Abstract: An MCA radio data communication system linking a base station and a plurality of terminal stations by radio channels through a control station, wherein note is taken of the facts that one radio channel can be occupied for only a certain occupied time T and that even after the completion of one data communication the radio channel is held for within a certain holding time t (T>t). The present invention allows each of a plurality of terminal stations to share the same radio channels without a channel assignment operation. A communication end signal is simultaneously broadcast upon completion of a first data communication and so that another terminal station demanding a second data communication starts its data communication promptly upon receiving the communication end signal without a channel assignment operation.

Abstract: A message is transmitted on a subcarrier of a main carrier frequency of a radio station. The message is displayed simultaneously with the audible reproduction of the radio program. The message is capable of being displayed dynamically by having different portions thereof sequencing through the display device until the entire message is concluded and/or using a variety of possible display attributes, such as scrolling and flashing. One feature involves scanning the radio band for a station that carries the message. Scanning of a plurality of subcarriers at each station is also performed. One embodiment transmits the message during the "dead time" of other programming normally transmitted on the same subcarrier. The alphanumeric characters of the message are preferably converted prior to transmission into a signal with an average value of zero. The converted characters are decoded at the receiver.

Abstract: A method for use in a cellular radio telephone system for controlling, in at least one mobile station, rescanning operations of paging channels in the system, wherein the mobile station is operationally connected to at least one base station. The method involves broadcasting a rescan message from the base station to the mobile station at predetermined intervals during operation of the base station. Pages to be sent to the mobile stations are stored immediately following broadcast of the rescan message until such time as all mobile stations have had an adequate opportunity to carry out the rescanning operation.

Abstract: A spread spectrum receiver subsystem for utilization in a CDMA cellular telephone having a searcher receiver for scanning the time domain so as to use the PN processing gain and time discrimination properties of spread spectrum coding to determine the location in the time domain and the received signal strength of multiple receptions of a pilot signal traveling upon one or more physical propagation paths to reception. The searcher receiver provides a control signal indicative of the received pilot signals of greatest strength and corresponding time relationship. A data receiver receives spread spectrum communication signals accompanying each received pilot signal and is responsive to the searcher control signal for acquiring and demodulating a spread spectrum communication signal, concomitant with the pilot signal of greatest signal strength, and thus providing a corresponding information bearing encoded output signal.

Abstract: A method for optimizing antenna orientation in a cellular radio telephone system with respect to a predetermined criterion of signal level includes the steps of orienting the antenna in a selected direction, sensing a selected received signal in a predetermined frequency range, mixing the selected received signal with the control signal so as to generate a corresponding intermediate frequency signal in an intermediate frequency transmission path, measuring a selected parameter of the intermediate frequency signal and then altering the orientation of the antenna while subsequently repeating the required steps. The preferred antenna orientation can be determined by examining the results of the various measurements and selecting an antenna orientation which maximizes the signal level of the desired received signal.

Abstract: The present invention includes a method and apparatus for broadcast distribution of messages and information. Included within the present invention are means for selectively broadcasting messages to specified locales. Further, only the appropriate receiver within that locale operates to receive the message. At the receiver, the message is transmitted to or receivable by the appropriate recipient. In the event that a message is inadvertently lost or transmitted with noise induced errors means are provided for requesting a retransmission of the message.

Abstract: A safeguard device having a transmitter produces a high-fequency signal modulated with a code signal word and a receiver having an alarm device is controlled thereby. To protect the transmitter from unauthorized use and to achieve an expansion of its utility, a switching device is provided having a memory for storing a code word and an input unit for a password. The switching device includes a comparing device and code signal generator. The comparing device enables the transmitter when an input password matches with a stored code word. The code signal generator selectively produces either an alarm or a reset code signal word to modulate a high-frequency signal. When the transmitter is switched to the active transmitting state, the appropriately modulated high-frequency signal is emitted. At the receiver, the alarm device is either activated or switched off depending on the code signal word received.

