scispace - formally typeset
Search or ask a question

Showing papers on "Communications system published in 1972"


Journal ArticleDOI
TL;DR: A unified model is developed and then used to analyze the queueing behavior of the star and loop systems, providing insight into the performance of these systems.
Abstract: Recent advances in computer communications are discussed including computer-traffic and channel error characteristics, optimal fixed message block size, statistical multiplexing, and loop systems. A unified model is developed and then used to analyze the queueing behavior of the star and loop systems. Numerical results for selected traffic intensities and message lengths, given in graphical form, provide insight into the performance of these systems.

114 citations


Patent
22 Sep 1972
TL;DR: In this article, a Kalman filter technique is employed to update the short-term navigational information derived from the inertial navigation system in each user aircraft with the long-term navigation information obtained from the time synchronized ranging system, so that the highly accurate georeferenced information from the airborne controller is provided to each member of the community of user aircraft.
Abstract: Method and apparatus are provided for the tactical nagivation and communiion of a community of aircraft. Each of the aircraft in the community is provided with an inertial navigation system capable of providing accurate short term navigational information and a time synchronized ranging system capable of providing accurate long term navigational information. One of the aircraft is designated as the airborne control unit and establishes a relative grid coordinate system within which the community of aircraft operate. The origin of the relative grid is established by the airborne control unit. When stationary ground time synchronized ranging system units are present, highly accurate georeferenced information may be supplied to the airborne control unit by operation of its time synchronized ranging system. When such ground units are not present, accurate georeferenced information may be obtained by the airborne controller from navigational systems such as satellite, Loran or Omega systems. The remaining or "user" aircraft in the community determine their position in the relative grid by interrogating the airborne control unit with their time synchronized ranging systems. A Kalman filter technique is employed to update the short term navigational information derived from the inertial navigation system in each user aircraft with the long term navigational information obtained from the time synchronized ranging system, so that the highly accurate georeferenced navigational information from the airborne control unit is provided to each member of the community of user aircraft. Novel computer programming permits each aircraft in the community to derive navigational information having the best characteristics of navigational information available from several sources, so that very accurate navigation in the area defined by the relative grid is made possible. The system of the invention may also perform communication and identification functions for the members of the tactical community.

111 citations


Journal ArticleDOI
David C. Walden1
TL;DR: A system of communication between processes in a time-sharing system is described and the communication system is extended so that it may be used between processes distributed throughout a computer network.
Abstract: A system of communication between processes in a time-sharing system is described and the communication system is extended so that it may be used between processes distributed throughout a computer network. The hypothetical application of the system to an existing network is discussed.

99 citations


Journal ArticleDOI
Robert E. Kahn1
31 Jul 1972
TL;DR: An introduction to computer-to-computer networks and resource sharing is provided and some aspects of distributed computation are discussed.
Abstract: The development of resource-sharing networks can facilitate the provision of a wide range of economic and reliable computer services. Computer-communication networks allow the sharing of specialized computer resources such as data bases, programs, and hardware. Such a network consists of both the computer resources and a communications system interconnecting them and allowing their full utilization to be achieved. In addition, a resource-sharing network provides the means whereby increased cooperation and interaction can be achieved between individuals. An introduction to computer-to-computer networks and resource sharing is provided and some aspects of distributed computation are discussed.

73 citations


Journal ArticleDOI
TL;DR: A survey of the principles, parameter values and classes of AMF's and their tradeoffs with digital matched filters (DMF's) when viewed in the context of future systems applications, employing many codes and operating bandwidths in excess of several MHz.

44 citations


Patent
30 Oct 1972
TL;DR: In this article, the authors describe a communication and computation system where the processors communicate with each other and with other devices via a loop of continuously circulating data, which is comprised of channels which are time multiplexed on a bit basis in a repeating sequence.
Abstract: A communications and computation system wherein the processors communicate with each other and with other devices via a loop of continuously circulating data. The loop of data is comprised of channels which are time multiplexed on a bit basis in a repeating sequence. Further loops may be made of data circulating at lower speeds by extracting one of the channels from the main loop. The processors may each have a further time division multiplex loop attached thereto wherein one of the processors monitors the errors in each of the remaining processors for providing a centralized indication of system errors.

