Hitachi Denshi Kabushiki Kaisha

Tohoku Electric Power Company, Inc.

Fuji-tekku Kabushiki Kaisha

Osamu Suzuki

Sakari Ohira

Kenichi Suzuki

Mitsuo Shiraishi

Fujio Sumi

Kazuo Suzuka

A communication system for performing bidirectional communications substantially simultaneously between a telephone line and a radio communication system by using a single-frequency carrier. A base station includes a first radio transceiver and a line connector disposed between the first radio transceiver and the telephone line. A terminal station includes a second radio transceiver. Each of the first and second radio transceivers has a control unit, a transmitter unit including a signal compressor, a synchronizing signal generator and a modulator, and a receiver unit including a signal expander. The control unit sets the line connector to an interconnecting state in response to a connection request signal from the telephone line or the terminal station, while establishes a communication enabling state between the telephone line and the terminal station during a connection processing period. After the communication enabling state has been set up, a speech enabling state is established between the telephone line and the terminal station. The connection processing period is changed over to a speech period after the communication enable state has been established, to thereby allow communication between the telephone line and the terminal station.

Communication system interconnecting telephone line and single-frequency

In radio communication system in which single frequency simultaneous transmission and reception is performed, a speech audio signal is divided by a predetermined time interval. A transmission time and a reception time are allotted in the predetermined time. A time-compressed signal is transmitted during the transmission time, and a time-compressed signal transmitted from other transceiver is received during the reception time and it is decompressed to the original length. The transmission time and the reception time are alternately repeated to transmit and receive the audio signals substantially simultaneously by a single frequency, and the audio signal is reproduced from the received signal. When communication with a telephone set is to be established, a DTMF signal is used as a dialing signal to call the telephone set from the transceiver. The DTMF signal is time-compressed and then transmitted along with the speech signal. A transmission timing of the DTMF signal is controlled, and the generated DTMF signal is temporarily stored in a memory. When the transmission of the DTMF signal can be completed before the transmission time is switched to the reception time is determined, and if it can, the DTMF signal is read from the memory and transmitted.

DTMF signal transmission method in single frequency simultaneous

A radio apparatus having a unit for receiving a first signal from a first transceiver compressed in time by a predetermined rate, a unit for reproducing a first original signal from the first signal, a unit for receiving a second signal from a second transceiver compressed by the predetermined rate during the reception period of the first transceiver, a unit for reproducing a second original signal from the second signal, and a unit for adding the first and second original signals and outputting the added signal.

Radio apparatus for simulataneously transmitting and receiving signals

Growing community of inventors

Sayama, Japan

Osamu Suzuki