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AssigneeChiba Communications Industries, Inc.
InventorsKatsutaka Kotezawa, Toshimi Onodera, Setsuo Hayashi, Fujio Shimanuki
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A radio communication system for simultaneous telecommunication between a calling station and a called station using a carrier of single frequency for carrying audio information, in which a time division pulse signal within the audio frequency range is generated for synchronous transmission and reception of the audio signals in these stations in time division fashion. The audio signals received at a station during one pulse interval are delayed and combined with the signal portion received during the one pulse interval to provide a composite signal comprised of the same audio signal in two successive pulse intervals. Voice control means are also provided so that the radio communication system can make continuous signal transmission and reception in time division fashion when audio information to be transmitted is applied to the microphone, and the system can be placed in the receiving mode when such input is not applied to the microphone.
In a radio communication system for effecting simultaneous telecommunication between a first and a second station each including a transmitter and a receiver and using a carrier of a single frequency which carries audio signals, at least one of said stations comprising first means for providing a pulse train comprised of a series of time division pulse signals, each of which pulse signals has a predetermined time interval of from 10 msec. to 100 msec., controller means for enabling said receiver to output the audio signals received during the time interval of certain ones of said pulse signals in said series, output means for said receiver over which said audio signals are provided, delay means connected to said output means for delaying said audio signals for a predetermined time, and composite signal means connected to said output means and said delay means for providing a composite signal which is comprised of the audio signals as output by said receiver in a time interval successively followed by the same audio signals as delayed by said delay means for said predetermined time, and means for coupling said composite signal to associated audio signal reproducing means for reproduction purposes.
In a radio communication system for effecting simultaneous telecommunication between a first and a second station each including a transmitter and a receiver and using a carrier of a single frequency which carries audio signals, at least one of said stations comprising first means for providing a pulse train comprised of a series of time division pulse signals, each of which pulse signals occurs in a predetermined time interval, controller means for enabling said receiver to output the audio signals received during the interval of certain ones of said pulse signals in said series, output means for said receiver over which said audio signals are provided, delay means connected to said output means for delaying said audio signals for one time interval, composite signal means connected to said output means and said delay means for providing a composite signal comprised of the audio signals as output by said receiver in a time interval followed by the same audio signals as delayed by said delay means, a transmitter input means for applying audio signals to said transmitter, said controller means including audio detector means for detecting said audio signals, transmitter starter means, control means for enabling said transmitter starter means in response to detection of an audio signal on said input means by said audio detector means, a signal level comparator having a first input connected to the output of said receiver, a second input connected to an output of said first means, and gate means for enabling said transmitter starter means only in response to receipt of an enabling signal by said signal level comparator over each of said first and second input circuits.
In a radio communication system for effecting simultaneous telecommunication between a first and a second station each including a transmitter and a receiver and using a carrier of a single frequency which carries audio signals, at least one of said stations comprising first means for providing a pulse train comprised of a series of time division pulse signals, each of which pulse signals occurs in a predetermined time interval, said pulse signals of said pulse train having a repetition frequency which is within the audio frequency range, controller means for enabling said receiver to output the audio signals received during the interval of certain ones of said pulse signals in said series, output means for said receiver over which said audio signals are provided, delay means connected to said output means for delaying said audio signals for one time interval, and composite signal means connected to said output means and said delay means for providing a composite signal comprised of the audio signals output by said receiver in one time interval followed by the same audio signals as delayed by said delay means, whereby two sets of identical audio signals appear successively as a composite signal, and means for coupling said composite signal to audio reproducing means for reproduction purposes.
Dependencies are inferred from the claim text.
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Term ended 6 Dec 1994 (estimated)
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This invention relates to the art of simultaneous telecommunication between radio stations, and more particularly to a radio communication system for simultaneous telecommunication between radio stations, using a carrier of single frequency for carrying audio information signals, in which a time division pulse signal of low frequency is generated for the transmission and reception of the audio information signals in time division fashion, and the audio information signal received in time division fashion is reproduced in a unique manner to improve the intelligibility of the reproduced audio information.