42 citations


Patent
26 Jan 1972
TL;DR: In this article, the authors propose a train communication system in which trackside transponder devices containing coded information as to track gradient, speed restrictions etc, pass this information to the receiver equipment on the train on receipt of an activating signal from a transmitter on a train.
Abstract: This invention relates to a train communication system in which trackside transponder devices containing coded information as to track gradient, speed restrictions etc, pass this information to receiver equipment on the train on receipt of an activating signal from a transmitter on the train. The system is operative to declare a fault if a transponder, at an expected location for said transponder, fails to respond to the activating signal so as to fail to pass information to the receiver equipment.

37 citations


Patent
22 Feb 1972
TL;DR: In this paper, groups of data transmitters are connected to data retrieval circuitry through switch circuits, which are selectively addressed by a predetermined code to provide communication between all of the transmitters of the group and data retrieval circuits.
Abstract: A communications system, such as a cable television system, embodies an arrangement for data transmission which utilizes a combination of time and frequency division. Groups of data transmitters are connected to data retrieval circuitry through switch circuits which are selectively addressed by a predetermined code to provide communication between all of the data transmitters of the group and data retrieval circuitry. The transmission of data from transmitters in the other groups are blocked until the appropriate address code is sent to the associated switch circuit. Circuitry utilizing a synchronous or non-synchronous clock is provided for generating a message marker along with the data pulse train.

36 citations


Patent
07 Aug 1972
TL;DR: In this paper, a distributed PABX system for accomplishing distributed PAS functions without tying up lines or channels of communication for each communication is presented. But the processing and handling of the address codes is accomplished locally at the subscriber stations by the user himself by a technique which facilitates the implementation of such conventional PAS function as call transfer, call storage, call forwarding and call hold.
Abstract: A system for accomplishing distributed PABX functions without tying up lines or channels of communication for each communication. Station identifying address codes are assigned to the subscribers with a plurality of address codes being available to a single subscriber at a given time. The address codes are stored in registers located at the subscriber stations and transferred to receiving stations to effect communication. The processing and handling of the address codes is accomplished locally at the subscriber stations by the user himself by a technique which facilitates the implementation of such conventional PABX functions as call transfer, call storage, call forwarding and call hold. The subscriber terminals are connected in a communications network wherein the subscribers communicate on the transmission media using a predetermined period format. The period format includes assigned portions for handshaking and distribution of address codes as well as portions for communicating textual data. Generally, an originator goes off hook and dials the handshake address code of the party he desires communication with. This address code is placed in a REQUEST FOR SERVICE subperiod of the period (P) on the transmission line. At the receptor terminal, a distributed address code is received for identifying the communications between the two terminals. Each subscriber is provided with registers for storing the address codes to be used by respective communicating subscribers. The possible address codes stored by these registers includes address codes providing handshake identification codes, transferee address codes identifying those subscribers which a given subscriber desires to transfer or forward calls to, the addresses of subscribers calling a given subscriber when such given subscriber is busy with a third party and, essentially, includes the addresses associated with any subscribers which the given subscriber is or will subsequently speak to, or transfer calls to. An address selector and control circuit controls the entry and removal of the address codes into and out of the address registers. The control circuit is connected to both a keyboard for receiving telephone operation command codes, and to an address code detector so as to control the entry and removal of address codes on the transmission media.

34 citations


Patent
14 Aug 1972
TL;DR: In this article, a multi-address two-way communication system with a control channel is proposed, in which a master position is interconnected with a plurality of remote positions only over the AC power lines serviced by the same AC power distribution network.
Abstract: A multi-address two-way communication system with a control channel. A master position is inter-connected with a plurality of remote positions only over the AC power lines serviced by the same AC power distribution network. The master position contains a source of RF signals, an RF signal modulator and circuitry for energizing the RF signal source and the RF signal modulator to provide a very large number of unique signal combinations. Each remote position contains a decoder circuit which identifies and responds to a signal combination unique to it. A multiplicity of AC power lines in an AC power distribution network are coupled together by frequency selective coupling devices to permit signalling and communication between positions in separated AC power lines in a large building.