Abstract: A system of transmission with amplitude modulation for the transmission of signals of all types, analog and/or digital, requiring high performance characteristics with respect to the noise induced by the transmission channel, comprising, at transmission, means for the suppressed carrier amplitude modulation of a useful signal and means for the amplitude modulation, in phase quadrature with said modulated useful signal, of a service signal, making it possible, at reception, to remove the ambiguity on the polarity of the demodulated useful signal. Thus it enables the transmission of signals in suppressed carrier modulation mode, hence with a good signal-to-noise ratio, without losing the polarity of the signal. The transmitters and receivers according to the invention also enable the transmission and reception of the signals modulated in SCAM, VSBAM or VSBSCAM modes.

Abstract: A warning broadcast system features control signal means, preferably digital, for confirming transmission path integrity prior to broadcast of a spoken warning message. A radio receiver (1) in an alarm center has an auxiliary carrier reception stage (4) which feeds a decoder (5). A coincidence circuit (6) has a first input (7) connected to the decoder output for inputting the received broadcast control signal and a second input (8) for inputting a directly-coupled control signal via a delay line (9) from the control signal generator (10) of the alarm center. When the control signals at the imputs (7, 8) of the coincidence circuit (6) coincide, an output signal (14) actuates a release (15) for the spoken warning message. If a plurality of transmitters (3) having different frequencies are networked, separate receivers (1,1', . . . ) set to the respective frequencies can feed their respective outputs (14, 14', . . . ) to an AND-gate (16) which triggers release (15).

Abstract: A unique speakerphone for celluar telephones includes in the transmit audio path between microphone 112 and transmitter 118, a transmitter mute switch which disconnects the audio path to the transmitter from the microphone 112, and a transamit gain amplifier that is controlled to lower the feedback the microphone can pickup from the speaker 110. In the feedback path to the radiotelephone receiver 120 from the cellular base station 122 and the land line telephone system 124, the speakerphone includes the controlled amplifier 106 which is fed into the speaker mute gate, and the speaker 110 to close the feedback loop. De-emphasized audio is sampled by the A/D 102 on both the microphone-to-transmittr side of the loop and the receiver-to-speaker side of the loop. The microcomputer 104 is able to detect and eliminate howl, as well as determine whether howl exists, from the A/D sampling.

Abstract: A VCR schedule controller receives broadcast data over antenna (1) or cable (2) by a programmable tuner (3), which is connected to a teletext receiver (4). The teletext receiver (4) is connected to a microprocessor (5). Microprocessor output (11) is connected to a video display generator (10), used to create text for television receiver (60) to display a message from the microprocessor (5). After processing embedded data in a broadcast, the microprocessor (5) generates a cue for display on TV receiver (60). Remote control receiver (20) receives a command from a remote controller (22) from a viewer input in response to the cue. Remote control receiver (20) supplies a control signal to cause the microprocessor to store the embedded data in memory (9). The microprocessor then issues a message to the display generator (10) as an acknowledgement of the viewer input. The microprocessor (5) monitors the system clock (6) and compares it with stored schedules from the embedded supplemental data.

Abstract: A method for calibrating a remote pilot unit is provided wherein both the pilot receiver and the pilot transmitter are calibrated. A test signal of a known magnitude is applied to the pilot unit and the magnitude actually received by the pilot receiver is determined. The two magnitudes are compared and a correction signal is determined. To calibrate the remote transmitter, a signal of a nominal magnitude from the transmitter is applied to a measurement device and the determination is made by the measurement device of the actual magnitude applied. The actual magnitude and the nominal magnitude are compared and a transmitter correction signal is determined. The receiver correction signal and the transmitter correction signal are stored in permanent memory within the pilot unit. This process is repeated at a plurality of frequencies to provide a signature for both the transmitter and the receiver.

Abstract: The communications system of the present invention defines a complete feedback path consisting of first and second transceivers and an appropriate signal path. Each transceiver comprises a detector and a signal source capable of generating a signal at one of two frequencies. The detector in each of the transceivers is a two state device tuned to respond only to a predetermined desired difference frequency. If the desired difference frequency signal is present, the detector provides and output signal in a first state; if the desired difference signal is not present, the detector provides an output signal which is in a second state. The signal source can be a voltage controlled oscillator, a pair of single frequency oscillators, a synthesizer, or any signal source capable of being electrically switched between two frequencies. Data can be exchanged between the transceiver pair only when the desired difference frequency is present.

