Hitachi Denshi Kabushiki Kaisha

Fuji-tekku Kabushiki Kaisha

Hitachi, Ltd.

Tohoku Electric Power Company, Inc.

Tohoki Electric Power Co., Inc.

Nobuo Sekiguchi

Sakari Ohira

Fujio Sumi

Kenichi Suzuki

Yoichi Kaneko

Yukinari Fujiwara

Kazuo Suzuka

Mitsuo Toya

Takashi Kurokawa

Norio Takahashi

Katsumi Takahashi

Kiyoyuki Isawa

A transceiver having a transmitting unit and a receiving unit for performing substantially simultaneous communication with another transceiver in both directions by using a single frequency carrier. The transceiver includes a unit for generating a synchronizing signal for alternately switching between a transmission time period and a reception time period of the transceiver at a predetermined period, a signal processing unit for converting an input signal into a compressed signal by compressing a time axis of the input signal by a predetermined ratio, and affixing the synchronizing signal to the compressed signal, a unit for supplying the compressed signal with the synchronizing signal to the transmitting unit during the transmission time period, and a unit for reproducing an original signal from a signal transmitted from the other transceiver and received by the receiving unit during the reception time period, by expanding a time axis of the signal by a predetermined ratio. The transceiver further includes a signal detecting unit for detecting an absence/presence of the input signal and generating an output signal corresponding the absence/presence, and a control unit for controlling the operation of the signal processing unit in accordance with the output signal of the signal detecting unit. The control unit controls operation of the signal processing unit to transmit only a signal related to the synchronizing signal to the other transceiver, when the signal detecting unit generates the output signal representing an absence of the input signal for a predetermined time period.

Transceiver controlled by absence/presence of input signal

A voice transmission method and apparatus in a duplex radio system are disclosed in which a voice signal to be transmitted in a constant period of time is subjected to 1/N time compression, N being a numeral not smaller than 2.0. The time-compressed voice signal is supplied to a transmitter as a modulating signal and a transmitting operation is performed by the transmitter in synchronism with a period of time when the modulating signal is inputted to the transmitter. A receiving operation of receiving a time-compressed and modulated signal transmitted from the transmitter to demodulate it is performed by a receiver in a period of time other than the period of time when the transmitting operation is performed. A demodulated signal is subjected to N-ple time expansion to obtain a reproduced receive voice signal, and both the transmitting operation and the receiving operation are repeated at the constant period of time. In the voice transmission method and apparatus, a predetermined band of a signal corresponding to said signal to be transmitted, which is in a voice band, is extracted with a predetermined band width. The extracted signal is shifted to any band which is in the voice band and is other than the extracted band. A signal corresponding to the shifted signal is supplied to the transmitter as the modulating signal.

Voice transmission method and apparatus in duplex radio system

In a radio station system utilizing multi-channel transmission and reception frequencies of the type comprising a transmitter and a receiver wherein the frequency difference between the transmission and reception frequencies is made to be equal to an intermediate frequency, there is provided a source of multi-frequency signal which determines the multi-channel transmission and reception frequencies. The output of the multi-frequency signal source is utilized directly as a local oscillation signal of the receiver and the frequency of the output of the multi-frequency signal source is shifted by a modulated wave having a frequency twice the intermediate frequency and the frequency shifted output is utilized as the transmission frequency.

Radio station system

Growing community of inventors

Kodaira, Japan

Nobuo Sekiguchi