29 citations


Patent
24 Nov 1972
TL;DR: In this paper, the authors proposed data terminals for use in a TDMA communication system which provides the individual data terminals with synchronization error measurements and other commands, and each individual data terminal is capable of transmitting a narrowband coarse synchronization signal in response to a system command, thereby permitting rapid initial synchronization to be achieved.
Abstract: The present invention relates to data terminals for use in a TDMA communication system which provides the individual data terminals with synchronization error measurements and other commands. Each individual data terminal is capable of transmitting a narrowband coarse synchronization signal in response to a system command, thereby permitting rapid initial synchronization to be achieved. The disclosed data terminals transmit data in burst fashion at one uplink bandwidth, and receive downlink data at a second, narrower bandwidth.

Patent
24 Nov 1972
TL;DR: In this article, a processing repeater for use in a TDMA communication system which is capable of providing the individual data terminals with synchronization error measurements and other control data is presented.
Abstract: The present invention relates to a processing repeater for use in a TDMA communication system which is capable of providing the individual data terminals with synchronization error measurements and other control data. In the particular embodiment disclosed, the processing repeater is also capable of receiving a narrowband coarse synchronization signal from an inactive data terminal in response to an interrogation command, thereby permitting rapid initial synchronization to be achieved. The disclosed processing repeater is also capable of controlling the demand assignment process for the allocation; of time slots in response to either narrowband or wideband call requests from inactive or active data terminals respectively.

Patent
14 Feb 1972
TL;DR: In this paper, a communications system and method for transmitting and receiving two independently timed (asynchronous) binary data signals on a quadri-phase carrier is presented, where each channel is demodulated and applied to a corresponding descrambler.
Abstract: A communications system and method for transmitting and receiving two independently timed (asynchronous) binary data signals on a quadriphase carrier. The four phase ambiguity ordinarily resulting from quadriphase transmission and reception is overcome by uniquely identifying each input channel, for example, by scrambling. In reception each channel is demodulated and applied to a corresponding descrambler. The descrambler outputs are sequentially examined to recognize any non-random characteristic of the data signals; recognition indicates connections from the demodulator to the descrambler in the correct sense. If there is no recognition, the connections are reversed and the scrambler outputs are again examined until recognition is achieved thus providing the original binary data signals.

Patent
Hedges Walter Paul1
10 Jan 1972
TL;DR: In this article, a portable unit is carried by a maid or other personnel and is adapted to be coupled to a communication channel which may be present for another purpose, such as the telephone lines which provide telephone service to the rooms, a television antenna cable, or any other communication channel available.
Abstract: System for indicating the condition of hotel rooms or the like having a computer coupled to a memory and to display devices, with a communication channel extending from the computer to remote points, such as individual hotel rooms. A portable unit is carried by a maid or other personnel and is adapted to be coupled to a communication channel which may be present for another purpose. For example, the communication channel may be the telephone lines which provide telephone service to the rooms, a television antenna cable, or any other communication channel which is available. The portable unit includes a circuit for transmitting and receiving signals, and switches coupled thereto. When used with a telephone line, the portable units can be coupled thereto through an acoustic coupler, or a receptacle can be provided for the unit which is directly wired to the line. The portable unit or the receptacle can also include a circuit which is uniquely wired or switched for each room, so that a signal can be sent on the line which identifies the room and the particular portable unit, and which provides information representing the operation of the switches of the portable unit. The portable unit may include batteries for energization of the circuit therein. The information supplied on the communications line is coupled to the computer and stored in the memory thereof, and selectively read out on a visible display and/or printer as desired.