Abstract: A video program system (VPS) signal superimposed on a television signal is continuously stored in an input buffer. A determination process circuit determines whether or not the VPS signal stored in the input buffer is a normal signal. When the VPS signal stored in the input buffer is a no-signal, a count value of a no-signal counter is counted. When the count value of the no-signal counter exceeds a predetermined count value, the circuit determines that the VPS signal detected from the television signal is the no-signal. When VPS signals corresponding to various programs are stored in the input buffer, a count value of an error counter is counted. When the count value of the error counter exceeds a predetermined count value, the circuit determines that the input state of the VPS signal detected from the television signal is unstable. When the same VPS signal is continuously stored in the input buffer, the circuit determines that the VPS signal detected from the television signal is a normal signal.

Abstract: A two-way communication system for transmitting command signals to and receiving operating data from a winning machine utilized in underground mining operations. The system includes a send-receive facility positioned remote from the winning machine for transmitting command information to the winning machine. A receiving means is positioned at the winning machine for receiving signals sent by the send-receive facility, and a transmitting means is positioned at the winning machine for transmitting signals corresponding to operating data of the winning machine. The send-receive facility receives the information transmitted by the transmitting means, and a separable memory is separably attached to the send-receive facility for storing such operating data and the command information. Because the memory is separable, the memory may be removed to allow the data contained therein to be analyzed at a remote location.

Abstract: A system is disclosed for transmitting a sensed temperature from a transmitter to a remote receiver over a modulated carrier through the atmosphere. The transmitter and the receiver are battery powered and include timing circuitry having low power consumption. The transmitter and the receiver are both cyclically turned on for a relatively short period and off for a relative long period with the receiver's on cycle being synchronized with the occurrence of the transmission of the modulated carrier. The receiver further employs techniques to minimize the effect of noise on the reception of the transmitted data which can occur from extraneous signal sources broadcasting in the same frequency band or from environmental noise.

Abstract: The power transmitted by an r.f. transmitting and receiving station, such as a mobile station, to a fixed base station, is controlled as a function of power received by the mobile station to obtain a constant receiving power level in the fixed station despite variations in the relative location of the stations. The power received by the mobile station is measured and sampled at predetermined instants. At each predetermined instant, the power to be received by the mobile station at a following predetermined instant is estimated as a function of the measured power, to derive an estimated power. R.f. signal power transmitted by the mobile station is reduced between the successive instants in proportion to the estimated power.

Abstract: A radio communication system comprises a base station for periodically transmitting a power saving signal and an information signal, a repeater station for relaying the signals, and a plurality of terminal stations for communicating with the base station through the repeater station. The repeater station includes power saving circuitry which responds to the power saving signal by cutting off power supplies to its major power consumptive components during a preset interval which alternates with an active interval during which power is supplied to the components.

Abstract: The invention relates to a method and apparatus for transmitting data signals between a master station and a plurality of terminal stations connected at different points of a transmission line, in which a correction of the attenuation distortion caused by the transmission line is carried out in the receiving station. The method transmits a plurality of signals prior to the start of a regular transmission which is used by the receiving station to determine the appropriate gain it requires to compensate for the attenuation of the specific section of the transmission line to be used in the regular transmission. The gains are set in the receiving amplifiers of the receiving stations and stored in associated memory modules.

Abstract: A multi-bit program identification signal is transmitted in the audible band with a program signal, and a receiver detecting the program identification signal automatically sets a predetermined minimum volume for reproduction of the program information. The volume control circuitry at the receiver can be made responsive to any one of a plurality of different program identification signals.

Abstract: The apparatus of this invention is a system for providing frequency synchronization and predictable phase output of the transmitted signals of a multi-channel frequency division multiplexed communications system.

Abstract: A modem is operated in a half-duplex mode having various elements which are trained on data and which are locked up while data is not exchanged, thereby eliminating the need for a preamble. A preamble is used only if the period between successive transmissions exceeds a preselected threshold.

Abstract: In a system in which an information signal is transmitted along with digital data from a transmitter to a receiver, transmitter circuitry is provided which produces digital data indicative of parameters relating to noise reduction for the information signal, and receiver circuitry is provided responsive to the digital data so as to optimize reception of the information signal. In one embodiment of the invention, one of a plurality of different pre-emphasis levels is applied to a signal and digital data is produced according to a value of pre-emphasis added. The digital data and the pre-emphasized signal are then transmitted. The receiver decodes the digital data and adds a corresponding amount of de-emphasis to the received information signal. In another embodiment the digital data indicates an optimum value for a parameter to be applied to a threshold extension demodulator in the receiver.

