Hitachi Denshi Kabushiki Kaisha

Hitachi, Ltd.

Japanese National Railways

Fuji-tekku Kabushiki Kaisha

Tohoki Electric Power Co., Inc.

Takashi Kurokawa

Kenichi Suzuki

Sakari Ohira

Michio Fujiwara

Yasuo Ishii

Fujio Sumi

Kazuo Suzuka

Nobuo Sekiguchi

Katsumi Takahashi

Akoi Otani

Harumi Nagasawa

Yoshio Akutsu

Masujiro Matsuo

Sigeru Ogawa

Schun'ichi Itoh

Kiyoyuki Isawa

Daisuke Takei

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

An ac type line concentrator for use in a data communication system, comprising a crosspoint switch circuit. The crosspoint switch circuit is constituted by a plurality of crosspoint switches capable of switching an analog signal (hereinafter referred to as an analog switch), so that a carrier signal modulated by a data signal may be transferred from one of m incoming lines connected with m terminal units to a selected one of n(n&lt;m) outgoing lines connected with a central unit through the ac type line concentrator without being demodulated.

AC type line concentrator

Growing community of inventors

Hachioji, Japan

Takashi Kurokawa