In the exchange of information between a calling station and a called station by radio communication units using a carrier of single frequency, the operator in the called station manipulates the radio communication unit upon termination of transmission of a message from the calling station so that he can now transmit his message to the calling station. In such manner of information exchange, however, free conversations like those over a telephone line cannot be attained. In other words, the operator talking by the radio communication unit in the calling or called station cannot say yes or no while the other is talking. Further, at least one hand of the operator in each of the two stations is occupied for the exclusive purpose of switch-over of transmission and reception of audio information signals since such switch-over must be manually carried out. Thus, there has been a strong demand for a radio communication system for simultaneous telecommunication which is capable of automatic switch-over of transmission and reception of audio information signals. However, in the field of information exchange between radio stations, a radio communication system for simultaneous telecommunication capable of automatic switch-over of audio information signals transmitted from and received by radio communication units using a carrier of single frequency has not yet been realized for the reasons described in detail below.
A radio communication system for simultaneous telecommunication capable of automatic switch-over of audio information signals transmitted from and received by radio communication units using a carrier of single frequency can be realized and successfully put into practical use when the transmission and reception of the audio information signals in the calling station and the called station are carried out in synchronous fashion utilizing a time division pulse signal of high frequency. Such a system cannot however be realized due to the fact that a high frequency signal used in such manner for the purpose of time division transmission and reception does not inevitably fall within the limited frequency band prescribed in the laws including the Radio Law.
FIG. 1 is a block diagram of a preferred embodiment of the present invention and shows the structure of the radio communication system in one station.
FIG. 2 shows waveforms appearing at various parts of the system shown in FIG. 1.
FIG. 3 is a block diagram of another preferred embodiment of the present invention having voice control means and shows the structure of the radio communication system in one station.
FIG. 1 is a block diagram of a radio communication system preferably used for simultaneous telecommunication embodying one form of the present invention. The radio communication system shown in FIG. 1 is disposed at least in a calling station (referred to hereinafter as a station A) and a called station (referred to hereinafter as a station B). Referring to FIG. 1 showing the radio communication system in the station A, a signal transmitting route and a signal receiving route have a common antenna 1. This antenna 1 is connected in usual manner to the input terminal 2a of an FM (or AM) receiver 2 of known structure which is part of the signal receiving route. A received modulated signal is subject to detection in the receiver 2 and the audio signal thus obtained appears at the output terminal 2b of the receiver 2. The output terminal 2b of the receiver 2 is connected to the input terminal 3a of an audio delay element 3 and to one terminal 4a of a composite audio signal output circuit 4. This audio delay element 3 acts to delay the audio signal input by a predetermined delay time and may be a known bucket relay circuit or a bucket brigade device (BBD) consisting of a capacitor and a field effect transistor (FET). The composite audio signal output circuit 4 connected at one input terminal 4a thereof to the output terminal 2b of the receiver 2 may be a hybrid circuit comprising a two-input transformer. The other input terminal 4b of the composite audio signal output circuit 4 is connected to the output terminal 3b of the audio delay element 3. Thus, the audio signal output of the receiver 2 and the audio signal output of the audio delay element 3 are applied to the input terminals 4a, 4b of the composite audio signal output circuit 4, and a composite audio signal appears at the output terminal 4c of the composite audio signal output circuit 4 to be applied through a power amplifier 5 to a speaker 6. In the signal transmitting route, a microphone 7 is connected through an audio signal amplifier 8 to the input terminal 9a of an FM (or AM) transmitter 9 of known structure, and this transmitter 9 is connected at the output terminal 9b thereof to the antenna 1 in usual manner.