Abstract: The remote control system having symmetrical signaling circuits for radio communications is coupled to a single wire line/audio channel and permits two or more units, base stations and/or remote consoles, to be coupled to the single wire line. Each signaling circuit comprises a wire line coupler for coupling to the wire line, an audio input line and an audio output line. An automatic gain control circuit is coupled between the wire coupler and the audio output line and a filter and line driver are coupled between the audio input line and the wire coupler. A control unit including a microprocessor, a tone encoder, a tone decoder, a timer, a clock, and a memory is coupled by output lines to the automatic gain control circuit for controlling the modes of operation thereof which include a slow decay mode, a fast decay mode, an adapt mode and a hold gain mode. The output from the gain control circuit is also routed through a band pass filter and a limiter to the control unit.

Abstract: A data terminal suitable for home use and having the ability to communicate in both bit synchronous and character asynchronous formats is provided. When a user places a call to a database, the terminal automatically detects whether the database is operating in the bit synchronous or character asynchronous format by examining the received signal for a specific character stream. In response to the presence or absence of this character stream, the terminal automatically configures its receiver and transmitter to communicate in the desired format. This frees the user from the task of modifying a synchronous/asynchronous setup parameter each time a different database is accessed.

Abstract: The remote control system having symmetrical signaling circuits for radio communications is coupled to a single wire line/audio channel and permits two or more units, base stations and/or remote consoles, to be coupled to the single wire line. Each signaling circuit comprises a wire line coupler for coupling to the wire line, an audio input line and an audio output line. An automatic gain control circuit is coupled between the wire coupler and the audio output line and a filter and line driver are coupled between the audio input line and the wire coupler. A control unit including a microprocessor, a tone encoder, a tone decoder, a timer, a clock, and a memory is coupled by output lines to the automatic gain control circuit for controlling the modes of operation thereof which include a slow decay mode, a fast decay mode, an adapt mode and a hold gain mode. The output from the gain control circuit is also routed through a band pass filter and a limiter to the control unit.

Abstract: A general purpose data control terminal which permits multiple terminal control. The terminal is programmable thereby permitting compatability with a wide range of communications systems. The unit is microprocessor based and includes a keyboard, and display, and utilizes acknowledge and retransmission logic for improved reliability.

Abstract: A general purpose data control and information system particularly well adapted for multiple unit radio communications providing reliable enhancement to normal voice systems. The system provides addressing capability along with data transfer and utilizes handshake and retransmission protocol to enhance flexibility and reliability. The system utilizes fixed length signalling packets, with error correction encoding, to permit data transfer, transmitter identification and control and status monitoring.

Abstract: FM transmission system in which, besides program content, an auxiliary carrier of, for example 57 kHz, is radiated, which auxiliary carrier is modulated by an announcement recognition (AR) signal and by a region or radio-station recognition (RR) signal, the AR and RR signals being low-frequency, AM modulations on the auxiliary carrier. To enhance recognition of an AR signal, e.g. between 142 and 170 Hz, is enhanced, in spite of reception difficulties, for example due to multi-path reception and the like, by decreasing the modulation of the 57 kHz subcarrier by the RR signal to 30% or less, while the AR signal is modulating the subcarrier, so that the AR modulation may extend to 60 and even 90% modulation. Multiple AR frequencies can be used, for example to characterize different announcements, e.g. in different languages, or of different characteristics, such as traffic, news, sports, or others, recognition of the AR signal in the receiver permitting switch-over from other reproduced programs, e.g.

Abstract: In a time-division multiple access (TDMA) communication network, a power saving system interleaves a power saving control signal at periodic intervals with a selection signal and information signals and transmits the interleaved signals from a master station to slave stations. A plurality of power cut-off circuits are associated respectively with the slave stations for individually cutting off power supplies to the slave stations for a predetermined period in response to the control signal. A detector is provided for detecting the moment a connection is being established, identifying the slave station establishing the connection and selectively inhibiting the power cut-off circuit associated with the identified station from responding to the control signal, while allowing the remainder of the power cut-off means to respond to the control signal.