Journal ArticleDOI
David Cox1, D. Reudink
TL;DR: As the number of radio channels available to a communication system increases, the system becomes more efficient in handling the fluctuations in offered traffic and changing the radio-channel reuse interval also affects the per-channel traffic carried by a dynamic-channel-assignment system.
Abstract: Dynamic channel assignment in mobile communications systems is able to cope with varying nonuniform spatial user demand. It also readily handles the normal randomness in offered traffic. This study presents system performance data for radio systems having 8, 20, 40, 80, and 120 radio channels available and a radio-channel reuse interval of 4 base-station coverage areas. Data are also presented that compare performance of a 30 radiochannel system with a reuse interval of 3 base stations, a 40 radiochannel system with a reuse interval of 4 base stations, and a 50 radio-channel system with a reuse interval of 5 base stations. The results are obtained from a computer simulation of a onedimensional network laid out along a line. As the number of radio channels available to a communication system increases, the system becomes more efficient in handling the fluctuations in offered traffic. Changing the radio-channel reuse interval also affects the per-channel traffic carried by a dynamic-channel-assignment system.

Patent
24 Feb 1972
TL;DR: An all weather emergency reporting telephone call box employing a hands-free communication system is provided in this paper, where the call box uses a speaker and microphone coupled through electronic circuits which provide handsfree operation for voice reception and transmission.
Abstract: An all weather emergency-reporting telephone call box employing a hands-free communication system is provided. The call box uses a speaker and microphone coupled through electronic circuits which provide hands-free operation for voice reception and transmission. The housing is formed of heavy material in a configuration selected to minimize the opportunity for vandalism. Direct communications access to the emergency station can be gained by opening a door which operates a micro-switch and prepares the system for hands-free operation.

Patent
17 Mar 1972
TL;DR: In this article, a communication system with baud rate detection capability is presented, which includes a processor, a plurality of terminals, and a communication device for coordinating transmission of communications between the processor and terminals at a variety of baud rates.
Abstract: A communication system with baud rate detection capability. In a preferred embodiment of the system, the system includes a processor, a plurality of terminals, and a communication device for coordinating transmission of communications between the processor and terminals at a variety of baud rates. Each baud rate of a system corresponds to a unique baud-rate-code and each baud-rate-code is an interval of time. The signal by which each communication is transmitted includes a baud-rate-code as represented by at least one time interval between signal state transitions The communication device detects the signal state transitions representative of the baud-rate-code and concurrently records the time of occurrence of each detected transition. From a pair of recorded times, a transition interval is computed and correlated with one of the baud-rate-code time intervals to identify a correlated baud-rate-code. The baud rate corresponding to the correlated baud-rate-code is indicated and a transmission of a communication is decoded in accordance with the indicated rate.

Patent
04 May 1972
TL;DR: In this article, a switchable communications system utilizing frequency division multiplexing is shown for providing communication between a plurality of stations, each including a synthesizer and each operated from a single reference frequency.
Abstract: A switchable communications system utilizing frequency division multiplexing is shown for providing communication between a plurality of stations, each including a synthesizer and each operated from a single reference frequency. Each station is assigned a fixed home frequency at which it transmits information. When calling, the synthesizer within the calling station adjusts the transmit frequency of that station to correspond to the receive frequency of the called station, which automatically adjusts the receive frequency of the calling station to correspond to the transmit frequency of the called station. Full duplex transmission is thus permitted between any and all stations within the communications system through the utilization of a wide range acquisition synthesizer within each station.

Patent
Y Ching1
13 Nov 1972
TL;DR: In this article, a differential pulse code (DPC) communications system is described, where the transmitter quantizes differential signals on two quantizing scales having different numbers of levels, and the combined signal is transmitted to a receiver which may either utilize the higher quality signal or re-transmit either the lower and/or high quality signal, without requantization and the error associated therewith, to yet another receiver.
Abstract: A differential pulse code communications system is disclosed wherein the transmitter quantizes differential signals on two quantizing scales having different numbers of levels. The combined signal is transmitted to a receiver which may either utilize the higher quality signal or re-transmit either the lower and/or higher quality signal, without re-quantization and the error associated therewith, to yet another receiver; the quality of the signal re-transmitted being determined by the bandwidth of the re-transmission channel.