The radio communication system further includes synchronizing and time division pulse generating means. Referring to FIG. 1, the input terminal 10a of a synchronizing circuit 10 is connected to terminal 2c in the portion of the receiver 2 which is capable of detecting arrival of the transmitted modulated signal, that is, the input terminal 10a of the synchronizing circuit 10 is connected to the squelch circuit or AGC circuit when the receiver 2 is an FM receiver or an AM receiver. The operation of this synchronizing circuit 10 is such that the output signal of the squelch circuit or AGC circuit is amplified and rectified to obtain a digital signal (binary on/off signals) and this digital signal is applied as a trigger signal to a digital counter which counts clock pulses continuously for a predetermined period of time of 10 msec to 100 msec to produce a pulse used for synchronization. In other words, the synchronizing circuit 10 in the station B is generating a train of time division pulses when the stations A and B are initially placed in the transmitting mode and the receiving mode respectively, and upon arrival of the transmitted signals at the station B together with the carrier, the output signal of the squelch circuit or AGC circuit in the receiver 2 in the station B is applied to the synchronizing circuit 10 in the station B so that the synchronizing circuit 10 in the station B can operate in synchronism with that in the station A. A TTL circuit may be used as this synchronizing circuit 10. For the purpose of attaining synchronization, a pilot signal (synchronizing signal) may be incorporated in the modulated signal in usual manner. In such a case, the structure of the circuit will be slightly different from that shown in the block diagram of FIG. 1. However, any detailed description as to such modified circuit is unnecessary since such manner of synchronization is commonly known in the art. The output terminal 10b of the synchronizing circuit 10 is connected to the input terminal 11a of a transmitter -- receiver controller 11. This transmitter-receiver controller 11 includes means, for example, a flip-flop which is inverted each time the pulse appearing after the counting operation for the predetermined period of time by the counter in the synchronizing circuit 10 is applied from the counter so that the time division pulses can appear at the output terminals 11b, 11c of the transmitter-receiver controller 11. This transmitter-receiver controller 11 is connected at the output terminals 11b, 11c thereof to the transmitter 9 and receiver 2 respectively to control the same. Specifically, output terminal 11c of the transmitter-receiver controller 11 is connected to the high-frequency amplifying state of the receiver 2 and the output terminal 11b is connected to the frequency multiplier in the transmitter 9.
The operation of the radio communication system shown in FIG. 1 will be described with reference to FIG. 2. Suppose, for example, that the radio communication system in the station A is in the transmitting mode and that in the station B is in the receiving mode. An audio signal having a waveform as shown in FIG. 2a appears at the output terminal of the microphone 7 in the station A to be applied to the transmitter 9 after being amplified by the audio amplifier 8. A modulated audio signal is applied from the transmitter 9 to the antenna 1 to be transmitted to the station B. At this time, the synchronizing circuit 10 and transmitter-receiver controller 11 in each of the radio communication systems in the stations A and B are applying a low-frequency pulse signal b (FIG. 2) consisting of pulses having a pulse width of 10 msec to 100 msec to the transmitter 9 and receiver 2 in the stations. Thus, in response to the application of this time division pulse signal b shown in FIG. 2b to the transmitter 9 and receiver 2 in the station A, the transmitter 9 and receiver 2 are alternately turned on and off. Similarly, in response to the application of the time division pulse signal C shown in FIG. 2c to the transmitter 9 and receiver 2 in the station B, the receiver 2 and transmitter 9 in station B are alternately turned on and off in synchronism with the transmitter 9 and receiver 2 in the station A. Thus, the transmitter 9 in the station A is energized only during each period of time corresponding to the pulse width TtA in which the time division pulse signal b takes the high level. The modulated audio signal a shown in FIG. 2a is interrupted during the subsequent time interval Tra whereby the signal output from transmitter A appears as a discontinuous signal as shown in FIG. 2d. This discontinuous signal waveform shown in FIG. 2d is transmitted from the antenna 1 in the station A toward the station B. In the space in FIG. 2d, that is, in the pulse interval TrA shown in FIG. 2b, the radio communication system in the station A is placed in the receiving mode, hence, that in the station B is placed in the transmitting mode.