Abstract: Radio telephone apparatus for use in an underground railway system comprises two base stations 3, 4 respectively located at successive railway stations 1, 2. The base station 3 feeds a radiating cable 7 extending in the tunnel bore towards the base station 4 which feeds a radiating cable 12 extending in the tunnel bore towards the base station 3. When a train travels from the station 1 to the station 2, the mobile radio on the train effects call handover, ie transference of communication with cable 7 to communication with cable 12. To ensure no interruption in a call during handover, an attenuator 16 is incorporated in the cable 7 adjacent its end, such that the mobile radio effects call handover to the cable 12 before losing communication with the cable 7, even at the maximum possible speed of the train.

Abstract: A system and method is disclosed for distributing a radio frequency (RF) signal within a building structure or other structure not readily transparent to radio frequencies. The RF signal originates at a wireless local loop (WLL) base station and is intercepted by a main antenna on the building structure. The intercepted RF signal, which is contained in a RF bandwidth, is distributed throughout the building structure over a low bandwidth medium, e.g., in-building cabling, which has a transmission bandwidth below the RF bandwidth. In order to accomplish this, the system has a global reference oscillator for distributing a global reference tone of high stability to the entire system. Local oscillators controlled by this global reference tone deliver RF reference tones of high stability required for mixing the RF signal to obtain an intermediate frequency (IF) signal which is fed through the low bandwidth medium to remote sites.

Abstract: The invention provides radio communications with an up-down signal link. In accordance with the purpose of the invention, as embodied and broadly described herein, the invention is directed to a method, system and computer readable medium with program instructions (hereafter collectively referred to as "the invention"). The invention includes receiving a downstream signal in a receiver portion of an outdoor unit, producing in the receiver portion of the outdoor unit an intermediate frequency (IF) signal from the downstream signal, and processing the IF signal in the receiver portion of the outdoor unit to produce a clean line code signal.

Abstract: A system and method for transmitting a radio frequency (RF) signal in a RF bandwidth over a low bandwidth medium, e.g., in-building unshielded twisted pair (UTP) cabling, which has a transmission bandwidth below the RF bandwidth. The system has a unit for receiving the RF signal and a global reference oscillator for distributing a global reference tone of high stability to the entire system. Local oscillators controlled by this global reference tone deliver RF reference tones of high stability required for mixing the RF signal to obtain an intermediate frequency (IF) signal which is fed through the low bandwidth medium to remote sites. A 10 base T cable network, often pre-existing in many building structures, provides a suitable, cost effective low bandwidth medium for such RF communication. Two of the four twisted pair cables of a UTP cable are sufficient to support bi-directional communication.

Abstract: A radio communication system between a mobile station on a vehicle and a stationary station in which a uniform field intensity is obtained in a direction of a width of a road so that a good communication can be performed irrespective of a position of the vehicle on the road. A mobile station is provided on the vehicle. A stationary station communicating with the mobile station includes at least one pair of antennas located with the road therebetween so that the antennas generate an electric field having a substantially uniform intensity in a direction of a width of the road.

Abstract: Implemented on a vehicle, a communication system used to notify a passenger of an incoming telephone call. The communication system includes a telephony system assigned to one or more passenger(s) of the vehicle. The telephony system includes a passenger control unit ("PCU") and a passenger control handset ("PCH") coupled to the PCH, both having processing capability. Either of these units may process telephone information transferred to the telephony system, and in response of detecting a telephone call command, perform a call notification scheme to indicate to the passenger(s) that an incoming telephone call has arrived.

Abstract: Individual channels are centrally and tunably selected for emission in a distributed wireless communications system. A high-frequency signal received at a central antenna is down-converted such that a selected channel corresponds to a predetermined frequency range. Non-selected channels are filtered out. The selected channel is transmitted to remote locations over commonly available transmission lines, up-converted, and re-emitted. The transmitted channel is chosen by tuning the frequency of the local oscillator used for down-conversion. A high-stability global tuning signal is used to tune and stabilize the local oscillators used for up-conversion. The global tuning signal is generated by frequency-dividing the down-conversion local oscillator signal by a fixed number, while the up-conversion local oscillator signals are generated by frequency-multiplying the global tuning signal by the same fixed number. Phase-locked loops are used for frequency multiplication and stabilization.