Patent
02 Oct 1972
TL;DR: In this article, a communication system by which a plurality of substantially simultaneously transmitted different subscription programs may be selectively individually displayed on a common display channel provides premises access monitoring in addition to such display.
Abstract: A communication system by which a plurality of substantially simultaneously transmitted different subscription programs may be selectively individually displayed on a common display channel provides premises access monitoring in addition to such display. A multiplexed communication signal containing a plurality of different program information signals and a plurality of command signals is provided to a plurality of display devices which are capable of substantially simultaneously displaying different selected program information displays from the plurality of such signals in response to selected program information signals. Each display device has an associated means for controlling the selection of these programs which is connected to a common condition responsive means, such as a computer. The control means includes means for demultiplexing the communication signal and for generating a given program information selection control signal in response to a uniquely identified command signal which control signal, when mixed with the demultiplexed plurality of subscription program information signals, provides the selected one at the frequency of the common display channel. The computer and common communication signal path thereto are utilized to provide premises access monitoring, in which instance an optical card reader utilizing fiber optics provides input conditions to the computer indicative of both the status of the door to the premises and the authorization of the entrant, a randomly selected insertable card providing the information to the computer through the reader. Such reader may employ a modulated light source, light polarization, or space and/or time diversity in order to increase the security of the reader. In addition, a pair of separate input devices, such as a card reader and a door position sensor may be utilized for such monitoring.

Patent
11 Dec 1972
TL;DR: In this article, a power feed arrangement provided as a safety measure in a communications system of the type in which two terminal stations are connected by at least one transmission path which transmits information signals from one of the stations to the other through information signal repeating means.
Abstract: A power feed arrangement provided as a safety measure in a communications system of the type in which two terminal stations are connected by at least one transmission path which transmits information signals from one of the stations to the other through information signal repeating means. Two sources (one at each station) supply energizing current along the transmission path to the repeating means, and, in addition, a monitoring signal is generated at each station to be transmitted along the transmission path to the other station and detected at that other station. If one of the monitoring signals is not detected, the energizing current supply sources are disconnected from the transmission path. Provision is made to ensure that the supply sources can only be connected to the transmission path following successful transmission and detection of the monitoring signals, and for testing the current output of the sources and the impedance of the transmission path prior to operation of the system.

Patent
F Serracchioli1, U Steindler1
25 Jan 1972
TL;DR: In this paper, a data communication system between a central computer and data terminals, in which a group of terminals is connected directly to the central computer through a concentrator, is described.
Abstract: A data communication system between a central computer and data terminals, in which a group of terminals is connected directly to the central computer and another group of terminals is connected to the central computer through a concentrator. The concentrator connects a terminal, which is ready to transmit, to the central computer in such a manner as to be transparent to the flow of the data.


Patent
A Tomozawa1, H Ford1
02 Oct 1972
TL;DR: In this paper, a satellite transponder communication system operating in a time division multiple access mode, each earth station transmits data in a burst format, and each Earth station apparatus is arranged in modular form enabling many forms of data to be included within a station''s burst of transmission.
Abstract: In a satellite transponder communication system operating in a time division multiple access mode, each earth station transmits data in a burst format. Each earth station apparatus is arranged in modular form enabling many forms of data to be included within a station''s burst of transmission. Individual terrestrial interface modules receive data, voice, etc. in various forms and convert the data, voice, etc. into bit format suitable for inclusion in the transmitted burst. A multiplexer at the transmitter is controlled by a programmable memory to select and determine the order in which bits are extracted from the various terrestrial interface modules and entered into the bit stream of the transmitted burst. The receiver includes a demultiplexer controlled by a programmable memory to properly demultiplex the bit stream of the received burst and to direct the demultiplexed blocks of bits to respective ones of the terrestrial interface modules. The memories are provided with at least two sections to enable a change in burst format without loss of communications. At the multiplexer one section controls the format while a new program is written into the other section. A similar arrangement is provided at the receiver. A memory status signal is included in the station''s burst and this status is detected by the receive stations. When the multiplexer memory is to be switched from one section to another the status signal changes. The status signal is transmitted as part of the signalling portion of the burst preamble.

