling is used to provide channel amplitude and phase information for the detection of antipodal signals. Channel estimates generated in the receiver are fed back to control the transmitter power and rate. Power division and rate control rules are derived, and it is shown that definite performance improvement over diversity systems is obtained. Because of the requirement of small loop propagation delays, the technique is mainly applicable to low data rate multitone modems for short range HF channels.

Extremely Low Frequency (ELF) Communication to Submarines

Abstract: An ELF (extremely low frequency) communication system has been proposed for communication from land to submerged submarines. We present an analytical study of conceptual feasibility of such a system and discuss some of its properties. We find no fundamental technical reason why such a system is infeasible. The present work yields the general structure of the receiver, and estimates for the important parameters of such a system. Nonlinear processing ahead of the FSK (frequency-shift keying) receiver in the submarine appears essential. Such processing greatly reduces the effects of atmospheric noise due to nearby lightning storms, and hence, makes reliable operation possible at much smaller transmitter power.

The Audit of Organizational Communication.

Abstract: The objective of this paper is to provide a conceptual and methodological structure for the examination of organizational communication processes. To fulfill this purpose, there is presented, first, a logic for the identification of communication systems, and then, a method by which these systems can be examined, audited, or evaluated. Organizational communication is defined as a system in terms of purpose, operational procedures, and structure. The achievement of organizational goals is stated as the purpose of organizational communication; and for the particular organization unit, this is accomplished through the appropriate employment of communication networks, communication policies, and communication activities. Four communication networks are identified: (1) regulative, (2) innovative, (3) integrative (maintenance), and (4) informative-instructive. To further the explicit identification of the organizational communication system, an exploratory taxonomy of communication activities is exhibited. It i...

Burst frequency shift keying data communication system

Abstract: A communications system for transmission of low density digital data from a plurality of transmitters to a common receiver. It is a burst-mode frequency shift keying (FSK) communication system useable with a master antenna television (MATV) system that minimizes mutual interference between outputs of a large number of transmitters individually located with TV sets. The transmitters are combined with converters for transmission of programs through the system to individual TV sets as controlled by the users, and with information such as TV channel in use, room number identification, and specialized information such as completion of maid service, fire, and burglary alarms transmitted back through the system. In one system the transmitters use a carrier frequency of 12MH z , a frequency at the lower end of the passband of a coax system with FSK modulation at an equivalent switching rate of 20KH z and modulation index of 5 accepting a RF channel loading of up to 700 simultaneous users.

Business machine communication system and data display

Abstract: A business machine for communicating with remote and/or local data devices. A multiplexer selects the device to communicate with the business machine and sequences the operation of the machine through its several steps under control of a central processing unit. Those data devices with which the business machine communicates on a party line are coupled to the multiplexer through a communications controller which detects Attention signals, requests access to the memory, and in response to acknowledgement of access, transfers characters between the data device and the memory. The controller receives a block check character but generates a modified block check character which simplifies the utilization of that check. A video display can be provided with the business machine. The business machine is organized to permit clearing of the display screen independently of clearing of the corresponding memory locations and to permit rapid scrolling of text on the display screen, even when a relatively low speed microprocessor is utilized for the central processing unit.