Abstract: A device for implementing a multimedia communication dissemination system is disclosed herein. The communication system integrates heterogeneous satellite transmission systems, local area computer networks, and the public telephone system to implement a flexible, high-speed communication system. The preferred communication dissemination system includes a broadcast server for broadcasting an information signal, a mobile base station for receiving the information signal broadcast from the broadcast server, and a local area network for distributing information received by the mobile base station. The preferred mobile base station includes a receiver for receiving information signals transmitted from a broadcast server, a network interface for distributing processed information signals, and a software proxy process for processing information signals. A software proxy process controls the dissemination of information through the network.

Abstract: A radio-frequency (RF) distribution system carriers multi-carrier RF signals having frequencies above 500 Mb over existing electric power wiring between a transceiver and one or more antennas. The transceiver and antennas can be connected to the power wiring, disconnected from the power wiring, relocated, and reconnected to the power wiring without installing conventional transmission lines.

Abstract: A wireless local area network includes a plurality of stations each comprising a data processing machine connected to a radio send-receive interface. Each data processing machine includes an interface controller for sending a message containing an address designating a destination station and for receiving messages addressed to it. The network further includes a repeater including a radio send-receive interface connected to a radiating cable passing near all the stations to receive all messages sent by the stations, to modify these messages to indicate that the message has passed through the repeater and to retransmit these messages over the radiating cable. The radio send-receive interface of each station ignores any messages not sent by the repeater. The wireless local area network finds an application in computer networking.

Abstract: A data receiving system has a radio frequency unit for demodulating a series of signals transmitted at a carrier wave frequency, a local oscillating unit for generating a demodulating frequency used for the demodulation of the series of signals, an equalizing unit for removing a distortion of the series of signals demodulated in the radio frequency unit, a phase shift estimating unit for taking out phase information from the series of signals, calculating a time changing rate of the phase information and estimating a phase shift caused by a difference between the carrier wave frequency and the demodulating frequency according to the time changing rate, and a correcting unit for correcting the series of signals transmitted from the equalizing unit according to the phase shift to remove the phase shift from the series of signals.

Abstract: A system and method for distribution of RF communication signals. First RF communication signals are downconverted in a first signal processing subsystem and transmitted to a second signal processing subsystem via twisted-pair cable. The downconverted first RF communication signals are upconverted at the second signal processing subsystem to provide recovered first RF communication signals, and the recovered first RF communication signals are transmitted via an antenna. Operating power for the second signal processing subsystem is provided from the signal processing subsystem, and the second signal processing subsystem determines the occurrence of an event and transmits autonomous information signals thereabout to the first signal processing subsystem.

Abstract: A system and method for transmitting a radio frequency (RF) signal in a RF bandwidth over a low bandwidth medium, e.g., in-building cabling, which has a transmission bandwidth below the RF bandwidth. The system has a unit for receiving the RF signal and a global reference oscillator for distributing a global reference tone of high stability to the entire system. Local oscillators are controlled by adjustment signals derived from this global reference tone to deliver RF reference tones of high stability required for mixing the RF signal to obtain an intermediate frequency (IF) signal which is fed through the low bandwidth medium. The global reference tone is preferably delivered through the same low bandwidth medium to desired locations, such as remote coverage sites in a network for cellular communications, cordless telephony, local RF communications, interactive multi-media video, high bit-rate local communications.

Abstract: In a wireless communication apparatus arranged by an indoor unit, an outdoor unit, and a cable used to connect the indoor unit with the outdoor unit, a gain of an amplifier is automatically set. This amplifier amplifies a lowered level of a signal caused by a cable loss. To perform such an automatic gain setting operation, a cable loss equalization system is used in this wireless communication apparatus. The cable loss equalization system compensates for a reduction in a level of a main signal caused by the cable.