Patent
11 Jul 1972
TL;DR: In this article, a controller for each path has a memory for storing at allocated locations the digital addresses of each pair of linked terminals, together with digital words to be transmitted (e.g., digitized voice samples) that were developed at the linked terminals.
Abstract: A time division multiplex communication system uses a signal path in the form of cable loops along which terminals for digital data or for voice communication (e.g., telephone hand sets) are coupled at convenient points. A controller for each path has a memory for storing at allocated locations the digital addresses of each pair of linked terminals, together with digital words to be transmitted (e.g., digitized voice samples) that were developed at the linked terminals. At a certain time period, the controller transmits a signal message containing a terminal address and a digital word via the path, so that the addressed terminal recognizes its own address and accepts the digital word (and, if a voice sample, converts it back to an audio signal for operating its telephone receiver). In response, the terminal sends a digital reply message which is stored by the controller until the time period for sending it to the other linked terminal.

Patent
12 Oct 1972
TL;DR: In this paper, a communication system using differential phase shift-keying (DPSK) transmits and receives binary data without requiring timing or phase reference signals without ambiguity as to the data content.
Abstract: A communication system using differential phase-shift-keying (DPSK) transmits and receives binary data without requiring timing or phase reference signals. The system encodes and modulates the data at the transmitter, and decodes and demodulates the data at the receiver, without ambiguity as to the data content.

Journal ArticleDOI
A. G. Fraser1
TL;DR: A focus on some of the problems of coordination, synchronization, error control, signaling, stream multiplexing, and switch control is obtained in a discussion of a detailed specification for a paticular computer-communications system interface.
Abstract: Future systems that combine computers, digital terminals, and communications equipment present design optimization problems that require reconsideration of the traditional functional responsibilities of the respective subsystems. Several “standard” interfaces, by means of which computers and digital terminals connect to the communications systems will be required. When specifying these interfaces, consideration must be given to problems of coordination, synchronization, error control, signaling, stream multiplexing, and switch control, in addition to minimizing the technological interdependence of specific subsystem designs. A focus on some of the problems is obtained in a discussion of a detailed specification for a paticular computer-communications system interface.

Patent
23 Aug 1972
TL;DR: In this article, a space diversity communication system is presented in which the effects of signal fading are reduced through the cooperative receipt by closely spaced antenna sensor elements and the processing in a hybrid network of signals originally transmitted as a single intelligence-modulated carrier, though susceptible of multiple path propagation.
Abstract: A space diversity communication system is presented in which the effects of signal fading are reduced through the cooperative receipt by closely spaced antenna sensor elements and the processing in a hybrid network of signals originally transmitted as a single intelligence-modulated carrier, though susceptible of multiple path propagation. Sum and difference signals are developed for analysis in a novel diversity signal selector or combiner. In one form, the latter may develop signals for electronically steering the system receptivity pattern so as to maximize the reception signal-to-noise ratio.

Patent
F Brown1
10 Aug 1972
TL;DR: In this paper, a data communications system has capacity for serially transferring data between a first and a second location, where the data and the clock pulses are modulo two serially added to produce a transmitted data stream.
Abstract: A data communications system has capacity for serially transferring data between a first and a second location. There is a transmitter at the first location with the transmitter capable of storing data prior to transmission. A series of clock pulses is generated having a duty cycle less than one-half. The data and the clock pulses are modulo two serially added to produce a transmitted data stream. There is a receiver at the second location. The receiver receives the transmitted data stream and obtains from the data stream bit synchronization and data.

Journal ArticleDOI
TL;DR: It is concluded that under certain conditions, the presence of a limiter can improve the performance of the system and a simplification of previous work is presented when an infinite clipper is introduced at baseband in the detector.
Abstract: This paper examines the performance of a two-link digital communication system operating in the presence of Gaussian noise on both links when bandpass limiters are inserted into the system. The product of the signal time duration and the noise bandwidth for the systems under consideration is small. It is concluded that under certain conditions, the presence of a limiter can improve the performance of the system. Also, a simplification of previous work is presented when an infinite clipper is introduced at baseband in the detector.