Abstract: A single sideband communications system conveying a message through a transmitter to one or more predetermined receivers which are enabled by a coded squelch signal unique to the predetermined receivers is disclosed. The transmitter comprises means to angle modulate both the pilot signal and the information bearing single sideband signal with the coded signal at a predetermined deviation and to transmit the resulting signal.Each receiver frequency control means tracks the frequency excursions of a selected portion of the transmitted signal up to predetermined limits so that the message can be demodulated without frequency distortion being introduced. Each receiver demodulates the coded squelch without interfering with the message demodulation or tracking functions and activates the receiver squelch of those preselected receivers.

Abstract: In a power supply system for use in a radio communication system comprising a base station for transmitting and receiving radio signals, one or more repeater stations for repeating the radio signals, and a terminal station communicating with the base station through the repeating stations, the base station comprises means for transmitting synchronizing signal pulses at a predetermined period for effecting a battery saving type power supply. Each of the repeater station and terminal station comprises means, responsive to successive reception of a predetermined number of the synchronizing signal pulses, for effecting intermittent battery saving at a period substantially equal to the period of the synchronizing signal pulses during occurrence of the synchronizing signal pulses.

Abstract: To decode control signals from a mixture of signals including audio signals, such as music, voice or speech, in which the control signals are within the audio range, for example 2,350 Hz, on which a low-frequency signal, for example in the 100-200 Hz range is modulated, the control signal in the form of a control tone is filtered and demodulated by band pass filters (1,3), demodulators and rectifiers (2,4), and then applied to a timing circuit (5) which provides an output signal if and only if the demodulated control tone is continuously applied during the timing interval thereof. Suitable timing intervals are about 1 second, to provide an output signal which can switch a flipflop (7) on, for example to command radiation of a particular type of recognition signal by the transmitter (13), the setting of the flipflop (FF) (7) being fed back to the timing circuit to change the timing interval thereof to a lesser amount, for example 1/2 seconds, to provide for a shorter signal to cause resetting of the FF (7).

Abstract: To permit simultaneous transmission of command codes, in binary command words, with traffic or other announcements, being broadcast over an FM transmitter which has a 57 kHz subcarrier AM modulated by an announcement recognition (AR) signal, for example 125 Hz, use is made of the long response time of AR switching elements to provide, before the AR switching element (13) can respond, decoding of a command word at a clock rate which is fast with respect to the response time of the long switching time constant switching element (13).

Abstract: A signal processor processes communication signals for a communication link by extracting amplitude information from the signal and converting this amplitude information into two signal tones. The frequency information of the communication system is transmitted as a constant amplitude signal with two narrowband FM control channels. Each control channel is used to transmit one of the two tones. After the communication signal is received, the two tones are removed from the narrowband FM control channels and are used to generate control signals that will control a variable gain amplifier and transfer the amplitude information back to the constant amplitude signal thereby facilitating the reception of the communication system.

Abstract: A transmission system develops a binary encoded data train having a message and a header preceding the message. The data train is applied to a carrier frequency to modulate the carrier using FSK techniques. The header includes synch signals, one or more address signals, a message length signal and control signals separating the above signals. One or more personal receivers receive the message if responsive to one of the address signals in the header. An address signal may address a unique personal receiver, a selected group of or all such personal receivers. Each receiver is sequentially activated and deactivated, being activated to detect a synch signal. If synch signals are detected, the receiver remains activated to determine if an address signal identifies such receiver to receive the message. A received message is stored digitally and may be selectively displayed in alphanumeric characters when convenient for the recipient.

Abstract: Subscriber access to the television transmissions of a cable TV system or other wired program transmission is governed by switching means in the remotely controlled unit to which the subscriber's receiver is connected, which switching means is enabled or disabled in response to information coded on the power flow which energizes the controlled unit. The power to the controlled unit may be coded at the cable TV power supply in response to a separate modulated RF carrier signal transmitted to all power supply units from the cable television broadcast central station, or other central location. Stated in other words, a program control center generates binary coded instructions including address words which are conveyed in a wired signal transmission system to multiple subscriber stations by encoding in a special way the output of a power supply used to supply energization to portions of the system.