Abstract: A distribution system for a passenger entertainment system (30) that provides appropriate in-line amplification and equalization of an entertainment signal carried on a common bus (40). The distribution system is comprised of a network of zone management units (ZMUs) (42a, 42b, . . . 42n) and seat electronics units (SEUs) (48a, 48b, . . . 48n) connected to the bus. Each ZMU contains a variable gain amplifier in series with the bus to amplify the entertainment signal carried on the bus. Each ZMU also contains a variable slope compensation network (84) that is continuously adjusted to equalize the amplitude of the entertainment signal across the signal bandwidth. Each SEU contains a variable gain amplifier in series with the bus to amplify the entertainment signal carried on the bus. Each SEU also contains a fixed slope compensation network (330) that may be switched in series with the bus to equalize the amplitude of the entertainment signal across the signal bandwidth.

Abstract: A transceiver system for interfacing digital modems with radio frequency signals including an antenna, an antenna interface system and a modem interface system separated by a cable. The antenna is placed in a location having optimal reception and in close proximity to the antenna interface system. The cable couples the antenna interface system to the modem interface system. The modem interface system includes a two state variable attenuator and an attenuation register that are configured to either reduce the strength of the receive (Rx) signal when the modems are located near a base station, or to transmit the Rx signal without attenuation when the concentrated subscriber unit is at a more distant location. The outgoing, or transmit (Tx), signal is also attenuated in a similar manner to the incoming signal. A signal loss detection system includes a detector located in the modem interface system that receives an oscillating signal transmitted from the antenna interface system through the coaxial cable.

Abstract: A radio frequency communication system utilizing a radiating transmission line for simultaneously communicating audio and video signals is disclosed. The video signals convey video information and the audio signals convey narrow band computer data or audio information. The communication system also provides several separate channels allowing simultaneous audio communication between a plurality of mobile stations. The communication system is intended to be used in environments where radio waves do not propagate well, such as in underground mines. The communication system comprises at least one amplification unit connected to the radiating transmission line for periodically amplifying the audio and video signals. The amplification units have a separate amplifier for amplifying each of the signals and each amplifier is connected to the transmission line in parallel. The amplifiers utilize transistors operating in the linear region.

Abstract: A medium-frequency radio transmission system is formed by installing a receiving antenna for receiving an amplitude-modulated medium-frequency radio wave at the rooftop of an existing building, receiving the medium-frequency radio wave, coupling the received medium-frequency radio wave to an existing distributing cable or distributing conductive piping with or without a coupler for said radio wave, and transmitting the radio wave to a predetermined floor. At the predetermined floor the basement or tunnel of an existing building such as underground shopping mall, underground parking lot, underground railway, road tunnel or deep space of massive building is provided with a coupling such as an existing loop-like or linear wiring or piping line with or without coupler.

Abstract: The object of the invention is to employ a single amplifier for both the transmit and the receive signals in an RF repeater for interfacing with a base station for exchanging transmit and receive signals in a time division duplex cordless telephone system. A multicarrier amplifier having an input and an output and a transfer switch connected to the amplifier output and the amplifier input and having first and second switch states. The operation of the switch is controlled so that the transmit and receive signals are amplified by the amplifier. The other object is to chain RF repeaters so that the handset can roam over a roamer corridor covered by the RF repeaters. The RF repeaters are provided with a dedicated signal link.

Abstract: A radio frequency communication system utilizing a radiating transmission line is disclosed. During normal operation, a mobile communication unit near the radiating transmission line can communicate with other mobile communication units near the transmission line as well as with the base station. The communication system is redundant in that if a portion of the communication system fails such that communication signals cannot be communicated through the fault the communication system will continue to operate and communication signals from any mobile communication units near the radiating transmission line will be transmitted and received from the base station. The communication system is particularly suited for use in underground mines in which event the base station can be located at the surface, and the mobile communication units are generally located in the mine shafts.

Abstract: An RF repeater arrangement for exchanging transmit and receive signals between a handset and a base station in a wireless telephone system automatically compensates for attenuation losses. The RF repeater arrangement includes first and second RF repeater parts connected by a signal conduit, the first part interfacing with the base station and having a signal level detector for detecting the level of the transmit signal, a microprocessor controller for quantizing and encoding the signal level detected by the level detector and a modulator for modulating the signal level data and outputting the modulated signal level data to the signal conduit.

