Hitachi, Ltd.

Yagi Antenna Co., Ltd.

Hiroshi Nakase

Jiro Kashio

Tetsuhiko Hirata

Susumu Nakayashiki

Matsuaki Terada

Hiroyuki Wada

Takeshi Harakawa

Kazuo Yagyu

Yoshinori Bekki

Osamu Ebina

Motoyoshi Morito

Jun Okada

Koichi Kunimasa

Masahiro Fuse

Shigeru Oshima

Takahiko Nishizawa

A base-band and broad-band coexisting communication system comprises a transmission path, a plurality of first data terminal units outputting data to be transmitted in the form of pulse signals (base band signals), a plurality of second data terminal units for outputting data to be transmitted in the form of modulated signals (broad band signals) each having a center frequency within a predetermined frequency range, and a plurality of low-pass filters, each connected to each of the first data transmission units, for cutting off high frequency components of the base band signal outputted by the first data terminal device at a predetermined cut-off frequency which does not overlap with the broad band signals.

Communication system for coexistent base band and broad band signals

A station diagnosis method in a communications network system including a closed ring transmission line and a plurality of data stations which can be connected to the ring transmission line by a plurality of line concentrators disposed in the ring transmission line wherein an internal ring transmission line is formed in the line concentrators so that the operation states of the line concentrators are diagnosed by transmitting diagnosis data through the internal ring transmission line.

Network system diagnosis system

At least two packet exchangers are interconnected through an external transmission line to transmit a data packet. Each packet exchanger comprises a main controller for processing the data packet sent from a packet terminal, in a data link level and a packet level, and a connecting unit for sending the data packet sent from the main controller to the external transmission line and sending the data packet sent from the external transmission line to the main controller.

Packet exchange data transmission system

Growing community of inventors

Fujisawa, Japan

Hiroshi Nakase