Abstract: An emergency telecommunications system wherein the distress signals are transmitted repeatedly in successive sequences each comprised of a detect interval during which an alarm signal is transmitted and of a message transmit interval during which the distress message itself is transmitted indicating particularly the identity of the ship, its location and the nature of distress. During the detect interval, the transmitted signal is comprised of a carrier phase modulated by a sub-carrier, the frequency of the latter being a multiple of the information transmission speed. During the message transmit interval, the information is superposed to the sub-carrier by phase binary modulation. The presence of an alarm signal during each detect interval is detected in an alarm receiver monitoring the receive frequency band simultaneously in several channels of different narrow bandwidths so as to generate a control signal which indicates the presence of a distress signal in anyone of the channels.

Abstract: A system which automatically corrects the wave-form of a signal of a given frequency passing over a transmission path, over which a carrier double-sideband amplitude-modulated by a complex tone and extending across the given signal-frequency band is transmitted in the signal-frequency band as a combined wave with the signal. At the receiving apparatus the reconstructed modulated carrier is used as a standard to correct the waveform of the signal from distortion caused by the transmission path, using sampling, reconstruction, comparison and gain-variation methods. The modulated carrier is eliminated from the corrected signal at the output of the receiving apparatus by sampling and reconstruction methods. Sampling and modulation frequencies and phases are derived from the carrier.

Abstract: A sub-audible in-band tone system is disclosed for identifying an FM stereophonic radio broadcast which is specially encoded, as with dynamic range improvement encoding or quadraphonic encoding, for example, A constant frequency pilot tone is added at a low level (e.g. at -70dB) to the transmitted signal at or near the upper frequency limit of the audio frequency spectrum (15 kHz). The audio spectrum is not notched or otherwise altered to accommodate the tone. FM stereophonic receivers detect the pilot tone by heterodyning the received tone with a stable mixing signal at 15.2 kHz derived from the 19 kHz FM stereo pilot tone. The shifted frequency tone is passed to a low frequency narrow band detector which can control a visual display and switch in appropriate signal decoding circuitry when the tone is detected.

Abstract: The invention is directed to a remote equipment control system having a low duty cycle communications link between a remote command transmitter and a remote receiver. The remote receiver is controllingly coupled to the equipment. The remote command transmitter includes a means to transmit a message signal of set time duration at a preselected message separation interval. The message signal has a unique address portion and a command portion.The remote receiver includes a decoding unit and a timing circuit. The decoding unit is responsive to the unique address portion of a received message to provide an enabling signal to be delivered to the timing circuit. The timing circuit upon receipt of the enabling signal provides an output to the decoding unit to prevent entry of any message signal to the decoder for a time duration matching the preselected message separation interval and allowing entry of a message signal for a time duration matching the time duration of the message signal.

Abstract: A superheterodyne radio receiver which is simultaneously tuned to receive both signals selectively tuned within the general AM broadcast spectrum and signals transmitted at the intermediate frequency, as defined in the receiver. The receiver responds to predetermined coded signals on the broadcast intermediate frequency signal to inhibit the local oscillator in preference to subsequent information broadcast on the intermediate frequency.

Abstract: In a multi-channel mobile radio telephone system with multiple base stations covering different geographical areas, mobiles may move freely from area to area and automatically originate and receive calls to and from a landswitched telephone network by direct dialing to and from anywhere in the system by means of a Roving Mobile Call System (RMCS). Mobile subscribers operating out of range of their home base stations (where they are registered for billing purposes) may originate any class of call via any base station in the system and be billed by the home base station by means of intercommunicating base stations in a Roving Mobile Ticketing System (RMTS). Provision is made for tariff sharing as necessary by participating stations. All call signalling and central signalling is performed out-of-band. Call signalling from any base station to mobiles is common to all radio channels transmitted by that station.

Abstract: A method and apparatus for controlling the gain of receivers in a computer-to-computer communications network using intelligence in the signal to control the receiver gain. Each of the computers in the communications network has associated therewith a transmitter and a receiver for transmitting and receiving data from one or more of the other computers in the system. Preferably, each such receiver has associated therewith an automatic gain control circuit which operates automatically to increase the gain when low level signals are received and to decrease the gain when high level signals are received. At least one of the receivers and preferably each receiver in the system has associated therewith a memory device for storing compiled data indicative of the anticipated signal level from every other transmitter in the system.