Abstract: A repeater system in a communication system including a base station and a mobile unit provides a communications link between the base station and the mobile unit when the mobile unit is located in an environment that is substantially closed off to high radio frequency communication between the base station and the mobile unit. The repeater system has a first linear two-way frequency converter including a high frequency port for two-way coupling to the base station and a low frequency port for two-way coupling to a low frequency signal that is capable of distributing radio frequency power through the closed environment. The low frequency port is connected to a cable which propagates and receives low radio frequency power within the closed environment.

Abstract: In a radio blind zone system, a master unit and a slave unit are respectively situated at an existing station and a radio blind zone and connected together by a coaxial transmission path. The master unit feeds a load current to the slave unit which includes a relay amplifying device or a tower-top amplifying device. The master unit is capable of detecting an error occurred in the slave unit by detecting a change in the load current applied to the slave unit.

Abstract: A medium-frequency radio transmission system is formed by installing a receiving antenna for receiving an amplitude-modulated medium-frequency radio wave at the rooftop of an existing building, receiving the medium-frequency radio wave, coupling the received medium-frequency radio wave to an existing distributing cable or distributing conductive piping with or without a coupler for the radio wave, and transmitting the radio wave to a predetermined floor. At the predetermined floor the basement or tunnel of an existing building such as underground shopping mall, underground parking lot, underground railway, road tunnel or deep space of massive building is provided with a coupling such as an existing loop-like or linear wiring or piping line with or without a coupler.

Abstract: A long transmission link for two-level information which is interrupted at spaced intervals in order that the signal's level-crossing information may be extracted and passed on. This level-crossing remodulation process discards amplitude information and retains and retransmits only the times of level crossing. By making the receiver of each remodulator sufficiently wide-banded, the overall link is protocol and bit rate independent in the sense that it can pass any of a wide variety of binary digital signals without requiring reclocking at each stage as is done with conventional regenerators. The preferred embodiment includes an application to multi-wavelength long optical transmission links, and this multi-channel approach avoids many problems associated with optical amplifiers.

Abstract: A data setting system for terminal units using an optical wireless signal includes in the respective terminal units a data storing device and a receiving device for the optical wireless signal and, in a data operating device separate from the terminal units, an operating device for preparing and transmitting a setting signal to the terminal units. The setting of data in the respective terminal units employed in a remote supervisory and controlling system using a multiplex data transmission is thereby possible from a remote position from the terminal units through the optical wireless signal.

Abstract: A radio calling system includes a central control station simultaneously broadcasting a calling signal of an arbitrary pager terminal, and a plurality of radio transmitting stations coupled to the central control station. The plurality of radio transmitting stations simultaneously transmit the calling signal received from the central control station at the same radio frequency. The calling signal transmitted from the radio transmitting stations reach the arbitrary pager terminal and at least a neighboring one of the radio transmitting stations.

Abstract: In a secure trunked communication system that includes a central controller, communication between a distribution panel and a limited number of console interface units may be achieved in the following manner. At power up or upon a reset condition, the distribution panel transmits a status check message to each console interface unit in the system. Console interface units that are active respond by transmitting an acknowledgement. Upon receiving the acknowledgement, the distribution panel transmits the addresses of the active console interface units to the central controller. When the distribution panel receives secure information from the central controller, it interprets the information to identify a target console interface unit and transmits the received secure information to the target console interface unit.

Abstract: A multiport repeater for a local area network installation has (in addition to its conventional functions) means for storing access rules for the items of equipment connected to it. It reads a portion of each frame, which may be all or part of the destination address segment and/or of the source address segment and/or of the control segment of each incoming data frame, or it could be a frame or protocol identifier incorporated in opening bytes of the data segment. It compares the data that it reads with the stored access rules to determine whether the frame is permitted or not. If not, the repeater modifies the frame which it is in the course of re-transmitting, for example by overwriting it with meaningless digits or by encrypting it. It may also report the source address, destination address and reason for deciding to modify the frame to the network controller.

Abstract: An intersystem communication path (20, 67) can be established on an as needed basis. Already established paths are fully utilized before new paths are established. Already established paths can be automatically disconnected when no longer needed, or when existing calls can be merged on to fewer lines. Dial up lines can be mixed with dedicated lines. If desired, excess capacity can be guaranteed to accommodate high traffic conditions and/or other conditions that precipitate a likely need for communication services between systems.

Abstract: An RF repeater arrangement for use in linking cordless handsets to a base station, has RF repeaters spaced from a common power supply unit and so distributed over an area to be serviced by the power supply unit that each of the RF repeaters is spaced from at least one other of the RF repeaters by a distance which is less than the range of coverage of the handsets. The power supply unit has a DC power supply connected to supply DC power to said a cable inner conductor, and RF repeaters each have an antenna for exchanging the radio signals with the handsets, transmit and receive circuits and a DC power pick-up connected to the co-axial cable inner conductor for powering the respective RF repeater.

Abstract: A high-throughput bidirectional data communication channel is formed of a pipelined plurality M of stages, connected to the input/output (I/O) port of each of the pair of devices using the channel, and configured to allow interruptibility of data transmission by either device connected to the channel; either device may be sender or receiver and transmission of data may be interrupted by either device for any number of cycles and resumed without loss or duplication of data at the receiver. The channel uses pipelining to achieve longer distance parallel transmission of N plural data bits, while maintaining the maximum high speed throughput. The channel, and its associated data transfer protocol, supports bidirectional transmission of data between the two sourcing/terminating devices with maximum throughput being achieved by transmitting a word of parallel data during every clock cycle.

Abstract: A communication system serving a plurality of radio units in a frequency blocked area includes a remotely controlled and remotely configurable network of radiating coaxial conductors. The radiating coaxial conductors, along with associated amplification devices, are arranged to provide radio communication to an area around the network using radio frequency radiation released by the plurality of radiating cables. Remote control to the system is provided by a control station which transmits control data to the amplification devices through the network of radiating coaxial conductors. The amplification devices are arranged to control the radiating coaxial conductors in such a way that, in response to receiving the control data, the radiating coaxial conductors may be reconfigured to overcome faults occurring in the system.

Abstract: A simulator system adaptable to an actual craft or existing simulator is disclosed. The system comprises computer hardware and software capable of simulation, combinations of simulations and networked simulations. Computer inputs come from sensors attached on or near control and operation members. Computer output is sent to overlay displays and other components. Visual, audio and motion cuing systems are added to increase realism where appropriate to the simulation. All equipment may be quickly and easily installed or removed so as to make maximum use of an otherwise inoperative craft or allow for diversity and upgrading of existing simulators. By the use of computer program modifications and component construction, the system may be used to simulate a wide variety of craft, including air, ground, naval and space craft.

Abstract: A system, according to an embodiment of the present invention, comprises a coupler, a remote antenna, and a handheld GPS receiver. The remote antenna has a microstrip RHCP receiving element and a low noise amplifier (LNA) powered by the coupler over an interconnect cable. The coupler has a slotline antenna and a driver circuit. The coupler re-radiates GPS satellite signals received by the remote antenna with a slotline antenna to the GPS receiver. In a typical installation, such as a car, a user holds the GPS receiver while in the front seat. The coupler mounts to the windshield and the cable runs to remote antenna mounted on the roof of the car. The coupler can then re-radiate GPS satellite signals effectively to the GPS receiver even when the two are separated by as much as six feet. The shielding of GPS signals by the metal of the car is thereby avoided as a problem that can prevent operation of the GPS receiver.

Abstract: A method and apparatus for establishing communication paths includes a portable transceiver carried or worn by a company representative, for communicating in a wireless mode of operation with a stationary base station, thereby enabling the representative to move freely about for performing multiple tasks. A plurality of customer stations outside of the company building are connected electrically to the base station, which includes a switching arrangement to select an individual one of the customer stations for connection to a base station transceiver. The portable transceiver includes a single input device in the form of a push button paging switch for each customer station. The single device causes a customer station to be selected, a communication link to be established and terminated, and controls both the customer and the representative audible communications.

Abstract: A passenger aircraft video distribution system distributes modulated RF signals provided from a central signal source to be used at each passenger seat. The RF signals are distributed by means of various RF components, including amplifiers (90, 14a, 164, 24a, 24b, 34a), taps (180, 210) and splitters (108, 182, 214). In order to ensure proper RF levels for best tuner operation, each of a number of stations in the distribution system is provided with a variable gain amplifier (90, 14a, 164, 24a, 24b, 34a) controllable by a microprocessor (92, 50a, 220, 52a, 56a, 216). A separate service line (222, 224, 226, 228, 230, 232, 234) enables a central microprocessor to monitor RF levels at different stations to automatically provide, via the same service line, appropriate gain control signals to obtain proper RF levels. The monitored RF levels are also employed for diagnostic purposes.

Abstract: A wireless communication system is adapted to be used as an intercom system in a multiple customer station configuration. A customer service representative portable transceiver communicates wirelessly with a stationary base station to enable the representative to move freely about, and thus be able to perform other tasks. The base station is connected electrically to a group of substantially similar physically spaced apart remote customer drive up stations. Each of the remote stations includes a call initiating device for enabling a customer at a drive up station to request communications with the representative. The base station includes a signal generator, which responds to a call initiating device requesting a communication link. A transmitter responds to the generator to send an attention attracting signal to the representative's transceiver, so that the representative can cause the establishment of an audio communication link to a selected customer station.

Abstract: A regenerative RF bi-directional communications system is provided for establishing RF coverage within a RF block tunnel area. The system uses a plurality of cascaded amplifier stages for periodically regenerating signals which are transmitted and received along a series of radiating cable length which link base station transceivers to hand-held or like mobile communication units. An intermediate frequency distribution system is used so that the required level of amplification is achieved through the several cascaded amplifier stages at the level of low-power IF signals generated from the original RF signals in conjunction with the appropriate oscillator and pilot signals. The IF distribution system restricts the cascading effect occurring due to the plurality of cascaded amplifier stages on the relatively low-power IF signals, thereby producing a negligible amount of intermodulation.

Abstract: An alternate home channel for a land mobile transmission trunked communication system designates one of a plurality of repeaters for a given site or coverage zone as an alternate home repeater. The control signals transmitted over the subaudio band for all home channels repeaters in that site are also duplicatively transmitted over the subaudio band of the alternate home repeater. Each mobile transceiver will be programmed with two channel numbers. One for the home repeater and the other for the site alternate home repeater. When the power is turned on, the mobile transceiver determines which repeater to monitor by scanning both the home and alternate home channels. When a valid control message is detected on either channel, that channel becomes the monitor channel. Operation of the mobile transceiver is then generally similar to prior operation, with the exception that the monitor channel (either home or alternate home channel) is used instead of just the home channel.

Abstract: A repeater for receiving data transmitted thereto via a first transmission medium, transmitting that data over AC power lines to a remote location and re-transmitting that data from the remote location via a second transmission medium. The data is applied to the AC power lines by frequency modulating an FM carrier and supplying that modulated carrier to the power lines by way of a bandwidth limiting circuit. At the remote location, a resonant circuit in combination with a reject circuit receives the modulated FM carrier from the AC power lines and passes only an extremely limited band of FM signals to a tuned amplifier which, in turn, supplies the band-limited FM signals to a demodulator.

Abstract: In a data communication system, such as an earth station for a satellite communication system, a level control unit enables control of an amplitude of a data signal which is reduced in a cable, regardless of the form of the data signal. The data communication system includes a first system including a unit for sending a continuous signal having a first frequency and a data signal having second frequency, a cable, and a second system for receiving both sent signals through the cable. The second system includes a unit for correcting an amplitude of the data signal on the basis of an amplitude of the continuous signal to a predetermined level. The second system may also include a unit for further correcting the amplitude of the data signal on the basis of the frequency difference between the data signal and continuous signal, so that the amplitude is adjusted at the second frequency.

Abstract: A non-reciprocal bidirectional duplexer includes a first transmission medium extending from a first terminal to a third terminal; a second transmission medium extending from the second terminal to the third terminal; and a plurality of non-reciprocal, bidirectional phase shifting elements, coupling the transmission mediums and spaced along them; each of the phase shifting elements includes means for amplifying a signal in a first direction from the first to the second transmission medium and for amplifying a signal in the second direction from the second to the first transmission medium; and means for establishing a phase differential between the signals moving in the first and second directions.

Abstract: A downlink between a communications dispatch console and a digitally trunked radio repeater system site controller efficiently transfers message data between the site controller and the console over a standard 9.2 kilobit per second landline. A downlink trunking card identical in structure to trunking cards used in the preferred embodiment system for RF channel signal processing interfaces the site controller with the landline link. A similar trunking card on the other side of the landline link interfaces the dispatch console processor with the landline link. Message protocol and format is translated between the site controller and the landline link and between the landline link and the dispatch console. Data buffering at each end of the landline link maximizes data transfer rate over the landline, and in addition, a priority scheme insures that more important messages are transmitted over the downlink before less important messages.

Abstract: A radio communications system operational within the medium frequency range for underground mine communications, coupling MF carrier signals into existing conductive channels extending to within the mine and devices within the mine and coupled to the conductive channel for receiving the MF carrier signals and communicating with portable and mobile transceivers operational within the MF frequency range and in the common seam mode.

Abstract: A data transmission system utilizing a power line comprises a transmitter (1), a receiver (2) and a repeater (5) coupled to a power line (3). Control data including a start code in the form of a high frequency signal is transmitted from the transmitter (1) in superposition on an alternating current of the commercial power supply using the power line. The repeater receives the control data transmitted from the transmitter, thereby to store the control data in a memory responsive to the start code. The control data is then read from the memory after the lapse of a predetermined period of time and is retransmitted to the receiver in a predetermined level. The receiver receives the control data, thereby to control an apparatus being controlled such as a relay, whereupon the same transmits in a return manner the data representing a control state thereof. The repeater receives the data and transmits the same to the transmitter.

Abstract: A data transmission system utilizing a power line comprises a transmitter (1), a receiver (2) and a repeater (5) coupled to a power line (3). Control data including a start code in the form of a high frequency signal is transmitted from the transmitter (1) in superposition on an alternating current of the commerical power supply using the power line. The repeater receives the control data transmitted from the transmitter, thereby to store the control data in a memory responsive to the start code. The control data is then read from the memory after the lapse of a predetermined period of time and is retransmitted to the receiver in a predetermined level. The receiver receives the control data, thereby to control an apparatus being controlled such as a relay, whereupon the same transmits in a return manner the data representing a control state thereof. The repeater receives the data and transmits the same to the transmitter.

Abstract: A radio communication system for use in tunnels, mines, buildings or other shielded locations in which a pair of radiating transmission lines (30), (31) extend through such location in spaced coextensive relation to each other. Each transmission line (30), (31) has at least one unidirectional amplifier (32), (33) interposed therein with the sense of the unidirectional amplifier (32) of one transmission line (30) being opposite to the sense of the unidirectional amplifier (33) of the other transmission line (31). Each of the amplifiers (32), (33) has a gain which is less than the coupling loss between the transmission lines (30), (31). Two or more mobile transceivers (35) in the location served by the system are coupled to the transmission lines (30), (31) by electromagnetic wave propagation in space in order to communicate directly with each other at a given radio frequency within the frequency range of the system.

Abstract: A regenerator for providing detection, remodulation, and retransmission of a digital data signal propagated in the differential mode over a pair of bundle conductors of a power line. The electric power signal, propagated in the common mode over the same bundle conductors, is conducted through the regenerator and provides a power supply voltage for the regenerator electronics. A series of electrical traps prevent the electric power signal from being conducted into that portion of the regenerator utilized for processing of the data signal. The regenerator also includes bypass switches for by-passing the regenerator electronics when a power supply voltage sufficient to operate the electronics is unavailable.

Abstract: An improved multipoint access data communication system with collision detection provides a duplicative communication medium, network interface units adapted for connection to transceivers on both media, transceivers adapted for connection to a plurality of network interface units, and a local collision detection circuit associated with each transceiver for detecting collisions between transmissions simultaneously attempted by two or more network interface units connected to the transceiver.